RE: McIntosh C-20 preamplifier

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Posted by Michael Samra (D) on March 14, 2014 at 19:03:47

In Reply to: McIntosh C-20 preamplifier posted by audiogatorjim on March 14, 2014 at 16:07:53:

Jim
The C20 can be a hell of a preamp..I know because I frequently use mine.
They do need upgrading in a sort of big way but they are incredible when they are done.
The big thing I do is tack on four 35uf poly film caps in the power supply for the first two filtering stages in the power supply..They normally use a pair of 40uf electrolytics after the 3.3k resistor off the 6x4,I put in 70uf of polys in the next two sections and I mount two more single section polys on top where the two multi section cans went.Basically it's 100% film cap power supply in the high voltage B+.
The next thing you want to do is rebuild the DC filment supply with a pair of Schottkeys and a pair of 4700uf Nichicon Golds in place of the 1000uf caps that were in there.
Then you want to use a combo of k40s and Teflon caps for couplers and you want you want to change the grid to ground resistors to a good metal film or bulk film type.This is my old one I did and I put all silver micas on the top side in place of the old ceramic caps..Notice how I mounted these caps underneath with tie straps..I removed the straps for this photo when I took the picture but they are back on..When you upgrade this way,you can always put it back to original with no ramifications.
The improvement in this preamp as far as signal to noise and dynamic range and accuracy is nothing short of phenomenal.I also put in coaxial silver stranded wire on top in the critical parts of the signal path.
I have rebuilt 9 C20 preamps for people and the last four I've rebuilt I did this way, and people just loved them.Both of my C20s I have done like this and I sold the first one I rebuilt a year ago for a nice sum to a guy in Chicago that was too good to pass up.
Now I have one but I guess I didn't need two anyway lol.

"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

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Follow Ups Full Thread

Topic - McIntosh C-20 preamplifier - audiogatorjim 16:07:53 03/14/14 (13)

RE: McIntosh C-20 preamplifier - Michael Samra 21:31:36 03/14/14 (6)

RE: McIntosh C-20 preamplifier - audiogatorjim 07:14:39 03/15/14 (5)

RE: McIntosh C-20 preamplifier - Eli Duttman 09:39:00 03/15/14 (4)

RE: McIntosh C-20 preamplifier - Michael Samra 15:32:05 03/15/14 (3)

Here is how I rank some amps I have owned for the 57's - audiogatorjim 17:00:48 03/15/14 (2)

RE: Here is how I rank some amps I have owned for the 57's - Brian Levy 17:01:13 03/17/14 (0)

RE: Here is how I rank some amps I have owned for the 57's - Michael Samra 16:40:46 03/16/14 (0)

RE: McIntosh C-20 preamplifier - dls123 19:38:32 03/14/14 (2)

RE: McIntosh C-20 preamplifier - Michael Samra 19:51:19 03/14/14 (1)

RE: McIntosh C-20 preamplifier - dls123 23:26:11 03/14/14 (0)

RE: McIntosh C-20 preamplifier - Michael Samra 19:03:47 03/14/14 (0)

one word: Noisy... - crooner 17:21:08 03/14/14 (1)

RE: one word: Noisy... - Michael Samra 19:43:36 03/14/14 (0)

Follow Ups

RE: McIntosh C-20 preamplifier - Michael Samra 19:03:47 03/14/14 (0)

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