"The Crank" germanium accident

[lopsided]

Hey guys,

so I happened to build a germanium diodes Crank (http://hammer.ampage.org/files/The_Crank.gif ) by accident. Couple of months ago i ordered a bunch of 1N34a diodes. Shipping took a couple of weeks and somehow I forgot what I ordered and thought i ordered 1N914s. At that time I had no experience with either of them so I build some circuits with Ge instead of Si diodes.

One of them is Mark Hammer's Crank. I actually liked it a lot this way, and even though the sound was a little different then described by Mark (the dirt is different, I use it for kind of punky indie-rock sound), I put it into an enclosure and began using it live.
Now when I've found out about the mismatch, I would like to try the sound as it was intended by the author, but would love to keep the sound that it has now too.

My question is, can I switch both clipping stages with one DPDT switch? This way I wouldn't be able to completely disconnect the diodes but just one of their connection, the other would be always hanging to the circuit. I tried to ASCII draw it:

|--|<----| (Ge)
|           |---------o (Sw1a)
|-->|----|                              \
|                                            \   (SW1a)
|                                              o------ (to opamp output)
|
|--|<----| (Si)
|           |---------o  (Sw1a)
|-->|----|
|
|
(to inverting opamp input)



the other half of the DPDT would switch the second clipping stage. Will this work, or will the hanging diodes interfere in the sound?

Jakub

[Phorhas]

It should easily work. Many builders use this technique

[Joe Hart]

I don't believe the "hanging diodes" will do anything. They won't conduct at all. Hope this helps!
-Joe Hart

[Mark Hammer]

Thanks for the report, and pleased that you like it so much.

If you have enough of them (and I understand that "a bunch" might mean not enough to get the job done, after all other project commitments are considered), one thing you might ry is to simply substitute a series of Ge diodes for silicons.  So, for stage 1, install a pair of back to back Ge diodes, followed by another back to back pair, and use a switch to simply shunt one pair, so that you go from 4 diodes to 2.  The same thing applies (with more diodes, of course) for stage 2.

[digi2t]

I've also used the diodes switching scheme as well, but I also incorporated a trimmer to adjust for any volume differences. Mainly good for sym. /asym. applications, but Mark had a thread on that somewhere as well. Works very well. You can also set it up as a sort of boost.

[boogietone]

Should work just fine. If you are using a toggle switch, why not use two spdts and switch each set independently for more double mint fun?

[MikeH]

I've also used the diodes switching scheme as well, but I also incorporated a trimmer to adjust for any volume differences. Mainly good for sym. /asym. applications, but Mark had a thread on that somewhere as well. Works very well. You can also set it up as a sort of boost.

Yeah, be careful when switching between diodes- If you have your amp cranked up and switch from Ge to the other the sound will be LOUD.  And you might end up with that Back to the Future opening scene scenario.

[Mark Hammer]

+1

Ge diodes can have a forward voltage as low as 190mv in some instances, and silicon as high as 620mv.  The volume jump between those two ceilings can be substantial.

[arma61]

I've also used the diodes switching scheme as well, but I also incorporated a trimmer to adjust for any volume differences. Mainly good for sym. /asym. applications, but Mark had a thread on that somewhere as well. Works very well. You can also set it up as a sort of boost.

Yeah, be careful when switching between diodes- If you have your amp cranked up and switch from Ge to the other the sound will be LOUD.  And you might end up with that Back to the Future opening scene scenario.

+1

Ge diodes can have a forward voltage as low as 190mv in some instances, and silicon as high as 620mv.  The volume jump between those two ceilings can be substantial.

So didgi2t where/how is the trimmer installed ? got a TS with switching diodes and this big difference in volume!


btw love the analogy with BTTF movie   


thx

[boogietone]

Not sure how to implement the following. There are probably several ways. But, back to the independent switches, if you used two dpdt switches (toggle or stomp), you could use the second pole of each to switch a resistor in and out or the circuit to cut/raise the gain depending on whether you have Ge or Si in play. Use a trimmer to match by ear if needed.

[digi2t]

So didgi2t where/how is the trimmer installed ? got a TS with switching diodes and this big difference in volume!

I can't find Marks thread on that at the moment, but if you check here;
http://www.diystompboxes.com/smfforum/index.php?topic=91162.0
you'll see how I incorporated Mark's scheme into this pedal. Basically the timmer is just before the volume, to catch the volume boosts when switching diode sets. It's a DPDT footswitch, one side to switch diodes, the other side to switch the trimmer in or out.

Hope that helps,
Dino

[lopsided]

Thanks a lot Mark and all you guys for the help and advice!
When I have some time, I'll take the clipping section out, experiment with different arrangements, and probably do a small diodes daughterboard, as there is not much space left on the original vero.
I actually already have one spare stompswitch and pot in the enclosure (I tried switching the pots for additional gain switch, but it didn't work as expected so I disconnected it), so there is room to try different switching possibilities. I'll post then what I decide for.

Thanks again!

J.