[sdiy] anti pop mosfets in minibrute

[Adam (synthDIY)]

Hmmm, ok, this is getting weird now.

I was sure Brian posted this exact same comment a few days ago.

Of course, I might simply be posting from inside some sort of Moebius loop or other ... if so, please ignore

I'll try to find my medication

A

> On 28 Apr 2024, at 7:18 pm, Paulo Constantino via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> Hilarious. They're labeled "anti plop"
> 
> In my experience, this sort of anit-pop feature is designed with depletion mode FETs, which conduct to ground when there is no power. As soon as the device powers up, the Gate turns off the FET, and the signal reaches the output.
> 
> I learned about this feature the first time I repaired someone else's home stereo equipment. The cheap solution was to just remove the FET. It had failed such that it was conducting all the time, even when the Gate was positive. I suppose it must have been a p-channel, but I don't remember. I think that I later came back and installed the correct FET, just so the owner would not get a 'pop' on the channel with the failed (and removed) FET.
> 
> The Mini Brute schematic shows an enhancement mode FET, though, so the schematic is already "wrong" in terms of what I would expect. Is this designed to only mute the headphone output for a brief moment after the power is turned off, and then the mute disengages once the capacitor is drained?
> 
> Paul
> 
> On Sun, 28 Apr 2024, 10:15 Ingo Debus via Synth-diy, <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>> wrote:
>> 
>> 
>>> Am 25.04.2024 um 09:54 schrieb René Schmitz <synth at schmitzbits.de <mailto:synth at schmitzbits.de>>:
>>> 
>>> I would have used two NMOS in anti-series instead.
>>> 
>> What is also puzzling me: why are there two anti-pop circuits? The only reason for two series resistors (instead of just connecting both tip and ring via a single resistor to the amp output) I can think of is that there’s still some signal at the tip when a mono plug is inserted. But why two MOSFETs? Using a single resistor instead of R646/R647 and a single MOSFET would have done the trick too, no?
>> 
>> Ingo
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