Diode selector on overdrive

quaternotetriplet · Post by **quaternotetriplet** » 01 Jan 2009, 09:31

anyone who knows how to do this mod??
would appreciate pictures. thanks

TubeDude22 · Post by **TubeDude22** » 01 Jan 2009, 15:10

It's basically a rotary switch to select different combinations of clipping diodes & LEDs. This is what Ibanez did on the TS9DX Tubescreamer.

puppiesonacid · Post by **puppiesonacid** » 01 Jan 2009, 15:27

quaternotetriplet wrote:anyone who knows how to do this mod??
would appreciate pictures. thanks

something like this

Post by **modman** » 01 Jan 2009, 20:54

quaternotetriplet wrote:would appreciate pictures. thanks

assymetrical clipping diodes in TS like circuit

symmetrical clipping diodes in TS-like circuit

no clipping diodes in TS-like circuit

quaternotetriplet · Post by **quaternotetriplet** » 02 Jan 2009, 00:20

thanks. How about germanium to schottky diode selector??

Dirk_Hendrik · Post by **Dirk_Hendrik** » 02 Jan 2009, 21:49

shottky... doesn't that mean..." no signal left"?

IggY · Post by **IggY** » 03 Jan 2009, 07:41

Dirk_Hendrik wrote:shottky... doesn't that mean..." no signal left"?

another saying goes like this:

modman wrote:
Mr. G. wrote:In a TS style clipping section, what would be the difference between using 2 or 4 diodes/LEDs? Would one produce more gain than the other? Is there much, if any, difference in the overall tone/feel?
They will not bring the gain down, but more diodes equals less output.
Overall tone/feel is very subjective, maybe what some would call 'more compressed' is for others 'very tight'

You should trust your own ears only. Experiment with sockets or breadboard!

https://www.freestompboxes.org/viewtopic ... 071#p43071

whassup?

RnFR · Post by **RnFR** » 03 Jan 2009, 08:04

puppiesonacid wrote:
quaternotetriplet wrote:anyone who knows how to do this mod??
would appreciate pictures. thanks
something like this

not sure why it's not posting puppies' diagram, but-

i think the option with the most choices for switching would to have led's hardwired into the pedal, then do like the switch above, but make sure that it is an ON/OFF/ON switch. then you can put 2 germanium diodes on one side and 2 silicon on the other. not sure if the assymetrical option above will work because you have to have a lower forward voltage that than the the LED's. probably would still work w/ ge's, maybe not with silicon.

JiM · Post by **JiM** » 03 Jan 2009, 15:53

IggY wrote:
modman wrote:They will not bring the gain down, but more diodes equals less output.

whassup?

This is true in a tubescreamer-like clipping stage, where the diodes are in the feedback loop of an opamp (logarithmic amplifier).
On the contrary, when diodes clippers to ground are used on the signal path, more series diodes increase output volume as the threshold sums up.

Therefore a Schottky diode, with a very low threshold, will eat almost all signal in a Dist+ but provide subtle clipping in a TS. And it's about right for a passive overdrive inside your guitar

By the way, there is no need for a DPDT for this mod : you can switch only one end of the diode pairs, and leave the other connected all the time. But a DPDT can be easier to solder.

RnFR · Post by **RnFR** » 03 Jan 2009, 16:48

obviously there are a lot of options here- maybe the op can specify what kind of overdrive etc.

Fuzzer · Post by **Fuzzer** » 03 Jan 2009, 17:57

No, I'm sorry Jim, It might be two different arrangements, a Dist+ clipping stage, or a tubescreamer clipping stage, but the same applies, as you put more diodes (more threshold voltage) there is more volume, and less distortion.

This is wht I wrote on the thread Iggy referenced;

The important thing is the forward voltage of the diodes, and how they sum up; the more voltage threshold there is, the less distortion the clipping scheme will give, because the signal has more space to go without getting clipped. That also affects the volume you get out of the circuit, because if you clip at too low a level, then you will have low output.

One thing to keep in mind is the conduction characteristic curve of the diode may have an influence in sound, germanium diodes turn on differently than silicon diodes in terms of current against voltage, so, in the same circuit, if you have a symmetric silicon diode pair with a threshold of 0.6 [V], it might not sound the same as a symetric arrangement of four germanium diodes with the same voltage threshold.

quaternotetriplet · Post by **quaternotetriplet** » 05 Jan 2009, 00:56

Is this right?? How will i put this one on my zendrive clone??

Fuzzer · Post by **Fuzzer** » 05 Jan 2009, 01:48

The Zendrive;
In the first Operational Amplifier stage, you've got a network between inverting input and output.
In parallel you have;
A potentiometer (with a resistor between two of its terminals),
A small capacitor
---------
A series of two diodes and a MOSFET
A series of a diode and a MOSFET

These last two series you have to take away, an then connect the arrangement you are showing between OpAmp's output and inverting input instead of OUT and GND in the drawing.