DIYstompboxes.com

DIY Stompboxes => Building your own stompbox => Topic started by: jplebre on May 14, 2011, 02:47:36 PM

Title: switching diodes - dpdt switch before or after diodes?
Post by: jplebre on May 14, 2011, 02:47:36 PM
Hey all

was trying to do a mod to the next pedal - add a choice of diodes.
Was thinking of the ovbious - to add a dpdt switch and switch between the original and a socket that I can change at any time to test diodes, etc.

Now, something began to bugger me. The diodes are reversed (in parallel) so they affect both "sides" of the waveform.
On the example of something like Electra or Dist+, if I only use the pins for input/output, both sets of diodes would be connected to the earth. The diode that allows current to pass from the earth, even the one in the bypassed switch, wouldn't that still affect the signal? The opamp still taps the 0v so...

Guess question is... can parallel diodes (still in contact with the earth) have an effect on the sound even though they are not in the signal path?
Would it be more sensible to apply the switch before or after the diodes? (between signal and diodes or between diodes and ground)?

Thanks
J
Title: Re: switching diodes - dpdt switch before or after diodes?
Post by: blooze_man on May 14, 2011, 03:54:43 PM
I'm 99% sure it doesn't matter.
Title: Re: switching diodes - dpdt switch before or after diodes?
Post by: jplebre on May 14, 2011, 05:23:34 PM
someone else supporting a success rate higher than (say) 85% and I'll try to implement this :)
Title: Re: switching diodes - dpdt switch before or after diodes?
Post by: LucifersTrip on May 14, 2011, 05:37:48 PM
can you post a schematic so we can be perfectly clear what you're doing?

this?
(http://fuzzcentral.ssguitar.com/schematics/electradistortion.gif)

If so, I switch between different sets of parallel reversed diodes all the
time and I use a SPST switch. You only need to disconnect one of either end of the pair ...and it's no longer in the circuit.
Twist the diodes together so you're only dealing with 2 leads total.
Title: Re: switching diodes - dpdt switch before or after diodes?
Post by: jplebre on May 14, 2011, 05:52:34 PM
It's one of the pedals I want to include it in.

And also on the MXR Dist+ (tonepad)
Title: Re: switching diodes - dpdt switch before or after diodes?
Post by: blooze_man on May 14, 2011, 10:49:39 PM
An spst at either end of the diodes will work.
Title: Re: switching diodes - dpdt switch before or after diodes?
Post by: jplebre on May 15, 2011, 07:29:58 AM
Cool ty guys!
I am thinking of including the cap as well on the bundle so I can try the diff between different caps