My 2204 has more gain than I'd expect

  • Thread starter Thread starter ledvedder
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ledvedder

ledvedder

Well-known member
Wondering if anyone could give me some tips on things to check with my 2204 build. It seems to have much more gain than I'd expect. I've measured the cathode resistors and bypass caps. All are within spec. Even without the bright cap, it stays pretty gained up even at lower preamp volumes. Bias is good. This is the layout that it's built from.
Screenshot_20221220_195056_Acrobat for Samsung.jpg
 
I'm going through the circuit, testing the capacitor values. 2 of the 500pF silver mica caps are reading close to 700pF. The bypass cap across the 470k voltage divider, and the cap going into the tonestack. Would that increase the gain?
 
It would lower the high pass frequencies making them pass more high mids along with the highs which will add gain. Get too greedy and the amp could go unstable.
 
glpg80 said:
It would lower the high pass frequencies making them pass more high mids along with the highs which will add gain. Get too greedy and the amp could go unstable.
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Do you think I should replace them. Does a 180-200pF difference make a noticeable impact?
 
ledvedder said:
Do you think I should replace them. Does a 180-200pF difference make a noticeable impact?
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Keep them and enjoy a stable amp with more gain. Or go bigger and figure out how much your amp can take until it’s unstable and then back off a few hundred pF and leave it :)
 
glpg80 said:
Keep them and enjoy a stable amp with more gain. Or go bigger and figure out how much your amp can take until it’s unstable and then back off a few hundred pF and leave it :)
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I didn't mean to go larger 😂 I meant should I replace them with caps that test correctly at 500pF?
 
I have went as high as .0022 on the voltage divider with good results but it all depends on the rest of the circuit. I like 500pf for the treble cap.
I don't like silver micas.
 
What would you recommend? Ceramic, Mallory, orange drop?
 
screamindemon said:
I have went as high as .0022 on the voltage divider with good results but it all depends on the rest of the circuit. I like 500pf for the treble cap.
I don't like silver micas.
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I have tried 0.0022 on the CF when I was experimenting with a Dirty Shirley circuit. I didn't like it overall... I think that plus no cap across the voltage divider made it too dark. But I really liked the 0.0022 on the CF with a #34 type of circuit.
 
Well, I'm all ears for cap type recommendations based on the application 😁 So far, I've used ceramics for bright caps and Mallory for coupling caps. Some Wima caps in my Origin.
 
By experimenting you will find what you like personally. Tone is subjective.
 
believe it or not I actually don’t like WIMAs. He’s right, it’s too subjective.
 
Does anyone know where I could get good multi packs of various brands and values?
 
ledvedder said:
Does anyone know where I could get good multi packs of various brands and values?
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You’re dancing in the deep end now bud. I know famous modders and builders right now that can’t get parts they need to deliver amps and I’ve been working with a few manufacturers to work out substitutions so orders can stay maintained. You’ll just have to do what you can to find things.
 
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