Thank you, RG Keen ...

[Shea]

... for writing PCB Layout for Musical Effects.

It gave me the info I needed to make this:

[bob p]

Don't keep us in suspense forever -- tell us what it is!

[Mark Hammer]

Well, the diode pair beside one of the chips says its a distortion of some kind.

[Shea]

Yes, it is a distortion type thing. It's a mutation of the tube screamer circuit.

Instead of putting the diodes in the feedback loop of the first gain stage, I have one non-inverting gain stage followed by two inverting stages with gains of -1. The way I usually run it, there is one diode in the loop of the first inverting stage that clips one half of the waveform, and a diode in the loop of the second inverting stage that clips the other half. I do it this way because (a) I think the diode-in-the-feedback-circuit thing sounds better with inverting stages than it does in non-inverting stages, and (b) by having separate stages that each clip one half of the waveform, with a coupling cap between them, it gets a little duty-cycle modulation going on.

Also, the diode in the second clipping stage is connected to the wiper of a 100k pot, which substitutes for the feedback resistor. That makes a simple asymmetry control.

And, by using a pot with a SPDT switch on the back, I have it set up so that when the asymmetry control is turned all the way down, it closes a switch that brings in another diode in the first clipping stage, for perfectly symmetrical clipping a la Tube Screamer.

At the end is a two-band (treble and bass) active EQ.

[MattT]

But did you use the silver solder (the 'secret')?

What's it sound like?

[Shea]

But did you use the silver solder (the 'secret')?

What's it sound like?

2%, baby!

As for how it sounds, I don't mean to sound boastful, but I'm very pleased with how it turned out. The tone is much more open-sounding and wide-ranging than a typical Screamer-type pedal, and the texture of the distortion and the overall feel of playing through it (if you know what I mean) are a lot more like a cranked tube amp. I guess that's what they all say, isn't it? Others may disagree, but I designed it for myself to fix the things that I personally don't like about most dirt pedals, and it worked.

Shea

[cbarrow7625]

That sounds like a great idea! Wanna share the circuit? We'd all love to see it.

[David Schwab]

But did you use the silver solder (the 'secret')?

Eventually we will all have to use silver solder...

I'm holding out as long as I can so I don't have to get a new soldering iron!

[Mark Hammer]

2%, baby!

As for how it sounds, I don't mean to sound boastful, but I'm very pleased with how it turned out. The tone is much more open-sounding and wide-ranging than a typical Screamer-type pedal, and the texture of the distortion and the overall feel of playing through it (if you know what I mean) are a lot more like a cranked tube amp. I guess that's what they all say, isn't it? Others may disagree, but I designed it for myself to fix the things that I personally don't like about most dirt pedals, and it worked.

Shea

No shame in being proud of something that worked out as you planned it in your mind's eye my friend. Happened to me numerous times, and its a great feeling.

The basic TS circuit has to be one of THE most widely modded circuits out there. What's sort of ironic is that the number of people who have modded it, whether one-offs for personal use or to be marketed as a pedal, testifies at the same time to how much people like it, and how dissatisfied they are with the basic unit. Weird, huh?

[Shea]

That sounds like a great idea! Wanna share the circuit? We'd all love to see it.

Just finished this:

[Mark Hammer]

Oh hell, no wonder you like the sound of it, it's VERY methodical and attentive in almost every part of the circuit. It's like a banana split if it were a pedal, with every little pleasure-enhancing nuance a person might want. Kudos to you, my friend. Well done!!

You should post this over at the DIY Stompboxes forum, but before you do put the text information in the corner that identifies YOU, your rights to it, and a date and version number (not that you'd ever really want to improve/a;ter it).

Thanks for sharing. Again, nice work.

[Shea]

Oh hell, no wonder you like the sound of it, it's VERY methodical and attentive in almost every part of the circuit. It's like a banana split if it were a pedal, with every little pleasure-enhancing nuance a person might want. Kudos to you, my friend. Well done!!

You should post this over at the DIY Stompboxes forum, but before you do put the text information in the corner that identifies YOU, your rights to it, and a date and version number (not that you'd ever really want to improve/a;ter it).

Thanks for sharing. Again, nice work.

Thanks Mark!

How's this?

[Mark Hammer]

Perfect!

[Shea]

One unpleasant quirk - noisy bypassing

I tried it out at a band rehearsal yesterday, and the only thing about it I didn't like is that it makes a pretty loud noise when I switch it on or off.

I figure the two possible causes are (1) the 2-meg pulldown resistor at the input is too large, or (2) the Tiawanese 3PDT stompswitch that I'm using has noisy contact bounce.

I hope the problem is #2, because I sized that input resistor and the bias feed resistor on the 1st opamp stage right at the point where I didn't hear any high-end loss. So I'd rather not reduce that input pulldown resistor if I don't have to.

Also, I have other pedals with that switch that make noise when you stomp 'em. If the switch is the problem, I'd experiment with other methods, like some kind of JFET switching or maybe a millenium bypass using one of those little keyboard switches (assumming they're quieter).

Other than that switching noise, the pedal was a real pleasure to use.

Shea

[cbarrow7625]

Really nice! Thanks for the schematic. I'm going to have to try it out.