JCM 800 Mod Demo

Modded for extra gain and low mids.
Fitler caps have also been changed using TADs.
The quiet bit is just guitar volume rolled back.
The pics are a sort of step by step of the changes.

Category:

Music

Tags:

• JCM
• 800
• Demo
• gain
• resonance
• depth
• metal
• Marshall
• tone

[gmuchiutti5150]

Great! Can you give me some details of the mod ? you didn't added an extra preamp tube or another gain stage, right ? thx, bye. (:

[PaoloJM]

@gmuchiutti5150 No, no extra gain stages. Dropped the 10k cathode res on V1b to 5k. Changed the 470k with the 470p across on the pot divider to just a 68k. Changed grid wires to shielded type. There's a resonance mod fitted also.

[and1424]

Hello! Great sounding amp! Wanted to know how many wires you shielded other than stock ones. Just the one to 68k grid resistor ??? Saludos!

[PaoloJM]

@and1424 hi. none of the wires were shielded in the original jcm800s. this is an '81 model. i've used shielded wire for the input to grid one as you suggested.

[luisgarciaalanis]

what is the mod to give it more gain?

[PaoloJM]

@luisgarciaalanis

There's a few, in different places through the preamp.

Adding small amounts at each stage is best IMO.

Do you want actual details?

[hirskdubbi]

too fizzy

[JayPshred]

Not enough gain try again

[MrSandydillon]

that sounds awesome very cool deep

[Guitarbque]

wow - beefy !!

[EuphorbusBTB]

nice it sound fuller, there's allways the cascading RR mod, between V1 and V2, like I did on my 73' JMP 50. The bees knees!

Marshall is working on powerscaling, mark my words, they are going to bring it out on some of their vintage stuff, soon...

[4711shaun2]

this sounds fantastic PaoloJM.. can you go into more detail re the mods here beyond what you've already given.. like the specific gain increases at various stages in the preamp ? i'm getting a '79 2204 shortly and will try some of these out with it.. thanks.. bye.