Questions for the JCM800 emu builders...

[debutvm]

I really want to tackle a jcm800 emu pedal on my next build. I have been doing some reading and it seems that the emu is a bit on the bright side. If i build the pedal and want to take away some brightness what could be done? Also whats your all' s take/ review of the jcm800 build.\?

-Kyle

[Ronsonic]

Link please. I know how to tame a real one, but it'll be easier to describe when we're both looking at the same schematic.

Ron

[Xavier]

Put a 2n2 cap to ground at the output (you can add it directly from lug 3 to the back of the output pot) , that's a value to start with. You can try other values too.

[Rafa]

Hi:
Sorry but I dont which simulator youre talking about: Thunderchief ?
                                                                             LXH2 ?
                                                                             http://www.4thlevelmedia.com/JCM800Emulator-Parts.jpg ?
Does it have a tone control if so change the cap of the trebele
Rafa

[Ronsonic]

Put a 2n2 cap to ground at the output (you can add it directly from lug 3 to the back of the output pot) , that's a value to start with. You can try other values too.

That's crude and probably muddy. I'm thinking along the lines of removing a bright cap as we would in a real amp. Either / and / or the cap bypassing the volume pot or the one bypassing the 470K resistor.

With a schem I can give a part number and do this nicely.

Ron

[MetalGod]

I always prefer 47nF caps in the tonestack on my own amps - maybe give this a try with the pedal sim.

It's no surprise that the pedal turned out bright since that 'JMP' circuit IS bright - famously so.   I always like a 100pF cap between the plate and cathode of the first gain stage in these amps as it rolls off the extreme icepick treble and also stops the amp from squeeling.

I'd also change the 2.2nF cap from the 1st gain stage plate (drain) to a 22nF cap - MUCH beefier tone without any mud.

Lastly, the 4700pF cap on the gain pot is overkill - 100pF is more than enough and will give you more range of clean-into-overdrive tones.