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Vintage Asylum Classic gear from yesteryear; vintage audio standing the test of time. |
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Vintage Asylum Classic gear from yesteryear; vintage audio standing the test of time. |
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In Reply to: Two thumbs up for Don Sachs posted by banpuku on December 20, 2013 at 16:10:17:
Aw shucks... thanks guys! I just finished a KT550 for a customer and it sounds fantastic. I didn't want to gush about it because that always raises core prices! However, in this case there are so few of them and everyone knows anyway. Jim McShane and I discussed a few improvements and then I did them. I posted a few photos on my site in the gallery page, but I didn't want to post here because that is sort of advertising and I think that is a no no on this forum. However, given that this amp is not for sale, it is being shipped back to its owner after the crazy shipping damage season that is Xmas, I guess it is ok. You can check it out the link at the bottom of this post. There are a few pieces on that page, but the KT550 has three photos and they will scroll by. Here is what Jim and I cooked up.1. We added a separate screen supply since there was room on the bracket.
2. Of course totally beefed up the doublers and filters ala the citation II
3. I put in diodes to split each channel's B+ and screen supply before the filter caps, also added a pair of CL150 on the B+
4. Added cathode and screen resistors.
5. Improved grounding using a nice bus on the PS bracket
6. K40 caps as the main couplers and all those terrible electrolytic signal path caps are Solens now.
7. Good quality resistors everywhere and silver micas for the little feedback capsI had to basically rewire the amp to pull all the old brittle wire. The original design had the output tube cathodes going through the meter switch to a single ground point. The meter was toasted on this one so I just grounded each cathode through its resistor to the ground bus. I then installed small tip jacks on the rear for each output tube so you can bias it without opening it up. Works great. To do AC balance you can just take the reading across each tube pair as well. Works like a charm. Also added the nice big Belden AC cord we make up for the Citation II.
Amp is stunningly good. Not much else I can say. Very much like a Citation II...no surprise, the circuit is very similar and Stu H designed them both. Old boards are a pain, but I found all the bad spots and fixed them. It should run another 40 years now!
Wish Santa would leave me a KT550 core under the tree!
cheers,
Don
Edits: 12/20/13
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Follow Ups
- RE: Two thumbs up for Don Sachs - dls123 18:34:50 12/20/13 (2)
- RE: Two thumbs up for Don Sachs - Michael Samra 13:20:51 12/21/13 (1)
- RE: Two thumbs up for Don Sachs - dls123 08:54:10 12/22/13 (0)
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