Taiway „High Quality“ Switch Problem

[lars-musik]

Hello Forum,

hopefully you have some advice for me. I bought about 40 switches of these 3PDT because they seemed good at first tests (https://www.musikding.de/3PDT-footswitch-compact-Taiway).
Now I build a quite gainy pedal (a 1981DRV derivate - schematic here https://www.pedalpcb.com/docs/PedalPCB-Informant.pdf but true bypassed in my case) and experience strange noises when switching. It almost seems like the pedal has an intermediate switching state between on and off. There's a short "blip" if I press the button. If I am fast enough it is almost inaudible, but if I press the button by hand and deliberately slow, the kinda oscillating noise can be stretched out some.

Here's a quick video I made.

https://www.youtube.com/watch?v=N50jB1mTRLM

Any ideas why, when and how not?

Thanks, Lars

[Kipper4]

Ouch my ears. That's nasty Lars.
Couldn't tell you why it's happening. I've never heard that before from a switch.
Weird......

[lars-musik]

Indeed. Unfortunately not the only incident. A friend for whom I built one of those pedals set me on the trail. Now I reproduced it with a second and third built.
With the switch changed to an old-fashioned model the problem's gone....
https://www.youtube.com/watch?v=NKztDdm-G74

[willienillie]

I suppose all multi-throw switches are either BBM or MBB, and whichever this one is (guessing BBM), doesn't get along with this application.  It might be something that could be cured with a resistor across the contacts, to keep whatever it is you're switching from hanging "open" for a brief period.

[lars-musik]

I suppose all multi-throw switches are either BBM or MBB,

There seems to be no datahseet available, so I tried to measure resistance in the half-pressed state but didn't get a good reading. Either way make before break or the other way round shouldn't rersult in these sounds. I suspect that the input throws and the output throws might be a little of sync, so that one already switches while the other hasn't done so yet. A bit like having only the output cable connected and the input floating.

[Fancy Lime]

Most switches are BBM and that is usually what you want. MBB means you get the effect connected in parallel with the bypass wire. Since the output of the effect has much more signal and much much lower impedance than the input, this means that the signal is fed back through the bypass wire. E voilá, oscillation. But that should only happen if you wire this thing true bypass. I guess this is the reason why the provided a buffered bypass out. Are you using the buffered out or are you running true bypass?

Cheers,
Andy

[GGBB]

I suspect that the input throws and the output throws might be a little of sync, so that one already switches while the other hasn't done so yet. A bit like having only the output cable connected and the input floating.

Try adding a pull down resistor directly on the output jack from tip to ground. Not an ideal solution but might prove your assumption above.

[Fancy Lime]

Has this issue ever been resolved? I was pondering buying some of those.

Andy

[lars-musik]

Hi Andy,

no, it hasn't. I had to change some of these switches because the problem remained. Only in high(er) gain circuits. Seems to be no problem in Tremolos and the like.