Stewart Pinkerton wrote in
:

On Fri, 04 Feb 2005 09:56:03 GMT, R wrote:

Stewart Pinkerton wrote in
m:

On Sat, 29 Jan 2005 04:01:15 GMT, R wrote:

Eiron wrote in
:

R wrote:

The only downside I know of (as long as both amp channels are
matched) is that permissable load impedance is doubled...IOW, if
your amp is rated for 4 ohms minimum, in bridged mode you can only
connect an 8 ohm load.

jak

That depends on the amp.
I know of at least 2 amps where the opposite is true. IOW, when in
normal mode impedance ranges are from 16 ohms to 0.5 ohms. When in
bridge mode the impedance range is 8 ohms to 0.25 ohms.

Nope, that statement remains wrong for the amps you mention, because
the reference is to *parallel* operation, not bridged.

BTW, you are attempting to use a probably unique range of amplifiers
(SS with output transformers) to 'prove' a point which is simply *not*
true for 99.99% of available SS amps. And you still got it wrong!

In that case the bridging is done by shorting the left and right
channels together at both input and output (with accurate balance
of gain and offset, and appropriate resistors to limit current).
so the voltage gain is the same and current capacity doubled.

Normal bridging doubles the voltage gain and leaves the
current capacity unchanged.

The amp in question can do either.

Nope, those amps are *not* intended for bridged use, and have no such
connection option. It's quite possible that an attempt to engage
bridged operation, by series connecting the output transformers as one
would for a valve amp, would destroy the amplifier.

One can indeed simply tie inputs and outputs together and is called
mono-parallel. The other method runs one channel through an inverter
and the resultant signal 180 degrees out of phase with respect to the
other and is called mono-bridged.

The output impedance is halved for parallel and doubled for bridged.

The output power is doubled no matter which method you choose.

Nope, given adequate current reserves, the output power is
*quadrupled* for bridging, and remains the same for parallel
operation. If you're talking about some POS valve jobby, then of
course the output transformer taps make the whole thing moot.

Don't believe me. I don't care. No, it is not some "POS valve jobbie"
either. Please remember that I said that it "depends on the amp".

It's SS, but it uses output transformers, hence my comments apply.
That (very unusual, posibly unique) series has the same speaker
coupling system as valve amps, hence the same rules are in force. I
"don't believe you" because you are just plain wrong, and clearly
don't understand bridged operation.

The owners manual certainly would indicate my statement to be true.

No, it wouldn't. Please learn to read clear specifications.

The point I made was simply this: Depending on the amp and the load, one
could have ones cake and eat it too. I do have to admit their 500 and 600
watt versions are a rather unique amp in that it can drive a 4 ohm load to
full power no matter if it is in parallel or bridged mode. Was it a bit
of a cheat? Yes, because there are very few SS amps with an output
transformer (actually autoformer in this case).


In
addition they have made the same "error" in their 600 watt and 500 watt
versions as well as one of their current amp offerings.

Here is the link to the owners manual for the 300 watt version.
http://berners.ch/McIntosh/Downloads/MC2300_own.pdf

Their current offering indicates that the power is doubled when in
parallel.

Sure - but not into the same load on the same transformer taps. Since
you don't seem to understand the basics, this means that while it can
put out 600 watts into 4 ohms, it does this by using the 8 ohm taps in
parallel operation. Hence, if you had quoted the *full* output specs,
you'd see that the 'power doubling' does *not* apply to a 15 ohm load,
the highest available tap.

I understand quite well thanks and yes, one won't realize full power using
a 16 ohm load when in parallel and one certainly won't realize full power
transfer when the load is not connected to the appropriate tap.



OTOH, my trusty Krell is rated at 200 watts/channel into 2 ohm loads,
and at 800 watts into the same 2-ohm load when bridged.


The Krell is like most other SS amplifiers and the behaviour you cite is
what I would expect. My old Carver amp exhibited that same behaviour.


http://www.mcintoshlabs.com/mcprod/....%5CMC402om.pdf

In case you don't have acrobat the specifications say:

"Power Output Stereo
Minimum sine wave continuous average power output per
channel, all channels operating is:
400 watts into 2 ohm load
400 watts into 4 ohm load
400 watts into 8 ohm load

Power Output Mono Parallel
Minimum sine wave continuous average power output is:
800 watts into 1 ohm load
800 watts into 2 ohm load
800 watts into 4 ohm load"

See above for another example of unequal comparisons re load
impedance.


I am not sure what you mean.


I should have qualified my last statement to say "The output power is
doubled no matter which method you choose with this amp."

Unfortunately, there is only *one* method, since bridging is not a
recommended option. Learn to RTFM..........

There is a switch on their 500 watt and 600 watt versions that has 3
positions. Stereo, mono-parallel, and mono-bridged. I must admit that
they don't have the ability to run in bridged mode with their latest
offerings, but they certainly did in earlier models. It is also apparant
that the requirements for their 500 and 600 watt designs was slightly
different than with their later amps.

There is more than one disadvantage to having an autoformer in an
amplifier. One being the additional weight and the other being the
additional cost. The advantages however are obvious and far outweigh the
disadvantages in my opinion.

r