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1: Tubes Asylum, RE: Any Info/Opinions on Realistic 7591A Tubes? (0.00)
Posted by AA6U on 2023-05-30, 10:37:42 (71.83.178.24)
I know they don't look the same. I think the tubes are mislabeled regarding country of manufacture. However, I decided not to buy them. Thanks for the input. .......
2: Tubes Asylum, RE: Any Info/Opinions on Realistic 7591A Tubes? (0.00)
Posted by AA6U on 2023-05-30, 07:39:08 (71.83.178.24)
They look identical and test nearly the same. Only the markings are different. .......
3: Tubes Asylum, RE: Any Info/Opinions on Realistic 7591A Tubes? (0.00)
Posted by AA6U on 2023-05-29, 17:38:32 (71.83.178.24)
They are a matched quad. .......
4: Tubes Asylum, RE: Any Info/Opinions on Realistic 7591A Tubes? (0.00)
Posted by AA6U on 2023-05-29, 07:44:58 (71.83.178.24)
I don't have access to them and I'm not sure I can get good photos of them from the seller that would help identify the mfr. They are standard octal base, not coin base. .......
5: Tubes Asylum, Any Info/Opinions on Realistic 7591A Tubes? (0.00)
Posted by AA6U on 2023-05-28, 23:27:55 (71.83.178.24)
I have a chance to buy a quad of good used Realistic 7591A tubes at an okay price, but I know nothing about the Realistic brand of 7591s. I know Radio Shack did not make their own tubes, and I don't k .......
6: Vintage Asylum, RE: Did Marantz Ever Install Sprague 160P Caps in the 8B as Stock? (0.00)
Posted by AA6U on 2021-01-20, 13:38:30 (71.84.242.62)
Yes, that is correct. As a follow up to this thread, I replaced the black beauty caps with new polypropylene caps and it sounds a lot better (ESR if black beauty caps was 13 ohms and the new ones mea .......
7: Vintage Asylum, RE: Did Marantz Ever Install Sprague 160P Caps in the 8B as Stock? (0.00)
Posted by AA6U on 2020-12-29, 17:43:39 (71.84.242.62)
That is how it appears. .......
8: Vintage Asylum, RE: Did Marantz Ever Install Sprague 160P Caps in the 8B as Stock? (0.00)
Posted by AA6U on 2020-12-28, 22:04:21 (71.84.242.62)
I tested the ESR in the Black Beauties and it was about 14 ohms vs. 0.5 ohms for polypropylene caps that I use in audio equipment refurbishing. Leakage was within limits and they hadn't drifted in val .......
9: Vintage Asylum, RE: Did Marantz Ever Install Sprague 160P Caps in the 8B as Stock? (0.00)
Posted by AA6U on 2020-12-28, 08:35:19 (71.84.242.62)
I tested the ESR in the Black Beauties and it was about 14 ohms vs. 0.5 ohms for polypropylene caps that I use in audio equipment refurbishing. Leakage was within limits and they hadn't drifted in val .......
10: Vintage Asylum, RE: Did Marantz Ever Install Sprague 160P Caps in the 8B as Stock? (0.00)
Posted by AA6U on 2020-12-27, 22:21:43 (71.84.242.62)
Although the Black Beauties may be stock, I think I'm going to replace them to be protect the output tubes and transformers. I will save them in case I sell it, and the next owner can reinstall them i .......
11: Vintage Asylum, RE: Did Marantz Ever Install Sprague 160P Caps in the 8B as Stock? (0.00)
Posted by AA6U on 2020-12-27, 19:50:00 (71.84.242.62)
Thanks! That's what I wanted to know. .......
12: Vintage Asylum, RE: Did Marantz Ever Install Sprague 160P Caps in the 8B as Stock? (0.00)
Posted by AA6U on 2020-12-27, 12:27:24 (71.84.242.62)
Someone suggested that, but it looks like someone in the recent past unsoldered them to test them, probably for leakage, so that is not going to be revealing on their originality. However, that may be .......
13: Vintage Asylum, RE: Did Marantz Ever Install Sprague 160P Caps in the 8B as Stock? (0.00)
Posted by AA6U on 2020-12-26, 09:05:43 (71.84.242.62)
Yes, resale value is my reason for asking the question. The 8b works now with the 160P black beauties but with low bass. If the black beauties are not original, then I won't have any qualms about rep .......
14: Vintage Asylum, Did Marantz Ever Install Sprague 160P Caps in the 8B as Stock? (0.00)
Posted by AA6U on 2020-12-24, 14:02:01 (71.84.242.62)
I bought a Marantz 8b several months ago and it works fine, except that it is somewhat lacking on the lower end compared to numerous other amps I own and have worked on. It has the original Goodall ca .......
15: Inmate Systems, AA6U's McIntosh (0.00)
Posted by AA6U on 2020-12-24, 13:54:00 (71.84.242.62)
AA6U 's McIntosh System
IP Address: 71.84.242.62
Last Update: December 24, 2020 at 13:54:00
Amplifier: McIntosh MC30 MC60 MC240 MC275 MC2205; Marantz 8B; Fisher KX-200; Bedini 25/25
Pr .......
16: Amp/Preamp Asylum, Schematic for Magnecord PT6BNX Preamp/Mixer (0.00)
Posted by AA6U on 2020-08-15, 22:33:53 (71.84.242.62)
I need to service a Magnecord PT6BNX-1-112A preamp/mixer/amp from an old tape recorder. It is a two-channel unit with two meters and uses two pairs of 6AQ5 tubes for the output. Other tubes are .......
17: Tubes Asylum, RE: Marantz 8B with Bob Hovland Mods? (0.00)
Posted by AA6U on 2020-06-12, 10:58:01 (71.84.242.62)
I would be curious to see what mods Sid Smith had for the 8B. The stock one I'm looking at has had the selenium rectifier replaced with a silicon one, protection diodes installed for meter protection .......
18: Tubes Asylum, RE: Marantz 8B with Bob Hovland Mods? (0.00)
Posted by AA6U on 2020-06-12, 09:30:22 (71.84.242.62)
Thanks for the input. The guy selling the 8B has both the stock version and the Hovland-modified version and I will be able to listen to both for comparison. I'm just wondering if the Hovland-modified .......
19: Tubes Asylum, RE: Many of my trading partners want just that.... (0.00)
Posted by AA6U on 2020-05-25, 14:12:44 (71.84.242.62)
Restuffing is a major pain, especially with painted cans such as on the 8B. I just mount the new caps inside the chassis. However, I know anal people would have a fit over that. I also know several an .......
20: Tubes Asylum, RE: It has nothing to do with being a purist... (0.00)
Posted by AA6U on 2020-05-25, 13:28:23 (71.84.242.62)
I believe it would be impossible to find NOS power supply can capacitors identical to the ones used in the 8B. Even if you did, they likely would be bad after sitting on the shelf for decades. If you .......
21: Tubes Asylum, RE: Marantz 8B with Bob Hovland Mods? (0.00)
Posted by AA6U on 2020-05-25, 13:21:31 (71.84.242.62)
Only the bias rectifier was selenium. The B+ ones are silicon. Yes, it does sound great on B&Ws. .......
22: Tubes Asylum, RE: These things are so system dependent... (0.00)
Posted by AA6U on 2020-05-25, 07:58:02 (71.84.242.62)
I wouldn't hesitate to buy one in which someone had upped the power supply capacitor values. However, tweaking the values of coupling or bypass capacitors is a totally different matter as is changing .......
23: Tubes Asylum, RE: Marantz 8B with Bob Hovland Mods? (0.00)
Posted by AA6U on 2020-05-24, 22:44:45 (71.84.242.62)
If I buy it, I think I'll buy the unmodified unit and just replace the electrolytics. .......
24: Tubes Asylum, RE: These things are so system dependent... (0.00)
Posted by AA6U on 2020-05-24, 22:41:35 (71.84.242.62)
Increasing the capacitance is a totally reversable mod. If you're a purist, replacing a selenium rectifier with a silicon one and adding a series resistor to provide the correct voltage technically m .......
25: Tubes Asylum, RE: Marantz 8B with Bob Hovland Mods? (0.00)
Posted by AA6U on 2020-05-24, 22:22:58 (71.84.242.62)
After getting a lot of responses, I agree about getting an unmolested one. Also, Robert Hovland is definitely still around. You can contact him via email at: roberthovland (at) earthlink (dot) net [re .......
26: Tubes Asylum, RE: Are you interested in sound quality or preserving monetary value? (0.00)
Posted by AA6U on 2020-05-24, 17:30:38 (71.84.242.62)
One thing that I found is that you are responsible for any mods that are made and it will almost assuredly decrease the resale value as buyers question what was done. I do a lot of refurbishing work o .......
27: Tubes Asylum, RE: Yes Scott, I mean that they devalue the amp. Just answering the primary question. nt (0.00)
Posted by AA6U on 2020-05-24, 14:44:57 (71.84.242.62)
That's what I thought. Thanks for your input. The consensus is universal that I should get the unmodified one. .......
28: Tubes Asylum, RE: Marantz 8B with Bob Hovland Mods? (0.00)
Posted by AA6U on 2020-05-24, 14:20:43 (71.84.242.62)
I'm using them on Bowers & Wilkins 803 Nautilus speakers. I've found them to be very revealing when evaluating the nuances of amps and preamps. .......
29: Tubes Asylum, RE: Marantz 8B with Bob Hovland Mods? (0.00)
Posted by AA6U on 2020-05-24, 12:04:41 (71.84.242.62)
So far, the 8B edges out my Mcintosh MC30, MC240, MC60 and MC275, but not by a whole lot. However, I made an easily-reversable mod to each of the Mac amps that replaces the !2AU7s with 6CG7s. I did A/ .......
30: Tubes Asylum, RE: Yes, they do. nt (0.00)
Posted by AA6U on 2020-05-24, 11:36:57 (71.84.242.62)
That is what I thought. The one with the tube adapters that allow use of 6AU6 in place of the 6BH6 does not permanently change it, but does seem to help the soundstage to some extent. I think that is .......
31: Tubes Asylum, RE: Yes, they do. nt (0.00)
Posted by AA6U on 2020-05-24, 09:51:42 (71.84.242.62)
Viridian- I'm not sure I understand your response "Yes, they do. nt" to "My primary question is whether the Hovland modifications decrease the resale value of the 8B." Do you mean "Yes, they do"? ::: .......
32: Tubes Asylum, Marantz 8B with Bob Hovland Mods? (0.00)
Posted by AA6U on 2020-05-23, 21:29:57 (71.84.242.62)
I am considering buying a Marantz 8B. However, I have a choice between two different units with significant differences. The first is electronically original (except for replacement of the selenium re .......
33: Tubes Asylum, RE: Hickok 539B Low Grid & Screen Voltages- Help! (0.00)
Posted by AA6U on 2009-09-22, 21:33:44 (71.93.160.227)
Michael- Thanks for the input. I found the trouble: one of the receptacles on the 5Y3 socket that goes to one of the plates was missing hence only half of the tube was working. I replaced the socket a .......
34: Tubes Asylum, Hickok 539B Low Grid & Screen Voltages- Help! (0.00)
Posted by AA6U on 2009-09-21, 20:49:28 (71.93.160.227)
The Hickok 539B I'm working to restore has low screen voltage (49v on high) and the grid voltage will only go up to -20v. The 5Y3 is good (I've tried several different tubes). If I disconnect R18 from .......
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