VFE Windbag (delay/reverb) - volume drop/muffed sound when engaged

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Bobb_Lobblaw
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Post by Bobb_Lobblaw »

windgabgutz.jpg
Hello,
I'm building a VFE Windbag and I'm having an issue.
Everything seems to be working fine, but I get a steep volume drop and a muffled under-the-blanket sound when engaged. If I crank the volume, I can hear everything doing what it's supposed to do delay, reverb, envelope, etc...just at a very low and muffled volume like a hi pass filter.
I checked the voltages, and they are a bit off, but I'm not sure what to do about that. If it matters, I subbed a TL072 for the OPA2134 and I subbed a TC1044SCPA for the TC7662B. Oh, and my DM doesn't have an mV setting.
Any help is greatly appreciated.

https://www.madbeanpedals.com/projects/_folders/VFE/pdf/Windbag.pdf
Thanks.
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Bobb_Lobblaw
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Post by Bobb_Lobblaw »

Hello,
I'll try again...
I'm having an issue with the Windbag. https://www.madbeanpedals.com/projects/ ... indbag.pdf.
I get a steep volume drop and a muffled under-the-blanket sound when engaged.
Tracing the audio signal it hits the relay which then sends to R1. The signal going in to R1 is strong..coming out the other leg it's severely dropped and muffled. I reflowed R1, I switched R1 out for another 220K and the same vol. drop/muffle happens.
If I crank the sound, I can hear everything doing what it's supposed to do delay, reverb, envelope, etc...just at a very low and muffled volume.

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x-tn
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Post by x-tn »

Bobb_Lobblaw wrote: 22 May 2023, 01:42 The signal going in to R1 is strong..coming out the other leg it's severely dropped and muffled. I reflowed R1, I switched R1 out for another 220K and the same vol. drop/muffle happens.
IC1 may be faulty. Try another TL072 or a similar dual op-amp.

Also measure R24 (10 Megaohms).

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Bobb_Lobblaw
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Post by Bobb_Lobblaw »

Thanks for the reply!

Staring forlornly at the schematic, I think R1 is actually supposed to drop the volume of the signal on its way into the op-amp (I've tried a couple of different TL072s with no change), and then into PT2399...But it never gets re-amplified and it's just too muffled.
So, I socketed R1 and tried several resistor values lower than the original 220K, and I can get the volume up to a usable level. But I can't seem to clean up the muffled audio signal. It's like cranked a low-pass filter sound..
Could I possible wire a tone pot somewhere?

Thanks,

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