Diodes Switching

All frequent questions on switching: true or not true bypass, transistor-based or mechanical.
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ezugaru
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Post by ezugaru »

Hi guys I'm working on building my first overdrive, however I've read about symmetrical and asymmetrical clippping, so I would love to know how to wire my diodes using a toggel swtich to select between symm/asymm clipping, I wan to keep one of the 1N34A on the board and where should be placed the another one, just solder the wires to the toggle switch where I can select between the 1N34A for symmetrical or the 1N914 for asymmetrical, I think I should go 2PDT , but I'm not clear on how to qwire them, thanks for your kindness :) :D
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Groovenut
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Post by Groovenut »

Something like this would work. In one position the switch shorts the diode on its terminals, in the other the signal passes through the diode.
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ezugaru
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Post by ezugaru »

SDo, I should use an on/on spst? just got confused seeing 2 lugs on the toggle switch :shock:
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Post by Groovenut »

You can use an on-off spst, or one side of a spdt, or one side, one column of a dpdt. as long as the diodes are wired as shown it should work. Sorry about the label on the pic. SPDT is an error on my part :slap: , but as long as the diode is wired between the common lug and one of the throw lugs it should work fine.

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ezugaru
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Post by ezugaru »

Thank You my friend, but I have one more question ... For example, lets think the upper position is on (1N34) and middle position is off (1N914) .. if I turn the switch on then it will be a symmetrical clippping setup, but, if I turn it off to run the asymmereical , won't the signal go troguth the 1N914 and then troguth the 1N34A???
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Post by Groovenut »

ezugaru wrote:Thank You my friend, but I have one more question ... For example, lets think the upper position is on (1N34) and middle position is off (1N914) .. if I turn the switch on then it will be a symmetrical clippping setup, but, if I turn it off to run the asymmereical , won't the signal go troguth the 1N914 and then troguth the 1N34A???
If we think of "on" as the switch connecting the switch contacts, then the signal is routed around the 1N914 leaving only the 1N34As in the signal path. This would give symmetrical clipping. If the the "off" position breaks the switch contacts the signal then flows through the 1N34A on the left as well as the 1N34A and the 1N914 on the right giving asymmetrical clipping.

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Post by ezugaru »

Oh! I got it now, but then the signal won't be double theated for going into 2 diodes in series? I mean the asymmetrical clipping won't sound diffenrent as going 1N34A -> 1N914 as 1N34A -> 1N34A -> 1N914 ?
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Post by Groovenut »

ezugaru wrote:Oh! I got it now, but then the signal won't be double theated for going into 2 diodes in series? I mean the asymmetrical clipping won't sound diffenrent as going 1N34A -> 1N914 as 1N34A -> 1N34A -> 1N914 ?

Sometimes pictures are better. In the top example of the circuit, the switch is open giving a 1N34 in anti-parallel with a 1N34 and 1N914 in series. This yields asymmetric clipping as you can see in the scope readout (one peak is almost 1.5v the other is a little more than .75v). In the bottom example the switch is closed, shunting the 1N914 giving two 1N34s in anti-parallel yielding symmetric clipping as you can see in the scope readout ( both peaks are equal at just a little more than .75v)
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Post by Groovenut »

I re-read your first post and it seems I may have misunderstood how you wanted your diodes aligned :slap: . If you want to substitute a 1N914 for one of the 1N34a the you can use a SPDT and connect the common to ground with a diode to each other lug. Let me know if this is closer....
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Post by ezugaru »

Hi my friend! tha last one wasexactly what I as looking for :D , I want to just switch betwwen 2 different diodes to give symmetrica or asymmetrical clipping to the overdrive. But I'm thankful for your previous help, I've learn a things :D
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Post by skylark44 »

Not to "thread jack", but could I ude this same mod for a passive "overdrive"...in a guitar (replacing the tone cap & control)? :mrgreen:

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Post by Groovenut »

skylark44 wrote:Not to "thread jack", but could I ude this same mod for a passive "overdrive"...in a guitar (replacing the tone cap & control)? :mrgreen:
You could, but the clipping is limited to the diode forward voltage. You would probably have to use Schottky or Germanium to get any clipping at all because the guitar pickup voltage is so very small. Typically less than 1Vpp.

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Post by skylark44 »

I've used BAT46 Schottkey diodes, so what Germaniums would I use? (IN34s? :scratch: )...and what would the difference in tone be? :hmmm: . :mrgreen:

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Post by ezugaru »

Hi!!! You know? I becam with a wild idea about the switching ... my plan is to have Germaniun Sym/Asym clipping and Germaniun/LED sym/asym clipping ... but I have some doubts .... i did a schema, I've planning using SPDT on/off/on switches, but I dont know i going in the off position while using the overdrive will damage the unit. Thios is the schema, do You have any suggestion? of course to use germaniun/germanium or germanium/led the other should be in the of position :s

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Post by ezugaru »

Sorry for the double reply ... but this just came to my head ... separated sym/asym germanium and sym/asy led clipping would be awesome.... I made this schematic, Please help me to check if it is correct, the last 2 switches are 3PDT on/on mini toggles.

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Post by ezugaru »

I guess I just got excited at the idea and didnt realize the 3PDT are too much and DPDT would be enough???
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