• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Speaker/amp switcher for test bench

cardoctordav

cardoctordav

Member
Building a speaker-amp switcher for my bench and have a brain buster (at least for me!) My switcher will need to do the following: Switch between two sets of speakers and between two amplifiers. One amplifier is my shop power amp and the other is the amplifier under test. Problem is; I wish to have both amps always connected to a set of speakers. I need to be certain that the amplifiers are NEVER connected together.
HELP!!!

Dave Bagwin
 
Register to hide this ad
If you want to make it yourself, you need two four-pole double-throw make-after-break (or centre-off) switches. One will switch between two full sets (including speaker grounds) of amplifier outputs, the other will switch between two sets of speaker inputs (including speaker grounds).
 
DaveVoorhis said:
If you want to make it yourself, you need two four-pole double-throw make-after-break (or centre-off) switches. One will switch between two full sets (including speaker grounds) of amplifier outputs, the other will switch between two sets of speaker inputs (including speaker grounds).
Click to expand...

Won't do it. The unconnected amp will not see a speaker load. If you think this can be done as you describe, please provide a schematic.

It could be done with relays, but would be a bit more involved.
 
toddalin said:
Won't do it. The unconnected amp will not see a speaker load. If you think this can be done as you describe, please provide a schematic.

It could be done with relays, but would be a bit more involved.
Click to expand...
That's true, the unconnected amp won't see a speaker load, but I assume the unconnected amp would be turned off. Why would it be turned on?
 
Multiple relays actuated simultaneously can easily accomplish this task, as long as "never unconncected" doesn't include very, very brief switching discontinuities. You can even have switches that do "switch amps", "switch speakers" and "switch all" if you wish. Two 4PDT relays with suitable contact ratings/materials will do the job. There won't be a "both speakers" option, however.
 
Actually, this is a piece of cake and can be done with a 4pdt switch (Occam's Razor) or a relay (for mono).

You would need to make two for stereo. Alternatively, if you used relays, you could trigger two at once for stereo, or use an 8PDT switch or relay. They do exist and can be purchased on the 'bay.

Also, if you used two switches for stereo, you could run one channel of an amp through one set of speakers and the other channel through the other set simultaneously, for what ever reason (e.g., simultaneous direct comparison).

See my schematic.
ScreenHunter_217_Dec_01_12_21.jpg
 
Last edited:
toddalin said:
Because that's what he asked for. :rolleyes:
Click to expand...
You're right, I missed "I wish to have both amps always connected to a set of speakers."

But it seems an odd requirement to have both the shop amp and DUT running simultaneously, and it's trivial and arguably more useful without it. Perhaps the OP can clarify his intent.
 
DaveVoorhis said:
But it seems an odd requirement to have both the shop amp and DUT running simultaneously, and it's trivial and arguably more useful without it. Perhaps the OP can clarify his intent.
Click to expand...

Not odd at all. I do it all the time. Comparing a reference amplifier with a repaired/restored one instantly (my comparator also does that).

I would not be using a 4PDT switch to do it. Yes it can be done, but it's not ideal. Build a scalable unit with relays, use separate relays DPDT for each amplifier/speaker pair and a self cancelling DPDT pushbutton array. By their very nature, they are break before make. (as long as you aren't pushing two buttons in at once...)
 
restorer-john said:
Not odd at all. I do it all the time. Comparing a reference amplifier with a repaired/restored one instantly (my comparator also does that).
Click to expand...
Yes, but you've got lots of amps and it makes sense to compare a known good model X with a newly-repaired model X. Why would the OP want to do simultaneous swapsies between his (presumably) unchanging shop amp and a repaired amp with two pairs of speakers?
 
DaveVoorhis said:
Yes, but you've got lots of amps and it makes sense to compare a known good model X with a newly-repaired model X. Why would the OP want to do simultaneous swapsies between his (presumably) unchanging shop amp and a repaired amp with two pairs of speakers?
Click to expand...

Because he's thoroughly testing and comparing on an easy pair of speakers and difficult pair of speakers. Maybe he wants to soak test the amplifier on some sacrificial speakers and has another pair for critical listening.

Who knows, he probably just wants all the possible combinations like I do. :)
 
restorer-john said:
Because he's thoroughly testing and comparing on an easy pair of speakers and difficult pair of speakers. Maybe he wants to soak test the amplifier on some sacrificial speakers and has another pair for critical listening.

Who knows, he probably just wants all the possible combinations like I do. :)
Click to expand...
Ah, fair enough. Personally, I find it offensive that someone would want something that deviates even slightly from exactly what I would do under the same circumstances, but as I've grown older I've become increasingly inured to the fact that some people just want to bask in wrongness and sin. :biggrin:
 
I'm all kinds of confused here. The only reason I can see to keep a load on the amp would be to avoid thumping the speakers when switching amps.
For that I leave some phones plugged in to the back and forth subject amps. Otherwise volume down or power down.
 
I would imagine that this goes way beyond the test bench.

There are any number of people out there, and on this forum, who whould like nothing better than to be able to use either of their two favorite amps through either of their two of their favorite speaker systems at the flip of a switch (and never have to worry about something being disconnected or shorted) with the added benefit that both systems could be played simultaneously, if desired. You read requests for this/similar things all the time on the forum. :cool:
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom