Marshall JH-1 "Jackhammer" tweaks ...

[MartyMart]

A friend of mine has been gigging with one of these and was finding it to be
too "muddy" and with no top end clarity, schem is here :

http://diystompboxes.com/pedals/schems/JH-1.pdf

Mods :
All the 220n inter-stage caps reduced to 100n ( X3 )
1uf electro from IC1-B to a 470n poly cap
68n off IC2-A ( C6 ) to a 15n
One of the clipping LED's changed to another 1N4148

It's now much clearer and less muddy ( A/B with another unmodded one )
The network between IC3A and IC2B has me a little stumped, but looks like
feedback loop gain and roll off, so could offer some additional improvements.

If anyone has any more thoughts let me know ?

Enjoy,

Marty.

[bancika]

I don't like my JH either. Dist mode is total shit, tried it with several guitars and amp and nothing but mud even with bass set to 0. Ovedrive is OK, but not for solos cause it totally lacks sustain. I'm gonna sell it 

[b_rogers]

i have a jackhammer also..it isnt a stellar pedal but the tone control section is great and it really adds a nice "thump" to a wimpy amp. the shortcomings of course being the mud.

i have been waiting for someone to come up with some tweaks for this one for a long time. i think the pedal has some real potential.


i will try the mods tonight and see how it goes

[MartyMart]

Good luck with trying the mod, the caps are all listed on the schemo and the PCB.
Here's a "working" sound now that it's done :

Through a clean or just breaking up valve amp ...
Mode: OD or Dist
Volume: 12 o'clock
Gain: 12 o'clock to 2 o'clock
Bass: 9 o'clock
Treble: 4 o'clock
Contour: hard right ( 5.30 ! )
Freq:  about 8/9 o'clock

This gives me very much a TS-9 tone at medium gain, small tweaks of the "Freq" part of
the dual concentric knob make a HUGE difference in tone.
I don't like either mode with the gain "maxed out" .... just sounds like poo !

MM

[b_rogers]

i tried the tweaks last night and it sounded quite a bit better, but lost the thump that i like about the pedal.

i am gonna try doing each swap one at a time tonight and see if i can retain the thump and still clear up some of the mud. maybe adding some clean signal to the last stage?

im pretty impressed at how they crammed all of that circuitry in such a small package.

i do think this pedal has the potential to soud great. i currently use the highway89 like a gritty treble booster in front and get some pretty convincing hotrod marshall tone out of it.

[MartyMart]

I can get the "thump" back by turning up the bass pot to 3 o'clock and adjusting the
contour/freq a bit.
The "thump" and "mud" was what I intended to remove though ! 

MM