Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Captain chunkulus on December 07, 2019, 09:22:22 pm
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Any of you guys know a simple way temporarily mute a signal while changing channels so the relays don't pop while changing channels? Thanks.
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cascaded 555 timers configured as one-shots. the first 555 mutes, the second 555 switches. the first timers' time constant longer than the second. ~250ms to mute 100ms switch. better yet; use vactrol opto coupled varistors, such as the VTL5C3, etc..
--pete
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Better to minimise / cure the ‘pop’ rather than introduce momentary muting circuits?
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Better to minimise / cure the ‘pop’ rather than introduce momentary muting circuits?
This seems better to me. I already have relays installed that are switching the channels and such. Just get popping when changing channels. Any simple fixes for this?
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Yes, a time delay works, but is not optimal especially when playing live. One solution may be a 1M R across the SW section of the relay. This also works for manual SW's. Another possibility is a snubber diode circuit: https://en.wikipedia.org/wiki/Flyback_diode (https://en.wikipedia.org/wiki/Flyback_diode)
Also see the annexed files.
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Better to minimise / cure the ‘pop’ rather than introduce momentary muting circuits?
This seems better to me. I already have relays installed that are switching the channels and such. Just get popping when changing channels. Any simple fixes for this?
If you post schematic, it will be easier to help you.
As for a temporary mute circuit, a simple solution using a fet and rc network triggered by the relay switching is used by some manufacturers. I think Engl amps has this.
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This unit is to be put in parallel with the contact of the switch (done for solve your kind of problems - didn't has a high price)
(http://el34world.com/Forum/index.php?action=dlattach;topic=14021.0;attach=30628;image)
(https://i.imgur.com/Pnfod0z.png)
Expecially Read this (and other link)
http://www.kemet.com/Lists/ProductCatalog/Attachments/146/F9000_GenInfo_RCUnits.pdf (http://www.kemet.com/Lists/ProductCatalog/Attachments/146/F9000_GenInfo_RCUnits.pdf)
https://it.rs-online.com/web/p/condensatori-per-reti-rc/0209213/ (https://it.rs-online.com/web/p/condensatori-per-reti-rc/0209213/)
http://el34world.com/Forum/index.php?topic=14021.ms (http://el34world.com/Forum/index.php?topic=14021.ms)
Franco
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Better to minimise / cure the ‘pop’ rather than introduce momentary muting circuits?
This seems better to me. I already have relays installed that are switching the channels and such. Just get popping when changing channels. Any simple fixes for this?
If you post schematic, it will be easier to help you.
As for a temporary mute circuit, a simple solution using a fet and rc network triggered by the relay switching is used by some manufacturers. I think Engl amps has this.
What is an example circuit for the fet/rc network your talking about? Is this it basically?
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What is popping - The coil or the audio switched circuit?
The back emf of a dc coil is best de energised with diode; RC snubbers are used for ac coils.
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Well, I'm using a dc supply for the relays and a mechanical switch to make and break the connection to the negative side of the supply.
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A dc relay coil needs a (reverse biased) diode connected across it (or between the switched coil end and circuit common), fitted in close proximity.
Any regular power diode should do the job, but as they’re cheap and readily available, these days I’d use UF4007.
The big advantage of dc relays in this application is that its back emf spike can be so easily and effectively mitigated (ie compared to ac coils).
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Well, I'm using a dc supply for the relays and a mechanical switch to make and break the connection to the negative side of the supply.
Again, without a schematic it's difficult to help you.
Doesn't have to be fancy. Make a simple drawing on paper and take a photo with your phone, then upload here.
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+1