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2 amplifiers into 1 pair of speakers

K

kevinrt

pfm Member
I have a turntable/passive pre/valve amplifier connected to my speakers most of the time for listening to music.
I can connect the TV into this system as well, but would rather not put hours of use on the valves just for TV.
I also have a solid state integrated which I would ideally like to use with the TV, but I don’t really want a second pair of speakers in the room.
The speakers have bi-wire terminals (linked) so I have the extra set of binding posts to connect up a second amplifier. Obviously I would only switch on one amplifier at any time but, I could forget to switch one off, and am assuming that this would be a bad thing.
Also there are other people in the house that use these systems, and they won’t understand what’s going on, likely leading to both amps on at the same time.
Am I right to assume it would be a bad thing to have 2 amplifiers connected to a pair of speakers, and switched on, even if only one was playing sound?
Has anyone got a workaround that might help?

regards

Kevin
 
The important thing to remember is that you shouldn’t really run the valve amp without a load. The Beresford switch, at least when I enquired, doesn’t switch in a dummy load for the amp that isn’t in use.

Of course, in practice we would switch off the valve amp when switching to the SS amp but it is easy to make a mistake. When I had a similar setup I made up a switch unit but can’t remember quite how I did it; sorry not to be more helpful.
 
Thanks for your replies.

The lack of a dummy load does seem to kill the idea of a simple switch.

I do remember a dealer getting in a panic when he was demoing a valve amp for me, after he had switched on the amp without cables attached at the speaker end.

Kevin
 
I had a similar conundrum, didn’t want to burn valves in the Leak, and ended up with the extra speakers, Genelecs in my case, just plonked on top of my bigger speakers.
 
ryder said:
If I were you I would disconnect a pair of speaker cables and let them lie on the floor. Only connect the cables when you want to listen to that one amp.
Click to expand...
As a general rule of thumb, valve amps don't do well when open (i.e. no load), whereas, solid state typically don't do well when shorted. As such, switching back and forth between any two amps into the same speakers needs care, especially so, if going between tube and solid state. Disconnecting at the speaker ends and letting the cables lie on the floor may not be a good way to go, especially so, with others about. Barring use of an amp/speakers switch (with tube amp turned off at all times when not in use) it would be safest, if not most convenient, to change speaker connections at amplifier end.
 
Note of caution with the Beresford - both amps must be turned off before switching per the instructions:

OPERATION:
1. Make sure that each audio amplifier is switched OFF, or that the speakers’ output selector on the amplifiers is in the OFF position.
2. Press and select Amplifier A or B on the TC-7220 MKII front panel, depending on which amplifier you wish to listen to.
3. Press and select Speaker A or B on the TC-7220 MKII front panel, depending on which speaker pair you wish to listen to.
4. Now switch ON the amplifier(s).
 
Baldwin Audio used to do a unit for exactly that purpose, along with a good few other useful bits of kit. I have one for A-B'ing speakers and amps and it does present a dummy load for valve amps unlike the Beresford.

Unfortunately Paul Baldwin passed away in September, so no longer available.
 
I have seen switcher boxes on eBay from the likes of Douk Audio, with dummy loads that can be switched in and out. I can’t comment on the quality.
 
I think you'd be better off with a separate system as Alex S suggested. Small active speakers straight out of the tv would work a treat and be easier for the rest of the family to use. Keeps it simple and less risky for your main gear.
 
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