Monobridging causing more distortion?

adam2434

I've read a couple times here that amp monobriding creates more distortion than stereo operation. I have only heard this here.

Is this really true and what is the basis for it?

I don't see why this would inherently be true.

Thanks,

Adam

madmax

I'm not sure this is really true. Of course the distortion number increases but so doesn't the power. I could see the possibility of more crossover distortion depending upon how a given amp is set up to be bridged. Good question! Maybe someone els will have more knowledge.
madmax

steveinaz

I've never heard of such a thing. Amps that can be bridged typically give distortion specs in bridged mode as well.

whitetruk

my 2 cents worth i think all that really changes is the damping factor and of course the power rating i dunno good luck i tried bridging did not like it i now have mono amps

reeltrouble1

My personal experience with mono-bridging tells me its a good thing. The gear being bridged is always going to matter. The dynamic headroom of the NAD I bridged increased when bridged along of course with the amount of power. I dont have the spec sheet in front of me but don't recall any sig. change in distortion.

RT1

WilliamM2

Yes, bridging the amp will increase distortion, but it should still be fairly low.

I have a Rotel RB951MkII, It's rated 50wpc @ .03%, or 150watts bridged at .1%. Triple the power, and triple the distortion when bridged.

reeltrouble1

Still fairly low distortion on a little amp like that Rotel. I will check the NAD sheet which I think was 400w and see what the increase in distortion level is.

RT1

heiney9

Depends on the quality of the amp. Generally the distortion figure will be slightly higher in bridged mode, but no where near a figure to be concerned with. Don't get wrapped up in just using specs to evaluate audio components, you'll miss out on alot of great gear.

H9

unc2701

The distortion at a given wattage will be about the same in bridge mono for most the power range- up until the rating where the single chanel starts to distort. The specs usually quote higher distortion because it's at the very top end of what the amp can do and they want to run the amp hard enough to get a nice round number. For example, a rotel might give you 50 watts at 0.03 %THD. You can keep on crank it until the fuse blows, but you'll get more & more distortion; At 65 watts it might be at 0.1%; at 75 it might be 0.7%. So-

1)once the distortion starts to hit, it's exponential, so that last few watts will add a lot of distortion.
2)The Rotel mentioned above at 25 watts probably has nearly identical distortion bridged vs stereo; and lower distortion at 50 watts for bridge mono (0.03% vs probably 0.003%), and way lower after that (probably under 0.01 until about 125 watts).

I'll try to find a distortion vs power graph to explain this better.

reeltrouble1

reeltrouble1 wrote:

The gear being bridged is always going to matter.

RT1

H9--Right on my man. Listening is the greatest spec of all.

RT1

Tour2ma

^^Pretty much fits what I was thinking.

TDH will be greater at rated output, but will be lower in the normal operating range being that it is a lower percentage of the output.

adam2434

Thanks for the replies so far. I'm not worried about distortion numbers and certainly don't hear anything that makes believe that I'm creating significant distortion with my amps bridged.

Distortion will increase as you get closer to the max/clipping point, independent of bridging or stereo operation. For a given amount of wattage, whether bridged or stereo, distortion would be at a similar level. I think that's what I'm hearing in most of your replies. If so, this confirms what I always thought to be the case.

I was just curious because someone in another thread made a general statement that monobridging produces more distortion than stereo operation and I wanted to dig into this a little further to determine if this is a "known fact" that I had just not heard before.

F1nut

Another side affect of bridging is heat and since heat causes increased wear and tear on your amp(s), it's something to consider.

disneyjoe7

F1nut wrote:

Another side affect of bridging is heat and since heat causes increased wear and tear on your amp(s), it's something to consider.

Maybe true since I bridge my Parasound Halo A23 for 400w also, but with Parasounds warranty so wtf how could I be wrong?


Quote by H9
Don't get wrapped up in just using specs to evaluate audio components, you'll miss out on alot of great gear.

Right on H9

adam2434

Fortunately, my amps barely get to "luke warm" even after hours of use at moderate volumes. I don't think heat is a problem.

Before I had the amps, my receiver would get pretty toasty though.

Adam

unc2701

F1nut wrote:

Another side affect of bridging is heat and since heat causes increased wear and tear on your amp(s), it's something to consider.

It shouldn't be any more heat than 4 ohm speakers in stereo. Maybe 5% more btu's since both sides will be doing the same signal, but not enough to be worried about.

Emlyn

unc2701 wrote:

It shouldn't be any more heat than 4 ohm speakers in stereo. Maybe 5% more btu's since both sides will be doing the same signal, but not enough to be worried about.

Here's Parasound's recommendation for bridging their Halo amps. The same heat dissipation/audible distortion rules would follow for most, but not all, home audio amps if they are run in bridged mode:

In normal operation, the left and right amplifier channels each amplify both the positive and negative halves of the musical signal. In bridged mono
operation, the A 21’s entire left channel drives only the positive half of the musical signal and its entire right channel drives only the negative half of the
musical signal. This doubles its voltage swing. This doubled voltage swing enables the A 21 to deliver nearly double its 400 watts per channel 4 Ω
power, or 750 watts, into a single 8 Ω speaker. The audible benefit of this higher power is increased dynamic range, or headroom, so that musical peaks
can be reproduced with less distortion. Considering that musical peaks and crescendos require 10-100 times as much power as average listening levels,
this added headroom is a substantial advantage for unrestrained, undistorted listening, even if your average listening level is moderate.

Bridging allows an amplifier to deliver more power into a single speaker because in this mode, the load appears to the amplifier as only half of its rated impedance. Thus, the single 8 Ω speaker appears as a 4 Ω load and a 4 Ω speaker appears as only a 2 Ω load. The A 21 is not capable of driving 2 Ω for extended periods because it will draw more current and generate more heat than it can dissipate. We strongly recommend against using speakers rated at less than 8 Ω when bridging.

Less distortion, but more heat is the norm when operating an amp in bridged mode.

Tour2ma

But Parasound's "more heat" statement is tied to the case of the apparent 2-ohm load.

Other than the owner pushing a bridged pair a bit harder than one in stereo (because it just sounds so damn good), I can't see a significant heat factor.