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Amplified Parts
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|-+  British Style
| |-+  JCM 800 2203, 2204, 2550, 2555
| | |-+  JCM 800 2204 - JMP 2204 QUESTION
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Author Topic: JCM 800 2204 - JMP 2204 QUESTION  (Read 7484 times)
hotguit
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« on: August 27, 2009, 04:03:16 PM »

Hi
I've noticed that in my 1985 JCM 800 2204 (horizzontal inputs) there are two 10K 1 W res. while in my 1978 JMP 2204 only one (the circuit is the same, one with pcb mounted pots, the other with chasis mounted pots) SEE PICTURE
Why? how does it affect the tone?
Is it a good idea remove it and put a jumper (on jcm 800?)
thank you
hot


* CERIATONE 2204 1.JPG (219.16 KB, 1348x890 - viewed 977 times.)
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cmoore
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« Reply #1 on: August 27, 2009, 07:38:54 PM »

Does one amp have a choke, and the other does not?
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hotguit
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« Reply #2 on: August 28, 2009, 08:58:23 AM »

both have choke.
Same circuit, different layout
hot
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DanLurie
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« Reply #3 on: September 15, 2009, 10:28:40 AM »

It's an extra decoupled stage in the high voltage line. It provides more filtering to the preamp.  I believe it's part of the original circuit. The filtering is a good thing in a higher gain amplifier. No need to jump it.

How do the two amps compare in sound??
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hotguit
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« Reply #4 on: October 15, 2009, 01:41:17 PM »

jmp has a warmer and creamier tone and starts overdriving at about 12 o clock (preamp pot)
jcm is harsher and les compressed; it starts overdriving at about 14 o clock
bye
hot
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Kitarist
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« Reply #5 on: October 18, 2009, 11:33:25 PM »

What kind of mod do you need to do to transform a JCM into a JMP?

Thanks!!!
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