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Wondering if anyone could help with how to bypass tone controls on a Fisher X-101-C. Dealing with an ago with potentially bad PC packets or whatever they're called.
Any help appreciated.
Dave
Follow Ups:
I upgrade tone controls with no loss in sound quality. I dislike the ceramic caps in those PECs too. Keeping the tone controls allows tuning an amplifier to the speakers and listening room response.
I believe new manufactures deleted tone controls based upon marketing hype that any tone control is bad news. Plus, it saves the manufacture bread boarding a quality design and money.
I don't always need them, but when I do, I am glad they are there.
Dave
Have you tried replacing the caps and resistors with higher quality parts? Maybe, do one channel and compare it to the other (left stock).
Coupling caps are K40s, most of the resistors test within 2% of spec, I see no reason to think they are not sufficient quality. Power supply is new. Most things seem about right but frequency balance is quite different channel to channel, does not change with swapped tubes, so I believe the issue may be with the PECs.
Dave
You will need a grid resistor,(Rg) because the DC connection is through the PEC. Any high value (about one Meg) should work fine there.
If you have too much gain, add series resistor Rs. 220k-330K should be fine there. trim to taste.
go read the articles that Dave Gillespie wrote on audiokarma, he has a number of thoughts on how to PROPERLY bypass the tone controls in Fisher gear...
I found a thread where he details modding an X-101-C, he gives all the details right up to the bypassing of tone controls and the thread ends (2012) with promises of a schematic for bypassing...
I'll look for other stuff he's written there, thanks.
Dave
Yes, those PECs are a PITA. Simply bypassing the tone controls may leave you with excessive gain and a "hair trigger" volume control.Contact AA sponsor Jim McShane. Jim will get you squared away with discrete parts to replace the trouble makers.
Eli D.
Edits: 03/16/15
I replaced the tone PECs on my Voice of Music 1448 and it made a very nice difference. It got rid of the distortion I was hearing and really cleaned up the quality of the sound, but as Eli said, they were a pain in the arse.
It took quite a while for me to figure out how to wire it up. I had to take out both PECS and start with a clean slate before I could accurately interpret the schematic and figure out what goes where. It IS worth the effort.
Larry D.
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