[sdiy] Muting circuits for line out

[David Huss]

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> on behalf of 
> Benjamin Tremblay via Synth-diy <synth-diy at synth-diy.org>
> *Sent:* 08 May 2025 13:56
> *To:* synth-diy mailing list <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> 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> 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 <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>
>>>
>>> <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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