Amp Switch (2 amps into 1 Set of Speakers)

[Pepperamip]

Having recently re-bought an Amptastic mini-1 to go into my main system which already comprises a Quad 306, I've decided to build my own amp switch box. In other words a speaker wire switch to save me having to unplug the speakers at either a. the amps or b. the speakers themselves.

This is the first hifi type thing I've built so it may be a bit rough around the edges but it should hopefully do exactly what I need it to when it's complete. I'll be using a single 4PDT toggle switch and 12 speaker binding posts.

Had some MDF lying around so I'm using that for the case:

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Leaving the front and back panels removable to aid in the soldering and testing and if I need to gain access in future (excuse the vinyl covering I know fake black marble isn't going to be to everyone's taste but again had it lying around) The labels are just off a hand held labeling machine:

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The toggle switch I'll be using should be identical to this:

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Once the toggle switch and binding posts arrive I'll stick up a few more pics to show the progress.

[Pepperamip]

Just make sure the switch is break-before-make, not make-before-break. A momentary short could do some damage.

I've read about the dangers of this Andrew. The switch is an On > Off > On design so does exactly that.

[walpurgis]

I don't like the idea of switch contacts in line with speaker cables.

[StanleyB]

Looking forward to seeing the finished item. But if you are not happy with the end result, just remember that I already designed and sell something similar with a double switch and a metal case.

[Pepperamip]

I don't like the idea of switch contacts in line with speaker cables.

Get what you mean here Geoff but with all the switching and electrical circuits within each box you and everyone else uses, does it really make that much difference? I'll be using good speaker wire inside the switch with silver solder and heat shrink to isolate everything. I agree it it's maybe one more extra unnecessary link in the chain but to what detriment in real terms?

[Pepperamip]

Looking forward to seeing the finished item. But if you are not happy with the end result, just remember that I already designed and sell something similar with a double switch and a metal case.

Stanley, this is obviously the Ferrari of amp switches..........mine will be Dacia Sandero, but I'm hoping, with similar results just not as pretty.

[walpurgis]

I agree it it's maybe one more extra unnecessary link in the chain

You summed it up there Paul.

[Pepperamip]

You summed it up there Paul.

Well i did but my point was is that of all the things that can effect the signal path on the way to the amp speaker outputs, adding a switch in that final chain is propably the least of anyone's worries when it comes to the final result. Maybe I'm being naive in that respect and if I am then I'd happily listen why.

[struth]

not keen on them from a safety position, but sound wise if right switches and cables are used not sure there will be much degradation if any to note.

[Andy831]

I have used Stanley's switch for years, never had a problem and my cloth ears certainly cannot detect whether the sitch is in the system or is out of the system and the speakers are being fed a direct signal.

Just saying!

[Barry]

The only concern with your arrangement is that the amplifier that is not selected is not given a load. The danger is that this amplifier could be switched on by accident without a load. To provide 'safety' loading would necessitate the use of an 8-pole double throw 'break before make' switch, and one where the time between 'break' and 'make' is very short.

As to the possible degradation of the signal through the insertion of another set of contacts, well provided the current rating of the switch is high enough the effect will be minimal.

I once built a switch box to switch the output of my amplifier to either speakers or headphones. I used a military (aviation) grade, 20A rated, Cutler-Hammer 4PDT switch. When switched to the headphone position, the amp was loaded by 10W 8Ohm metal-clad resistors, with the headphones fed via series 0.5W 100 Ohm resistors.

[Barry]

True, but most transistor amps are quite happy with no load, or should be.
The OP's amps are a Tripath switching amp and a Quad 306. I think both of those should be ok with no load.

Yes, I knew the Quad amp would be OK, but didn't know about the switching amp.

So, no problem. :)

[spendorman]

Well, I'm guessing that the switching amp will be ok with no load. Disclaimer to the OP: don't blame me if your house burns down :lol:

The guy that built my very good class D TPA3116 amp told me not to run it without speakers connected.

[StanleyB]

Get some 100 Ohms cement resistors of 5 or 10W rating. You'll need 4 pieces. One for each RCA/PHONO connector.

[Pepperamip]

I'll do this Stanley, thanks, by one for each RCA do you mean both ends connect to the one socket?

[Barry]

RCAs? Is that a typo, or are you using RCA connectors for your speaker connections?

[StanleyB]

I'll do this Stanley, thanks, by one for each RCA do you mean both ends connect to the one socket?
Each resistor should be connected from the signal pin to the ground pin on the same connector. If you want to, email me and I can send you a diagram back attached to the email.

[daddydj]

I am interested in the progress of this idea.
I run two systems in one room; AV system and a system for stereo. I am sick of unplugging and replugging everytime I go from system to system.
I was originally trying to figure out how to implement a home theatre bypass, but an amp switching facility would suffice.
StanleyB I like the look of your basic unit and the idea of the dummy load. How does this work in practice?

[Pepperamip]

Morning all, just thought I'd give an update on the progress of my speaker wire switch.

The parts I was waiting on arrived from China and seem well made to my un-trained eye. I also found the MDF I was using way too thick for the front and back panels so I cut out 2 pieces of ply wood instead.

Here's the front and back of the front panel with the on>off>on switch wired in:
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And here's the back panel with the gold plated (questionable) speaker binding posts. Theres a bit too much space between each set of 4 for my liking but hopefully only an issue aesthetically.
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I'll post up some final pics once the binding posts are wired in and it's all been screwed together.

[StanleyB]

I am interested in the progress of this idea.
I run two systems in one room; AV system and a system for stereo. I am sick of unplugging and replugging everytime I go from system to system.
I was originally trying to figure out how to implement a home theatre bypass, but an amp switching facility would suffice.
StanleyB I like the look of your basic unit and the idea of the dummy load. How does this work in practice?
You press the two switches on the TC-7210 (Left and Right speakers) to switch over between amps. That's how simple it is :). It's quickly becoming popular with valve amp owners since valve amps need a load at all times.

[StanleyB]

Morning all, just thought I'd give an update on the progress of my speaker wire switch.
That's looking great Paul. Any idea what finish you'll give to the wood?

[Stryder5]

If you have front pre-out on A/V amp connect interconnects from the pre-amp to an input on the stereo amp, remove front speaker leads from A/V amp and connect to speaker terminals on stereo amp, turn everything on, match the volume of A/V amp and stereo, volume will now be controlled by A/V amp.




I am interested in the progress of this idea.
I run two systems in one room; AV system and a system for stereo. I am sick of unplugging and replugging everytime I go from system to system.
I was originally trying to figure out how to implement a home theatre bypass, but an amp switching facility would suffice.
StanleyB I like the look of your basic unit and the idea of the dummy load. How does this work in practice?

[Pepperamip]

That's looking great Paul. Any idea what finish you'll give to the wood?

Thanks Stanley. Prob not that visible in my pics but I've used some vinyl wrap type sticky back plastic and it's your staple hifi black marble (like all hifi cases should be made from :) Actually doesn't look as bad as it sounds but luckily it will be hidden away out of sight.