Rat clone diodes switching

[Bananagab]

Hi!

I'm in the process of building a Rat clone with 6 different clipping stages. I just want to make sure I understood the way to wire a rotary switch for that purpose. Does that seem right to you?

[PRR]

> Does that seem right to you?

It didn't.... until I saw that you know how to use bus notation correctly.

Yes, follow the numbers through the fat lines to the skinny lines. The only oddity I see is #4 is missing somewhere.

[Bananagab]

Yeah I don't know yet what diodes I will put for #4 lol.

Thank you very much

[antonis]

Can't get particular bus notation but you can save one switch position by having clipping configuration of the higher voltage drop permanently connected..

[Steben]

Yeah I don't know yet what diodes I will put for #4 lol.

Thank you very much

Low voltage Zeners (<3V)
Trust me.
Connect them in back to back in series.

[antonis]

Low voltage Zeners (<3V)
Connect them in back to back in series.

Any particular benefit in comparison with an antiparallel pair of V_Z = V_ZZ + V_F..??

[Mark Hammer]

Call me a spoilsport, but I'm not all that convinced that selection of 6 different diode arrangements/types will yield anything of particular value in a Rat, no matter how effectively wired.

The gain factor is SO high, and the op-amp so completely saturated, that unless one is using a higher supply voltage, pretty much every diode arrangement will give you close to a square wave, if the gain is anywhere above half.  Besides, much of the clipping you hear in a Rat starts to come from the op-amp itself, and not the diodes.

Personally, I think a far more productive arrangement might be to have a simple choice between a pair of Si diodes and LEDs, and a pot to adjust the relative gain of the highs and lows.  That would likely get you far more sonic variation, especially at medium and lower gain settings.

[Bananagab]

Call me a spoilsport, but I'm not all that convinced that selection of 6 different diode arrangements/types will yield anything of particular value in a Rat, no matter how effectively wired.

The gain factor is SO high, and the op-amp so completely saturated, that unless one is using a higher supply voltage, pretty much every diode arrangement will give you close to a square wave, if the gain is anywhere above half.  Besides, much of the clipping you hear in a Rat starts to come from the op-amp itself, and not the diodes.

Personally, I think a far more productive arrangement might be to have a simple choice between a pair of Si diodes and LEDs, and a pot to adjust the relative gain of the highs and lows.  That would likely get you far more sonic variation, especially at medium and lower gain settings.

Hmmm interesting. Might do that. It's the first guitar schematic I attempt to mod. Where would you put a pot to adjust the gain?

[Steben]

Low voltage Zeners (<3V)
Connect them in back to back in series.

Any particular benefit in comparison with an antiparallel pair of V_Z = V_ZZ + V_F..??

Not THAT much, but less components and less room for misstakes.

I do agree with mr Hammer that an overload of diodes is unnecessary.
You could narrow to 2 or 3 positions and choose those after testing some combinations.
The minimum gain in a rat is 1 on the other hand, which means at low gain settings the opamp does not yet clip.

[Mark Hammer]

Call me a spoilsport, but I'm not all that convinced that selection of 6 different diode arrangements/types will yield anything of particular value in a Rat, no matter how effectively wired.

The gain factor is SO high, and the op-amp so completely saturated, that unless one is using a higher supply voltage, pretty much every diode arrangement will give you close to a square wave, if the gain is anywhere above half.  Besides, much of the clipping you hear in a Rat starts to come from the op-amp itself, and not the diodes.

Personally, I think a far more productive arrangement might be to have a simple choice between a pair of Si diodes and LEDs, and a pot to adjust the relative gain of the highs and lows.  That would likely get you far more sonic variation, especially at medium and lower gain settings.

Hmmm interesting. Might do that. It's the first guitar schematic I attempt to mod. Where would you put a pot to adjust the gain?

The Rat employs two ground legs.  The 560R/4u7 leg provides for a maximum gain of 180x, down to 60hz (note that the drawing shows a 100k Gain pot, and some will show 150k).  The 47R/2u2 leg provides for a maximum gain of over 2000x ( ) for content above 1.5khz.  Cut the connection between the two resistors and pin 2.  Replace the 560R resistor with 470R, and wire up a 100R pot (or trimmer) such that the wiper goes to pin 2 on the op-amp, one outside leg goes to the (now) 470R resistor and the other outside leg goes to the 47R resistor.  When rotated fully in one direction, the 100R is summed with the 470, and removed from the other leg, and you end up with essentially stock.  As you subtract resistance from the low-frequency leg and add it to the high-frequency leg.  Rotated fully the other way, you end up with a maximum gain of 680x for content above 980hz, and a max gain of 450x for content above 145hz.  In other words, the pot/trimmer shifts the balance of how much the mids and highs are amplified, vs how much the entire signal, including frequency content below the higher band, is amplified.  ALL of those various max gain possibilities will exceed the headroom of the op-amp and push whatever diodes you use into hard clipping.  And being able to restore the relative gain of lows vs mids and highs to stock allows for an easy comparison.

This is an idea that has been pursued for a number of years:  https://www.diystompboxes.com/smfforum/index.php?topic=63408.0

[Bananagab]

Call me a spoilsport, but I'm not all that convinced that selection of 6 different diode arrangements/types will yield anything of particular value in a Rat, no matter how effectively wired.

The gain factor is SO high, and the op-amp so completely saturated, that unless one is using a higher supply voltage, pretty much every diode arrangement will give you close to a square wave, if the gain is anywhere above half.  Besides, much of the clipping you hear in a Rat starts to come from the op-amp itself, and not the diodes.

Personally, I think a far more productive arrangement might be to have a simple choice between a pair of Si diodes and LEDs, and a pot to adjust the relative gain of the highs and lows.  That would likely get you far more sonic variation, especially at medium and lower gain settings.

Hmmm interesting. Might do that. It's the first guitar schematic I attempt to mod. Where would you put a pot to adjust the gain?

The Rat employs two ground legs.  The 560R/4u7 leg provides for a maximum gain of 180x, down to 60hz (note that the drawing shows a 100k Gain pot, and some will show 150k).  The 47R/2u2 leg provides for a maximum gain of over 2000x ( ) for content above 1.5khz.  Cut the connection between the two resistors and pin 2.  Replace the 560R resistor with 470R, and wire up a 100R pot (or trimmer) such that the wiper goes to pin 2 on the op-amp, one outside leg goes to the (now) 470R resistor and the other outside leg goes to the 47R resistor.  When rotated fully in one direction, the 100R is summed with the 470, and removed from the other leg, and you end up with essentially stock.  As you subtract resistance from the low-frequency leg and add it to the high-frequency leg.  Rotated fully the other way, you end up with a maximum gain of 680x for content above 980hz, and a max gain of 450x for content above 145hz.  In other words, the pot/trimmer shifts the balance of how much the mids and highs are amplified, vs how much the entire signal, including frequency content below the higher band, is amplified.  ALL of those various max gain possibilities will exceed the headroom of the op-amp and push whatever diodes you use into hard clipping.  And being able to restore the relative gain of lows vs mids and highs to stock allows for an easy comparison.

This is an idea that has been pursued for a number of years:  https://www.diystompboxes.com/smfforum/index.php?topic=63408.0

Something like that?

[Mark Hammer]

EXACTLY!

Will it fulfill your every distortion dream?  Probably not if you were pondering a 6-way switch.  But I think you'll find plenty to appreciate.  Best of all, it will be very easy to transform it back into a stock Rat without much fuss.

[Ben N]

Why not leave the LEDs connected all the time?

[antonis]

Why not leave the LEDs connected all the time?

Only with a ON-OFF-ON switch to have the option of clean (in the mean of diode unclipped) output too..
If not, you're right Ben..
(but SPST vs SPDT cost difference is chickenshit..)