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.
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.
Regards
Ian Menkins
Australia
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.
WARNINGS:
Consider when switching:
Always turn amplifiers off before switching, or reduce the volume on both amplifiers to zero before switching.
Switching
under full volume may cause a very loud clunk into the speakers and
this is undesirable and may damage equipment in the long term.
Always
follow the manufacturers advice on load ratings. Do not overload an
amp. This rule applies whether you are using it through a switch box or
independently. It is also very bad practise to link two amps together
to "boost" the amplification, unless the amps are specifically designed
for such use. Most are not.
Additional points: A lever or bridge control could possibly be devised, whereby all 6 switches can be switched simultaneously.
An 8 (or more) channel switcher could also be devised simply by adding an extra two (or more) toggles and output connectors.
