Bryston 2WSB switch box to choose amp that drives speakers


I really want to be able to choose between a low power amp for tv/background music and my good amp for serious music sessions. I'm tired of amp rolling, have posted recently about this and got good advice not to use two sets of speakers cables but only one live amp. So I'm thinking of a device like the Bryston, but have the speaker outputs be the amp inputs and the amp input be the speaker output. As long as only one speaker is selected at a time...electrically that should work. My only concern looking at the schematics is that the red positive leads are wired together and the black negative leads are switched. Could this still cause voltage to be applied to the unpowered amp? If so would swapping polarity work? There's a schematic on this page. 
https://reverb.com/item/10151350-bryston-2-way-speaker-switch-box-model-2wsb-sc1
Any help on this would be greatly appreciated.
treynolds155
First, a couple of corrections, with respect to the Bryston switchbox:

1) Ignore my previous comments about make-before-break vs. break-before-make. I hadn’t noticed that the Bryston unit provides a separate and independent switch for each of its two signal paths.

2) Bryston’s setup diagram that is shown in one of the photos at the link provided in the OP states that it is the black binding posts that are common to all inputs and outputs, which of course directly conflicts with their schematic that is also shown.

In any event, per my other comments I would rule that device out.

I can’t tell if the Russound switchbox Tony (Tls49) linked to would be suitable, because there is no indication as to whether or not it switches both + and -. Also, if the impedance of your speakers is in the vicinity of 4 ohms your S200 amp (rated at 100 watts per channel into 8 ohms) might be a bit too powerful for it, given the 150 watt power handling spec of the switchbox.

Regarding the Niles SPK-1 both gentlemen referred to, if I understand correctly it is designed to be switched by the switched AC outlet of a Receiver or other component that it would be used with. If neither of your amps provides such an outlet that may be an issue.

Perhaps a look through all of Niles’ switchbox offerings would prove useful, if you haven’t already done so:

https://www.nilesaudio.com/products/all/speaker-selectors/all

I did take a quick look through the various pro-oriented switchers that are carried by B&H Photo Video, but everything I saw there had some combination of uncertainties, involving power ratings that would be marginal at best and/or whether or not the unit switches both + and -.

Best regards,
-- Al
Thanks again Al for really digging in there to help out!! I think there's two versions of Bryston's switch so that may be the difference between common + or - rails. Regardless...probably not safe either way. I looked at Nile's site and their DPS-1 specifically states two amps switched to one pair of speakers but nothing specific about both +/- being switched and it sounds like their binding posts are anemic so probably not the quality I'm looking for.  

I'm starting to think a custom one is the way to go. I found this four pole/double throw on/off/on switch:
https://www.grainger.com/product/HONEYWELL-Toggle-Switch-24D454

All I'd need is a project box and some Cardas binding posts and wire. As long as the switch wasn't noisy it should work great. Thoughts?

Thanks 
Tim
Looks perfect. Nice find!

Also, Digikey sells it for a somewhat lower price:

https://www.digikey.com/product-detail/en/honeywell-sensing-and-productivity-solutions/4NT1-1/480-21...

Best regards,
-- Al

P.S: Keep in mind that if the lower powered amp happens to be a tube amp that has output transformers, it should not be operated without a load connected to its outputs, especially if it is being provided with an input signal.
I can confirm that the Niles SPK-1 switching both +/- terminals by using two 12V DPDT relay rated 8A @ 250V internally. The 12v trigger can simply use a 12V DC adapter.
https://www.amazon.com/Gxilee-100-240V-Converter-Household-Electronics/dp/B01FXF6AEQ
That's a great price Al. I like that it has an off position in the middle, no way for the two amps to be mixed. This whole thing may seem crazy to some but I'm really looking forward to being able to just flick a switch for what amp I want to use. 

I'll post pics when this is built, I've updated my system pics for my recent updates. Pales in comparison to a lot of the systems here but she's mine and it does sound real good...especially when the Threshold is in play. 

Thanks for all the links and help guys!!
Tim