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Topic: How to share 1 pair of speakers between 2 amps? (Read 5881 times) previous topic - next topic
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How to share 1 pair of speakers between 2 amps?

I already have a cheap sony 5.1 receiver (STR-DE475)  but i use it rarely for surround, mostly for stereo listening therefore, i think i could buy a power amp and connect my squeezebox directly to it
but then the front speakers needs to be shared between the power amp and the 5.1 receiver - how do I do that?
I dont want the signal to go through the receiver, and BTW the receiver doesn't have 5.1 line out (it's cheap shit)
What i'm looking for is a kind of switch between the speakers and the amplifier and receiver

I can see that some switches for one amp and 2 pairs of speakers are available, but what about the opposite? two amps and one pair of speakers?

An automatic switch, that switches to the amplifier with signal, would be preferrable

How to share 1 pair of speakers between 2 amps?

Reply #1 –
Wouldn't it be the same switch from one amp to two speakers as from two amps to one speaker?

Certainly don't expect anything automatic.

How to share 1 pair of speakers between 2 amps?

Reply #2 –
Quote from: CSMR on
Wouldn't it be the same switch from one amp to two speakers as from two amps to one speaker?


Maybe, but i don't know if these switches contains anything else than just a switch... And if the switch supports parrallel connection to both pairs of speakers, it'll make a short circuit between my amplifiers

How to share 1 pair of speakers between 2 amps?

Reply #3 –
Quote from: CSMR on
Wouldn't it be the same switch from one amp to two speakers as from two amps to one speaker?

Certainly don't expect anything automatic.

For a manual switch, yes it would be the exact same thing. Just get something with some reasonable heft to it -- you don't want to put 100 watts through a dinky little 5mm switch. Also a good idea would be a three position switch of the A/off/B type -- that insures that connection is broken before switching. this looks very good if you want to make in yourself in a little project box; it would be an easy job for a soldering beginner.

An automatic switch would be possible, but doubt if you're going to find anything off the shelf. And be very cautious if you did find something... Two amps to one speaker is unusual. The big thing is that you must make sure that the device will never connect both sources at once. I can think of how this would be done with transistors, but I'm no EE to design the thing. (I also don't know if transistors would affect the sound.)

How to share 1 pair of speakers between 2 amps?

Reply #4 –
I found this one:
http://www.b-tech-int.com/BT32.html

Looks good, and costs 250 DKK (43 USD) in a local store in denmark

How to share 1 pair of speakers between 2 amps?

Reply #5 –
DO NOT use any kind of switch between an amplifier and the loudspeakers, if you don't want to ruin the soundquality! The reason is that speakercables transport a much higher signal/electricity, and a switch will therefore have a much bigger negative impact. It is much safer (soundwise), even if it's not recomended, to have a switch in the signal path. It all depends on how critical you are to soundquality

How to share 1 pair of speakers between 2 amps?

Reply #6 –
Quote from: Inocybe on
DO NOT use any kind of switch between an amplifier and the loudspeakers, if you don't want to ruin the soundquality! The reason is that speakercables transport a much higher signal/electricity, and a switch will therefore have a much bigger negative impact. It is much safer (soundwise), even if it's not recomended, to have a switch in the signal path. It all depends on how critical you are to soundquality

So the same mechanism will have more relative effect on a higher level signal than a lower level one? You seem to have got that the wrong way round.

How to share 1 pair of speakers between 2 amps?

Reply #7 –
No, I haven't  The reduction in soundquality is bigger when using a switch between amplifiers and the loudspekers. This is of course depending of the rest of your equipment. Most/all of the switches is of low quality, meaning reduced sound quality, additional resistance and some power loss. Have even heard about switches that don't cut the 1. amplifier soon enough before the 2. is turned on. Not good for the amplifiers, or the speakers. Also, some gives a "tick" noise when switching, and this can blow the tweeters if power is high enough.

If you must have a switch, build it yourself using high quality components, including a good relay (with a delay).

Good luck

How to share 1 pair of speakers between 2 amps?

Reply #8 –
Quote from: Inocybe on
No, I haven't  The reduction in soundquality is bigger when using a switch between amplifiers and the loudspekers. This is of course depending of the rest of your equipment. Most/all of the switches is of low quality, meaning reduced sound quality, additional resistance and some power loss. Have even heard about switches that don't cut the 1. amplifier soon enough before the 2. is turned on. Not good for the amplifiers, or the speakers. Also, some gives a "tick" noise when switching, and this can blow the tweeters if power is high enough.

If you must have a switch, build it yourself using high quality components, including a good relay (with a delay).

Good luck

Using a changeoever relay with break-before-make contacts (which would be usual) would eliminate the possibility of connecting both amps. A simple double-pole double-throw switch, provided it also is break-before-make (most are), is not going to affect the sound quality if it's of a decent mechanical standard and suitable electrical rating.

I don't doubt that some components are of poor quality, but they'd need to be seriously mismatched to affect sound quality to an audible degree. More likely you could melt the contacts of an inadequate switch before you'd actually hear a problem. The contact resistance for even a modest switch will be in the milli-ohm range, which is at least a couple of orders lower than most speakers. A relay that you suggest will be no better in that regard.

Most amps can tolerate an open circuit but switching amps at high power is not sensible, (inductive) speakers could cause significant transient voltages, so switching when both amps are off would be safest.

How to share 1 pair of speakers between 2 amps?

Reply #9 –
Quote from: Inocybe on
No, I haven't  The reduction in soundquality is bigger when using a switch between amplifiers and the loudspekers.

I'm not saying that's not true, but if it is it's certainly not for the reasons you gave.

How to share 1 pair of speakers between 2 amps?

Reply #10 –
To be really safe, you should only switch with the amps off.

As for making things sound worse, as long as the switch isn't electrically inadequate, I don't think the OP needs to worry. He did describe the existing device as "cheap shit".

Mind you, in a "good" set up, I wouldn't use switches like this.

Cheers,
David.