[sdiy] anti pop mosfets in minibrute

[rburnett at richieburnett.co.uk]

Yes. Very strange. Definitely a glitch in the matrix.

-Richie,

On 2024-04-28 10:37, Adam (synthDIY) wrote:
> 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> wrote:
>> 
>> Am 25.04.2024 um 09:54 schrieb René Schmitz <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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