Is there a sound quality downside in using an amplifier that is
bridged? I've heard various things about this, not to mention that
some of what I've read says speakers will sound better when the amp is
bridged given the increase of its power. Thanks

soinie wrote:
Is there a sound quality downside in using an amplifier that is
bridged? I've heard various things about this, not to mention that
some of what I've read says speakers will sound better when the amp is
bridged given the increase of its power. Thanks

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

"Mark D. Zacharias" wrote in message
...
Certainly noise (a constant value from each "1/2" amp channel), would
amount
to 4 times the amount of a single-ended model. (The residual noise voltage
is doubled.)

And so is the signal voltage, thus S/N ratio should be the same in both
cases.
In fact it's quite possible that because the signal is correlated and the
noise is not (or at least not as much) then the S/N ratio of a bridge amp
could be lower. Other factors may have more influence though.

MrT.

"Mark D. Zacharias" wrote ...
Certainly noise (a constant value from each "1/2" amp channel), would
amount to 4 times the amount of a single-ended model. (The residual
noise voltage is doubled.)

Since noise is random and uncorrelated, does it really behave
the same way as coherent signals?

Richard Crowley wrote:
"Mark D. Zacharias" wrote ...
Certainly noise (a constant value from each "1/2" amp channel), would
amount to 4 times the amount of a single-ended model. (The residual
noise voltage is doubled.)

Since noise is random and uncorrelated, does it really behave
the same way as coherent signals?

No.

The signal voltage for any given listening volume would be the same. The
noise would still be doubled in voltage, hence 4X it's contribution to the
distortion figure. This seems fairly obvious.

Let's hear from Krueger, Pinkerton and the rest. They'll be able to tell us
what other distortion issues arise from bridging. As I said, I'm not an
engineer, and if I stray too far into area of theory, I'm certain to get my
ass handed to me.

Mark Z.


"Mr. T" mrt@home wrote in message
...

"Mark D. Zacharias" wrote in message
...
Certainly noise (a constant value from each "1/2" amp channel), would
amount
to 4 times the amount of a single-ended model. (The residual noise
voltage
is doubled.)

And so is the signal voltage, thus S/N ratio should be the same in both
cases.
In fact it's quite possible that because the signal is correlated and the
noise is not (or at least not as much) then the S/N ratio of a bridge amp
could be lower. Other factors may have more influence though.

MrT.

"Mark D. Zacharias" wrote in message


Certainly noise (a constant value from each "1/2" amp channel), would
amount to 4 times the amount of a single-ended model. (The residual
noise voltage is doubled.) Noise qualifies as distortion. Certain
other types of distortion would effectively be higher as well, I
would presume.
I'm not an engineer, I should hasten to add, but someone out there
will surely add to this thread.

Depends on the nature of the noise. If it is plain old random noise, then
the noise sources in the two power amps are uncorrelated. That means that
they sum geometrically (square root of sum of squares). If they are equal
amplitude, then they sum to the square root of two times either.

As others have pointed out, the signals sum with ordinary arithmetic. So,
dynamic range *increases* by about 3 dB.

"soinie" wrote in message



Is there a sound quality downside in using an amplifier that is
bridged?

Essentially, bridging is generally used as a means to increase the amount of
current the amplifier provides to a given load. This increase is obtained
at the significant cost of halving the number of channels.

If you bridge an amp, the availble output signal voltage is roughly doubled.
Therefore, the current delivered to a reasonably linear load is increased
proportionately. Current drain is related to stress on the amplifier, so
bridging necessarily increases the stress on the amplifier. Nonlinearity in
the amplifier is related to stress provided by the load, so bridging
necessarily increases the nonlinearity of the amplifier.

I've heard various things about this, not to mention that
some of what I've read says speakers will sound better when the amp is
bridged given the increase of its power.

Bottom line, the sound of an amplifier running out of power, or clipping is
pretty nasty. Avoiding clipping is of paramount importance in high fidelity
applications.

Modern amplifiers are generally quite linear when run below clipping.
Therefore, additional nonlinearity due to bridging can often be quite
acceptable and unnoticeable from the standpoint of listening pleasure.

Modern amplifiers are generally congenitally overbuilt for high fidelity
purposes because of FTC regulations. Therefore, they may be more suitable
for bridged applications than a cursory examination of their specs might
suggest. This varies from rock sound reinforcement and certain car audio
purposes where amplifiers are more likely to be congenitally clipped,
overloaded and overstressed.

It comes down to practicality and economics. When you bridge a power amp,
you double the number of amplifiers required for the same number of
channels. If a correspondingly more powerful amplifier has disproportionate
higher cost, then bridging can be economical. If you already have a
bridgeable amplifier, it generally costs less to double the number of
amplifiers, than it does to get all new, more powerful amplifiers.

OTOH, if a more powerful amplifier has a vastly superior price/performance,
then it can be more economical to simply get bigger amplifiers.

I have built quite a number of amplifiers -- one of the easiest to bridge is
that based upon National Semi's "Overture" series amp chips -- if careful
attention is paid to layout, the distortion specs can be quite good.

the PDmax for the devices used in a bridged amplifier is increased by a
factor of 4 -- so there can be quite a lot of thermal stress.

I will post on ABSE a picture of the THD vs frequency for an LM4780 based
bridged amplifier.


"Arny Krueger" wrote in message
...
"soinie" wrote in message



Is there a sound quality downside in using an amplifier that is
bridged?

Essentially, bridging is generally used as a means to increase the amount
of
current the amplifier provides to a given load. This increase is obtained
at the significant cost of halving the number of channels.

If you bridge an amp, the availble output signal voltage is roughly
doubled.
Therefore, the current delivered to a reasonably linear load is increased
proportionately. Current drain is related to stress on the amplifier, so
bridging necessarily increases the stress on the amplifier. Nonlinearity
in
the amplifier is related to stress provided by the load, so bridging
necessarily increases the nonlinearity of the amplifier.

I've heard various things about this, not to mention that
some of what I've read says speakers will sound better when the amp is
bridged given the increase of its power.

Bottom line, the sound of an amplifier running out of power, or clipping
is
pretty nasty. Avoiding clipping is of paramount importance in high
fidelity
applications.

Modern amplifiers are generally quite linear when run below clipping.
Therefore, additional nonlinearity due to bridging can often be quite
acceptable and unnoticeable from the standpoint of listening pleasure.

Modern amplifiers are generally congenitally overbuilt for high fidelity
purposes because of FTC regulations. Therefore, they may be more suitable
for bridged applications than a cursory examination of their specs might
suggest. This varies from rock sound reinforcement and certain car audio
purposes where amplifiers are more likely to be congenitally clipped,
overloaded and overstressed.

It comes down to practicality and economics. When you bridge a power amp,
you double the number of amplifiers required for the same number of
channels. If a correspondingly more powerful amplifier has
disproportionate
higher cost, then bridging can be economical. If you already have a
bridgeable amplifier, it generally costs less to double the number of
amplifiers, than it does to get all new, more powerful amplifiers.

OTOH, if a more powerful amplifier has a vastly superior
price/performance,
then it can be more economical to simply get bigger amplifiers.

"Mark D. Zacharias" wrote in message
...
The signal voltage for any given listening volume would be the same. The
noise would still be doubled in voltage, hence 4X it's contribution to the
distortion figure. This seems fairly obvious.

Not really. Remember, you are doubling noise, which will be different in
the two channels. If you sum two uncorrelated noise signals, the noise
power goes up only 3dB (doubles the power, not quadruples).


Let's hear from Krueger, Pinkerton and the rest. They'll be able to tell
us
what other distortion issues arise from bridging. As I said, I'm not an
engineer, and if I stray too far into area of theory, I'm certain to get
my
ass handed to me.

Mark Z.


"Mr. T" mrt@home wrote in message
...

"Mark D. Zacharias" wrote in message
...
Certainly noise (a constant value from each "1/2" amp channel), would
amount
to 4 times the amount of a single-ended model. (The residual noise
voltage
is doubled.)

And so is the signal voltage, thus S/N ratio should be the same in both
cases.
In fact it's quite possible that because the signal is correlated and
the
noise is not (or at least not as much) then the S/N ratio of a bridge
amp
could be lower. Other factors may have more influence though.

MrT.

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.


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.

--
Eiron.

"Mark D. Zacharias" wrote in message
...
The signal voltage for any given listening volume would be the same. The
noise would still be doubled in voltage, hence 4X it's contribution to the
distortion figure. This seems fairly obvious.

To you maybe, why don't you do some actual measurements and get back to us.
Fact is, that to maintain the same signal level, we can reduce the gain, and
hence the noise drops. The S/N ratio remains the same or better, as I said.

You should also know that noise is NOT distortion, That is why such a
measurement is called Noise *AND* Distortion.
A *PROPER* THD or IMD measurement does NOT include noise outside of the
measured frequency bands. This is pretty easy to do correctly these days
with DSP techniques.

Let's hear from Krueger, Pinkerton and the rest. They'll be able to tell
us
what other distortion issues arise from bridging. As I said, I'm not an
engineer, and if I stray too far into area of theory, I'm certain to get
my
ass handed to me.

A better method is to do some research of your own, until you understand
what is being said.

MrT.

Mark D. Zacharias wrote:
The signal voltage for any given listening volume would be the same.
The noise would still be doubled in voltage, hence 4X it's
contribution to the distortion figure.
This seems fairly obvious.

It might seem obvious, but it's still wrong, nonetheless.

First, the definition of "distortion" is not agreed upon. If
you mean the added components to the signal as a result of the
non-linear properties of the amplifier, whoichm BTW is the
commonly accepted definition of dfisortion when used in reference
to audio amplifiers, no, it does NOT contribute to the distortion
figure).

But, specifically to the contribution of noise:

Unless by some miracle the noise voltage at each and every instant
in both amplifiers is identical in amplitude, the noise WILL not
and CAN not add as you claim. Indeed, assuming you're talking about
noise generated in each of the amplifier channels, that noise will
be completely uncorrelated.

For those that have studied such topics, it's in fact obvious
that two uncorrelated noise sources of the same RMS level,
adding the noise voltages WILL NOT result in double the noise
voltage, but only the sqrt(2), precisely because they are
uncorrelated.

As I said, I'm not an engineer,
Yes, the evidence before us supports your assertion.

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.


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.

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.

Maybe one can have one's cake and eat it too as most speakers are 4 ohms
and there are taps for 1, 2, 4, and 8 ohms.

r


--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.

On Sat, 29 Jan 2005 10:02:48 +1100, "Mr.T" MrT@home wrote:


"Mark D. Zacharias" wrote in message
...
The signal voltage for any given listening volume would be the same. The
noise would still be doubled in voltage, hence 4X it's contribution to the
distortion figure. This seems fairly obvious.

To you maybe, why don't you do some actual measurements and get back to us.
Fact is, that to maintain the same signal level, we can reduce the gain, and
hence the noise drops. The S/N ratio remains the same or better, as I said.

In a typical amplifier, the output voltage will increase by 6dB, but
the output noise will only increase by about 3dB, due to it being
uncorrelated (random, if you like). In some designs, you might even
gain a little more S/N if you sendipitously cancel PSU components by
the use of a differential system such as bridging.

You should also know that noise is NOT distortion, That is why such a
measurement is called Noise *AND* Distortion.
A *PROPER* THD or IMD measurement does NOT include noise outside of the
measured frequency bands. This is pretty easy to do correctly these days
with DSP techniques.

Um, well, there's some debate on that subject, as some authorities
maintain that anything not the desired signal is *by definition*
'distortion', and that of course includes noise, bith thermal and
PSU-related.

Let's hear from Krueger, Pinkerton and the rest. They'll be able to tell us
what other distortion issues arise from bridging. As I said, I'm not an
engineer, and if I stray too far into area of theory, I'm certain to get my
ass handed to me.

The issues which areis eare all to do with the fact athat the
effective load impedance is halved. All amplifiers have higher
distortion into low impedance loads.

A better method is to do some research of your own, until you understand
what is being said.

Inded, but these newsgroups can provide handy shortcuts! :-)
--

Stewart Pinkerton | Music is Art - Audio is Engineering

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.


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.

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.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"Stewart Pinkerton" wrote in message
...
In a typical amplifier, the output voltage will increase by 6dB, but
the output noise will only increase by about 3dB, due to it being
uncorrelated (random, if you like).

As I and many others have already pointed out.

You should also know that noise is NOT distortion, That is why such a
measurement is called Noise *AND* Distortion.
A *PROPER* THD or IMD measurement does NOT include noise outside of the
measured frequency bands. This is pretty easy to do correctly these days
with DSP techniques.

Um, well, there's some debate on that subject, as some authorities
maintain that anything not the desired signal is *by definition*
'distortion', and that of course includes noise, bith thermal and
PSU-related.

Not really. THD stands for Total HARMONIC Distortion, so anything not
harmonic by definition is not included.
IMD stands for Intermodulation Distortion, etc.

You can of course include noise in an overall sweeping statement called
"distortion" I guess, but I already clarified what I meant..

MrT.

Mr.T MrT@home wrote:

Not really. THD stands for Total HARMONIC Distortion, so anything not
harmonic by definition is not included.
IMD stands for Intermodulation Distortion, etc.

That's the abstract definition of an idea. Whan actually using a null
analyser, it doesn't know the difference, and unless you do spectrum analysis
on the results, what ever is left after the null is what you get, and a
percentage # compared to the total output is produced.

By itself, it's a pretty useless test, except maybe for production quality
control purposes and the most basic of design specifications.

On Fri, 4 Feb 2005 09:37:03 +1100, "Mr.T" MrT@home wrote:


"Stewart Pinkerton" wrote in message
.. .
In a typical amplifier, the output voltage will increase by 6dB, but
the output noise will only increase by about 3dB, due to it being
uncorrelated (random, if you like).

As I and many others have already pointed out.

You should also know that noise is NOT distortion, That is why such a
measurement is called Noise *AND* Distortion.
A *PROPER* THD or IMD measurement does NOT include noise outside of the
measured frequency bands. This is pretty easy to do correctly these days
with DSP techniques.

Um, well, there's some debate on that subject, as some authorities
maintain that anything not the desired signal is *by definition*
'distortion', and that of course includes noise, both thermal and
PSU-related.

Not really. THD stands for Total HARMONIC Distortion, so anything not
harmonic by definition is not included.
IMD stands for Intermodulation Distortion, etc.

You can of course include noise in an overall sweeping statement called
"distortion" I guess, but I already clarified what I meant..

No, you didn't, since your first statement was that "noise is NOT
distortion, That is why such a measurement is called Noise *AND*
Distortion."

I pointed out that this is a matter of debate, which it is.

You went on to correctly explain that IMD and HD can be separately
measured, but that's another matter. BTW, if you use a traditional
'distortion meter', which simply notches out the fundamental, then the
residual includes all forms of distortion, *including* noise.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

Stewart Pinkerton wrote in
:

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.


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.

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".

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

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"

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

r
--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.

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

Stewart Pinkerton wrote in
:

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.

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.

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.

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 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..........
--

Stewart Pinkerton | Music is Art - Audio is Engineering

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

wrote in message
...
Mr.T MrT@home wrote:

Not really. THD stands for Total HARMONIC Distortion, so anything not
harmonic by definition is not included.
IMD stands for Intermodulation Distortion, etc.

That's the abstract definition of an idea. Whan actually using a null
analyser, it doesn't know the difference, and unless you do spectrum
analysis
on the results, what ever is left after the null is what you get, and a
percentage # compared to the total output is produced.

Maybe you should read what I wrote originally. You are referring to S/N+D
measurement.
Spectrum analysis via DSP FFT is the more common technique for THD and IMD
these days.

MrT.

"Stewart Pinkerton" wrote in message
...
Not really. THD stands for Total HARMONIC Distortion, so anything not
harmonic by definition is not included.
IMD stands for Intermodulation Distortion, etc.

You can of course include noise in an overall sweeping statement called
"distortion" I guess, but I already clarified what I meant..

No, you didn't, since your first statement was that "noise is NOT
distortion, That is why such a measurement is called Noise *AND*
Distortion."

WHY did YOU snip it then????????????

Here it is again!!!!!!!!!!!!!

"A *PROPER* THD or IMD measurement does NOT include noise outside of the
measured frequency bands. This is pretty easy to do correctly these days
with DSP techniques."

What part of THD and IMD do you want me to explain?

MrT.

Mr.T MrT@home wrote:

wrote in message
...
Mr.T MrT@home wrote:

Not really. THD stands for Total HARMONIC Distortion, so anything not
harmonic by definition is not included.
IMD stands for Intermodulation Distortion, etc.

That's the abstract definition of an idea. Whan actually using a null
analyser, it doesn't know the difference, and unless you do spectrum
analysis
on the results, what ever is left after the null is what you get, and a
percentage # compared to the total output is produced.

Maybe you should read what I wrote originally. You are referring to S/N+D
measurement.
Spectrum analysis via DSP FFT is the more common technique for THD and IMD
these days.

I don't disagree with you, but was thinking of the more global
context, which still can be usefull in the aggregate under some
circumstances.