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post #1 of 36 Old 11-09-2010, 08:43 PM - Thread Starter
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my speakers are not biampable, I was curious about amps that offer internal bridging, the only 1 I can think of are the older classe cav 150's, are there any others, thanks
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post #2 of 36 Old 11-09-2010, 08:51 PM
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Quote:
Originally Posted by panzer View Post

my speakers are not biampable, I was curious about amps that offer internal bridging, the only 1 I can think of are the older classe cav 150's, are there any others, thanks

Just buy the proper size amp. Nothing I have read indicates ant advantage to passive biamping (biamping into a speaker with a passive crossover, as opposed to biamping via active crossovers, with no speaker crossover)

From what I have read, better to go with a 200 watt / ch amp (not biamped), than a 100 watt / ch biamp setup.

One thing you will read is that the low side needs a lot more power. So it's good to have a bigger amp for that reason.

Active biamping seems to be a different story, for technical reasons - it splits the line level signal itself, and seems to have the ability to sort of magically increase power over passive biamping (without requiring more amp power.)

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post #3 of 36 Old 11-09-2010, 09:45 PM
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my McIntosh MC7106 is bridgeable from 6 channels to 3 channels 300wpc which is how i'm using it for my front soundstage currently
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post #4 of 36 Old 11-09-2010, 11:04 PM
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Quote:
Originally Posted by MichaelJHuman View Post

Just buy the proper size amp. Nothing I have read indicates ant advantage to passive biamping (biamping into a speaker with a passive crossover, as opposed to biamping via active crossovers, with no speaker crossover)

The OP is asking about bridge amps. In that case, the answer is as a wise man once said: "Just buy the proper size amp." It's even worse to bridge amps than to bi-amp. Reduces the damping factor by half, increases the distortion and noise.
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post #5 of 36 Old 11-10-2010, 01:38 AM
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Quote:
Originally Posted by Roger Dressler View Post

The OP is asking about bridge amps. In that case, the answer is as a wise man once said: "Just buy the proper size amp." It's even worse to bridge amps than to bi-amp. Reduces the damping factor by half, increases the distortion and noise.

That is the first I have ever heard about increasing "noise" by bridging. are you saying i'm losing something by using bridged mode x 3 at 300wpc instead of using the 6 channels at their 150wpc standard mode? I would have to disagree at least to my ears as I hear no noise at all in either mode...but I certainly noticed the music open up by feeding the speakers more power.
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post #6 of 36 Old 11-10-2010, 05:19 AM - Thread Starter
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the reason for my post, is that I once owned the classe cav 150, it was much better in the bridged mode as opposed to using it as a straight 6 channel amp, there are a few classe cav 150's for sale on audiogon, but they are vastly overpriced considering their age, so I am looking for a new amp with similar capability's, thanks
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post #7 of 36 Old 11-10-2010, 06:19 AM
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Quote:
Originally Posted by Pure-Evil View Post

That is the first I have ever heard about increasing "noise" by bridging. are you saying i'm losing something by using bridged mode x 3 at 300wpc instead of using the 6 channels at their 150wpc standard mode? I would have to disagree at least to my ears as I hear no noise at all in either mode...but I certainly noticed the music open up by feeding the speakers more power.

why do you assume that if noise is increased you necessarily will hear it? Your amps have some degree of self noise however they are configured. Audibility depends on a variety of factors. Similarly if damping factor decreases, you may or may not notice an effect. Depends on what its increasing to, and how hard your speakers are to drive.
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post #8 of 36 Old 11-10-2010, 11:46 AM
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Quote:
Originally Posted by Pure-Evil View Post

That is the first I have ever heard about increasing "noise" by bridging. are you saying i'm losing something by using bridged mode x 3 at 300wpc instead of using the 6 channels at their 150wpc standard mode? I would have to disagree at least to my ears as I hear no noise at all in either mode...but I certainly noticed the music open up by feeding the speakers more power.

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Originally Posted by JHAz View Post

why do you assume that if noise is increased you necessarily will hear it? Your amps have some degree of self noise however they are configured. Audibility depends on a variety of factors. Similarly if damping factor decreases, you may or may not notice an effect. Depends on what its increasing to, and how hard your speakers are to drive.

JHAz is correct that noise is the least of the issues. I just included it for completeness. If the noise floor is dominated by the source signal, then the amp's noise will remain inaudible. Depends on the amp. Classe amps are certainly dead quiet. I presume McIntosh are, too.

As for "feeding the speakers more power" that would only be true if in single-amp mode the amp output was clipping. Yes, the bridge amp can swing roughly double the voltage. If your 100w amps were regularly clipping, then yes, bridging is a viable solution. But most systems are not suffering from inadequate voltage swing.

Consider: When we compare two amps of a given manufacturer with different power capabilities, and we sense the difference in "authority" (or however you want to describe it) that flows forth from the more powerful amp, that result is a consequence of having a stiffer power supply feeding more output devices with greater current control/capability (lower output impedance / higher damping factor). Think of it as two smaller amplifiers running in parallel as far as speaker control is concerned. In contrast, a bridge amp is two amps connected in series. The output impedances add, meaning the damping factor is cut in half, the distortion adds, the supply stiffness and drive current limits are the same. If the powerful amp sounds better because of the way it controls the speaker, the bridge amp is a step in the opposite direction.

And yes, the max power output figure also increases for the bridge connection, and that, I suspect, is one of the chief reasons people assume it is a better solution. But it's "empty calories" for typical users (sane power levels).

Quote:
Originally Posted by panzer View Post

the reason for my post, is that I once owned the classe cav 150, it was much better in the bridged mode as opposed to using it as a straight 6 channel amp, there are a few classe cav 150's for sale on audiogon, but they are vastly overpriced considering their age, so I am looking for a new amp with similar capability's, thanks

I've run my CAV-150 in bridge mode just to see what happened. Finding no benefit, I switched it back.
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post #9 of 36 Old 11-10-2010, 12:02 PM
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My apologies for confusing the question. Need sleep...

"But this one goes up to 11"
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post #10 of 36 Old 11-10-2010, 12:07 PM
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Quote:
Originally Posted by Roger Dressler View Post

The OP is asking about bridge amps. In that case, the answer is as a wise man once said: "Just buy the proper size amp." It's even worse to bridge amps than to bi-amp. Reduces the damping factor by half, increases the distortion and noise.

Roger, there are many of bridged amp measurements in the DIY forum. I have not seen measurements that show increased distortion and noise. I have not even read that opinion before and it would be a hot topic considering Passive subs use bridged amps all the time because it maximize power available.

In the subwoofer world where 4000Watts is needed, no one is buying a Monoblock 4000Watt amp. They are buying pro audio amps like the Marathon MA-5050 Amp using it bridged.

The distortion measurements do not change in audibility running off channel 1 or off bridged.

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post #11 of 36 Old 11-10-2010, 12:13 PM
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Doesn't bridging usually requiring Y'ing the signal and feeding the input stage of two amps with the same signal, then tying together the outputs?

Edit : Is common mode distortion eliminated by the bridging arrangement, or is distortion sort of "doubled"?

Seems the bridging is not really differential? You feed the speaker with a "normal" output, and an inverted output, which doubles peak voltage potential? But it would not really eliminate common mode distortion? Sorry I am confused and unclear about this.

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post #12 of 36 Old 11-10-2010, 12:15 PM
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Quote:
Originally Posted by penngray View Post

Roger, there are many of bridged amp measurements in the DIY forum. I have not seen measurements that show increased distortion and noise. I have not even read that opinion before and it would be a hot topic considering Passive subs use bridged amps all the time because it maximize power available.

In the subwoofer world where 4000Watts is needed, no one is buying a Monoblock 4000Watt amp. They are buying pro audio amps like the Marathon MA-5050 Amp using it bridged.

Totally understandable, and a reasonable solution. I take no issue with that at all.

Quote:


The distortion measurements do not change in audibility running off channel 1 or off bridged.

I did not say the increased distortion was audible, only that it was there. Look at any plot of response vs distortion for 8-ohm and 4-ohm loads. It's higher when driving the 4 ohm load. It may be small, it may be negligible. It's there.

If distortion or damping factor do not affect sound quality, then no problem. Just that some amp companies go to extreme lengths to improve these things--there must be some underlying reason for that. Or maybe it's just specmanship.

It's also a fair statement to say that a 300W bridge amp does not impart the same muscle as a 300w single-ended amp (all else being equal), even though they play equally loud. The operative characteristics for sound quality below clipping do not include the wattage rating.
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post #13 of 36 Old 11-10-2010, 12:58 PM
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Also, keep in mind that a bridged amp is loaded w/ only half the loudspeaker impedance. So, to a bridged amp, that 4 Ω speaker becomes a 2 Ω load. And many amps cannot safely supply enough current into such a demanding load. Thus, a good rule of thumb is not to bridge amps w/ speakers of nominal impedance lower than 8 Ω.

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post #14 of 36 Old 11-10-2010, 02:23 PM
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Quote:
Originally Posted by MichaelJHuman View Post

Doesn't bridging usually requiring Y'ing the signal and feeding the input stage of two amps with the same signal, then tying together the outputs?

No. You need a signal inversion in there somewhere. Bridgeable amps include that. In many stereo car amps, one channel is normal polarity, the other is inverted, so it's easy to bridge them simply by tying the two inputs together.

Quote:


Seems the bridging is not really differential? You feed the speaker with a "normal" output, and an inverted output, which doubles peak voltage potential? But it would not really eliminate common mode distortion? Sorry I am confused and unclear about this.

What do you mean by common mode distortion? Asymmetry? If so, then bridging mirrors that distortion so it happens both the positive and negative excursions instead of on one side only.
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Quote:
Originally Posted by panzer View Post

the reason for my post, is that I once owned the classe cav 150, it was much better in the bridged mode as opposed to using it as a straight 6 channel amp, there are a few classe cav 150's for sale on audiogon, but they are vastly overpriced considering their age, so I am looking for a new amp with similar capability's, thanks

A simple low cost, two channel amp can give you 3-500 watts of power(unbridged) for less than $400.
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Quote:
Originally Posted by MichaelJHuman View Post

My apologies for confusing the question. Need sleep...

It's alright Michael. You are only human after all.
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post #17 of 36 Old 11-10-2010, 02:39 PM
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Any 6 channel amp capable of bridging down to 3 channels is not gonna be much (or any) different than the same manufacturers 3 channel amp of double the rated power. As Roger pointed out, the possible pitfalls are decreased damping, increased noise floor, and limits on the power supply that would be designed properly for the 3 channel version. My 2 cents is to buy the biggest, baddest amp of the number of channels you need, not to look for bridgeable as a selling feature.
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post #18 of 36 Old 11-11-2010, 05:35 AM
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Quote:
Originally Posted by Roger Dressler View Post

Totally understandable, and a reasonable solution. I take no issue with that at all.

I did not say the increased distortion was audible, only that it was there. Look at any plot of response vs distortion for 8-ohm and 4-ohm loads. It's higher when driving the 4 ohm load. It may be small, it may be negligible. It's there.

If distortion or damping factor do not affect sound quality, then no problem. Just that some amp companies go to extreme lengths to improve these things--there must be some underlying reason for that. Or maybe it's just specmanship.

It's also a fair statement to say that a 300W bridge amp does not impart the same muscle as a 300w single-ended amp (all else being equal), even though they play equally loud. The operative characteristics for sound quality below clipping do not include the wattage rating.

Thanks for the clarification. Interesting discussion, I will still disagree with distortion values increasing or the opinion that bridging does not have the same muscle, I base my disagreement because of the AVS AMP measurement thread....Look at the high end QSC PLX3402

http://www.avsforum.com/avs-vb/showt...0#post12937520

The distortion measurement for 4 ohm bridged measurements is very close in value to the 8 ohm stereo measurement.


My concern is with 1000 Watts and greater....Im not sure why anyone is bridging amps for main speakers period.

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post #19 of 36 Old 11-11-2010, 05:41 AM
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The denon poa-a1hd is 10 channels which you can bridge to 5 channels without any problem. Both 8ohm and 4ohms are fully supported. The issue of the higher noise level is not a issue for me with my pre/pro the end result is still death silent when i run it at +10dB.

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post #20 of 36 Old 11-11-2010, 04:02 PM
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Quote:
Originally Posted by penngray View Post

I will still disagree with distortion values increasing or the opinion that bridging does not have the same muscle, I base my disagreement because of the AVS AMP measurement thread....Look at the high end QSC PLX3402

http://www.avsforum.com/avs-vb/showt...0#post12937520

The distortion measurement for 4 ohm bridged measurements is very close in value to the 8 ohm stereo measurement.

Thanks for the data link. It supports your point about distortion remaining about the same for that amp. But it also supports my general statement about distortion increasing with load, in that if you look at the direct 8, 4, and 2-ohm distortion figures (not the bridged mode), you can see the distortion increases quite clearly each time, between a factor of 3 to 10. Whatever magic is happening in that particular QSC amp in the bridge mode is not automatically going to accrue to our friend's McIntosh or other amps.
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post #21 of 36 Old 11-11-2010, 04:45 PM
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Quote:
Originally Posted by MichaelJHuman View Post

Just buy the proper size amp. Nothing I have read indicates ant advantage to passive biamping (biamping into a speaker with a passive crossover, as opposed to biamping via active crossovers, with no speaker crossover)

I disagree.

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post #22 of 36 Old 11-11-2010, 06:22 PM
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Many amps can be bridged [2ch bridged to mono, 4ch bridged to stero] to acheive a higher wattage output.

I'd establish the following:
- space [do you want one amp, multiple amps]

- output desired [I think the CROWN, pro amp company now a division of Harmon, has a tool to calculate power needed based on effeciecny of the speaker, impedance of the speaker, distance to listening position and desired SPL]

- budget

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post #23 of 36 Old 11-15-2010, 03:46 PM
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Hai,

I am still confused can someone explain clearly what the difference is between bridged and differential poweramps ?

It seems everytime if i see someone come close to explaining it somehow they don't and i want to learn . The following document claims they are the same. MichaelJHuman hinted to the question and ill repeat please someone explain to us simple people.

http://www.profusionplc.com/images/a...notes/an12.pdf

----
Bridged (Differential Amplifiers)
The primary difference between single-ended output amplifiers and bridged (or differential) output amplifiers is that the negative terminal of the bridged-output amplifier is active, supplying a voltage equal in amplitude and opposite in phase to the positive terminal. This effectively doubles the available voltage to the speaker load, quadrupling the output power capability (P=E2/R). However, since the negative terminal is active just as the positive terminal is active, the negative terminal must never be connected to ground, to chassis, or to any other amplifier terminal, at any time. Figure 2 shows a typical configuration for one channel of a bridged-output amplifier. Note that connection of the negative terminal to another negative terminal or to ground or even to chassis would short out the V2 voltage source, causing a very high current condition. Under such conditions, an amplifier without over-current protection would likely be damaged. As mentioned above, such a connection should never be made.
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post #24 of 36 Old 11-15-2010, 04:05 PM
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I think my point of confusion, when discussing this topic, was the input. If the input was single ended, is the amplifier differential? I guess it's differential, with the understanding that the entire signal path is not differential.

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post #25 of 36 Old 11-15-2010, 04:16 PM
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Quote:
Originally Posted by MichaelJHuman View Post

I think my point of confusion, when discussing this topic, was the input. If the input was single ended, is the amplifier differential? I guess it's differential, with the understanding that the entire signal path is not differential.

But how do you bridge without doing it differential ?. So the difference is if you feed 2 (pos & neg) signals into the amp or not ? Or that in the amp the single input signal is split and flipped and then bridged ? Since it has to be flipped if not you can't bridge them right ?

So differential means it can take balanced in (without splitting & flipping it internally) and bridge based on that ?

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post #26 of 36 Old 11-15-2010, 04:19 PM
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Some amps may be differential from their differential input to the output terminals. But others would have single ended input stages, regardless of whether they had balanced connections - I think.

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post #27 of 36 Old 11-15-2010, 04:25 PM
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Quote:
Originally Posted by MichaelJHuman View Post

Some amps may be differential from their differential input to the output terminals. But others would have single ended input stages, regardless of whether they had balanced connections - I think.

So differential tells us something about the input side of things and how the resulting bridge is done. For the first time it at least makes sense to me can someone confirm this for me ?. Also that would mean that any differential amp has to be internally bridged no ? How else is it differential if the neg and pos are not amped by themselves ?

recap :

single in bridged = signal is not balanced coming in and split and flipped before bridged

balanced in bridged = signal can stay differential and is bridged right away. The 2 signals never touch until the speaker(s).

Now if this is true for the first time i understand it *grin*.

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post #28 of 36 Old 11-15-2010, 04:52 PM
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I am no expert. But if the amp was fully differential, you would amplify both sides of the balanced signal with each "side" of the amplifier.

If the input to the amp is single unbalanced, that's not possible. It sends the signal to one amp, and the signal inverted to another amp. I guess the word differential applies, because of how the amps work together. But I would say it's not fully differential.

If you hook up a balanced connection, and the signal and inverted signal present on the balanced connection are sent to each amplifier in the bridge, I would say it's a fully differential situation - I guess

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post #29 of 36 Old 11-15-2010, 05:17 PM
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Quote:
Originally Posted by danielo View Post

But how do you bridge without doing it differential ?. So the difference is if you feed 2 (pos & neg) signals into the amp or not ? Or that in the amp the single input signal is split and flipped and then bridged ? Since it has to be flipped if not you can't bridge them right ?

So differential means it can take balanced in (without splitting & flipping it internally) and bridge based on that ?

Daniel.

Some times the input signal is split and inverted, amps that require this are generally those with the "bridged" switch on the back of them.

Alternatively some times 1 channel is always inverted. You just change the terminal labeling on the back so when used in stereo one channel doesn't seem to be out of phase.

For instance: Channel A would have the 'red' terminal driven by the amp and the 'black' terminal tied to ground. Channel B would have the 'red' terminal tied to ground and the 'black' terminal driven by the amp (but inverted). This results in both channels being in phase when in stereo but doesn't require any switch to run in bridged mode. In this case you either need to Y the signal externally, or some times there is still a switch on the back which enables an internal Y-ing of the signal.

You can't bridge two channels of a fully differential amplifier, or more accurately, each channel is already in a bridged configuration.
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post #30 of 36 Old 11-15-2010, 05:37 PM
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Quote:
Originally Posted by danielo View Post

So differential tells us something about the input side of things and how the resulting bridge is done. For the first time it at least makes sense to me can someone confirm this for me ?. Also that would mean that any differential amp has to be internally bridged no ? How else is it differential if the neg and pos are not amped by themselves ?

Let's divide and conquer. When talking about bridge amps, you can always think about it as two amplifiers driving one speaker. That never changes under the hood.

So all we have to consider is how those two amps get their respective input signals. They can be from:

a) two single-ended inputs (rare)
b) one single-ended input
c) one differential input

Let's take them one at a time:

a) This is the conventional stereo amp. Unless there is an external device used to invert the signal to one channel, it cannot be used in a bridge application.

b) This would include amps with "bi-amp" switches, be they home or car amps. The single-ended input feeds the positive amplifier directly. The same input signal feeds a unity-gain inverter, and that feeds the other amplifier for the negative output.

c) Differential input amps can be just like case a) except with a "differential" input jack added. More below.

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recap :

single in bridged = signal is not balanced coming in and split and flipped before bridged

Yes.

Quote:


balanced in bridged = signal can stay differential and is bridged right away. The 2 signals never touch until the speaker(s).

Yes, it's possible. But if the balanced source carries different audio levels, which is permissible in perfectly balanced audio (it's about the impedances, not the audio), then the amplifier will not reach its full output potential. Also, if the two amplifiers are not perfect (identical) in how they handle the interference noise imposed on the input connections, it may not cancel fully across the speaker terminals--degrading common mode rejection ratio. For both reasons, it might be safer to convert the balanced input to single-ended just as the audio enters the amp, be it by transformer or proper balanced to single-ended converter. Then go about treating that signal the same as any other bridge amp.
Roger Dressler is offline  
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