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DIY amplifier/speaker switching box


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I run two vintage amps (Sansui AU-517 and Kenwood KA-6100) and two sets of speakers (Usher S520 and Sound Dynamics 300ti) in my system, and I've always wanted to be able to run any set of speakers of any amp at any time, along with being able to switch quickly between two amps runnng one set of speakers.

To achieve this, Dad (skippy124) and I put our heads together and determined that a pair of 4PDT switches (one per set of speakers) would do the job nicely.

I've wired up each switch so that the Sound Dynamics are fed by the speaker 'A' ouputs of the amps, and the Ushers are fed by the speaker 'B' outputs. So, in effect, with both amps set to 'A', the switch feeding the Sound Dynamics speakers can be switched between either the Sansui or the Kenwood, and with both set to 'B', the Ushers can take their pick.

The switches are heavy duty 250V 32A switches so they should easily be able to deal with a pair of sub-100W/ch amps. The switch specs say less than 0.01 ohm contact resistance, so there should be hardly any insertion loss. I'll be buggered if I can hear any audible difference.

I mounted the switches in a little timber box that I had lying around. I will either stain, varnish or paint this at some stage once I decide what kind of look I want (ie, white, black, or a nice stained timber finish). There's a foam 'grommet' at the rear which provides some strain relief on the wiring (in conjunction with the cable-tie around the wires to prevent the wires from pulling through the foam).

It works perfectly, and makes switching between amps and speakers an absolute breeze. It sure beats mucking around behind the amps to switch speaker cables etc. Also, the ability to switch between amplification sources instantaneously means that proper A/B comparisons are so much easier to undertake.

So... what's the verdict? Does the Sansui or Kenwood (both 90% recapped and restored) sound better? I think I need some more listening time... they are both very damn close! Initial thoughts are that the Sansui is a little more refined, whilst the Kenwood is a bit more dynamic and in your face. There's bugger-all in it though - I'm splitting hairs here.

switchbox3.jpg

switchbox2.jpg

switchbox4.jpg

Edited by pete_mac
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Yeah, I reckon it should come up nicely.

I'l still undecided whether to label the switches or not. I know that the top switch is for the SDs and the bottom is the Ushers, and up = the uppermost amp and down = the bottom amp. I might just leave it as-is for a while until I make up my mind...

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Great job guys

I need to do something similar so I can chose rear surrounds or outside speakers off 2 channels of my power amp.

But in my case I need 2 inputs and 2 outputs for

1. RCA and

2. Speakers

Have been looking for a metal casing rather than timber so I can sit it on the power amp.

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I received a question on audiokarma.org re: how to wire up the switch, so I prepared a dodgy diagram. I figured it was worth posting here too.

The photo of the switch is taken from the rear to show the connection points. The switch 'lever' moves up or down in a vertical manner, relative to the position of the switch in the photo.

There are 12 connections on each switch.

The left picture with the vertical red lines shows the polarity of the speaker wire connections.

The right picture with the horizontal red lines shows the grouping of the switch connections based upon the inputs and output. Amplifier A is shown as the bottom row of connections. Amplifier B is the top row of connections. This way, when the switch lever is facing up, it corresponds with amplifier A, and down corresponds with amplifer B (it's more logical this way).

The speaker output is the centre row of connections. As you toggle the switch up and down, the centre 'speaker' connection remains as a constant, and you are switching between either the top or bottom row of contacts.

I hope this makes sense... I get the feeling that I have over-complicated this explanation!

Also, I found some specs on these switches... less than 0.01 ohms contact resistance, so the insertion loss should be negligible in my application and power levels.

switchbottomedited3.jpg

Edited by pete_mac
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Good work Pete + John. I've been busy building a pair of matched boxes - one to house this switch and another to house a DAC. I'll post pics once they're done.

I like all the "and"s in your signature :party

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  • 5 weeks later...

As promised, photos of my finished switch box. It took longer than planned, but I'm very happy with the results.

A lot of effort went into machining 2 pieces of rough sawn timber (jarrah/mahogany) into lots of little blocks, then assembling and lacquering (~10 coats), sanding, polishing, etc. The aluminium was an offcut I had sitting around that I cut, then "brushed" myself. I would have preferred black, brushed aluminium but didn't want to buy it.

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  • 1 month later...

Of course I can, but it's really skippy124 who should get the credit for the "design" and pete_mac who gets credit for drawing it up :mad:

All you need is a 4 pole, double-throw switch. The one we used was a cheapy from ebay that you can pickup from Here. Trouble is, that's an auction for a lot of 10 switches and I can't find a sale for the single switch we were able to buy. You could also buy This one as the only difference is there is a center-off position (as in, there's 3 positions with an extra position where no amp/speakers are connected). If you're the kind of person who wouldn't consider putting a cheap $5 switch in their hifi system, you could always order This switch which serves the same function, but uses silver-plated contacts. You can also search most large electronics shops for "4PDT" (an abbreviation of 4 pole, double throw) and find suitable switches - try to get 20A or larger.

For the wiring diagram, the one pete_mac posted above (post #5) is fine. If you have trouble understanding it, let us know and we'll try to help you out.

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  • 5 months later...

Hi All,

First post here, I've been reading this thread with interest.

I have a bi-amped 2ch system plus a separate AVR. I want to use my front speakers from both systems to cut down on the amount of clutter in my lounge. I've been looking for a bi-wireable speaker switch without success so started looking into building one myself hence how I ended up here.

A couple of questions: How do you calculate the requirements of the switch? I see that a 20A <0.01ohm switch is recommended, is this a failsafe catch all? I like the use of the cat5 wiring but is this sufficient when we all get embroiled in the speaker cable debates?

I'm thinking of either a 8PDT rotary switch or managing the switching by relays.

Any advice greatfully received.

Thanks,

Moose.

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Funny that you should bump this thread up... I noticed that Beresford are doing a speaker/amplifier switching box that provides a more formal approach to amplifier switching:

http://www.beresford.me/PP/TC2D7220_AUDIO_ROUTER.html

Regarding the amperage and resistance of the switches, I'm pretty sure that the above specs minimise the 'insertion losses' resulting from adding a switch into the circuit, as well as providing sufficient current capacity headroom for higher-power systems.

Sadly, my original switching box has been stored in the garage as my PC-based multi-amp/multi-speaker audio setup is no longer. I'm only running one amp and one pair of speakers on the PC now.

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A couple of questions: How do you calculate the requirements of the switch? I see that a 20A <0.01ohm switch is recommended, is this a failsafe catch all? I like the use of the cat5 wiring but is this sufficient when we all get embroiled in the speaker cable debates?

I'm thinking of either a 8PDT rotary switch or managing the switching by relays.

My understanding is that switches are rated by current rather than power, that's why we picked a 20A switch rather than say a "200w" switch - I don't think "200w" switches exist. The current you need to switch will depend on your amp. If you have one that was advertised as "High current" (Naim, Quad, etc) the 20A switch would be sensible (actual requirement is probably 10-15A). Something like a Tripath would probably be fine with a 1A switch, most amps fall in the middle.

If you can find an 8PDT switch that would do the job for you but relays may be a better way once you start talking about bi-wiring.

...and there's a reasonable following of CAT6 cable for speaker cable out there. Some people hold it in very high regard indeed and the ~5m set I use are certainly better than anything I can get from local electronics shops. There's plenty of construction techniques out there on the web, my favourite (and what I run) are the TNT TripleT design.

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  • 1 month later...

Great little switch box pete_mac. I'm gonna build me one!

MellowFellow: Beautiful job. I think mine will follow your lead of using binding posts instead of hard-wiring directly to the switches. But I disagree with your recommendation of 20A or higher. Any speakers that I'm familiar with that recommend fuses (AR, KLH, Advent) generally recommend fuses of 1 to 2 amps. There's just not that much current running to the speakers. I think a 5 or 6 amp 4PDT switch is plenty.

OTOH, here in the US I can get 20A switches on ebay cheaper than 6A switches from the electronics supply house (Mouser.com) so why not go for the bigger ones. Just saying it's not necessarily necessary.

Kent

Edited by JKent
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  • 7 months later...


Great little switch box pete_mac. I'm gonna build me one!

MellowFellow: Beautiful job. I think mine will follow your lead of using binding posts instead of hard-wiring directly to the switches. But I disagree with your recommendation of 20A or higher. Any speakers that I'm familiar with that recommend fuses (AR, KLH, Advent) generally recommend fuses of 1 to 2 amps. There's just not that much current running to the speakers. I think a 5 or 6 amp 4PDT switch is plenty.

OTOH, here in the US I can get 20A switches on ebay cheaper than 6A switches from the electronics supply house (Mouser.com) so why not go for the bigger ones. Just saying it's not necessarily necessary.

Kent

I only just noticed this post above. Sorry for the delay in my reply.

We chose a high current capacity switch as they have better quality, larger size contacts, therefore lower contact resistance. Current capacity wasn't really an issue... resistance was the primary consideration.

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