Onboard passive overdrive

Pickups, wiring schemes, switch techniques and onboard active electronics for guitars and basses
Post Reply
User avatar
JiM
Diode Debunker
Information
Posts: 967
Joined: 11 Mar 2008, 22:56
Completed builds: Completed builds :
Proco Rat
MXR MicroAmp in a volume pedal
TubeDriver (w/ NoS russian tube and big muff tone contol) + Phase 45 (w/ univibe cap ratio)
Dallas Rangemaster (w/ noisy OC75, negative ground)
SubCaster tube booster (w/ NoS russian tube, PtP)
Hot Harmonics
Music From Outer Space SubCommander in progress
Crackle Not OK
Simple bass blender in a 1590A
Bazz Fuss with a photo-darlington
Location: France
Has thanked: 70 times
Been thanked: 66 times
Contact:

Post by JiM »

Hi,
Did you ever heard about the Black Ice overdrive ? It's a StewMac product, claimed to add a bluesy crunch to any passive guitar, by replacing the tone cap by a small black cube-shaped device.
This thing is known to be a simple diode clipper to ground, using low-threshold Schottky diodes for un-amplified signal.
http://www.projectguitar.com/tut/blackice.htm
http://archive.ampage.org/threads/2/gtg ... Ice-1.html

I tried the Schottky clipper on my Epiphone SG, which has quite hot pickups. It seemed a bit harsh to my ears, losing a lot of volume. I went for assymetrical clipping with one Schottky and one silicon 1N4148, and i like it better. It's not really great sounding, but adds versatility. For example you can change the sound of another overdrive, it's a bit more dark and compressed.

The trick i've found, is that you don't need to loose your tone control when using this. I wired the diodes to ground and to the open lug of the 500k tone control, the wiper to the signal line, and the other lug to the tone cap. It's like a cap-to-diodes blend control. I've got normal tone operation from 0 to 7 (removing highs towards 0), and overdrive coming gradually from 7 to 10.

It was even a solder-less operation, as my Epi has the right tone wiring, i just pushed the leads of the diodes into the pot lugs fixations ! :roll:

Here are some waveforms (screenshots of Audacity, amplitudes not matched), showing assymetrical clipping.
Attachments
schottky.png
schottky.png (7.01 KiB) Viewed 1326 times
I only give negative feedback.

User avatar
NickS
Solder Soldier
Information
Posts: 170
Joined: 17 Jul 2007, 07:32
Location: Hampshire, UK
Has thanked: 8 times
Been thanked: 4 times

Post by NickS »

JiM wrote:The trick i've found, is that you don't need to loose your tone control when using this. I wired the diodes to ground and to the open lug of the 500k tone control, the wiper to the signal line, and the other lug to the tone cap. It's like a cap-to-diodes blend control. I've got normal tone operation from 0 to 7 (removing highs towards 0), and overdrive coming gradually from 7 to 10.
Clever!

User avatar
JiM
Diode Debunker
Information
Posts: 967
Joined: 11 Mar 2008, 22:56
Completed builds: Completed builds :
Proco Rat
MXR MicroAmp in a volume pedal
TubeDriver (w/ NoS russian tube and big muff tone contol) + Phase 45 (w/ univibe cap ratio)
Dallas Rangemaster (w/ noisy OC75, negative ground)
SubCaster tube booster (w/ NoS russian tube, PtP)
Hot Harmonics
Music From Outer Space SubCommander in progress
Crackle Not OK
Simple bass blender in a 1590A
Bazz Fuss with a photo-darlington
Location: France
Has thanked: 70 times
Been thanked: 66 times
Contact:

Post by JiM »

Thank you ! But it's mainly lazyness ... :oops: I didn't want to mess with unsoldering in my guitar just to try this, swap several diodes combinations, and maybe get stock wiring back. So i hooked the diodes on the available pot lug and ground, eventually turned the tone pot during first tests ... "hey, it's cool, let's keep it !"

I equipped the bridge PU only, for use on neck PU one can select both PU and cut the volume of the bridge PU.
It's so simple, anyone should give it a try :thumbsup
I only give negative feedback.

Post Reply