Troubleshooting a Two Rock Crystal (JM circuit)

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Thewayfarer
Posts: 14
Joined: Mon Nov 27, 2017 3:09 am

Troubleshooting a Two Rock Crystal (JM circuit)

Post by Thewayfarer »

Hey guys, pretty new here - so forgive me if this isn’t the proper venue for such a question.

I have a crystal with some NOS components. Opened it up a while back and saw the cap tied to the master volume was .0015 instead of .022 like both on the board and on every JM layout out there. What effect would this have on the amp, and should I change it to .022?

Again, sorry if this is the wrong venue for this sort of question. I figured you guys know more about this circuit and it’s influences than anyone else. I’ve only ever modded fenders, but browsing around here the last few days has really pushed me to want to learn more and eventually give it a go at a build. Anyways. Thanks.

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Last edited by Thewayfarer on Wed Nov 29, 2017 11:45 am, edited 1 time in total.
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xtian
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Re: Troubleshooting a Crystal

Post by xtian »

"Crystal" is the name of amp?

The cap you've circled is a coupling caps (couples the stages). Larger values (0.022uF) will let thru more bass frequencies; smaller values (0.0015) will cut the bass a bit.
I build and repair tube amps. http://amps.monkeymatic.com
Thewayfarer
Posts: 14
Joined: Mon Nov 27, 2017 3:09 am

Re: Troubleshooting a Crystal

Post by Thewayfarer »

Sorry, Two Rock Crystal. Essentially the JM circuit
brentm
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Re: Troubleshooting a Two Rock Crystal (JM circuit)

Post by brentm »

Interesting that the board silkscreen is 0.022uF but they substitute a 0.0015uF cap in that position.

Are you going to try to swap that cap out or leave it?
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