building an high power amplifier selector

[valvol4]

Hello,
I'm starting to build an amplifier selector, meaning a device which lets you switch between two amplifier using a pair of speakers.
The design requirements are:
- no compromise on sound quality, possibly no electronics on audio path.
- safety: it should be completely safe for both the amplifiers and the speakers, being usable also with both amplifier switched on
- it must handle lot of power, being compatible with 300+ wpc solid state amplifiers

I'm considering both mechanical operated solutions and relay ones, i find the latter to be more flexible (maybe to use this device as an A/B comparator sometime in the future) however this is not a requirement.

I'm sure you built something like this before and wanna hear your opinion

thanks!

[bonz]

hello,

I am also trying to build or find something similar. I have a pre-amp (rotel) that works wonderful with 2 channel sound (CDs, Phono, MDs). I also own a 6.1 channel a/v receiver (Marantz) that handles multiple channel movies pretty well (DVDs).

I want to use my existing amps (rotel) for my two front speakers (mirage m-990) along with my subwoofer (mirage ss-1500) for music thru my 2 channel pre-amp, but also want to use my a/v receiver (also with the speakers, amps, & sub) for movies.

I have been trying to find a very clean (audiophile quality) selector switch that I can use and not lose any sound quality - particularly with music. I also do not want any added crap that will distort my signal(s) in any way.

The only things I have been able to find are a/v selector switches made for game systems and multiple a/v setups. They do not appear to be high end in any way... But, maybe they are good enough???

I would also appreciate any suggestions or comments on this subject from anyone who has encountered this or similar situations...

Sorry I am not much help at the moment. If I find out anything, I will be sure to post it though.

Thanks,

Bonz

[cocolino]

I thought about this myself.
As I see it there are basicly only three feasible solutions:

1.) The simplest and cheapest solution would be a mechanical switch:
The problem IMO is simply there aren´t any switches which would be up to this task (at least I don`t know any readily available high-power switches).

2.) Switching with relays:
This would be the second easiest/cheapest solution.
In order You can switch any kind of amplifier (bridged or not) both speaker terminals (+/ground or +/-) have to be switched (applies to any of these approaches). To minimise contact resistance many relays in parallel would help.
With a simple switch (and a cable) in series with the relay-coils supply voltage a kind of "remote-control" could be implemented.

3.) Maybe even better would be an electromechanical solution:
I thought about a strong gear-motor which moves banana-plugs into corresponding jacks. I guess the motor torque must be quite high for this application. Also You´d need to include some sort of cam-switch to stop the motor once the connection is being made and vice versa when the plug/jack is disconnected.
This would be much more complicated to build and a gear-motor isn`t cheap either.


Under safety considerations I`d prefer solution Nr. 1) or 3.).
With 2.) a relais could fail or the contacts could wield together.
In this regard there is not much what could get wrong with Nr. 1.) or 3.) - either it works - or not.
Catastrophic shorts are practically impossible (when 3.) is properly and rigid built).

[valvol4]

Thank you for your reply!

Originally posted by bonz
I have a pre-amp ....(rotel) that works wonderful with 2 channel sound (CDs, Phono, MDs). I also own a 6.1 channel a/v receiver (Marantz) that handles multiple channel movies pretty well (DVDs).

that's my same situation

The only things I have been able to find are a/v selector switches made for game systems and multiple a/v setups. They do not appear to be high end in any way... But, maybe they are good enough???

most of them are not good at all: bad switches, bad conductors and worst of all, they are not compatible with bridged or balanced amps (see below)

Originally posted by cocolino
I thought about this myself.
As I see it there are basicly only three feasible solutions:

1.) The simplest and cheapest solution would be a mechanical switch:
The problem IMO is simply there aren´t any switches which would be up to this task (at least I don`t know any readily available high-power switches).

Have a look at part no. 266-2212 or 266-2234 in the italian rs-components (www.rs-components.it but it's also available in other countries): IP67 20 AMP 4 PIN 2 WAY STABLE.
It should work. Maybe it would be even better to use two of these (one per channel, with pins bound together in parallel).
Switching both pins would make this compatible with any kind of amplifier.

2.) Switching with relays:
This would be the second easiest/cheapest solution.
In order You can switch any kind of amplifier (bridged or not) both speaker terminals (+/ground or +/-) have to be switched (applies to any of these approaches). To minimise contact resistance many relays in parallel would help.
With a simple switch (and a cable) in series with the relay-coils supply voltage a kind of "remote-control" could be implemented.

That would be my first choice, but I am pretty worried about relays reliability. Which part would you use?

3.) Maybe even better would be an electromechanical solution:
I thought about a strong gear-motor which moves banana-plugs into corresponding jacks. I guess the motor torque must be quite high for this application. Also You´d need to include some sort of cam-switch to stop the motor once the connection is being made and vice versa when the plug/jack is disconnected.
This would be much more complicated to build and a gear-motor isn`t cheap either.

That's too complex to build from scratch, but I'm sure that some kind of stuff like this already exists, maybe in the industrial field...

Under safety considerations I`d prefer solution Nr. 1) or 3.).
With 2.) a relais could fail or the contacts could wield together.
In this regard there is not much what could get wrong with Nr. 1.) or 3.) - either it works - or not.
Catastrophic shorts are practically impossible (when 3.) is properly and rigid built).

Which kind of peak voltage and current we may find on high power amplifiers' outputs? 50V 10A ? more?