• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Selector Switches

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#23
Consider yourself a lucky guy. Most have input or output caps and when devices are already powered muting circuits don't have a function anymore. Switching both signal and GND will often have issues with GND potential differences and or charging/discharging coupling caps.

Only with some special measures and precautions like predefined/sequenced on/off switching and/or predefined source selection it is possible but that is not a thing to introduce in a normal family.
 
#25
That is not a work around, switching both signal and GND (also with the standard reference to GND) simply is very uncommon with almost any audio device for a few reasons. I am sure that your setup has some measures taken to prevent nasties. Try it with most ready built stuff and results won't be that positive in many cases.

My guess is that you have only a few sources and all of them connected to PE directly. No class II devices...
 
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#28
Yeah those are electro-mechanical relays. I would indeed change relays for known good ones like the excellent Takamisawa (now Fujitsu) like they use on the pictures. If you receive those with the kit then it's a bargain. I suppose you will get simple Fujitsu ones and not the RY series (https://www.mouser.de/datasheet/2/164/ry-914629.pdf). I use similar but self designed PCB's and never had a telecom relay fail on me not did I ever had static crackling etc. The build is way nicer and elegant when built with such a board. There is not much to criticise when using good quality relays for source selection in practice.

Sorry Eli but mercury is not a material we should use in DIY anymore. At least not by the average DIYer.
 
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#30
bloozestringer said:
Jean-paul, I also have an aikido preamp in the works I’d thought about using relays for the source switching. Could you point me in the right direction to look for units to either buy or pcb diy?
Click to expand...

I designed and made a 4 way relay switch and I have a few left. It uses 12V and a 4 position switch. Let me know if you're interested.
 

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#31
jean-paul said:
Did it (switching both input and GND) and recently tested the device again. No it is a recipe for loud plops. I thought of redoing it with 100 Ohm resistors always keeping each GND referenced to GND. That should solve it I think.

Switching unused inputs to GND solves crosstalk issues quite OK. Again, this is also way easier with relays.
Click to expand...

I did this (switching grounds) and have no pops between inputs and no crosstalk. I used an Electroswitch. Will try it again on a second similar build.
 
#32
"Non-shorting switches for source selection. Shorting switches for stepped attenuators." - Eli Duttman
Click to expand...
Be sure to get a shorting switch (make before break), by the way. - Rayma
Click to expand...

I'm replacing a faulty source selector switch in my BEWITCH 6550 (integrated) tube amp.

I'd like to know if there is a definitive view on whether the replacement selector should be SHORTING or NON-SHORTING.

It seems we have some opposing views above - or perhaps I have taken these comments out of context.

Expert recommendations sought.
 
#35
I've built a handful of little cast-Hammond-chassis boxes for friends and myself using an idea stolen from a commercial product of the 1990s ? 1980s?. Sorry can't give proper credit. The little boxes have three two pole triple throw center off switches and a volume control (Alps' larger black pots), with six (stereo) inputs and one (stereo) volume controlled output.

The three switches are arranged with all of their "outputs" paralleled and feeding the top of the volume control, each selecting between two inputs. Miniature snap-contact switches with gold contacts seem to last forever (or at least, longer than me). It is possible to connect one input to another, so one switch could be dedicated to a tape record out - tape play in role if needed. As a sign of respect to the user, nothing is labeled, although RCAphonoJack physical position clearly indicates hookup.

All good fortune,
Chris
 
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#36
I designed a 3 channel relay board PCB that I haven't smoke tested yet. It runs on the 6V DC filament supply using Fujitsu silver palladium with gold overlay contact relays. A ribbon cable will go to the rotary switch with 6V DC to select which relay gets energized. I started out using a selector switch but didn't like sending the input signal all the way from the back to the front then back again going past other AC fields. Made in Japan not China.

https://www.mouser.com/ProductDetail/817-RY-6WZ-K

https://www.mouser.com/datasheet/2/164/na-914632.pdf
 
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#37
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