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A few years ago I rebuilt my MC240 with Mike Samra's help and Jim McShanes parts, except I used all k40y caps. While it sounded very nice, there I was not enthused. Soon it developed a hum for about 30 seconds at startup. Turned out to be a bad filter cap. This week, again on Mikes advice, I swapped the (4) 47 k40's with 716p's, and the (2) .1 k40's at the input with Sonicap gen1. The C.C. 1meg grid to ground resistors were changed to film. The last change was to add 4 of his favorite 35uf bypass caps to the filter caps. I was quite surprised at the improvement. The highs opened up and the amp is very quiet. It's hard to qualify, but the background silence in passages is totally black now. I can call this amp done. I spent the last two days cleaning records and enjoying the amp. Now I can move on to preamp and speaker upgrades.
Thanks again Mike.
sf
Follow Ups:
are they connected to the power supply, which are already around 40 uf, or are these replacements for those caps, or are they cathode bypass caps that you changed to film/foil or something? Thanks
Randy
Those are 35uf film caps that I use for added decoupling in parallel with the 40uf lytic which we change to a 100uf lytic.The 35uf film caps are doing most of the work due to the film cap's efficiency and low ESR and ESL.Try putting a film cap off the GZ34 of that Scott 222 you are working on. Just use a 30uf or 35uf poly,nothing extra.Tell me what you think.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 03/19/17
Thanks, Michael, I did use the CDE poly cap after the 5AR4, that suggestion of yours has been golden and I have been doing that ever since!
I meant the 35uf film caps do most of the work.Aren't they amazing? The closet lytics I have heard to a film cap are the Panasonic ED series or the Philips BC series.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Yes, your suggestion for using the CDEs as well as using the block film caps in the power supplies is one I took to heart with great delight, thanks so much, Michael!
Good job Steve.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
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