"Meindert Sprang" wrote in message ...
"Larry W4CSC" wrote in message
...
Never, EVER connect two transistor amplifiers in parallel......

Actually, in high power car systems, they do exactly what you just said that
cannot be done. In such systems, each channel has two amplifiers, carrying
the signal in opposite phase. The speaker is connected to both outputs. This
way, the maximum voltage that can be created across the speaker is doubled.


First of all, to do what you describe (double the max. voltage) the amplifiers
would be connected in series not in parallel. Secondly, as you say, both
amplifiers are fed the same input signal in opposite phase, not different
signals as has been suggested. This technique is called "bridging" and has
been used for years in concert hall PA systems and other applications where
LOTS of decibels are desired (such as ridiculously over powered car stereos).
Connecting two transistor amps in parallel with different input signals is
only a good idea if both the VHF and the AM/FM radios are old and you'd like
to replace them but you wife won't let you because "they work just fine". ;-)
Don't do it.

Bob

"Bob Gough" wrote in message
om...

First of all, to do what you describe (double the max. voltage) the
amplifiers
would be connected in series not in parallel.

No. It's a bridge configuration.

Secondly, as you say, both
amplifiers are fed the same input signal in opposite phase, not different
signals as has been suggested.

That makes no difference. In fact, when both aplifiers get the same,
opposite signal, it stresses the amps most, because if one outputs maximum
positive voltage, the other outputs maximum negative. With different
signals, the difference in voltages is always lower on average.

Which reminds me of a configuration that was quite popular many years ago:
to create some sense of depth in a stereo signal, some people connected a
third speaker between the 'hot' ends of the stereo outputs.

So again, it is quite possible, the only requirement is that both devices
have roughly the same power output capability.

Meindert

"Bob Gough" wrote in message
om...

First of all, to do what you describe (double the max. voltage) the
amplifiers
would be connected in series not in parallel.

No. It's a bridge configuration.

Secondly, as you say, both
amplifiers are fed the same input signal in opposite phase, not different
signals as has been suggested.

That makes no difference. In fact, when both aplifiers get the same,
opposite signal, it stresses the amps most, because if one outputs maximum
positive voltage, the other outputs maximum negative. With different
signals, the difference in voltages is always lower on average.

Which reminds me of a configuration that was quite popular many years ago:
to create some sense of depth in a stereo signal, some people connected a
third speaker between the 'hot' ends of the stereo outputs.

So again, it is quite possible, the only requirement is that both devices
have roughly the same power output capability.

Meindert