I was hoping someone could enlighten me a bit about the JCM 800 #34 modification by Frank Levi.
I know it uses 6550 tubes and a beefed up output transformer (right?)
It also does some other things in the preamp section if I am understanding correctly.
Another thing I am wondering if there is a difference in the 2203 and 2203a models or if 2203 is just a shorthand people use for the 2203a
What are some of the things to look out for when doing a JCM project? Does anyone have the kind of tips that only come from experience?
Thanks in advance for anyone looking at this, would buy you a beer if I could and talk about this
Also yes I have been researching this on Google and will probably continue to do so but sometimes it helps hearing it from a person who knows
JCM 800 with a SIR 34 mod... what is it?
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Re: JCM 800 with a SIR 34 mod... what is it?
have never heard of a 2203a. Levi added a .1u bypass cap over the 10k cathode resistor. and a .47u over the 1k probably as well as a 150k from gain pot viper to ground if memory serveshermannbjorgvin wrote: ↑Mon Aug 03, 2020 9:55 am...6550 tubes and a beefed up output transformer ([NO!])
It also does some other things in the preamp section if I am understanding correctly.
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Re: JCM 800 with a SIR 34 mod... what is it?
Thanks Roe for pointing me in the right pathRoe wrote: ↑Mon Aug 03, 2020 1:02 pmhave never heard of a 2203a. Levi added a .1u bypass cap over the 10k cathode resistor. and a .47u over the 1k probably as well as a 150k from gain pot viper to ground if memory serveshermannbjorgvin wrote: ↑Mon Aug 03, 2020 9:55 am...6550 tubes and a beefed up output transformer ([NO!])
It also does some other things in the preamp section if I am understanding correctly.
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Re: JCM 800 with a SIR 34 mod... what is it?
I think he also replaced the 470pF cap over the 470K resistor (Before the gain pot) with a 0.0022uF cap. If you google #34 schematic you should find a few sources with the actual schematic. I think there's even one posted by Santiago who designed the AFD100 amp.