[sdiy] anti pop mosfets in minibrute

[René Schmitz]

On 28.04.2024 11:11, Ingo Debus via Synth-diy 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?


The two resistors; I would also say this is to keep it mono compatible. 
And to delimit the current in and out of the jack.

My conjecture would be that in the evolution of the design they first 
had the two resistors, and then on a later revision the mosfets .


You can do this with a single FET, but it needs to have lower Rds(on), 
and maybe not a jellybean SOT-23 part anymore.

If you use a single 2N7002 then the maximum attenuation becomes an 
issue. Rds(on) is 2ohms.

Which is in the same ballpark of the other resistors, i.e. the muting 
isn't going to be 100%. It keeps ~1/10th of the signal when muted.

Assuming you replace the two 22 ohms by 10 (or 11) ohms and a single 
FET, you have only an attenuation of ~1/5th.


Best,

  René


-- 
--
synth at schmitzbits.de
http://schmitzbits.de
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20240428/a0a2c91b/attachment.htm>