Tonepad tubescreamer, bypassed signal squeals

[JebemMajke]

Hello guys

I;ve built tonepad's TS 808, and the sound is huge. Fantastic, ofc this is not my first build, but it is the first one with this kind of issue.

Caps are wima, resistors are mostly 1% tolerance, but there are some 5% as well.

JRC4558, for no god damned reason but to stick to the original idea.

3pdt, AMZ truebypass way of wiring.

If i turn the drive pot all the way up, when bypassed there is a squeal ... an oscillation.

Do you have any idea how to fix this?

And inside of the box is somewhere between rats nest and clear

[bloxstompboxes]

Did you remember to put in a jumper in that 3rd diode space or are you using it? Had a similar situation myself but I can't remember at what point it squealed.

[JebemMajke]

Actually i am using only one diode slot, for on,off,on switch.

I'll try jumping those 2 slots and see what happens.

Thnx

But I am not sure if that is the problem. Because, it is truebypass, how something like that could cause a squealing problem?

Any other advice?

[bloxstompboxes]

I'd say that's definitely it then. I left one out, now that I think about it, because I was gonna add a switch to go between asymmectrical and symmetrical switching. I was rocking it before boxing it and had a horrible squeal. I can't view the PDF here at work, but if you are leaving out the the one on the far left, that should be the cause. Don't have the time, or the PDF, at the moment to go into the reason for the squeal while it's bypassed. I get to stay today to work on backlog while everyone else goes home early.

[JebemMajke]

I've just placed jumpers on those 2 slots, so I'll test it in 30 minutes, after my work is done

Thnx

[bloxstompboxes]

Wait!!! Sorry just saw that you said you were only using one diode. Don't jumper both of the slots!!!! Jumpering the two diodes in series will create a short that will force the current through there instead of the rest of the drive circuit. Someone else will have to chime in as I can't see the damn schem here.

Edit: In order to clip properly, you have to have at lease 2 diodes in parellel and in opposite polarities. So to get rid of the squeal, use one diode in the 2 diode series path and then jumper the other one. Then put one in the single diode spot. Should be the two rightmost spaces i believe. That way you'll have symetrical clipping. The 2 in series and one in parallel with them is assymetrical. If you're just testing, you can do this first and then set up the switch later.

[JebemMajke]

tonepad's pdf
http://www.tonepad.com/getFileInfo.asp?id=81

Well, that idea of using 2 diodes for me is not usable ...

You see i have on/off/on switch

With 2 leds, off, 4 germs

I don't need the usual, asim,sim

So, either I make my own pcb in Eagle and do the project all over again, with one diode place, or you please give me some sort of advice on how to fix this.

[bloxstompboxes]

I can visit tonepad and see other pdfs but, for some reason, the TS808 one won't come up here. That link is for the distorion plus, BTW.

With 2 leds and or 4 germs, you'll still have symmetrical clipping. But if you want to test it before boxing it up, you'll either have to temporarily wire the switch and those diodes now or temporairly solder in two of the diodes and the jumper. You gotta have one or the other to test it properly. Leaving the 3rd diode out just leaves that part of the signal open and you're left with one diode in parallel with the rest of the drive circuit and getting the squeal. The 2nd diode has no contiuity without the jumper. Do that and you just might as well leave it out. You could also breadboard that part first but you'll still have to solder wires in those pad locations. I assume you will be doing that anyway to wire up the switch. That might be the best way to go.

[JebemMajke]

Hm, that link opens ts 808/9 for me ...

Anyhow, how about just putting one side of the switch on the positive of d2 and other on negative of d3?

And just ignore d1?

I mean why the hell does it squeal when d2 and d3 are both ignored, shouldn't it work like there is nothing there?

[bloxstompboxes]

It's probably this crap PC I have at work.

If D2 and D3 are the two in series and D1 is the one in parallel with those two, then that should work. That is to say, as long as you have a proper symmetrical arangement of the diodes on your switch. Not sure how you plan to do the configuration. Are the germs all the same type or have you selected two different pairs?

I haven't been a member here long so I don't know your extent of knowledge in electronics. I apologize ahead of time if it appears I have been talking down to you.

[JebemMajke]

Thnx for considering my ego and emotions , it is ok. My understanding of electronics comes from experience only. I don't have enough time to read Ohm's law and similar books. I have to have 2 jobs, and this electronics thing, apart from music, is what is keeping me sane, at least a little bit. Plus we are both brainstorming here, so it's cool.

I have built lots and lots of pedals, but ts was never my cup of tea. Until recently.

leds asym like in this schem ( ps i know that these here are 1n4148's )
then Off
Germs 4 in a row, like in a bluesbreaker circuit


Ps Yes, d2 and d3 are in series.

[bloxstompboxes]

That TS-9 circuit has a symmetrical diode configuration. There would have to be a 3rd led in series with one of those two to be asym. They are just in opposite polarities. The second picture is the same as the first, no?

If D2 and D3 are in series, then go ahead and try what you were planning.

[JebemMajke]

Sorry for the 2 of the same picture

Here is my 4 diode way

Ps, i've tried  d2 positive and d3 negative ... but it is the same as using holes for d1 only.

Is making a new pcb, with one set of holes only going to fix my problem?

[karbomusic]

The free floating input that occurs due to true bypass is allowing it to oscillate which is bleeding into into your bypassed signal. If you are using a 3PDT footswitch you can auto ground the FX input when in bypass which will stop it. Or you could find the source and fix that but with higher gain circuits, sometimes its more definitive to just ground the FX input when bypassed.

IMHO, this is one of the necessary evils of tweaking this type of circuit, just the right tweaks here and there, sounds incredible but there is now some annoying anomaly such as a squeal. It reminds me of my programming side of life where I always tell people.. "10% of programming is making it do what I want, the other 90% is preventing the code from doing what I don't want". Now, I'm gonna go ahead and tweak anyway because dealing with such things are great experience, just wanted to mention how it's easy to inadvertently push past some unknown limit without expecting it. Fun stuff.

[JebemMajke]

How to ground the input?

this is the type of wiring i am using

[JebemMajke]

Should I do it this way?

[karbomusic]

Should I do it this way?

That's it. 

[JebemMajke]

I've actually went with tonepad offboard wiring no 5 http://www.tonepad.com/getFile.asp?id=76

It works

great

Thnx guys

[duck_arse]

I have built lots and lots of pedals, but ts was never my cup of tea. Until recently.

still not my cuppa T, but, money was involved. I built a similar recently (w/ dpdt and millenium), and it squealed at high gain settings, an unwanted first for me, too. so I put shielded to/from the (4) jax. and that fixed it. well, that, huge swearing and a mile of heatshrink. just thought I'd add this, even tho you fixxed.