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PostPosted: Sun Jul 22, 2012 2:43 pm 

Joined: Fri Nov 18, 2011 9:59 am
Posts: 28

Can anyone tell me how I can modify the OD1 so it will become a bass overdrive, strickly to be used for a bass guitar?


PostPosted: Tue Jul 31, 2012 11:41 am 
There may be some magic mojo (I mean some circuit tricks particularly suited to bass) that I don't know about, but broadly speaking any difference between a guitar and bass overdrive probably comes down to low frequency response, since the bottom note on a standard 4 string bass in standard tuning is around 40Hz compared to 80Hz odd on a guitar.

Low frequency response on any pedal is dictated by the size of the coupling caps and by rule of thumb for bass you can just double the value of the inter-stage coupling caps. C1 0.022uF > 0.047uF,C2 1uF > 2.2uF,C7 1uF > 2.2uF,C9 10uF > 22uF.
The OD1 also has a variable low pass filter and you could drop the range of that too by an octave by doubling the caps. C5 & 6 0.22uF > 0.47uF. It might be worth using plastic film caps for C5 & 6 if you can get them to fit. Oh - and it is worth using a value as low as 2K for the tone control which normally ships as a 25K in order to be close to the original Tube Screamer (except that the Tube Screamer uses a special W law 20K pot in that position). A 2K gives a much more even control of tone.

I would point out that this is all rule-of-thumb, I haven't calculated the bass roll-off for any of the existing values and you will sometimes find that a coupling cap value used in a guitar oriented pedal actually allows more than enough low end for a bass.

Otherwise the diode clipping distortion used in this pedal will do exactly the same thing for bass as it does for guitar.

If you change all of those caps the pedal will still work with a guitar although its timbre will be a bit different.

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