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1: Re: 845 SE Op points (6.14)
Posted by Jimmy on 2005-09-06, 09:03:53 (69.179.61.128)
Quite low primary impedance for a 845. I suggest a low voltage 845 SET design at 420-450 volts plate. Perhaps use the 6-ohm secondary on 8-ohm speakers for a reflected 4K back to the tube. I hope the .......
2: Re: Did you give it a try with ... (6.14)
Posted by Jimmy on 2005-09-06, 15:28:18 (69.179.61.128)
I have not completed the amp yet. Others state an 845 at high voltages sound a bit 'washed out' where as no one has negative comments regarding a low voltage 845 amp. My reasoning was I wanted 300B SE .......
3: Grossly oversized PS choke vs standard size....... (5.51)
Posted by Jimmy on 2005-08-03, 08:00:09 (64.91.48.81)
I am biulding a low voltage (550 vdc cathode bias) 845 SET amp. The PS is a CLC for the 845 tube and a seperate LCLC for the driver & preamp tube. Is it necessary to use a 10HY 500 ma choke with a DCR .......
4: Re: 845 cathode resistor (5.40)
Posted by Jimmy on 2004-12-23, 12:46:34 (207.89.249.39)
I wish to drive the 845 grids directly, thus have to 'float' driver up -80 volts or so at cathode. Perhaps, 700 plate with cathode resistor may be better. .......
5: PP 845 design recommendation........ (5.33)
Posted by Jimmy on 2004-12-24, 18:24:19 (207.89.249.76)
I deceided to drop the directed coupled driver to PP 845 design. I have approximately 650-700 volts plate available & can use fixed bias. What would be a good design recomendation? .......
6: 845 cathode resistor (5.18)
Posted by Jimmy on 2004-12-23, 09:02:14 (207.89.249.151)
I started a DIY PP 845 stereo amp. The applied plate voltage is 640 volts & as measured from plate to cathode target is about 565 volts (-75 volts bias from cathode resistor). I wish to operate about .......
7: Re: 845 OUTPUT TXFMR (4.46)
Posted by Jimmy on 2006-03-24, 08:04:19 (69.29.226.105)
What is the plate to filament voltage on your 845s? .......
8: Perhaps I should rethink ......... (3.71)
Posted by Jimmy on 2005-08-20, 20:00:45 (69.179.104.166)
my PP triode connected 6V6 & 1/2 assembled 845 SET? .......
9: 'Except I never heard a zero NFB PPT amp yet' (3.68)
Posted by Jimmy on 2006-07-07, 16:10:15 (69.179.58.131)
I have as I built two such designs in monoblocks. Both use quality MQ iron and simular PS of LCLC to another LC for the small signal tubes. One is PPP 45s & other is triode connected PPP 6V6s. Both ar .......
10: Does weight count? (3.65)
Posted by Jimmy on 2005-09-05, 13:10:25 (69.179.61.128)
The seperate power supplies (2) for the 845 monoblocks weigh 45 lbs each. .......
11: Re: 845 Filament DC supply (3.61)
Posted by JIMMY on 2005-08-01, 11:04:19 (69.179.60.210)
Chokes in the positive rail or both positive & negative rails? .......
12: Re: Project? (3.50)
Posted by Jimmy on 2005-05-15, 13:09:01 (69.29.225.147)
www.kandkaudio.com has Lindahl products with the LL1688 manufactured for 845 in SET applications. Published on line $275 each, but I am unsure of the sonic performance. .......
13: Re: 6P5G -) KT66Triode LC -) 845 Yummmm (3.41)
Posted by Jimmy on 2004-09-07, 08:03:31 (207.89.249.125)
I learn a long time ago, tubes react differently in different circuits. I may end up trying different tubes. Tnx for recommendation. .......
14: Ground rules for presenting an idea (3.32)
Posted by Jimmy on 2006-07-24, 05:40:43 (69.29.9.63)
I learned years ago when addressing various groups of engineers with a different idea, documentation as to why it is better was paramount. Next, I had to present it with a smile (hard to perform on th .......
15: Re: It is fairly well known AC...... (3.25)
Posted by Jimmy on 2005-08-11, 12:56:59 (207.118.234.90)
DC removes hum issues on ultra high efficiency speakers. 2.5 volt filament tubes are not so much an issue, but a 10 volt 845 can be an issue. .......
16: 845 grid leak resistor value (3.23)
Posted by Jimmy on 2005-08-09, 10:04:06 (207.118.234.107)
With 550 VDC plate & cathode bias, is a 100K grid leak resistor a low enough value to prevent run away? .......
17: Re: 8 SE watts/channel, no 300bs please (3.19)
Posted by Jimmy on 2006-04-24, 12:45:17 (64.91.48.114)
Low voltage 845 SE. Driver tube makes for a difference in sonics. I have not enough experience with a large lot of tubes, but the 46 triode connected sounds good. .......
18: Re: Which 845 operating points should I shoot for to get 8 watts? (3.19)
Posted by Jimmy on 2005-12-11, 04:05:57 (69.29.226.183)
I would stay at 600 vdc if the highest primary impedance is only 5K. A common issue is too low a primary impedance produces less than best quality sonics. .......
19: Re: 845 Filament DC supply (3.18)
Posted by JIMMY on 2005-08-01, 08:33:31 (69.179.60.210)
Common mode noise- The cathode (filament) resistor is bypassed with 100uF poly cap to ground & a 30uf cap is placed from the B+ rail to the filament. .......
20: Re: An obvious question: single-ended from PP amp by killing drive to one side? (3.18)
Posted by Jimmy on 2005-10-23, 09:13:11 (69.29.10.197)
Tre- Per my ears, the DIY PP45s I built outperformed a DIY SET with parallel 45s using the same front-end tubes. Although SET parallel 45s is very good, I could not get used to the SET sonics in that .......
21: Re: Power supply design for 845 amp - questions (3.09)
Posted by Jimmy on 2005-02-22, 11:59:47 (207.89.249.148)
If I had any options on your high-end project, I would use a LCLC filter. However, regarding the CLC filter, the peak to average current is a consideration. I like to derate transformers spec'ed at 20 .......
22: Re: Low DCR PS on 813 amp (3.09)
Posted by Jimmy on 2006-07-17, 05:30:26 (69.29.225.172)
Low DCR is very expensive & I believe that is the resistance (no pun intended) from many to try it. I am going that simular route on my SE 845 amp. Fortunately, that DIY amp was designed with a remote .......
23: Assume reply to dave..... (3.06)
Posted by Jimmy on 2005-08-13, 11:32:49 (69.179.57.227)
I am using 37 volts AC into a simple bridge rectifier with a .12HY choke input to a 4700uF cap. Next, I will use three RC sections with a resistor for more voltage drop & filtering. The caps are all 4 .......
24: Re: any new DHT tubes out there? (2.99)
Posted by Jimmy on 2006-07-06, 06:59:36 (69.179.58.131)
Build a low voltage 845 (500-550 volt) SET. Tube is new manufacture out of China & sounds as good as NOS 845s plus are reliable. Low voltage is reported to sound better than high voltage designs at 65 .......
25: Re: New 845B review in Tubes Asylum (2.99)
Posted by Jimmy on 2004-06-23, 11:02:29 (207.89.249.46)
Ed, your post has my interest. I like PP amps with a carefully designed PP interstage driver transformer. Perhaps a DIY 845 PP amp is in my future after considering quad PP 2A3 with less power output. .......
26: Re: Any updates on Edcors? (2.99)
Posted by Jimmy on 2006-02-15, 14:53:49 (69.179.56.133)
Yes, built an 845 SE using Edcor 25-watt frame size IE lam gapped stack audio transformer with a 5K primary & a single 8-ohm secondary. Edcor is a good performer & compared to Plitron, close in perfor .......
27: Not a flamer here.................Low DCR PS (2.84)
Posted by Jimmy on 2006-08-02, 08:38:34 (69.29.9.154)
My last post on low DRC ever. Per more experiments, I find the following: 1) I did not hear a difference on a preamp. Drawing a few ma at steady state is most likely the reason. The single tube per ch .......
28: Edcor Audio Transformers (2.79)
Posted by Jimmy on 2006-01-04, 05:36:08 (207.118.232.10)
I have been experimenting with Piltron 3050-SE & the new Edcor 25-watt rated IE gapped audio transformers on an 845 SET. Both transformers are rated 5K primary & used at 550 volts DC. I have not looke .......
29: Re: Nah... Like this (2.75)
Posted by Jimmy on 2004-12-26, 09:01:01 (207.89.249.35)
I have some input transformers including the Edcor. I am just a bit leary of transformers in any preamp or driver stage. Tnx for all your info. I enjoy a neutral sounding amp with crystal clear & deta .......
30: Re: "Music Angel" 845 SET - a Safety Moment (2.71)
Posted by Jimmy on 2006-05-08, 05:21:28 (69.179.61.91)
Years ago with tube type amateur equipment, the floating series cap was insulated with thick paper cardboard sleave over the can. Not the best either, but covered with a steel screen cover. If I was d .......
31: Re: min, reactance also works well with Max reactance (2.67)
Posted by Jimmy on 2004-07-17, 08:38:19 (209.172.29.207)
I always like reading your posts. Anyways what does 'all the trouble of hg' mean? I have not cut any chassis holes & might be able use the 816s. Shamefully, I backed away from the 845 project & back t .......
32: Re: Parallel ECC99 vs EL84 in triode as 2A3 driver (2.65)
Posted by Jimmy on 2006-08-02, 05:34:08 (207.118.234.5)
A GE oval plate EL84 triode connected is a good driver. Although I never performed this as a driver, in triode as an output tube the GE EL84 is a very good tube sonically & the best EL84 I heard from .......
33: Re: 6P5G -) KT66Triode LC -) 845 Yummmm (2.62)
Posted by Jimmy on 2004-09-07, 06:05:20 (207.89.249.110)
Fine business on your project. I am building a preamp based upon the Gary Prim CCS 76 circuit design. I am changing the first preamp 76 tube to a Tung-Sol 6P5GT round black plate, then to the VT-76 tu .......
34: Re: Question - how physically large is your amp's power supply? (2.51)
Posted by Jimmy on 2005-09-03, 08:32:13 (64.91.49.215)
The power transformers are not low DCR thus not oversized at all. The pair of chokes and one oil cap eats up about 1/2 the chassis. I cheated and used a electroyltic the first cap & an oil on the seco .......
35: Re: tube tester for 845 300B needed (2.51)
Posted by Jimmy on 2006-03-12, 09:44:48 (69.179.63.250)
A Western Electric model tube tester manufactured by Hickok has 300B settings. I also know my Hickok 752A I sold a few years ago has 811 test parameters. Thus, I could test simular 572B tubes. or, eve .......
36: Re: 845 SE Op points (2.41)
Posted by Jimmy on 2005-09-06, 11:07:49 (69.179.61.128)
Understand the low voltage design is only 8-10 watts output (I did not perform a load line). The concern is about lower audio transformer primary impedance designs. This can be viewed in tube manuals .......
37: Opinions (2.33)
Posted by Jimmy on 2006-09-24, 06:17:57 (69.179.63.22)
We all hear differently. I am sensitive to harmonics and require an accurate amplifier without any smearing in the midrange. Most tube amps will not perform to my requirements. For example, I can not .......
38: Re: I should have explain cost better......... (2.30)
Posted by Jimmy on 2006-04-29, 20:59:21 (69.179.56.218)
I have used 80uF 500 Vac oil caps at 600 vdc. I do not feel easy about using 370 vac oil caps at 600 vdc. That 500 Vac cap measures 2-1/2" x 6-1/2". Are Solen 50uF & 100uF 630 volt caps larger than th .......
39: Dave, good question ....... (2.14)
Posted by JIMMY on 2005-08-18, 20:49:51 (69.179.105.18)
I have a lot of parts & experimented with them. The parts I listed consistantly perform well. If a DIY amp design does not perform as well as I believe it can, then I will further experiment. I do ret .......
Found total of 39 records, Query: 845, Author: jimmy in Tube DIY Asylum, Time: 0 sec.