Marshall Jackhammer JH1 mod

[tjburton]

Has anyone modded a JH1 Jackhammer?
I'm looking to add some presence to the circuit. I've heard that the JH1 is really an upgraded Marshall Shredmaster, so I've been looking at mods for the Shredmaster. On the shredmaster I've read on another post that there is a 1nf cap on the last opamp that could be changed to something like 220pf.

On the Jackhammer, this section of the circuit apperas to have several more parts than the shredmaster has. Can anyone give me suggestions on what caps (and suggested values) to change on the JH1 to give some more "air" to this circuit?

The JH1 schem is on Arron's site:
http://diystompboxes.com/pedals/schems/JH-1.pdf

Thanks for any info - Tim Burton

[tjburton]

Well I've made a few changes.. I halfed the values of C15, C17 and C24.

What I got was a little extra noise - not much extra guitar content in the highs. Could the highs be filtered even earlier in the circuit? Anyone have any suggestions?

Thanks,
Tim

[Ansil]

Well I've made a few changes.. I halfed the values of C15, C17 and C24.

What I got was a little extra noise - not much extra guitar content in the highs. Could the highs be filtered even earlier in the circuit? Anyone have any suggestions?

Thanks,
Tim

i played a couple of these while out at the music stores.   sorry i couldn't think of what to do to make this sound better, i have found no usefull tones with these at all.

[tjburton]

I would agree that the "distortion" mode of the pedal is useless - muffled and no upper harmonic content, pretty cheesy.

I do think there is hope for the OD side of the circuit. The contour and frequency controls work well, the clipping is very nice. My complaint is there is no upper harmonic content left in the effected signal - its all filtered out somewhere. It just has a sterilness to it. I think this could be a very good Medium Gain OD if I could find how to let more of the upper harmonic content through the circuit.

[b_rogers]

i would love to get the muffle out of my jh-1...the od side is almost good. dist side is mud. built like a tank though! tb too...

[b_rogers]

what about incap and outcap value? dont the values seem high?

[Ansil]

personally i dont' like to give up on any pedal but i must say that this is one that i would not mod i woudl put it up on ebay there is too much crap muffling the sound, you can mod it, but you will need to take out and or change half of the components.  its a fuster cluck

[tjburton]

ooops

[tjburton]

I haven't modded any pedals for a few months, so I'm up to the challenge right now. Its not going to ebay quite yet...

I have had a decent breakthrough though , I replaced the 1uf with a film cap and got some more clearity out of the OD side of the pedal. Combined with the other caps that I lowerd the values above I'm probably letting a bit "too much" through. I'm going to experiment with bringing some of those values back up as well as replacing other caps that are in the circuit wth film caps.  

Of course this helps the Distortion side to some extent, but it is still pure monkey farts (mudd). From the Schem I have it looks like instead of switching between two different sets of clipping diodes what they did was just "add" another set of clipping diodes and cap/resistor values to the OD setting - no wonder the thing sounds like mudd.

I'm thinking about making the the distortion side actually an asymetrical clipping (add an extra LED). And removing the "extra" res/cap that gets added to the circuit when the Distortion mode is on.

I do think it is worthy of putting it on my pedalboard to try to gig with now on the OD side, it was not before - I'll continue to dabble though. If anyone has any other ideas - please share.

Tim

[Kilby]

Personally I would suggest trying out the BluesBrealer 2 from marshall for an OD sound, I much preferred it to a TS.

Rob...

Hey I thought you would be promoting Big Fish rather than playing with pedals (sorry you must have heard that 10^6 times by now)

[tjburton]

Too busy working on Willy Wonka - promotion is not my gig .

just kidding...  - I can count on getting a few of those coments a week - back when I worked with some high-end graphics companies in the early 90's people would actually ask if I AM Tim Burton. I had to take advantage of the situation a few times.