Same Speakers - Multiple Receivers

[mandrix]

The commercial ones that degraded the signal were made to pass RF or video, not speaker power.

I suspect that's true. A long time ago when I was researching building my own, I remember a discussion about a unit with MOSFET's that was pretty bad. I don't now recall the details of the circuitry though.
My thinking I believe was to employ dpdt relays in lieu of a complicated circuit, but system changes meant I no longer needed a device. The mechanical switches I was using were pretty simple, but were prone to corrosion and needed cleaning about once a year.

 

[barfle]

A couple of things worth remembering (although they’ve ben hinted at earlier) - make sure the contacts are rated for the voltages and currents you will be pushing through them, and that the contacts are of the “break-before-make” configuration. That will insure that the two amplifiers’ outputs are not connected together.

 

[MidiMagic]

But the relay that substitutes the resistor for the speaker should be make before break.

 

[par4ken]

There are many switch boxes available on eBay, most from China they are lower cost than what you could build yourself. Units that are intended to switch one amp to multiple speakers are more common but you could just use it backwards. I even see a four channel switch box available.

Most do not bother to terminate the unused amplifier outputs. I don't believe that is a big issue. One unit says that it does use 100 ohm resistors to ensure that the amplifier output is never totaly open, that is something that could always be added if it is a concern, the resistors are of a high enough value that they could be simply left connected at all times.

Remember that vintage amplifiers almost always had headphone jacks. The headphones were connected via a series resistor, usually about 270 ohms, I've seen as high as 470 ohms. Those amplifiers did not blow (from too low of a load) when the headphones were plugged, in which case the speakers are disconnected!

Normally the unused amplifier would be left powered down anyway, so it's a moot point worrying about if it's outputs are terminated or not!

 

[LuvMyQuad]

I have used a 5 channel solid state Emotiva amp to power four height channels for years now with no ill effects to the unused channel

 

[MidiMagic]

There are many switch boxes available on eBay, most from China they are lower cost than what you could build yourself. Units that are intended to switch one amp to multiple speakers are more common but you could just use it backwards. I even see a four channel switch box available.

Most do not bother to terminate the unused amplifier outputs. I don't believe that is a big issue. One unit says that it does use 100 ohm resistors to ensure that the amplifier output is never totaly open, that is something that could always be added if it is a concern, the resistors are of a high enough value that they could be simply left connected at all times.

Remember that vintage amplifiers almost always had headphone jacks. The headphones were connected via a series resistor, usually about 270 ohms, I've seen as high as 470 ohms. Those amplifiers did not blow (from too low of a load) when the headphones were plugged, in which case the speakers are disconnected!

Normally the unused amplifier would be left powered down anyway, so it's a moot point worrying about if it's outputs are terminated or not!

Check what's inside your switcher first. I got two old stereo ones that were unsold for years. Each has load resistors in it that always make sure the amp is loaded with 8 ohms whether you have none, one, two, or three speakers operating. But it sometimes puts speakers in series. There is no way you could connect two amps to one pair of speakers with it.

Some of the amps that have headphone jacks that turn speakers off have contacts that add load resistors.

 

[kfbkfb]

Another idea - a single SPDT switch connected to the "-" speaker connection (maybe 1, maybe all 4) of each receiver, the switch (output) would be split into 4 wires for each of my 4 speakers.

I may be able to get by without cutting the power to one receiver or the other depending on which one is in use and just use the front panel power switches.


Kirk Bayne

 

[par4ken]

Another idea - a single SPDT switch connected to the "-" speaker connection (maybe 1, maybe all 4) of each receiver, the switch (output) would be split into 4 wires for each of my 4 speakers.

I may be able to get by without cutting the power to one receiver or the other depending on which one is in use and just use the front panel power switches.


Kirk Bayne

The simplest method is not always the best. Is this just a thought experiment about how simple/cheaply can I accomplish my goal?

As I recall there is a thread here someplace where someone built a switch box. It included pictures. Then the discussion shifted more about the best crimpers to use. If you can find it, it might provide a source of inspiration for you.

 

[kfbkfb]

https://www.gardnerbender.com/en/p/GSW-13/SPDT-Toggle-Switch

Got the speaker switch - it has a lot of product info for a simple switch.


Kirk Bayne