Fixed depth question..

lespaul6

lespaul6

Well-known member
Ive seen a 220k over a 4n7 spliced into the purple negative feedback wire and then connected to the 4ohm tap. Is it also possible to piggyback the 220k/ 4n7 to the negative feedback resistor on the board and get the same result? thanks
 
can you clarify what you have on the board already? Do you have a schematic?
 
Im going to do this JEL mod..... here is the schem
 

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  • jcm800_2204 JEL Spec.gif
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Working off that schem I attached above, I will be connecting the 2n2 to the low input wire. The 220k will be attached to that preamp push/pull pot- not sure where to attach that to be parallel, I forgot that it was a push/pull for the bright cap.

It looks like I will attach the 3k3 and 0.68uf piggy back on that very first resistor on the board to the left?

And if anyone can be kind enough to point out which 820 resistor gets the 22uf cap? and which 100k resistor gets the 470pf cap?

thanks for any help/advice
 

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Ok I got all the parts in today and connected everything up.... only question Im having is just how I should be connecting that 220k resistor to that push pull gain pot. I have it connected to the two lugs as pictured, should I have connected it a different way? I'm just getting a low volume bright signal with no gain or full volume. Everything looks to be connected well. I chopsticked around and there is no change. stumped
 

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I disconnected one of the legs of the 220k resistor on the gain pot and the full signal was returned- so that resister placement is what is neutering the signal and gain. The pot is push pull, that when pushed in, employs the normal marshall 2203 bright cap. When pulled out the cap is out of the circuit. I guess i'll try to connect the resistor to the pot some other way.... anyone know if there is a special way to parallel that resistor to a push pull pot?
 
Make it work first (using the red values), then get the switching.

This thread started as a fixed depth mod but now you're at the other end of the preamp. Did the fixed depth work? Also, I can't see those pics well enough to see anything.
 
Yes... fixed depth works. No problem there. Not sure what the issue is, but when i connect the 220k from wiper to ground it cuts out all the gain and volume. Its not supposed to do that so I imagine the way this push pull is wired is different somehow. Ill get a better pic up... everything is red is done already.
 
That’s my scheme, yeah the fixed depth must be in series with the NFB resistor. You can install it after the NFB resistor, but it works better when set before.
 
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