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Speaker Switch That Protects Tube Amplifier

A EE friend of mine and I are planning to build a switch box that will allow me to toggle between my Yaqin MC-30L tube amp and my Integra 50.1 receiver to power my speakers.

The current plan is a very basic setup that would require the tube amplifier to be shut down before switching so that it isn't left without a load.

The utopian goal would be to be able to switch between the two amplifiers with a single source feeding both (i.e. the Yaqin has an Apple Express for a source and the Integra has an Apple TV so both could be running from iTunes on my Mac) without risk of damage to the tube amplifier.

I'm assuming that this would be complicated at best and probably isn't worth it, but thought I should as before we purchase parts.
mceljo
mceljo OP
1,351 posts
 
Each channel will effectively have three parallel switched toggled by a single physical switch.
imhififan's avatar
imhififan
2,141 posts
 
Please refer to Is It Safe To Connect Speakers To Two Amps, Almarg and Hifihvn have very good advise on this.
imhififan's avatar
imhififan
2,141 posts
 
"Should I be concerned with the tube amp not being loaded for a instant when the switch is toggled?"
That depends, even though IF the tube amp has some sort of protection circuit built in, I won't risk it. Same thing on the ss amp, even though it has short protection, I wouldn't risk it either.
mceljo OP
1,351 posts
 
Imhififan - Your responses and link to the other thread made me dig into things a bit more. Thank you.

The revised plan is to use a heavy duty 4PDT toggle for each channel. The solid state receiver will be on/off, the tube amplifier will be off/on, and the 8 ohm 100W non-inductive dummy load resistor will be on/off. To bridge the instant between the speakers and the dummy load resistor on the tube amplifier we will also add 150 ohm 5W or 10W resistors on each channel based on the recommendation from the Niles manual that was linked. I'm not worried about my receiver as I often have it passing sound to the TV via HDMI with the speakers disconnected and hooked to the tube amplifier.

I'm interested to hear how the final switch box "sounds" as it will obviously add components to the signal path. Being completely objective may be a challenge in contrast to the negative placebo of knowing that the signal path has been compromised.
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