Here are the details: Connecting 2 amplifiers to one set of speakers: making an amp/speakers selector switch |
Amplifier selector with dummy load
Attached is a schematic of amplifier selector with dummy load for safely switching tube or solid state amplifiers. The selector is a Grayhill 44A45-02-03S three position shorting style rotary switch, one per channel. Center position is for "speaker off" to prevent both amplifier outputs shorted together.
The reason of using shorting style (make-before-break) rotary switch is to ensure both amplifiers will be connected to a load at all times, either to the speaker or a resistor dummy load.
44A45-02-2-03S Grayhill | Mouser
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Attached is a schematic of amplifier selector with dummy load for safely switching tube or solid state amplifiers. The selector is a Grayhill 44A45-02-03S three position shorting style rotary switch, one per channel. Center position is for "speaker off" to prevent both amplifier outputs shorted together.
The reason of using shorting style (make-before-break) rotary switch is to ensure both amplifiers will be connected to a load at all times, either to the speaker or a resistor dummy load.
44A45-02-2-03S Grayhill | Mouser
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Attachments
If you do not want to use dummy load for your switching circuit, a Grayhill 44A45-02-2-03S actually can switch two amps with one pair of speakers, please refer to the attached schematic. In this case, a shorting style 3 position rotary switch can be use but is not necessary, you can also use ON-OFF-ON toggle switch to get higher power handling capacity with lower cost.
https://www.mouser.com/Electromecha...0z2qmZ1z0z2qcZ1z0x8fvZ1z0x8gwZ1z0x8h3Z1y8pmra
If center OFF position is not necessary then a ON-ON toggle switch like the link provided by Galu should work as well, just be sure to use a break-before-make switch as rayma mentioned.
However, Not all solid state amplifier can be ON without load (like those without a Zobel network at output). Best to check with user manual for safe switching.
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@chrisng
I know this is an old thread, but this design is pretty darn clever!
I started looking into adding a class D SS amp that would share the same speakers with a SE tube amp that always need a load to be happy.
So, I need a switch, with all the right properties.
It should break before make, switch all 4 wires independently, swing a dummy load left or right so that said load is always present regardless of what amp has dominion over the speakers at any given time.
This purely mechanical solution is attractive, but what else is out there?
I imagine toggle switches and relays, etc.
?
Found this thread:
https://www.diyaudio.com/community/...le-a-b-c-switch-design-considerations.389692/
which makes me think I probably found a new rabbit hole
https://www.diyaudio.com/community/...le-a-b-c-switch-design-considerations.389692/
which makes me think I probably found a new rabbit hole
How do you ensure your amps always have a load on them?
I mean even during the switching.
another relevant thread: https://www.diyaudio.com/community/threads/tube-amp-with-no-spk-load.392468/
Add a resistor across the tube amp output is a good insurance to prevent damage if the speaker disconnected accidentally.
ElArte, you may find this thread at audiokarma.org interesting.
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A simple solution to preventing amps that do not tolerate not having speakers connected is...
Wait for it!.........................
Switch the amps while they are turned off!
Of course, that makes sense. Still, I think most people interested in these things are looking for protection in the event of a brain fart.