Trotsky drive question

[balno]

This is my second Trotsky overdrive, based on a design found here :



I'm really happy with this effect, it sounds great to my ear and I'm using this on stage.

Anyway, I'm thinking of an improvement. On this pedal, I get massive overdrive  even at the very beginning of VR1 pot. I'm planning to mod this in order to obtain more subtle variations and achieve a  lighter overdrive. I wish I could use the effect from an almost clean boost to the actual drive.

When seeing the schematic, I understand that VR1 and R1 are serial resistors with a range from 3.3K to 53.3K. VR2 is a classic volume pot as far as I can see.

So we've included a resistor from 3.3K to 53.3K connecting the transistor collector to +9v.

My knowledges in electronics are very basic and I wonder what will happen if I decrease R1 value. Let's suppose I try 2.2K or less, does this can damage the transistor ?

On a second thought, I guess I could try other diodes, but these ones sound cool and I don't feel like changing them.

Thanks in advance, I'm in real doubt.
 

[nocentelli]

The transistor itself is clipped by larger signals and the diodes square off the peaks of the already-overdriven transistor output.

Reducing the gain of the transistor by reducing R1 (to 2k2) or R2 (to 1M?) or increasing R3 (1k/2k2) will reduce the dirt, but you can also dial down the influence of those clippers in several ways, e.g. 10/20k linear pot from between clippers and ground, using LEDs or other diode devices with a higher Vf, or my preference would be using two antiparallel clipper pairs in series, which will sound similar but will need bigger peaks to clip and seemingly increase the "headroom".

If you are wanting to just mod that layout and keep it simple, R1/2/3 mods are easy but will alter the bias on the transistor, which may or may not be desirable. If you want to tinker a little, you could probably replace R3 with a 1/2k pot, wired as per fuzzface for the gain and leave R2+3 fixed at what sounds good and double the clippers to give some less dirty sounds.

[balno]

Thanks a lot for all this useful tips ! A giant step for my knowledge

I will breadboard all this this weekend and keep you posted.

Thanks again.

[balno]

You were right !...

I proceed a lot of tests and finally ended with 2 circuits :

Circuit A is a Trotsky without clipping. I fixed resistor connected to (+) at 3.3K, wich is the lower setting in the "Classic Trotsky". This provides and almost clean boost with only one volume pot.

I connect the boost in circuit B : another Trotsky with a switch selecting between two clipping modes : 1N34A (lot of dirt, but kinda muddy) or yellow leds (less dirt).

The whole stuff can go from slightly saturated boost to a nice Fuzz.

I'm going to try out two antiparallel clipper pairs in series, as soon as I figured out how it works.

I plan to mount evrerything in a 1590BB box with a pre/post switch to use boost and overdrive in any order.

Thanks.

[nocentelli]

balno wrote

I'm going to try out two antiparallel clipper pairs in series, as soon as I figured out how it works.

Here's the dual clipper pairs on the left hand side along with some other arrangements

[balno]

Awesome ! Thanks a lot

All the clipping methods in one schematic, what else ?

In a way, it reminds me of my Danelectro Cool Cat Transparent Overdrive V2. I don't use it anymore but it has a nice feature with a dip-switch inside allowing to select Blue Leds, Red leds and FET clipping or both of them.

I've ordered BAT41 just to see. This gives me a bunch of possibilities : 1N34A, 1N914, BAT41 and all sorts of leds.

So, back to tests for the best !

 

[balno]

This is what I ended up with. Can't wait to put that in an enclosure and rock it

[balno]

After a bunch of tests, I ended up with a new approach :

2 Trotsky drives in the same enclosure :

- the first acts more or less like a boost. It has no clipping stage but produces a kinda drive on higher settings (I replace the 50k linear pot by a 50k log for more control at the beginning of the course). This one has no volume pot.

- the second is based on the classic Trotsky with a switch for two 1N34a or two 1N914.

Last problem I have to solve : I wanna be able to switch the order of the two Trotskys.

For instance : "boost" the classic overdrive when soloing or provide a very high signal to the classic one, wich leads everything to a pretty nice fuzz with a lot of sustain. By using all the combinations, I can get almost everything between a barely inaudible really smooth drive and fuzz.

I found this schematic on the web :



Which is a bit confusing to me. The use of the true bypass footswitches is not what I'm used to (I always use the "guitar FX layout" offboard wiring which I find great). I can't figure out where to put the LEDs for instance though I draw some lines paper and the idea seems good.

Did someone used this kind of wiring and effect order switching settings ?

[balno]

Sorry guys, forget all about this, found all answer here

http://guitar-fx-layouts.42897.x6.nabble.com/Dual-Effects-One-enclosure-with-order-switching-td4994.html;cid=1500754635609-768