marshall Jackhammer mod?

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marshall Jackhammer mod?

Postby teddybear » 30 Nov 2008, 19:39

anyone had the schematic for mod?
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Re: marshall Jackhammer mod?

Postby xmikes » 18 Aug 2009, 23:19

Here are few ideas how to modify this pedal:

1.to get brighter sound on Distortion mode replace C22 with lower value (original 2n2, new between 220pF and 1nF). Value around 680p or 560p gives you similar tonality as Overdrive mode.

2.If you like asymmetrical clipping add another diode in series with D5 (I have used Ge diode 1N60). Output level is now higher then in Overdrive mode so maybe replacing R5 (220K) with lower value can be good idea.

3.You can also add another diode in series to one of two LED diodes, or use LED diode with different color (green). This cause asymmetrical clipping in Overdrive mode.
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Re: marshall Jackhammer mod?

Postby roseblood11 » 18 Aug 2009, 23:40

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

You could try NE5532AP or OPA2134 instead of the TL072´s...

Immo
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Re: marshall Jackhammer mod?

Postby nooneknows » 22 Aug 2009, 10:00

The component net just after the clipping stage is quite similiar to a standard Marshall/Fender type amp tone stack, I think it's an interesting point to look at, for example the 1K R8 to ground controls the amount of mid. You can use Tone Stack Calculator app (I don't' have the link around but it's easy to find it with google) inserting the JH1 values to experiment.
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Re: marshall Jackhammer mod?

Postby roseblood11 » 22 Aug 2009, 20:49

Maybe the most important mod for that whole series of pedals is a true bypass...

It´s explained here for the ED-1 compressor, should work for the jackhammer as well:
http://forum.musikding.de/vb/showthread.php?t=25781

(esp. post No #18 and #19):
Image
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Re: marshall Jackhammer mod?

Postby fransvanhelvoort » 27 Sep 2015, 21:08

I have a JH unused on the shelf for about 20 years. Total useless for single coil. Terrible sounds with anoying high freq sizzle. Wanted to throw it away. Till I saw the Wampler Triple Wreck schematic. The triple wreck emulates the sound of a Mesa Boogie Dual Rectifier. I listened to the demo's on You Tube and the pedal sounds very good. Suprise, The schematic is allmost the same as the Jackhammer. I made a mixture of the two. The upper part is from the Wampler en the rest is the original Jackhammer. How it sounds?? Compleet another sound, very nice and very heavy. Very usable in both the od and dist mode. This is a quite drastic mod but it is worth the work. I used the original print and the numbers in the schematic are the same numbers as on the printboard.
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Re: marshall Jackhammer mod?

Postby licho » 08 Feb 2016, 10:15

teddybear wrote:anyone had the schematic for mod?

Hello, if you'd like to keep great OD mode unmodified but change the crappy Dist mode, here is the simple but great mod:
- remove D4 or D5 (leave one 1N4148 only)
- disconnect CON8 (it will unplug C27 and R30)
That's all. It will transform useless Dist mode into OD mode but with asymmetrical clipping that sounds amazing. Try it!
You can also modify C12 (1uF electrolytic cap) to 220nF foil cap (to the original guv'nor spec) to reduce bass slightly in both modes.

Best regards,
Piotr
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Re: marshall Jackhammer mod?

Postby Mister_T » 12 May 2016, 11:18

licho wrote:Hello, if you'd like to keep great OD mode unmodified but change the crappy Dist mode, here is the simple but great mod:
- remove D4 or D5 (leave one 1N4148 only)
- disconnect CON8 (it will unplug C27 and R30)
That's all. It will transform useless Dist mode into OD mode but with asymmetrical clipping that sounds amazing. Try it!
You can also modify C12 (1uF electrolytic cap) to 220nF foil cap (to the original guv'nor spec) to reduce bass slightly in both modes.

Best regards,
Piotr


Just done this simple Mod , Both the distortion and Overdrive are very similar very slight difference in tone , but much prefer this to the muddy old distortion which for me was useless.
I also did the c22 mod on a guvnor2 which made the pedal come to life,

Thanks for posting these simple Mods
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Re: marshall Jackhammer mod?

Postby marushio_rima » 24 Sep 2018, 23:38

xmikes wrote:Here are few ideas how to modify this pedal:

1.to get brighter sound on Distortion mode replace C22 with lower value (original 2n2, new between 220pF and 1nF). Value around 680p or 560p gives you similar tonality as Overdrive mode.

2.If you like asymmetrical clipping add another diode in series with D5 (I have used Ge diode 1N60). Output level is now higher then in Overdrive mode so maybe replacing R5 (220K) with lower value can be good idea.

3.You can also add another diode in series to one of two LED diodes, or use LED diode with different color (green). This cause asymmetrical clipping in Overdrive mode.

in the jackhammer replace the c22 (red red red ) to 220pf (221 ceramic) , is it right?
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