Troubleshooting reverb circuit - solved

[Guy77]

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The signal is all but flat and both these last traces were with the Return pot up full. So, I am speculating that the cap can go even smaller than .01uF. It is barely, barely noticeable at .01uF and once you start to play it isn't noticeable at all if you aren't listening for it. We might go down as low as 750pF or 500pF with this cap, but I would still add it into the circuit, because without, it just isn't as good.




Stephen

[Edit: and yeah! A BIG thanks to everyone who helped me get there.]

Hi. Glad you found the cold solder. You mentioned that the cap across the Return pot could go smaller than .01uf and yes you can go a lot smaller. I actually use .005uf and it does the job of removing any noise perfectly.

Cheers

Guy

[Stephen1966]

Hi. Glad you found the cold solder. You mentioned that the cap across the Return pot could go smaller than .01uf and yes you can go a lot smaller. I actually use .005uf and it does the job of removing any noise perfectly.

Cheers

Guy

Thanks Guy, I have one of those I think. I will give it a try. I'm sure now, it doesn't need much.

[Stephen1966]

So finally, I have a 470p cap on the return pot.

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That's a very small incursion on the signal with a minimum loss of the reverb effect. I didn't have a 750p but I put the 470 in parallel with a 270 and honestly, didn't notice a great difference. In fact, there isn't a great difference between a .01 and a 470p. The effect is rather more qualitative than quantitative. A little noise from the return pot, but that's with it dialled all the way up and who needs to go there?

I did find that there is some degree of interactivity between the volume and the reverb. I tried recording it a very low level for my phone and when you don't drive the signal like that, into the reverb, the effect is diminished. Even at a low level, the recordings are not representative so there wouldn't be much point sharing them here. I have a hifi phone with lofi recording. Does anyone know of any good recording apps for Android that can handle higher recording levels without clipping or compressing the sound, I wonder?

Anyway, I'm buttoning this up now and getting to work on the new two-tube reverb with onboard Dumbleator. The latter - on paper at least - will allow me to drive the preamp harder, and then attenuate the signal so that the neighbours don't complain.