In article ,
Sanitarium wrote:

Hi Gurus... idiot here trying to make sense of things.

I always thought that a stereo amplifier running in bridged mono mode
inverts the mosfet output wave from one channel and couples that to the
other channel. This is how the circuit creates more power into one
channel.

How far off base am I?? :~)

Another thing. When a stereo amp is bridged mono pushing a 4 ohm load,
Is it true or false that the amps circuit sees this a a 2 ohm load? If
this is true, why?

Confused...
Garrett


Some amps always run with two channels inverted. That way a big bass
kick draws power from the positive power supply in one speaker and the
negative power supply in the other. It reduces the number of capacitors
that have to be packed into the amp. In such a case, the bridged mode
simply makes it mono.

Left + in --+---- non-inverting amp ---- Left + / Bridge +
|
| +--- Left -
Bridge switch (mono) |
| Ground --+--- Right +
|
Right + in --+---- inverting amp ---- Right - / Bridge -


Yes, bridging cuts the perceived output impedance in half. Think of it
this way. The two outputs are exactly opposite. Halfway inside the
coil they cancel to zero volts. It's like each amp is seeing a coil
half as long.


Cancels to zero volts
here in center
v
2 Ohms v 2 Ohms

^^^^^^^^^^^^^^^^^^^^
| |
| -- 4 Ohms -- |
| |
+ phase - phase