[sdiy] Muting circuits for line out

[Benjamin Tremblay]

Yes, I did read https://sound-au.com/articles/muting.html. 
Thanks. I think that transistor muting circuit is commonly used in commercial applications, and is okay as long as you can add your own buffer on the output. 
No zero-crossing discussion necessary this time.

Benjamin 

> On May 8, 2025, at 10:18 AM, David Huss via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> The legendary website of Rod Eliott (ESP) provides a good overview as well:
> https://sound-au.com/articles/muting.html
> 
> On 2025-05-08 15:12, Mike Bryant wrote:
>> Chapter 21 (well it was in edition 2) of Douglas Self's book on audio which should be on every audio engineer's shelf covers almost every way of muting a signal.  One of those should suit you.
>> From: Synth-diy <synth-diy-bounces at synth-diy.org> <mailto:synth-diy-bounces at synth-diy.org> on behalf of Benjamin Tremblay via Synth-diy <synth-diy at synth-diy.org> <mailto:synth-diy at synth-diy.org>
>> Sent: 08 May 2025 13:56
>> To: synth-diy mailing list <synth-diy at synth-diy.org> <mailto:synth-diy at synth-diy.org>
>> Subject: Re: [sdiy] Muting circuits for line out
>>  
>> The original design had the power switch on the volume knob. I suppose that was a way to mitigate this.
>> Benjamin Tremblay
>> 
>>> On May 8, 2025, at 8:44 AM, Benjamin Tremblay <btremblay at me.com> <mailto:btremblay at me.com> wrote:
>>> 
>>> Oh wait, I suppose the patent is for an fm signal that has not yet been demodulated.
>>> Benjamin Tremblay
>>> 
>>>> On May 8, 2025, at 8:30 AM, Benjamin Tremblay <btremblay at me.com> <mailto:btremblay at me.com> wrote:
>>>> 
>>>> 
>>>> Hello,
>>>> I have this lovely Univox JR-5 rhythm machine I have modded with knobs to control the sound mix. The original circuit was high gain but impedance sensitive so it summed current, not voltage and was very 
>>>> I added a simple op amp to handle the mix. When power is turned on there is a horrible thump that sounds like it is 100x too loud. 
>>>> I have been looking for a simple muting circuit. When I was repairing a Roland MC-909 I saw the muting circuit was little more than a pair of BJTs shorting the signal path. 
>>>> I also saw this novel patent which attenuates the signal without much voltage offset, maybe?
>>>> US4288753A - Muting circuit with operational amplifier - Google Patents
>>>> patents.google.com
>>>> <favicon.ico>
>>>>  <https://patents.google.com/patent/US4288753A/en>US4288753A - Muting circuit with operational amplifier - Google Patents <https://patents.google.com/patent/US4288753A/en>
>>>> patents.google.com <https://patents.google.com/patent/US4288753A/en>	<favicon.ico>
>>>>  <https://patents.google.com/patent/US4288753A/en>
>>>> I really just need to prevent that initial thump. I’ll pick up a relay if that is best. 
>>>> 
>>>> Is there an easier solid-state solution? I don’t mind adding another buffer stage at the output.
>>>> 
>>>> Benjamin Tremblay
>> 
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