Speakers and amplifiers switch

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I would like to introduce my loudspeakers and amplifiers switch.
I can plug in 3 stereo amplifiers and 4 loudspeakers pairs.
At the same moment I can use only one amp and 1-4 loudspeakers.
It is obvious that using more than one pair at once doesn't make sense :D
But I can turn on all 4 outputs if I wish to :)

Amplifiers are isolated from each other because I switch also grounds.
It is done in that way just to avoid ground loops and to make possible to use balanced amps or exotics like OTLs.

Amplifiers switch works in order: Amp1-OFF-Amp2-OFF-Amp3
It is done this way to make sure, that relays will have enough time to break path from current amplifier.

Best regards, Chris


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Very nice! I just finished assembling mine about a month ago; one amp in, 3 pair out.
May I suggest placing a zobel of 0.022-0.1uF and 10-12 ohms across the amplifier inputs to keep them stable when switching and at no load? This was recommended to me when I put mine together. I also placed 5A fuses on the amplifier ins after the zobel for protection of the speakers and amplifiers, and some Z131-20UL MOVs across the speaker outs to prevent arcing when switching. I assume your relays already have free-wheeling diodes internally.

Nicely done!
Hello Wolf_teeth

Thanks for advice about zobel - I am using zobel in my SS amp's output.
I am not sure if I need it at the end of my valve amps?
I'm switching without signal - just to prevent any arcing or other surprises.
I don't use my valve amplifiers without any load during the signal present.
So every time I am changing amp - the current one it muted or switched off.
And changing loudspeakers requires pause on the player.

I could use some kind of dummy loads for unused amps, but it would generate to much heat.
I'm the only one user of this device, only my mistake can cause some damage to the system.
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