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1: Tube DIY Asylum, I used 12 V SPS for heaters in many projects and they were generally fine with only one exception. (0.00)
Posted by cellailuca on 2024-03-30, 09:38:16 (79.19.247.57)
This is for example a 6080 OTL and the power supply is a 12V-220W SPS model. I had a nasty 8/16 KHz spurious coupling only in one case and I had to rearrange the layout. .......
2: Tube DIY Asylum, There are no limitations at all for streaming of free music content. (0.00)
Posted by cellailuca on 2024-03-29, 01:46:40 (79.19.247.57)
BT is a short range data link with speed up to 3 Mbit/sec. BT uses codecs for audio and video. BT audio codecs are exactly what is needed for free internet audio streaming. If I wanted to subscribe an .......
3: Tube DIY Asylum, Hint to get the filament voltage from a toroidal transformer. (0.00)
Posted by cellailuca on 2024-03-28, 09:28:00 (95.238.232.206)
When using a toroidal transformer of exuberant power for HT power supply it is possible to manually wire an auxiliary winding for filament supply. In most cases you get about 0.2-0.4 volt for each .......
4: Tube DIY Asylum, RE: Has BT overcome its sonic limitations? nt (0.00)
Posted by cellailuca on 2024-03-24, 23:49:01 (79.54.112.172)
What limitations? .......
5: OTL Asylum, RE: Reference 3A NEFES (0.00)
Posted by cellailuca on 2024-03-24, 09:11:17 (79.54.112.172)
Excerpt from Tube CAD Journal: "With a loudspeaker's passive crossover we want a flat frequency response and impedance and phase plots and steep crossover slopes. The first three are provided by the f .......
6: OTL Asylum, Luxman MQ 36 schematic (0.00)
Posted by cellailuca on 2024-03-19, 09:00:39 (79.54.112.172)
Wonderful amplifier! .......
7: OTL Asylum, Luxman MQ 36? (0.00)
Posted by cellailuca on 2024-03-19, 01:51:47 (79.54.112.172)
It seems a custom MQ36. .......
8: Tube DIY Asylum, Did you ever heard of 'transnova'? (0.00)
Posted by cellailuca on 2024-03-10, 05:11:35 (79.54.112.172)
John Broskie is a world class master of circuit analysis and design. In this post he is discussing the inner workings of this novel circuit (transnova) and why it could be applied to tubes too. :: .......
9: Tube DIY Asylum, For those interested in useful audio applications (0.00)
Posted by cellailuca on 2024-02-29, 03:40:53 (79.54.112.172)
These are smartphone screenshots of a SPL Meter and a spectrogram during playback of some jazz music at a subjectly comfortable level. These are tools that not even a professional laboratory had .......
10: Tube DIY Asylum, RE: I remain amused by this premise about said distortion as 3 to 5 percent distortion is found in ALL speakersnT (0.00)
Posted by cellailuca on 2024-02-29, 02:00:12 (79.54.112.172)
Do you know how SPL meters work? Have you ever tried whatever application that measures SPL on your smartphone? Do you know that the average SPL (as measured by SPL meters) at any point in the listeni .......
11: Tube DIY Asylum, RE: I remain amused by this premise about said distortion as 3 to 5 percent distortion is found in ALL speakersnT (0.00)
Posted by cellailuca on 2024-02-28, 07:34:42 (79.54.112.172)
It depends on power level and music content. I usually refer to ambient SPL (average/peak + SPL ambient noise floor) generated by a given amplifier instead of referring to amplifier power. In the aver .......
12: Tube DIY Asylum, RE: The Issue with These Tubes is Distortion (0.00)
Posted by cellailuca on 2024-02-27, 00:33:09 (79.54.112.172)
Still thinking in terms of mono-dimensional distortion? The matter is a bit more complex... .......
13: Tube DIY Asylum, The streamer Is connected via BT (0.00)
Posted by cellailuca on 2024-02-26, 10:01:05 (79.54.112.172)
I also use a mini FBQ Behringer equalizer. .......
14: Tube DIY Asylum, It Is a honest amplifier (0.00)
Posted by cellailuca on 2024-02-26, 09:55:18 (79.54.112.172)
I mainly use it to listen to classic music in streaming. The peak ambient SPL with this baby is above 80 dB. More than enough for normal listening (ambient noise floor is 28 dB). .......
15: Tube DIY Asylum, RE: A simple PP amplifier with 829B and 12AT7 (0.00)
Posted by cellailuca on 2024-02-26, 02:26:16 (79.54.112.172)
The top panel is made of a copper card for printed circuits. .......
16: Tube DIY Asylum, A simple PP amplifier with 829B and 12AT7 (0.00)
Posted by cellailuca on 2024-02-26, 02:23:11 (79.54.112.172)
I built this baby more than 10 years ago. For a couple of weeks it will be online again. .......
17: Tube DIY Asylum, More than 10 years ago... (0.00)
Posted by cellailuca on 2024-01-24, 03:00:56 (82.63.61.33)
I designed and built this baby. I am going to use it for some weeks now. After completion of rotation of the past tube projects still in my hands an year is gone. .......
18: OTL Asylum, RE: 6AS7G/6N13S sound quality & longevity ?'s (0.00)
Posted by cellailuca on 2024-01-16, 02:23:43 (82.63.61.33)
When many output tubes operate in parallel there is a sort of graceful degradation of performance over time. It may take more than a decade of use to notice any degradation. If the bias is stable IMHO .......
19: Tube DIY Asylum, There are valid alternatives... (0.00)
Posted by cellailuca on 2024-01-15, 01:43:16 (82.63.61.33)
There are valid and simpler alternatives with 6AS7 tubes. .......
20: Tube DIY Asylum, RE: When negative feedback is not beneficial (0.00)
Posted by cellailuca on 2024-01-10, 01:54:15 (79.27.244.174)
These are the V+ and V- outputs and the V+ spectrum with about 10 dB feedback. Apparently the distortion goes up to about -30 dBc with respect to the zero feedback case (-40 dBc). This is basica .......
21: Tube DIY Asylum, RE: When negative feedback is not beneficial (0.00)
Posted by cellailuca on 2024-01-10, 01:47:06 (79.27.244.174)
These are the V+ and V- outputs and the V+ spectrum with no feedback at all. It looks like an honest circuit. .......
22: Tube DIY Asylum, RE: When negative feedback is not beneficial (0.00)
Posted by cellailuca on 2024-01-10, 01:41:23 (79.27.244.174)
These are the simulated V+ and V- outputs when the circuit gain from input (1 V peak) to output is one. The massive feedback causes zero crossing distortion! .......
23: Tube DIY Asylum, RE: When negative feedback is not beneficial (0.00)
Posted by cellailuca on 2024-01-10, 01:36:40 (79.27.244.174)
This is the LT Spice model of the input circuit (cascode Schmidt) to experiment with. In simulation world we can apply perfect feedback. .......
24: Tube DIY Asylum, When negative feedback is not beneficial (0.00)
Posted by cellailuca on 2024-01-10, 01:31:15 (79.27.244.174)
Theory says that negative feedback always improves distortion. However there are examples from the past of commercial amplifiers with plenty of feedback and no particular sonic benefit. Why? The be .......
25: Tube DIY Asylum, Ampex 620 amplifier (0.00)
Posted by cellailuca on 2024-01-07, 06:30:33 (79.27.244.174)
Just in case. .......
26: Tube DIY Asylum, 2020/2021 project on line for Christmas. (0.00)
Posted by cellailuca on 2023-12-18, 02:08:06 (79.18.2.77)
After replacing an unstable tube and a conservative re-biasing today I have put in service this baby. .......
27: Tube DIY Asylum, RE: Can cascode have CCS on top instead of resistor (0.00)
Posted by cellailuca on 2023-12-05, 09:53:53 (79.18.2.77)
In the Morgan Jones "Valve amplifiers" book there is a chapter on the relative merits (and measured distortion) of many basic circuits, from concertina to cascode and SRPP, with and without CCS. ::: .......
28: Tube DIY Asylum, Excellent job! (0.00)
Posted by cellailuca on 2023-11-30, 08:34:46 (80.104.134.199)
I like it. .......
29: OTL Asylum, RE: feedback suggestion (0.00)
Posted by cellailuca on 2023-11-24, 10:11:43 (62.18.96.243)
Excellent hint. Thank you! .......
30: Tube DIY Asylum, RE: Group delay and phase IS far more complicated than any past discussion within this forum_nT (0.00)
Posted by cellailuca on 2023-11-19, 03:35:28 (79.32.219.245)
Not too much complicate. What is important is group delay flatness. In linear devices (and any audio equipment is extremely linear) the group delay is the Hilbert transform of amplitude response. Avoi .......
31: OTL Asylum, My 2008 DIY OTL (0.00)
Posted by cellailuca on 2023-11-16, 10:58:44 (79.32.219.245)
From time to time I put online one of my DIY tube amplifiers. This week I am listening to this baby. .......
32: Tube DIY Asylum, RE: Where's the tone control? (0.00)
Posted by cellailuca on 2023-11-14, 22:51:25 (79.32.219.245)
The small switch on the top panel is flat/hi&bass boost control. Wood is as good as other materials. I glued some aluminium foil on the inner box to avoid EMI. .......
33: Tube DIY Asylum, All 6SN7 amplifier with tone control after a year of use. (0.00)
Posted by cellailuca on 2023-11-14, 13:03:38 (79.32.219.245)
I use it with a K702 AKG headset. Studio quality at its best and no hum or noise. .......
34: Tube DIY Asylum, 15 years of DIY (0.00)
Posted by cellailuca on 2023-03-20, 10:43:54 (80.180.35.112)
I have started to publish my tube projects since 2007. .......
35: Tweakers' Asylum, Every 10-12 years... (0.00)
Posted by cellailuca on 2023-03-19, 10:11:04 (80.180.35.112)
It comes the time of replacing the foam/poliurathane suspension of the speakers (mid-woofer and/or woofer). This is the third time for my 1989 four way speakers. As I am getting older maybe n .......
36: Tube DIY Asylum, As a DIYer I always visit hi end events... (0.00)
Posted by cellailuca on 2023-03-06, 03:15:33 (95.239.220.103)
Hi end is very mature. Basically there is no improvement in audio reproduction since tens of years ago. All demos run with analog source, medium audio level around 70 dB SPL (85 dB S .......
37: Tube DIY Asylum, I don't think so (2 of 2) (0.00)
Posted by cellailuca on 2023-03-03, 07:26:50 (95.239.220.103)
Post 150. .......
38: Tube DIY Asylum, I don't think so (1 of 2) (0.00)
Posted by cellailuca on 2023-03-03, 07:24:31 (95.239.220.103)
Post 147. .......
39: Tube DIY Asylum, John Broskie is 'master and commander' of circuit analysis. (0.00)
Posted by cellailuca on 2023-03-02, 08:39:40 (95.239.220.103)
SE and PP revisited. .......
40: Tube DIY Asylum, RE: NFB in a PP DHT amp? (0.00)
Posted by cellailuca on 2023-02-08, 02:41:09 (79.19.247.69)
I built the same PP amplifier with and without NFB. I prefer the NFB unit, a friend of mine prefers the unit without. .......
41: OTL Asylum, RE: A possible update (0.00)
Posted by cellailuca on 2023-01-28, 09:18:03 (79.19.247.69)
Thank you for your suggestion. When I started to use LTSpice a few years later I found out that a single 5.2 Ohm resistor in series with the four cathode resistors of the -150V side could reduce disto .......
42: OTL Asylum, My 2008 OTL (0.00)
Posted by cellailuca on 2023-01-26, 08:22:07 (79.19.247.69)
Almost 15 years of flawless operation. .......
43: Tube DIY Asylum, RE: UL Distortion (0.00)
Posted by cellailuca on 2023-01-09, 09:56:36 (95.250.7.6)
About 15 years ago a toroidal transformer manufacturer (from Holland, if I remember correctly) was selling a special output transformer with multiple windings. The idea was to give to the user the pos .......
44: Tube DIY Asylum, Just for fun: what if... (0.00)
Posted by cellailuca on 2022-12-13, 12:51:22 (95.246.210.8)
What if I used transistors in a tube PP circuit? The answer is: you would get about the same theoretical performance. The following circuit with 2N3055 power transistors has an input impedanc .......
45: Amp/Preamp Asylum, RE: Like to try an inexpensive tone control? Schiit deals. (0.00)
Posted by cellailuca on 2022-12-13, 02:20:41 (95.246.210.8)
I use the Behringer mini equalizer and it is excellent. .......
46: OTL Asylum, RE: Certainly of the 4 30-to-60-Watt SETs I tried... (0.00)
Posted by cellailuca on 2022-12-06, 03:31:25 (95.246.210.8)
30 W is 14.7 dB more than 86 dB SPL/1W/1m. In a normal listening room (15-30 square meters, medium wall absorbption) this means than you can easily get more than 95 dB SPL. The comfort zone for 90% of .......
47: Tube DIY Asylum, Alternative solution (0.00)
Posted by cellailuca on 2022-12-03, 01:56:18 (95.246.210.8)
I have reduced the bias form 80 mA to 50 mA @600V... Still plenty of power available. This is one of the many advantages of DIY, you are the master of your design. .......
48: High Efficiency Speaker Asylum, RE: Really? (0.00)
Posted by cellailuca on 2022-11-29, 09:08:09 (79.31.239.227)
It is inside professional stage monitors. .......
49: High Efficiency Speaker Asylum, Has someone used this RCF speaker in a project? (0.00)
Posted by cellailuca on 2022-11-20, 06:41:20 (79.31.239.227)
Amy information will be appreciated. .......
50: Tube DIY Asylum, RE: Perhaps Not the Best Approach (0.00)
Posted by cellailuca on 2022-10-29, 00:56:16 (87.10.23.215)
In fact I usually use this 3W transformer amplifier for headphone listening. Clearly it is not SE. .......
51: Tube DIY Asylum, RE: 6080 headphone? (0.00)
Posted by cellailuca on 2022-10-27, 08:21:47 (87.10.23.215)
Maybe this will suit you fine. .......
52: Tube DIY Asylum, After 15 years of tube DIY... (0.00)
Posted by cellailuca on 2022-10-07, 09:36:40 (79.37.214.66)
I think to quit. I am no more interested in new projects and all components have become so much expensive. I will rather focus on maintaining the many amplifiers built so far. .......
53: Tube DIY Asylum, Energy prices out of control may put at risk tube amplifiers (0.00)
Posted by cellailuca on 2022-09-27, 09:56:25 (79.52.220.31)
After the likely sabotage of both North Stream 1 and 2 and because of the Biden decision to cut ties with Russia (in connection with Ucraine war) Europe is missing 30% of natural gas. Electricity a .......
54: Tube DIY Asylum, Energy prices out of control may put at risk tube amplifiers (0.00)
Posted by cellailuca on 2022-09-27, 09:40:39 (79.52.220.31)
After the likely sabotage of both North Stream 1 and 2 and because of the Biden decision to cut ties with Russia (in connection with Ucraine war) Europe is missing 30% of natural gas. Electricity a .......
55: Tube DIY Asylum, Loudness/tone control, why I like them. (0.00)
Posted by cellailuca on 2022-06-23, 02:45:27 (87.13.146.1)
I found out the frequency response (up to 14 KHz, my actual hearing limit) that suits me fine with my tube/SS audio gear for listening at an average ambient level of 75-85 dB SPL. For the .......
56: Tube DIY Asylum, Answer A (0.00)
Posted by cellailuca on 2022-05-24, 00:55:55 (87.19.159.136)
In order to reduce the Miller capacitance. .......
57: Tube DIY Asylum, Check by yourself... (0.00)
Posted by cellailuca on 2022-04-11, 10:30:38 (79.22.240.215)
This is what you can check with a smartphone while listening to your favourite music. .......
58: Tube DIY Asylum, Speakers and room acoustics are more important than amplifier power (0.00)
Posted by cellailuca on 2022-04-11, 09:50:24 (79.22.240.215)
In a very quiet, medium size, listening room the noise floor is around 25-30 dB SPL (average). With standard speakers it takes much less than 1 W to generate around 65 dB SPL (average). As the crest f .......
59: Tube DIY Asylum, RE: Need your experience for transfomer orientation (0.00)
Posted by cellailuca on 2022-04-09, 09:59:34 (79.22.240.215)
Why don't you just listen? .......
60: Tube DIY Asylum, RE: I thought you were talking about amps (0.00)
Posted by cellailuca on 2022-03-20, 10:54:18 (82.49.197.118)
By the way, I did not mention distortion, I only said that I built two units and my friend choose the zero feedback one for his home. I listened to both units for some time and I loved both because at .......
61: Tube DIY Asylum, You are right... (0.00)
Posted by cellailuca on 2022-03-19, 02:20:03 (82.49.197.118)
Psychoacoustics is a complex matter. "The brain performs auditory scene analysis. Psychoacoustics has just begun to investigate how the brain does this. It appears to be a daunting task; it is, like H .......
62: Tube DIY Asylum, If you are not shure if zero FB suits you fine then... (0.00)
Posted by cellailuca on 2022-03-18, 04:01:52 (82.49.197.118)
You build two amplifiers! This month I will use this baby. It is an all russian triodes, with 6/10 dB negative feedback (switchable), PP amplifier that I built in 2015. It was soon followed by a .......
63: Tube DIY Asylum, RE: I was thinking more along the lines of an adjunct to local weather reports (0.00)
Posted by cellailuca on 2022-03-15, 10:28:20 (82.49.197.118)
A special bullettin is published on Veteranstoday. .......
64: Tube DIY Asylum, Thank you! (0.00)
Posted by cellailuca on 2022-03-08, 03:43:16 (82.49.197.118)
Now I see. .......
65: Tube DIY Asylum, Who makes tubes today? (0.00)
Posted by cellailuca on 2022-03-08, 01:31:45 (82.49.197.118)
Old NOS tubes are fading away. Are we going to lose russian tubes too because of sanctions? It seems that for this hobby we will have available only the limited menu of chinese tubes. I recently purch .......
66: Tube DIY Asylum, The same technique... (0.00)
Posted by cellailuca on 2022-03-05, 03:34:18 (82.49.197.118)
... (a 220V lamp instead of PP tubes) can be used with existing hardware to ascertain if any hum noise comes from the PP tubes and/or the preceding stages. .......
67: Tube DIY Asylum, Did you check... (0.00)
Posted by cellailuca on 2022-03-05, 03:25:54 (82.49.197.118)
... if the noise disappears shortly after power off (when the amplifier still runs on PS capacitors charge)? .......
68: Tube DIY Asylum, A practical set up to check coupling between mains and output transformers (0.00)
Posted by cellailuca on 2022-03-05, 01:15:47 (82.49.197.118)
When using economy transformers (and/or brand new transformers) it is good practice to check any potential nasty coupling before installation. You can never know in advance if there is an excessive .......
69: Tube DIY Asylum, RE: LTSpice "Bolt" Model (0.00)
Posted by cellailuca on 2022-03-04, 21:35:58 (82.49.197.118)
It works in practice. .......
70: Tube DIY Asylum, RE: LTSpice "Bolt" Model (0.00)
Posted by cellailuca on 2022-03-04, 10:53:35 (82.49.197.118)
Look again at the schematic. Where is the 10 mH inductor? Is it before or after the diodes? Are you shure that somebody has ever done it? I only wrote that I made a small inductor with a bolt and that .......
71: Tube DIY Asylum, RE: LTSpice "Bolt" Model (0.00)
Posted by cellailuca on 2022-03-04, 09:32:21 (82.49.197.118)
L1 = 10 mHenry If you do not like an iron bolt to implement the small inductor you may wish to use an air core inductor instead. .......
72: Tube DIY Asylum, RE: How to use a bolt to improve hum spectrum (0.00)
Posted by cellailuca on 2022-03-03, 23:41:47 (158.148.175.194)
Good point. By the way, I am experimenting with one of my amplifiers with direct rectification of 220 V AC line and input isolation transformer. .......
73: Tube DIY Asylum, RE: This idea has been employed years past ... (0.00)
Posted by cellailuca on 2022-03-03, 22:56:15 (82.49.197.118)
I did not know. Thank you for sharing this information. .......
74: Tube DIY Asylum, RE: How to use a bolt to improve hum spectrum (0.00)
Posted by cellailuca on 2022-03-03, 22:54:08 (82.49.197.118)
This is an audio tube DIY forum. Why should I measure a lot of indirect things when I can simply listen to the sound of HT with an earphone and a DC block? If I can hear a difference (less high freque .......
75: Tube DIY Asylum, RE: How to use a bolt to improve hum spectrum (0.00)
Posted by cellailuca on 2022-03-03, 10:20:09 (82.49.197.118)
I am just experimenting on an existing amplifier (600V HT, 120 mA) and the bolt remains cold after hours of operation. So the eddy currents are not so strong... .......
76: Tube DIY Asylum, RE: How to use a bolt to improve hum spectrum (0.00)
Posted by cellailuca on 2022-03-03, 10:17:25 (82.49.197.118)
As inconsistent as your comment. .......
77: Tube DIY Asylum, RE: How to use a bolt to improve hum spectrum (0.00)
Posted by cellailuca on 2022-03-03, 09:34:51 (82.49.197.118)
I should check but I think that the increased noise floor is due to non steady state. The FFT refers to second 8-10 of the simulation, which is enough for getting steady state without inductor. As far .......
78: Tube DIY Asylum, RE: How to use a bolt to improve hum spectrum (0.00)
Posted by cellailuca on 2022-03-03, 08:56:52 (82.49.197.118)
Yes, the pink trace is the one with the small inductor. If you take also a look at the current pulses of the diodes you will see some rounding of the corners due to the small inductor. Basically you c .......
79: Tube DIY Asylum, RE: How to use a bolt to improve hum spectrum (0.00)
Posted by cellailuca on 2022-03-03, 06:10:24 (158.148.175.194)
The spectrum with no odd line harmonics is better. .......
80: Tube DIY Asylum, How to use a bolt to improve hum spectrum (0.00)
Posted by cellailuca on 2022-03-03, 03:29:27 (82.49.197.118)
A small inductor made of a bolt and copper wire improves the hum spectrum when using solid state rectification (see spectra with and without the small series inductor). .......
81: Tube DIY Asylum, RE: That's not the same thing (0.00)
Posted by cellailuca on 2022-02-24, 10:30:09 (79.52.211.17)
The title of the post was: "Experimental study of power supply positioning for non audible hum". That is exactly what I got (even with the earphone): non audible hum. By the way, depending on the ambi .......
82: Tube DIY Asylum, The concern comes from... (0.00)
Posted by cellailuca on 2022-02-24, 03:40:00 (79.52.211.17)
The fact that if you use high efficiency speakers in a quiet listening room (noise floor of 25 dB SPL or less) what was quiet enough with standard speakers is no longer quiet enough. .......
83: Tube DIY Asylum, RE: Do you use a shielded umbilical? (0.00)
Posted by cellailuca on 2022-02-24, 03:35:46 (79.52.211.17)
No. .......
84: Tube DIY Asylum, Take a look at the old Dynaco design (0.00)
Posted by cellailuca on 2022-02-24, 03:04:21 (79.52.211.17)
You can choose either balanced or unbalanced input. .......
85: Tube DIY Asylum, Amazing seems a bit too much.. (0.00)
Posted by cellailuca on 2022-02-24, 00:33:15 (79.52.211.17)
It is not OTL. It is a more conventional design. The output transformers (30 VA compact toroids) are inside the box and electrostatic shielding is made of grounded aluminium foil glued on the in .......
86: Tube DIY Asylum, Experimental study of power supply positioning for non audible hum (0.00)
Posted by cellailuca on 2022-02-23, 02:26:41 (79.52.211.17)
Having built a separated power supply for my latest project I have carried out an experimental study of the effect of power supply positioning w.r.t. inpul (long) line and main amplifier. .......
87: Tube DIY Asylum, Chasing hum down to the ultimate limits (0.00)
Posted by cellailuca on 2022-02-22, 08:49:57 (79.52.211.17)
It is common DIY experience that whatever we do in our projects sometimes some hum remains in the audio output (basically because the HT does not come from a DC battery). What we call output hum .......
88: Tube DIY Asylum, RE: Can a Voltage Doubler Work Right Off Of Line Voltage? (0.00)
Posted by cellailuca on 2022-02-20, 01:30:30 (79.52.211.17)
I bet that you take eventually care of the VA of the mains HT transformer more than the hundreds of microfarad of the last capacitor, don't you? Virtually unlimited VA (of AC 110/220 line) is only the .......
89: Tube DIY Asylum, RE: Can a Voltage Doubler Work Right Off Of Line Voltage? (0.00)
Posted by cellailuca on 2022-02-19, 01:41:47 (79.52.211.17)
I have built many power amplifiers with HT (300V and 600V) from direct rectification of 220V AC line. In this case you must use an input signal insulation transformer for obvious reasons. The main adv .......
90: Tube DIY Asylum, Bad HT fuse (0.00)
Posted by cellailuca on 2022-02-07, 01:57:17 (95.234.234.246)
It was only a bad HT fuse. I have replaced the 220 V NTC too as preventive maintenance. It was a great pleasure to find out the schematic inside as I have forgotten since then how it was made .......
91: Tube DIY Asylum, RE: After 11 years of service... (0.00)
Posted by cellailuca on 2022-02-06, 12:04:08 (95.234.234.246)
Thank you. At the time I tried to use a copper PCB card for the top panel. I made small sandpaper circles on the copper (like the barrel of a rifle) and then I poured abundant transparent paint on it. .......
92: Tube DIY Asylum, Today I have put this baby on line (0.00)
Posted by cellailuca on 2022-02-06, 10:59:47 (95.234.234.246)
It was built about 10 years ago and the top connettors should be replaced because they appear worn out by the tube heat. .......
93: Tube DIY Asylum, After 11 years of service... (0.00)
Posted by cellailuca on 2022-02-06, 09:41:28 (95.234.234.246)
Left channel is now deadly silent. It's time to repair. .......
94: Tube DIY Asylum, 0.25 mV RMS(0.35 mV peak) is close to practical perfection (0.00)
Posted by cellailuca on 2022-02-06, 08:52:30 (95.234.234.246)
If your amplifier can deliver more than 10 V peak the electrical dynamic range measured from the noise floor (0.35 mV peak) is about 90 dB. As the typical ambient noise floor of a quiet listening roo .......
95: Tube DIY Asylum, RE: the 12AT7 will be lower distortion if you put some resistance in series with each cathode. (0.00)
Posted by cellailuca on 2022-02-01, 00:29:34 (95.234.234.246)
Thank you for your suggestion. It makes something more than 3 W RMS per channel. With my speakers (86 dB nominal efficiency) in my listening room (25 square meters) this is equivalent to 65 dB SPL ave .......
96: Tube DIY Asylum, Output attenuation with NFB (0.00)
Posted by cellailuca on 2022-01-31, 10:35:39 (95.234.234.246)
If you do the same with and without NFB you can easily calculate the loss of gain due to NFB. For example if the output impedance without NFB is 3 Ohm and with NFB is 2 Ohm the loss of gain due to NFB .......
97: Tube DIY Asylum, Output impedance (0.00)
Posted by cellailuca on 2022-01-31, 10:26:25 (95.234.234.246)
One of the many advantages of using LTSpice is output impedance calculation. When the circuit of your amplifier is complete you have just to insert a 1 Volt AC generator in series with the loudspea .......
98: Tube DIY Asylum, RE: +1 (0.00)
Posted by cellailuca on 2022-01-28, 10:22:06 (95.238.239.101)
"Phase response is the Hilbert transform of amplitude response" has consequences. As negative feedback flattens and widens amplitude frequency response by reducing gain it improves in band phase linea .......
99: Tube DIY Asylum, "all amplifiers are a form of filter and therefore obey filter theory" (0.00)
Posted by cellailuca on 2022-01-28, 08:50:22 (95.238.239.101)
This should be set in stone. Filter theory clearly states: - Phase response is not delay. - Group delay is proportional to the phase response derivative w.r.t. frequency of phase response. - Phase res .......
100: Tube DIY Asylum, Power supply (0.00)
Posted by cellailuca on 2022-01-28, 03:06:19 (95.238.239.101)
The power supply was built many months ago... .......
101: Tube DIY Asylum, Schematic (0.00)
Posted by cellailuca on 2022-01-28, 02:52:56 (95.238.239.101)
This is the schematic of this wonderful amplifier. Listening to this baby is my real reward. .......
102: Tube DIY Asylum, The all 6SN7 amplifier with 12AT7 loudness control is up and running. (0.00)
Posted by cellailuca on 2022-01-27, 02:51:48 (95.238.239.101)
After initial bias adjustment everything is OK. Sweet sound, no noise and no hum at all. The loudness curve is beyond my best expectations. I will post the final schematic in the next future. .......
103: Tube DIY Asylum, RE: what headphones? (0.00)
Posted by cellailuca on 2022-01-25, 22:52:17 (95.238.239.101)
I use and old 32 Ohm AKG studio headphone. This is the first time it sounds so good and it reaches high SPL. .......
104: Tube DIY Asylum, RE: It takes shape 4 (0.00)
Posted by cellailuca on 2022-01-25, 22:49:16 (95.238.239.101)
2X110 V, 2X6V, greater than 30 VA toroid. One of the 6V outputs feeds the headphone with a 33 Ohm in series. .......
105: Tube DIY Asylum, Universal tone control follow on (0.00)
Posted by cellailuca on 2022-01-25, 10:16:14 (95.238.239.101)
It is working very well, exactly as calculated. I decided to implement it as loudness on-off by a switch. I recommend it for your projects. .......
106: Tube DIY Asylum, With only One 6SN7 it's an eccellent headphone amplifier... (0.00)
Posted by cellailuca on 2022-01-24, 07:30:01 (95.238.239.101)
I am listening with zero feedback and the loudness circuit seems quite right. In the next days I will receive 8 NOS 6H8C tubes (russian 6SN7) that I had ordered. .......
107: Tube DIY Asylum, RE: It takes shape 4 (0.00)
Posted by cellailuca on 2022-01-23, 02:11:15 (95.238.239.101)
Start of final integration. .......
108: Tube DIY Asylum, RE: IMD measurement (0.00)
Posted by cellailuca on 2022-01-20, 10:10:42 (95.238.239.101)
I only plan to insert one at the time (and eventually swap) the 8 output 6H8C tubes between channels to get a good current balance of each 4 tubes sets before bias adjustment. .......
109: Tube DIY Asylum, IMD measurement (0.00)
Posted by cellailuca on 2022-01-18, 01:30:48 (95.238.239.101)
I plan to use a set up made of some resistors, plus my PC (with FFT/IMD calculation software) and a couple of audio tones. .......
110: Tube DIY Asylum, RE: It takes shape 3 (0.00)
Posted by cellailuca on 2022-01-17, 02:42:46 (95.238.239.101)
So far, so good. .......
111: Tube DIY Asylum, What you really need to know... (0.00)
Posted by cellailuca on 2022-01-06, 00:58:47 (87.6.217.176)
About power and measured sine level. .......
112: Tube DIY Asylum, "Shorting R5 - hum almost gone" (0.00)
Posted by cellailuca on 2022-01-01, 03:45:43 (87.6.217.176)
This reinforces the magnetic coupling conjecture (the hum comes from the output transformer via the NFB wire). If this is the case there is no alternative but changing the relative position of transfo .......
113: Tube DIY Asylum, RE: Please help finding this darn hum (0.00)
Posted by cellailuca on 2021-12-31, 13:17:30 (87.6.217.176)
If the hum goes away when opening the NFB connection it is almost certainly magnetic coupling between mains transformer and output transformer. .......
114: Tube DIY Asylum, RE: Current reading different accross choke and resistor??? (0.00)
Posted by cellailuca on 2021-12-27, 01:37:34 (79.53.159.140)
Don't forget to take into account the internal impedance of the measuring device. When measuring voltage drop across two circuit nodes the meter impedance is very high. But when the meter is used in c .......
115: Tube DIY Asylum, It takes shape 2 (0.00)
Posted by cellailuca on 2021-12-19, 03:05:51 (79.47.194.102)
Work in progress. Star grounding scheme, short cables to the loudness switch and sensitive loudness circuitry housed in a shielded box will hopefully reduce noise. Plywood and aluminium foil are .......
116: Tube DIY Asylum, It takes shape (0.00)
Posted by cellailuca on 2021-12-15, 04:19:43 (79.47.194.102)
So far so good. .......
117: Tube DIY Asylum, Memories from the past (0.00)
Posted by cellailuca on 2021-12-13, 00:46:32 (79.47.194.102)
Interesting driver from Bruce De Palma. .......
118: Tube DIY Asylum, Just in case... (0.00)
Posted by cellailuca on 2021-12-08, 09:28:36 (79.49.239.99)
..somebody is able to do this minimal DIY. .......
119: Tube DIY Asylum, Pros and contras of a separate power supply (0.00)
Posted by cellailuca on 2021-12-04, 07:34:12 (79.49.239.99)
A separate power supply prevents by construction any magnetic coupling among mains power transformer and output transformers (and in general it reduces noise) but it requires DC and heater power li .......
120: Tube DIY Asylum, RE: How to calculate input impedance vs. frequency (0.00)
Posted by cellailuca on 2021-12-03, 03:00:02 (79.49.239.99)
The 'universal tone control' will be the input stage of my next amplifier and hence I am quite interested in knowing in advance any prospected loss when connected to a smartphone, a streamer or a stan .......
121: Tube DIY Asylum, How to calculate input impedance vs. frequency (0.00)
Posted by cellailuca on 2021-12-02, 01:02:47 (79.19.19.251)
When interfacing complex RC networks that are embedded in the feedback loop of a tube circuit (Bandaxall like loudness/tone controls or RIAA) it is worth to check the impedance vs. frequency respon .......
122: Tube DIY Asylum, RE: Cathode Stripping (0.00)
Posted by cellailuca on 2021-12-01, 23:10:14 (79.19.19.251)
The best way to program any power up sequence of HT equipment is Arduino that controls some relais. .......
123: Tube DIY Asylum, Hint for fast and economy prototyping (0.00)
Posted by cellailuca on 2021-12-01, 01:15:33 (79.19.19.251)
Sometimes you need an electrostatic shield for sensitive circuits (like this tone control breadboard) and you have not yet decided on the box to use. Here comes to the rescue plywood and alumini .......
124: Tube DIY Asylum, RE: so after sifting thru boxes after getting flooded (0.00)
Posted by cellailuca on 2021-11-28, 03:52:24 (79.56.197.35)
A friend of mine who lives in Venice (Italy), in addition to the basement pumps, has installed a system of pulleys and ropes to swiftly lift to the ceiling the forniture that contains his most preciou .......
125: Tube DIY Asylum, You are right... (0.00)
Posted by cellailuca on 2021-11-28, 02:31:26 (79.56.197.35)
I am so tempted to build it with the tone/loudness control depicted in the 'Universal tone control for DIY' of a previous post, just breadboarded. The loudness section can use either 12AX7 or .......
126: Tube DIY Asylum, RE: I avoid gear using 6SN7 tubes (0.00)
Posted by cellailuca on 2021-11-26, 09:30:04 (79.56.197.35)
I have many russian 6SN7 tubes (still available in quantity in Europe). Those coming from Ucraine are easily found on ebay. .......
127: OTL Asylum, OTL looks a bit different... (0.00)
Posted by cellailuca on 2021-11-26, 03:47:56 (79.56.197.35)
If I understand correctly the 'regenerator' is to generate balanced AC power. I have recently purchased an isolation transformer (500VA nominal, 400VA continuous operation) based on a toroidal transfo .......
128: Tube DIY Asylum, Study of a low IMD all 6SN7 amplifier (0.00)
Posted by cellailuca on 2021-11-25, 02:46:12 (79.49.212.251)
Sometimes a new asylum post makes you wonder about a novel 'what if'. A recent series of comments on IMD has triggered my interest in 'what if I replaced (mutatis mutandis) one EL84 .......
129: Tube DIY Asylum, That's the point! (0.00)
Posted by cellailuca on 2021-11-23, 04:23:45 (79.49.212.251)
Good enough is always good enough. Amplifier distortion in a normal listening room is never a problem. We like technical excellence and we pay a lot of attention to HD and IMD but what we really need .......
130: Tube DIY Asylum, RE: How to check sound pressure level and spectrogram (0.00)
Posted by cellailuca on 2021-11-22, 00:42:54 (158.148.171.121)
Just to put the numbers in perspective. The noise level in a quiet listening room is about 30 dB SPL. A generally pleasant average music level is about 65-75 dB SPL. In eccellent recordings the peak s .......
131: Tube DIY Asylum, RE: "AMPLIFIER DESIGNS FOR REDUCED IMD" (0.00)
Posted by cellailuca on 2021-11-22, 00:25:12 (158.148.171.121)
Just for sake of completeness, what is your preferred (average) listening level? 70 dB? 80 dB? 90 dB or more? .......
132: Tube DIY Asylum, How to check sound pressure level and spectrogram (0.00)
Posted by cellailuca on 2021-11-21, 10:51:11 (79.49.212.251)
There are a lot of apps for the smartphone that facilitate audio checks at home. They are also quite accurate. The pictures above show for example the time history of ambient sound pressure leve .......
133: Tube DIY Asylum, RE: "AMPLIFIER DESIGNS FOR REDUCED IMD" (0.00)
Posted by cellailuca on 2021-11-21, 08:22:20 (79.49.212.251)
IMD is a real problem only with dynamic audio processors. "In practise, the IMD side effects might appear very differently. Gently applied on rather dull signals they can even produce a sort of "excit .......
134: Tube DIY Asylum, Wonderful! (0.00)
Posted by cellailuca on 2021-11-21, 07:58:43 (79.49.212.251)
I like it. .......
135: Tube DIY Asylum, Above about 90 dB SPL... (0.00)
Posted by cellailuca on 2021-11-19, 07:36:26 (5.168.62.74)
Also the human ear intermodulates. You can find it immediately by covering the ears with your hands when exposed to too loud music. You will immediately feel less distortion. .......
136: Tube DIY Asylum, Good to know (0.00)
Posted by cellailuca on 2021-11-19, 00:59:31 (79.49.212.251)
Extracting maximum performance will likely improve transient behaviour too. Compression (even strong compression) is better than blocking (short silence after occasional overloading). .......
137: Tube DIY Asylum, RE: Single capacitor doesn't work (0.00)
Posted by cellailuca on 2021-11-18, 00:26:33 (79.49.212.251)
In sim world class A ends at about 10V peak into 8 Ohm. Occasional class AB operation allows to exceed 12V peak with increased intermodulation. These are the calculated tube currents and the corres .......
138: Tube DIY Asylum, RE: Allen Wright forced balance (0.00)
Posted by cellailuca on 2021-11-18, 00:19:33 (79.49.212.251)
40 mA @285V for each EL84 is full class A for most commercial tubes. .......
139: OTL Asylum, RE: Dickie - Macovski OTL amplifier (0.00)
Posted by cellailuca on 2021-11-17, 09:46:37 (79.49.212.251)
I built in 2008 a couple of 'simplified D&M'. .......
140: Tube DIY Asylum, RE: Allen Wright forced balance (0.00)
Posted by cellailuca on 2021-11-17, 08:13:20 (79.49.212.251)
There is basically no difference in performance (in sim world) between this circuit and the previous one. If I cut C7 to get close to my understanding of the 'Allen Wright variant' then intermodula .......
141: Tube DIY Asylum, Single capacitor doesn't work (0.00)
Posted by cellailuca on 2021-11-17, 07:52:18 (79.49.212.251)
I have just checked in sim world (on the onset of class B) if the single capacitor from cathode to cathode works: it unfortunately doesn't. When the upper tube requires for example 110 mA peak, as .......
142: Tube DIY Asylum, FMECA considerations in PP with current source (0.00)
Posted by cellailuca on 2021-11-17, 03:22:14 (79.49.212.251)
When using one current source for PP cathode bias it is assumed that the total current will approximately split between the tubes and some control is provided to correct minor imbalances. However, .......
143: Tube DIY Asylum, RE: FYI (0.00)
Posted by cellailuca on 2021-11-14, 10:15:02 (79.23.12.97)
Non c'è peggior sordo di chi vuole rompere il cazzo. .......
144: Tube DIY Asylum, Take a look at the Radiotron Handbook 4th ed. (0.00)
Posted by cellailuca on 2021-11-14, 08:55:28 (79.23.12.97)
Maybe you don't know why tone controls are important to compensate for listening at lower level than optimal one. .......
145: Tube DIY Asylum, Vertical push pull topology for 6AS7 tubes (0.00)
Posted by cellailuca on 2021-11-14, 04:58:56 (79.23.12.97)
In the past ten years I have built about a dozen power amplifiers with up to four 6AS7 tubes per channel based on this topology. The output transformer must be with with two isolated primaries f .......
146: Tube DIY Asylum, FYI (0.00)
Posted by cellailuca on 2021-11-14, 04:01:34 (79.23.12.97)
Radiotron Handbook 4th edition If you can master your designs the possibilities to correct tone response by manipulating the GNFB network are virtually infinite. It was well kown until recent times .......
147: Tube DIY Asylum, RE: Good point (0.00)
Posted by cellailuca on 2021-11-13, 03:24:46 (79.23.12.97)
Coglione, parlavo del mio amplificatore in fase di progettazione. Ci sono mille modi per modificare la risposta fuori banda e ad un ingegnare come me tu gli puoi solo pulire il culo. Se vuoi fare la p .......
148: Tube DIY Asylum, When winter comes it's OTL time (0.00)
Posted by cellailuca on 2021-11-13, 03:15:34 (79.23.12.97)
In 2008 I designed and built a couple of OTL amplifiers (one for me and one for my brother). It was my first time that a paper design was imported in LTSpice for study. You can learn a lot by simul .......
149: Tube DIY Asylum, RE: Good point (0.00)
Posted by cellailuca on 2021-11-12, 06:31:25 (158.148.177.247)
Ancora scassi il cazzo? .......
150: Tube DIY Asylum, RE: Good point (0.00)
Posted by cellailuca on 2021-11-12, 03:13:15 (79.23.12.97)
"I can't understand what are you saying. Walter" But you insist to post 'flames' against my posts. If you like it go ahead, I don't care (nummetenculo manco de' striscio). .......
151: Tube DIY Asylum, Good point (0.00)
Posted by cellailuca on 2021-11-11, 09:04:37 (82.61.101.52)
It should not be a great issue in a complete amplifier. In case of resonances of the output transformer the response can be promptly tamed above 20 Khz by the usual small cap in parallel to the NFB re .......
152: Tube DIY Asylum, RE: Universal tone control for DIY (0.00)
Posted by cellailuca on 2021-11-11, 05:04:03 (82.61.101.52)
I can certainly appreciate your comment but the count of components of the two circuits does not seem the same. In addition my proposed circuit exhibits a somewhat more aggressive bass and treeble boo .......
153: Tube DIY Asylum, Universal tone control for DIY (0.00)
Posted by cellailuca on 2021-11-11, 04:05:43 (82.61.101.52)
While analyzing a flexible tube loudness/tone control of mine for a next project (see link) I realized that it is also a sort of universal tone control. The pictures show, for sake of brev .......
154: Tube DIY Asylum, Loudness control or tone control? (0.00)
Posted by cellailuca on 2021-11-07, 08:31:16 (79.37.228.128)
When you want to play music at a moderate sound level, but still filling the room with balanced sound, you need a loudness control or a tone control. But for unknown reasons nowadays balance .......
155: Tube DIY Asylum, Basic Audio books for DIY people (0.00)
Posted by cellailuca on 2021-11-01, 04:37:23 (79.37.228.128)
Among many interesting audio books I recommend the three volumes 'Basic Audio' by Norman Crowhurst. .......
156: Tube DIY Asylum, RE: Think about the purpose (0.00)
Posted by cellailuca on 2021-10-31, 04:59:32 (79.37.228.128)
All my audio equipment that is connected to the isolation transformer IS NOT connected to ground. As simple as that. All my audio equipment is now floating (as all medical devices). If you don't like .......
157: Tube DIY Asylum, Think about the purpose (0.00)
Posted by cellailuca on 2021-10-31, 04:42:41 (79.37.228.128)
.......
158: Tube DIY Asylum, John Broskie had his own idea (0.00)
Posted by cellailuca on 2021-10-31, 01:27:33 (79.37.228.128)
It is amazing that after almost banning loudness and stereo controls from hi-fi/hi-end we finally re-discover them. .......
159: Tube DIY Asylum, Insulation transformer (0.00)
Posted by cellailuca on 2021-10-28, 08:53:26 (79.37.228.128)
I have recently purchased on Amazon an insulation transformer for all my audio equipment. It helps to prevent ground loops problems and it improves safety (as both AC power wires become 'neutral'). .......
160: Tube DIY Asylum, The GNFB is about 12 dB (0.00)
Posted by cellailuca on 2021-10-22, 00:41:47 (95.234.231.109)
If you take a look at the input circuit you can see the differential cathode feedback. Each output transformer is made of three 50VA-2X110V-2X6V toroidal transformers contained in the bottom box .......
161: Tube DIY Asylum, From the set of 'The Forbidden Planet' (0.00)
Posted by cellailuca on 2021-10-21, 10:47:45 (95.234.231.109)
After one year of tweaking I have finished this project. The design comes from the 1956 movie and it suits me fine. It is a tetrode amplifier, 15 Watt per channel (@50 mA bias), class A. T .......
162: Tube DIY Asylum, RE: Screen Regulation with VR tubes? (0.00)
Posted by cellailuca on 2021-09-20, 09:37:56 (87.1.223.120)
I successfully tried triode regulation. It is also possible to trim the bias current. .......
163: Tube DIY Asylum, RE: Losses in Output Transformers (0.00)
Posted by cellailuca on 2021-09-17, 10:39:29 (87.1.223.120)
A couple of dB of output power loss w.r.t. theoretical maximum output power is not so much and it is hardly audible in terms of SPL. .......
164: Tube DIY Asylum, Homemade capacitors (0.00)
Posted by cellailuca on 2021-09-10, 10:35:40 (87.1.223.120)
For those who wish to explore this possibility in their projects. For HT applications the plastic sheets used in printers for transparencies can be used instead of paper. .......
165: Tube DIY Asylum, Real tube DIY (0.00)
Posted by cellailuca on 2021-07-30, 08:54:25 (79.23.222.11)
Amazing... .......
166: Tube DIY Asylum, RE: Interesting blog page! (0.00)
Posted by cellailuca on 2021-07-03, 22:50:26 (87.18.213.50)
You are welcome! .......
167: Tube DIY Asylum, 12AU7 simulated characteristics vs. reality and HT noise (0.00)
Posted by cellailuca on 2021-07-03, 08:02:48 (79.33.140.40)
Some late news from John Broskie blog. .......
168: Tube DIY Asylum, RE: Unstable SRPP (0.00)
Posted by cellailuca on 2021-06-23, 03:54:23 (95.245.239.254)
Did you check if you still have motorboating without C2? .......
169: Tube DIY Asylum, RE: grounding schemes ... (0.00)
Posted by cellailuca on 2021-06-18, 22:59:56 (82.61.154.56)
If the problem were so rare it would not appear so often in the posts. All people that did not find the problem can ignore it. All others keep posting. .......
170: Tube DIY Asylum, RE: grounding schemes ... (0.00)
Posted by cellailuca on 2021-06-18, 12:38:08 (82.61.154.56)
As I have built many tube amplifiers with HT generated by direct rectification of 220V AC line (and safety input insulation transformer) I have seen the potential problem. This type of spectrum on .......
171: Tube DIY Asylum, RE: grounding schemes ... (0.00)
Posted by cellailuca on 2021-06-18, 12:01:19 (82.61.154.56)
Because the geometry of the three wires is never perfect (only in coaxial cables, as explained in the paper, is almost perfect). .......
172: Tube DIY Asylum, RE: grounding schemes ... (0.00)
Posted by cellailuca on 2021-06-18, 11:03:33 (82.61.154.56)
OK inside the same box but when connecting several boxes the problem develops and it can easily go out of control. .......
173: Tube DIY Asylum, RE: Ground loop! (0.00)
Posted by cellailuca on 2021-06-18, 02:08:44 (82.61.154.56)
The explanation is in the link that I posted. It takes time to read all the material but it is necessary. Otherwise you get lost with all the suggestions for a cut and try that do not work. ::: TOPIC: .......
174: Tube DIY Asylum, The ultimate solution... (0.00)
Posted by cellailuca on 2021-06-17, 01:12:56 (82.61.154.56)
That is. .......
175: Tube DIY Asylum, RE: Help! Hum problem with amp (0.00)
Posted by cellailuca on 2021-06-17, 00:56:34 (82.61.154.56)
An input transformer should solve the problem. .......
176: Tube DIY Asylum, RE: Link (0.00)
Posted by cellailuca on 2021-06-11, 10:22:04 (82.61.154.56)
By the way, if there is a grid resistor (instead of the grounded grid), depending on its value, the output becomes unbalanced with increasing frequency. .......
177: Tube DIY Asylum, RE: hearing loss (0.00)
Posted by cellailuca on 2021-06-10, 00:25:06 (158.148.179.254)
It is so sad that when you are young and your hearing is at its top you cannot afford hi-end and when you can afford hi-end your hearing is generally impaired. Even an equalizer cannot solve the probl .......
178: Tube DIY Asylum, RE: Huh?? (0.00)
Posted by cellailuca on 2021-06-09, 11:00:53 (82.61.154.56)
Good for you! About 10 years ago I was in a listening session at an high end fair. The seller was presenting his new loudspeaker line and how to install it in the living room in order to get the best .......
179: Tube DIY Asylum, All amplifiers should sound good enough because... (0.00)
Posted by cellailuca on 2021-06-09, 03:56:25 (82.61.154.56)
Good enough is good enough! I alternate six DIY tube amplifiers of mine and two SS commercial amplifiers (in the same listening room and with the same sources). The tube amplifiers are all PP and one .......
180: Tubes Asylum, The fusor tube (0.00)
Posted by cellailuca on 2021-05-28, 10:03:54 (87.21.214.149)
In 1960 this wonderful Farnsworth tube was operating up to 80 Kv. .......
181: Tube DIY Asylum, RE: SE amp with tranny hum, only thru speakers with tube phono preamp (0.00)
Posted by cellailuca on 2021-05-20, 09:55:03 (87.21.214.149)
Probabily because of the higher output impedance of the tube preamp. Low output impedance reduces the effects of any ground loop. .......
182: Tube DIY Asylum, Insulation transformers improve the situation (0.00)
Posted by cellailuca on 2021-05-10, 01:06:48 (82.49.197.181)
There are a lot of economy models with internal toroidal transformer. Most of them come with the ground connected to the output and an internal jumper for disconnecting the line ground from the out .......
183: Tube DIY Asylum, A simple check (0.00)
Posted by cellailuca on 2021-04-26, 09:26:06 (79.26.34.206)
As the filter capacitors allow some seconds of operation when powering off the unit you should check if the 'jittery noise' persists immediately after turning off the preamplifier. If it disappears th .......
184: Tube DIY Asylum, LT Spice would answer all your questions (0.00)
Posted by cellailuca on 2021-04-25, 02:09:21 (82.55.53.197)
You have only to become a DIY with simulations. .......
185: Tube DIY Asylum, I would rather use a cathode follower (0.00)
Posted by cellailuca on 2021-04-22, 03:56:46 (82.55.53.197)
I used a simple cathode follower to step down from 300V to around 200V the screen voltage. With a simple pot you can also trim the anode current (with either automatic or fixed bias) by simply vary .......
186: Tube DIY Asylum, See class AB operation (0.00)
Posted by cellailuca on 2021-04-20, 23:02:26 (82.55.53.197)
450V anode and 400V screen seem possible for some models. .......
187: Tube DIY Asylum, When using USA HW in Europe and the other way around (0.00)
Posted by cellailuca on 2021-04-18, 03:00:21 (79.23.12.179)
You may wish to use something like this. It can be also used as insulation transformer for safely testing tube gear. .......
188: Tube DIY Asylum, RE: Standby/Operate Switch on my Cary Super Amplifier (AE-25) (0.00)
Posted by cellailuca on 2021-04-12, 08:08:23 (79.23.12.179)
It turns on and off HT. .......
189: Tube DIY Asylum, Independent power supply (0.00)
Posted by cellailuca on 2021-04-08, 03:44:55 (79.23.12.179)
300V DC, 6.3V AC. .......
190: Tube DIY Asylum, See Morgan Jones (0.00)
Posted by cellailuca on 2021-04-05, 10:41:56 (95.246.210.132)
Page 115. .......
191: Tube DIY Asylum, RE: LTSpice study of EL84 UL PP (0.00)
Posted by cellailuca on 2021-03-26, 09:21:34 (79.18.247.240)
The inductors are simply modeling the UL output transformer (20%-80%). .......
192: Tube DIY Asylum, Experimental procedure (0.00)
Posted by cellailuca on 2021-03-26, 04:52:09 (79.18.247.240)
After my bad experience with a 'defective' toroidal transformer now I usually check magnetic coupling of mains transformers with output transformers. It is simple (once you have finished the HT cir .......
193: Tube DIY Asylum, LTSpice study of EL84 UL PP (0.00)
Posted by cellailuca on 2021-03-26, 03:22:32 (79.18.247.240)
I have never built an UL amplifier and so I will likely start with this one. At present I am locked down at home because of covid restrictions but the restrictions will be lifted, sooner or late .......
194: Tube DIY Asylum, RE: That's the same fomuula I use ... (0.00)
Posted by cellailuca on 2021-03-24, 03:00:43 (79.18.247.240)
If you remove with a hammer the magnetic shunt from a MOT of a microwave oven you can even... .......
195: Tube DIY Asylum, RE: When you do not have the 6.3V for heaters... (0.00)
Posted by cellailuca on 2021-03-23, 07:57:47 (5.168.85.136)
Flux is expressed in Weber and it is proportional to Amperspire. If you look into high voltage primary voltage is the driver. If you look into the low voltage secondary ampere is the driver. Don't be .......
196: Tube DIY Asylum, RE: Core Flux (0.00)
Posted by cellailuca on 2021-03-23, 07:13:14 (5.168.85.136)
It's a 200 VA core. I will use it for a simple stereo amplifier with EL84 and 6SN7 tubes. Core saturation should not be an issue. .......
197: Tube DIY Asylum, When you do not have the 6.3V for heaters... (0.00)
Posted by cellailuca on 2021-03-23, 04:38:31 (79.18.247.240)
But you have a mains toroidal transformer. You simply add the necessary windings and that's all. The calculation of the number of wire loops is trivial after measuring the voltage out of a few wire .......
198: Tube DIY Asylum, Behind the models (0.00)
Posted by cellailuca on 2021-03-22, 02:54:54 (79.18.247.240)
For those who build their own transformers (in Italian). .......
199: Tube DIY Asylum, RE: For sake of completeness... (0.00)
Posted by cellailuca on 2021-03-21, 13:16:46 (79.18.247.240)
.......
200: Tube DIY Asylum, RE-RE: If you do not trust simulations do not use simulations. (0.00)
Posted by cellailuca on 2021-03-21, 06:51:09 (79.18.247.240)
Thank you for your suggestion. By the way, I have already studied tens of tube books (RDH included) and I have already designed, simulated, built and tested more than 20 ORIGINAL amplifiers. Let's say .......
201: Tube DIY Asylum, If you do not trust simulations do not use simulations. (0.00)
Posted by cellailuca on 2021-03-21, 05:50:25 (79.18.247.240)
I personally trust simulations and even more if the measured data of the transformers are available. Your recommendation is similar to the airplane manufacturer who does not develop its flight simula .......
202: Tube DIY Asylum, To Dave Slagle... (0.00)
Posted by cellailuca on 2021-03-21, 05:03:32 (79.18.247.240)
It is curious that the values of L that I was using in simulations after some hand calculation were 20, 80, 80, 20 (sum 200) and 0.9. Using your suggested model the corresponding values of L are 1, 16 .......
203: Tube DIY Asylum, Thank you very much! (0.00)
Posted by cellailuca on 2021-03-21, 04:33:42 (79.18.247.240)
Thanks to your suggestion now I trust more the LTSpice model of an EL84 amplifier that I am studying. Comparing the simulation output of the model with the linearized model of the PP stage there is .......
204: Tube DIY Asylum, Low frequency response: Quite the opposite is true! (0.00)
Posted by cellailuca on 2021-03-20, 13:21:23 (79.18.247.240)
With LTSpice you can estimate the low frequency response (provided that you know the plate to plate impedance of the transformer and the resistance of the winding sections, either published or measure .......
205: Tube DIY Asylum, How to convert plate to plate impedance to turns ratio and to inductance (0.00)
Posted by cellailuca on 2021-03-20, 13:10:04 (79.18.247.240)
I use a simple method. Let's imagine to start from 8 Ohm speaker to get 6K 'plate to plate' (PP EL84 UL 20%-80%). 6K = (N1/N2) squared * 8 (N1/N2) squared = 6000/8 = 750 N1/N2 = square root (750) = 27 .......
206: Tube DIY Asylum, When modeling ultralinear a doubt arises.., (0.00)
Posted by cellailuca on 2021-03-20, 10:40:19 (79.18.247.240)
How to arrange the inductances corresponding to, let's say, 80% and 20% taps? If you buy a UL output transformer the terminals are clearly marked but when you use LTSpice you have to decide the ord .......
207: Tube DIY Asylum, You should try the simulation on your own. (0.00)
Posted by cellailuca on 2021-03-19, 09:31:29 (79.18.247.240)
There is a lot to learn from the analysis of simulations. In the case at hand the presence of the NFB alters the unbalance of the paraphase driver w.r.t, no NFB case. With no NFB the peak to peak sign .......
208: Tube DIY Asylum, The unbalance comes from the paraphase driver (0.00)
Posted by cellailuca on 2021-03-18, 23:59:30 (79.18.247.240)
The result is more or less the same as if one of the output tubes were heavily unmatched. .......
209: Tube DIY Asylum, For sake of completeness (0.00)
Posted by cellailuca on 2021-03-18, 10:50:02 (79.18.247.240)
The simulation of the complete amplifier (tetrode operation with GNFB) confirms the reported good performance (about 7W RMS maximum power). The harmonic distortion @8V peak into 8 Ohm is very .......
210: Tube DIY Asylum, RE: The paraphase phase splitter is alone. (0.00)
Posted by cellailuca on 2021-03-17, 13:09:38 (79.18.247.240)
Look again at the two schematics. In the first schematic NFB would be applied at the cathode of the upper triode. In the second schematic it would be applied in the tail of the 'concertina'. The simul .......
211: Tube DIY Asylum, The paraphase phase splitter is alone. (0.00)
Posted by cellailuca on 2021-03-17, 11:14:33 (79.18.247.240)
As it is shown in the schematic I have only simulated the phase splitter in isolation, at a reasonable output level, with no real FB applied. In order to get the real circuit I should add the output s .......
212: Tube DIY Asylum, RE: A 1962 B&O performer (0.00)
Posted by cellailuca on 2021-03-17, 10:01:00 (79.18.247.240)
You are right. By the way the original B&O NFB scheme results in more gain, less regular frequency response and dominant second harmonic! .......
213: Tube DIY Asylum, A 1962 B&O performer (0.00)
Posted by cellailuca on 2021-03-17, 08:57:46 (79.18.247.240)
I was quite curious about a very simple 1962 amplifier of B&O taken from the Lilienthal Engineering site (see link). It had a good reputation at the time. So I simulated, mutatis mutandis, .......
214: Tube DIY Asylum, RE: some unique CF (0.00)
Posted by cellailuca on 2021-03-17, 02:09:17 (79.18.247.240)
Many thanks. Excellent food for brain. I'll take a look at LTSpice simulations to check the claims. .......
215: Tube DIY Asylum, Exactly (0.00)
Posted by cellailuca on 2021-03-15, 04:18:55 (79.23.237.171)
. .......
216: Tube DIY Asylum, RE: A true DIYer does not complain... (0.00)
Posted by cellailuca on 2021-03-12, 07:15:45 (5.168.116.101)
That's why I don't use bee eax caps. Molten wax is much more difficult to fix or to return as defective. .......
217: Tube DIY Asylum, Hedge Cascode 1956 (0.00)
Posted by cellailuca on 2021-03-12, 03:50:55 (87.6.208.114)
SRPP, Cascode, nihil sub sole novum. .......
218: Tube DIY Asylum, Wonderful! (0.00)
Posted by cellailuca on 2021-03-11, 11:06:19 (87.6.208.114)
Congratulations TK. .......
219: Tube DIY Asylum, A true DIYer does not complain... (0.00)
Posted by cellailuca on 2021-03-09, 02:10:21 (87.6.208.114)
A true DIYer solves problems. And old linear DC power supply and a simple LM7805 board and the problem is gone. .......
220: Tube DIY Asylum, Tube manuals (0.00)
Posted by cellailuca on 2021-03-06, 08:57:59 (87.6.208.114)
Just in case... .......
221: Tube DIY Asylum, Are you serious? (0.00)
Posted by cellailuca on 2021-03-04, 23:08:06 (87.6.208.114)
MCAS of Boeing 737 MAX might be defined an 'invitation for disaster'. A broken tube is nothing. You just replace it. .......
222: Tube DIY Asylum, Heater-cathode max voltage (0.00)
Posted by cellailuca on 2021-03-04, 02:06:23 (87.6.208.114)
I built several SRPP where the potential heater-cathode voltage may potentially exceed 90 V (in case of connection of the heater power supply to ground). But if you leave the heater AC or DC power sup .......
223: Tube DIY Asylum, SRPP is similar to mu follower and... (0.00)
Posted by cellailuca on 2021-03-03, 10:00:12 (87.6.208.114)
Its PSRR (power supply rejection ratio) is good but not as good as differential. From Morgan Jones book. .......
224: Tube DIY Asylum, RE: For those tube DIY lovers who have never listened to Hi-Rez (0.00)
Posted by cellailuca on 2021-02-28, 22:53:57 (82.57.145.181)
You don't need, OK. "Nondum matura est, nolo acerbam sumere" .......
225: Tube DIY Asylum, RE: Not surprising (0.00)
Posted by cellailuca on 2021-02-27, 22:54:20 (82.57.145.181)
According to your explanation, as the total current is initially increasing over time, each successive half 40 Hz cycle is amplified a bit more than the preceding one, so that a tiny 20 Hz component d .......
226: Tube DIY Asylum, RE: Not surprising (0.00)
Posted by cellailuca on 2021-02-27, 22:44:15 (82.57.145.181)
It may certainly be the case. However a closer examination of the green waveform between 6 and 8 sec does not show any visible clipping at all. .......
227: Tube DIY Asylum, I would say yes (0.00)
Posted by cellailuca on 2021-02-27, 11:55:33 (82.57.145.181)
In the next days I will start tre trial of Qobuz. .......
228: Tube DIY Asylum, RE: For those tube DIY lovers who have never listened to Hi-Rez (0.00)
Posted by cellailuca on 2021-02-27, 08:19:01 (82.57.145.181)
So far, so good. Arylic S10 has arrived a few hours ago and it took 10 minutes to set up. I have found only a minor snag. It has to be battery operated because of a tiny hum when powered by the fac .......
229: Tube DIY Asylum, What happens to your tube amplifier at power up (0.00)
Posted by cellailuca on 2021-02-27, 01:59:07 (82.57.145.181)
It is widely accepted that tube amplifiers need some 10-15 minutes to warm up and that during that time the performance is somewhat impaired. In my experience, when powering up a cold tube am .......
230: Tube DIY Asylum, RE: For those tube DIY lovers who have never listened to Hi-Rez (0.00)
Posted by cellailuca on 2021-02-26, 11:48:34 (79.22.9.38)
Yes, I am about to receiving mine. The idea is to use the one month free trial offer of Tidal & co. for listening to HD music. In case I like it I will subscribe the service. .......
231: Tube DIY Asylum, For those tube DIY lovers who have never listened to Hi-Rez (0.00)
Posted by cellailuca on 2021-02-26, 10:43:34 (79.22.9.38)
If you were ever interested to listen to 'above CD' audio quality with your DIY tube gear you might be interested in this economy device. Sorry if this looks a bit off topic but seasoned people like m .......
232: Tube DIY Asylum, RE: SRPP (0.00)
Posted by cellailuca on 2021-02-26, 10:03:53 (79.22.9.38)
For a detailed analysis of SRPP see Morgan Jones book, page 120. In short, SRPP seems a poor choice w.r.t. mu-follower but it is immune from blocking. I built the driver of a PP amplifier of min .......
233: Tube DIY Asylum, RE: A practical way to use a surplus PP transformer as a choke for SE DIY (0.00)
Posted by cellailuca on 2021-02-25, 01:46:10 (79.22.9.38)
My experience with toroidal transformers says no. Resonant point is certainly above 20 KHz (upper limit of PC based audio cards). .......
234: Tube DIY Asylum, RE: A practical way to use a surplus PP transformer as a choke for SE DIY (0.00)
Posted by cellailuca on 2021-02-24, 03:01:51 (79.22.9.38)
Solid state CCS. .......
235: Tube DIY Asylum, RE: A practical way to use a surplus PP transformer as a choke for SE DIY (0.00)
Posted by cellailuca on 2021-02-24, 02:51:51 (79.22.9.38)
Proven CCS for serious work. .......
236: Tube DIY Asylum, A practical way to use a surplus PP transformer as a choke for SE DIY (0.00)
Posted by cellailuca on 2021-02-24, 02:27:58 (79.22.9.38)
If you have available an economy/surplus AC transformer (2X110V-'a few volts', or the like) there is a practical way to use it in SE circuits. The trick is to use a low voltage current source (a .......
237: Tube DIY Asylum, RE: SE UL & CFB, no NFB, and aging of tubes (0.00)
Posted by cellailuca on 2021-02-17, 04:23:44 (79.33.230.153)
Worn out tubes sound less louder than new ones (with or without FB). This is what is generally meant for 'loss of gain'. .......
238: Tube DIY Asylum, RE: terms (0.00)
Posted by cellailuca on 2021-02-16, 07:40:39 (79.33.230.153)
I built a couple of 'zero feedback' all triode amplifiers as well as their twins with about 8 dB of GNFB. Apart from a lower control of the bass of the 'zero feedback' units (I suppose because of the .......
239: Tube DIY Asylum, RE: SE UL & CFB, no NFB, and aging of tubes (0.00)
Posted by cellailuca on 2021-02-16, 00:59:57 (79.33.230.153)
When tubes age their gain goes eventually down. GNFB stabilizes gain. No GNFB, no stabilization. In other words, loss of gain and some channel imbalance of 1-3 dB may develop over time. Independent vo .......
240: Tube DIY Asylum, New PP amplifiers for DIY (0.00)
Posted by cellailuca on 2021-02-15, 08:05:00 (79.33.230.153)
If you want to experiment with new ideas by the same basic hardware this is the article for you. .......
241: Tube DIY Asylum, RE: Why is so important a low PS output impedance? (0.00)
Posted by cellailuca on 2021-02-15, 07:36:14 (79.33.230.153)
Thank you! .......
242: Tube DIY Asylum, RE: A simple all-triode DIY project for beginners (0.00)
Posted by cellailuca on 2021-02-15, 07:35:02 (79.33.230.153)
Direct link. .......
243: Tube DIY Asylum, A simple all-triode DIY project for beginners (0.00)
Posted by cellailuca on 2021-02-15, 03:36:22 (79.33.230.153)
Since 2008 I have built several units based on the schematic of this paper. The paper is in italian but the technical content is quite clear. https://www.academia.edu/37481355/Progetto_Amplificatore_a .......
244: Tube DIY Asylum, Why is so important a low PS output impedance? (0.00)
Posted by cellailuca on 2021-02-14, 09:33:16 (79.33.230.153)
Here a very clear explanation. http://lilienthalengineering.com/100-amplifiers-chapter-1/100-amplifiers-part-4 .......
245: Tube DIY Asylum, RE: DIY issue but Solid State (0.00)
Posted by cellailuca on 2021-02-13, 11:08:54 (79.33.230.153)
Please take a look at Rule 2 and Rule 3 at https://www.angelfire.com/electronic/funwithtubes/Amp-preamp_design.html I suppose that the 'problem' is not a problem at all, because it may be due the desi .......
246: Tube DIY Asylum, RE: That's what I couldn't tell (0.00)
Posted by cellailuca on 2021-02-12, 03:30:11 (80.181.216.42)
I do not want to interact with Tre' simply because I had already presented the rationale of my designs in many past posts and I don't want to repeat the experience of stupid criticism that forced me t .......
247: Tube DIY Asylum, RE: Nice PP amplifier with 6SN7 and 829B (0.00)
Posted by cellailuca on 2021-02-10, 23:02:02 (87.17.226.155)
You can but I won't. .......
248: Tube DIY Asylum, Nice PP amplifier with 6SN7 and 829B (0.00)
Posted by cellailuca on 2021-02-10, 10:52:00 (87.17.226.155)
I built this baby for a friend of mine more than five years ago. Yesterday he called me because of some noise in the left channel (that was fading away after a while). I just suggested to che .......
249: Tube DIY Asylum, Looking back (0.00)
Posted by cellailuca on 2021-02-05, 09:23:16 (87.17.226.155)
I built my first tube amplifier in 2008 (an OTL). Since then I have completed about twenty projects, designed and built from scratch. They were all original PP designs of mine. .......
250: Tube DIY Asylum, RE: Nice PP amplifier with 12AT7 and 829B (0.00)
Posted by cellailuca on 2021-02-03, 09:22:21 (79.25.117.122)
I am finalizing its manual (in Italian). https://documentcloud.adobe.com/link/review?uri=urn:aaid:scds:US:9eacd49d-2857-4350-8033-d13d45d47149 .......
251: Tube DIY Asylum, RE: Glamour Shot#3 (0.00)
Posted by cellailuca on 2021-02-03, 09:18:45 (79.25.117.122)
Wonderful! .......
252: Tube DIY Asylum, Mini equalizer for tube amplifiers (0.00)
Posted by cellailuca on 2021-01-29, 11:09:01 (79.49.148.10)
When listening to streaming music from the smartphone it is useful to have some tone/volume control in front of the tube amplifier. I like this one (Behringher Mini-FBQ). It comes without a wood bo .......
253: Tube DIY Asylum, RE: What to do with a wine box... (0.00)
Posted by cellailuca on 2021-01-28, 09:27:19 (87.10.220.82)
Schematic and how it is made. .......
254: Tube DIY Asylum, What to do with a wine box... (0.00)
Posted by cellailuca on 2021-01-28, 09:24:45 (87.10.220.82)
Several years ago I built this for my brother in law. He said that tube amplifiers were too difficult to build and I said I don't think so. He appreciated it much more than the original bottles .......
255: Tube DIY Asylum, RE: Nice PP amplifier with 12AT7 and 829B (0.00)
Posted by cellailuca on 2021-01-28, 06:20:05 (158.148.163.102)
Yes, I was 6AS7_6SN7. .......
256: Tube DIY Asylum, RE: Nice PP amplifier with 12AT7 and 829B (0.00)
Posted by cellailuca on 2021-01-28, 02:58:39 (87.10.220.82)
How it is made. By the way, heaters are powered by 3 led power supplies. .......
257: Tube DIY Asylum, RE: Nice PP amplifier with 12AT7 and 829B (0.00)
Posted by cellailuca on 2021-01-28, 02:54:59 (87.10.220.82)
- PP, Class A, 12 W (15W class AB) - Bias current set by 6SN7 cathode followers for each 829B. - Ultra low power supply impedance (direct rectification of 220V AC line) - Input insulation transform .......
258: Tube DIY Asylum, RE: Nice PP amplifier with 12AT7 and 829B (0.00)
Posted by cellailuca on 2021-01-28, 02:45:33 (87.10.220.82)
Schematic 2 .......
259: Tube DIY Asylum, RE: Nice PP amplifier with 12AT7 and 829B (0.00)
Posted by cellailuca on 2021-01-28, 02:42:50 (87.10.220.82)
Schematic 1 .......
260: Tube DIY Asylum, Nice PP amplifier with 12AT7 and 829B (0.00)
Posted by cellailuca on 2021-01-27, 10:11:41 (80.116.17.205)
I used this prototype to experiment with several options and after a year of tweaking I have finished the project. I am quite satisfied with the result. .......
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