switch speaker between two amplifier

How to switch between two amplifier?

A CD Player with variable output drives directly an output stage. At a receiver are attached all other devices, record player, tape and television. For listening the cd it was necessary to switch the speaker between the two amplifier. A switch can do this for us.

Umschalter für beide Verstärker Frontansicht auf der Rückseite die Lautsprecheranschlüsse offenes Gehäuse, die Verdrahtung ist einfach Schaltplan für den Lautsprecher Umschalter zwischen zwei Verstärker
Figure 1 input from amplifiers Figure 2 speaker terminals Figure 3 open box with switches Figure 4 shows schematic

The switch should have at least some amperes. Disadvantages using a switch, some milliohms addidional resistance. Should be switched only when the amplifier is switched off, if not reduce the volume at least to zero before switch.

The following text and diagramm, email from Ian Menkins:

Dear Ralf,

I read with great interest your page on switching two amps between one set of speakers. I have found a similar problem, but with modern surround sound amps, which work on 6 or more channels. I have devised a solution, based roughly on your design, but this one caters for 6 speakers. I wonder if there could be an easy way to switch all 6 switches simultaneously? do you know of any bridge-type switches that could achieve this? I will attach my diagrams. You may like to use this information on your web site.

Ian Menkins

How to switch multiple speakers between a 6 channel surround sound system and a conventional two channel (A+B) amplifier.

(figure from Ian)

Problem: You have upgraded to a 6 channel surround sound system but still want to play older devices (eg. turntables, tape decks) through the same speakers. You do not want to clip and unclip all the speaker wires from the connectors every time you change devices. Furthermore, the practise of joining the two amps together through the speaker connectors at the back of one amp can be risky and is not recommended. It is also possible that undesirable sound distortions may "bounce back" from the idle amplifier. This practise may also damage the amps in the long term, although there is very little literature on this subject.

Most modern surround sound / home theatre systems / amplifiers are digital and rely on the relatively strong input signals from CDs or DVDs. They are not designed with old equipment in mind. Often a preamp is required if you want a modern amp to detect the very soft signals coming from a turntable stylus for instance, and even then the sound may appear distorted or of lower quality than you achieved from your old amp. The old amps that had PHONO and AUX settings were designed to amplify the really soft signals from such devices. You do not want to buy an extra set of speakers to cater for the old amp!

Solution: A switch box designed to handle the switching of 6 channels between two source amplifiers. Quality disadvantages: Additional resistance, some power loss and a little reduced damping factor. Not a good idea for an absolute hifi purist. Use gold connectors and quality silver wire if you wish to keep resistance to an absolute minimum.

Thanks a lot Ian for sharing your solution.

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