Adding an external power amplifier

ski2xblack

ski2xblack

Audioholic Samurai
Ok thanks but I guess I'm getting mixed messages cuz right above, Peng says "there's no danger in doing it" unless i crank it up too high, which I don't?
He's right. If you only use a small amount of power for your desired listening levels, the amp 10 can probably do it. But it simply wasn't designed to push <2ohm loads when bridged, so there are limits, which you would exceed if you're a headbanger. The amp will be current limited into such loads, and have to dissipate more heat. So the prudent, cautious route would be to not bridge channels of the amp10.
 
P

philly

Junior Audioholic
He's right. If you only use a small amount of power for your desired listening levels, the amp 10 can probably do it. But it simply wasn't designed to push <2ohm loads when bridged, so there are limits, which you would exceed if you're a headbanger. The amp will be current limited into such loads, and have to dissipate more heat. So the prudent, cautious route would be to not bridge channels of the amp10.
Okay got it! sorry I'm still learning more of the technical sides of these things! so I should just change the switch on the back of the amp10 from BTL to biamp and everything should be ok?

Also my speakers are rated at 8 ohms, so how do I know if they're dipping resistance down too low?
 
ski2xblack

ski2xblack

Audioholic Samurai
Also my speakers are rated at 8 ohms, so how do I know if they're dipping resistance down too low?
That's an educated guess, based on the Stereophile review of an earlier version of your speakers posted upthread. Manufacturers are infamous for providing overly optimistic "nominal" impedance ratings.
 
lovinthehd

lovinthehd

Audioholic Jedi
Okay got it! sorry I'm still learning more of the technical sides of these things! so I should just change the switch on the back of the amp10 from BTL to biamp and everything should be ok?

Also my speakers are rated at 8 ohms, so how do I know if they're dipping resistance down too low?
Look at the impedance plot in the stereophile measurements ADTG posted in post 82....
 
everettT

everettT

Audioholic Spartan
Ok thanks but I guess I'm getting mixed messages cuz right above, Peng says "there's no danger in doing it" unless i crank it up too high, which I don't?
At low volume, but that is relative to each of us. I said the same thing and PENG did too, you can do it, but we wouldn't.
 
P

PENG

Audioholic Slumlord
Ok thanks but I guess I'm getting mixed messages cuz right above, Peng says "there's no danger in doing it" unless i crank it up too high, which I don't?
It is basically the same message, it is not really a danger as such, but the chance of resulting in damages would be higher when you BTL it, because of the impedance dips and some not too good phase angle points that your speakers seem to have. The increased chance is mitigated since you never go crazy on the volume.

So, if you have little kids who like to play with the remote, then set a maximum for the volume, such as -10. Again, no danger for responsible users.

Better still, since BTL is of no bebefit in your application, just put it back on normal and enjoy your fantastic AV10/Amp10.
 
P

philly

Junior Audioholic
It is basically the same message, it is not really a danger as such, but the chance of resulting in damages would be higher when you BTL it, because of the impedance dips and some not too good phase angle points that your speakers seem to have. The increased chance is mitigated since you never go crazy on the volume.

So, if you have little kids who like to play with the remote, then set a maximum for the volume, such as -10. Again, no danger for responsible users.

Better still, since BTL is of no bebefit in your application, just put it back on normal and enjoy your fantastic AV10/Amp10.
Thank you so much!
 
ski2xblack

ski2xblack

Audioholic Samurai
So I checked Genes review of the amp 10, and it seems to be quite a hoss. Of note for the context of your ( @philly ) questions was the following:
Caution: Marantz clearly states the Amp 10 should be used with 8-ohm nominal speakers when bridging, but I still couldn’t resist testing it into a 4-ohm load to see what it could produce. Be warned that when bridging an amp in a Bridge Tied Load configuration like this, each amplifier sees ½ the load impedance. Thus, each of the two amplifiers in the Amp 10 are really driving a 2-ohm load, which is a risk of over current at full power if the amplifier cannot handle it. When driving 4-ohm loads in bridged configuration, the Amp 10 produced 597wpc at 0.1% THD+N and 612wpc at 1% THD+N with 2CH driven. SINAD dropped a bit to 94dB or .002% THD+N. The Amp 10 didn’t like this and shut down with a red flashing illumination from the porthole. To anyone bridging the Amp 10, I caution doing so if your speakers are 4-ohm rated. I am currently running my 4-ohm Perlisten S7t towers in bridged mode without incident but I’m not running out to tell you to do similar.
 
P

philly

Junior Audioholic
So I checked Genes review of the amp 10, and it seems to be quite a hoss. Of note for the context of your ( @philly ) questions was the following:
"Hoss"? Thank I yes I did read that Benchmark as well and maybe I'm still confused. If my speakers are rated at 8 ohms [which he says are safe] and bridging halves the load impedance, wouldn't that mean they're driving 4 ohms/channel and that would still be safe? Sorry if I'm ignorant to all this! More so than knowing exactly what switch and connection to make, I'm just trying to understand how these things vary so much, particularly the impedance...
 
ski2xblack

ski2xblack

Audioholic Samurai
Hoss = quite powerful. She's a beast.

It seems your confusion is between "nominal" ratings of speakers vs. their actual (measured) impedance. Steep phase angles make the effective impedance even lower. It's the effective impedance that your amp has to cope with.

Your speakers are a perfect case study of this. They have a nominal 8 ohm rating, but their actual impedance is considerably lower. It would be more honest and accurate for B&W to have given them a 4 ohm nominal rating.

Fortunately, your amp can exceed 400w into a 4 ohm load, cleanly, and do so without bridging any channels. That's a lot of power on tap.
 
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lovinthehd

lovinthehd

Audioholic Jedi
Simply put impedance varies with frequency, and can be quite a bit, that's why we like to review measurements. The nominal rating isn't always meaningful, many 8 ohm speakers really should be rated lower.
 
P

philly

Junior Audioholic
Hoss = quite powerful. She's a beast.

It seems your confusion is between "nominal" ratings of speakers vs. their actual (measured) impedance. Steep phase angles make the effective impedance even lower. It's the effective impedance that your amp has to cope with.

Your speakers are a perfect case study of this. They have a nominal 8 ohm rating, but their actual impedance is considerably lower. It would be more honest and accurate for B&W to have given them a 4 ohm nominal rating.

Fortunately, your amp can exceed 400w into a 4 ohm load, cleanly, and do so without bridging any channels. That's a lot of power on tap.
Ok thanks!
 
highfigh

highfigh

Seriously, I have no life.
The currents in the two bi-wire cables are due to the different impedances at the speaker end, when the crossover network would have been seprated into two parts when the jumpers are removed.

That's the "electrical difference", in terms of SQ, as I said, should be no difference in 99.99% of the applications unless the wrong cables are used.
And this would be seen as different by the amplifier, how? Net impedance would be LPz+HPz=Totalz, right?
 
highfigh

highfigh

Seriously, I have no life.
Did anyone else notice that the OP (Mr Magoo) hasn't been back since asking the original question?
 
P

PENG

Audioholic Slumlord
Ok thanks!
As noted, you have very nice flagship class AVP and power amplifier, so it may be worth for you to understand the impedance and phase angle curves so that when you are ready to upgrade your speakers, you know what to look for, in order not to put your very nice but expensive equipment at risk unnecessarily.

Below is such a graph, but they are for the S2, so your S3 will have different characteristics, that could be very similar. So, let's assume they are similar enough and you can see the following potential concerns:

The solid curve is impedance versus frequency, and the dotted one is phase angle versus frequency.

- If you draw a line at 4 ohm, it is obvious that at between around:
85 and 195 Hz, 510 and 880 Hz, 1200 and 40,000 Hz, impedance dip below 4 ohms

- For much wider bands, impedance drops below 6 ohms

- At around 88 Hz, the phase angle is about (edit: 48 deg), such large phase angle would cause much more heat dissipation in the output stage of class AB amplifiers, but likely much less so in class D amplifiers.

So, that's why John Akinson noted the following:

There is also a current-hungry combination of 4 ohms and a –48° electrical phase angle at 88Hz. Although technically this is an 8 ohm design, I think it should be used with amplifiers that are comfortable with 4 ohm loads.
Gene, and some of us are suggesting that when using BTL, at the same output power, the current would be 2X that for "normal" connections, and that's why it is not advisable to use such configuration with 4 ohm nominal speakers.

Your speakers, if the curves are the same or similar enough to that of the S2, then it is not really 4 ohm nominal, but it does dip below 4 ohms in the range mentioned above.

That really isn't a huge concern because music contents and movie sound tracks don't play pure tones, so the chance for contents to demand the amplifier to play at those frequency dips will mot likely be for very short duration. Any decently designed power amplifiers can sustain much higher current for short durations.

The phase angle is also not a huge concern because it does not really result in higher current, that lots of internet forum members might think it would, because of Stereophile's undue (imo only) emphasize on their term know as EPDR (equivalent peak dissipation resistance). That term, while useful as it can be used conveniently to assess the effects of phase angle effects on power amplifiers, it also tend to mislead forum members who may not have deep enough understanding of electrical principles.

Regardless, in this case the "DPDR" will not be much lower than the 3.1 ohm dip anyway so let's not worry it. I just want to mention it, because sooner or later someone may throw that term of you and might care you (just ignore them if and when they do, take it as a cautionary note but not more than that).

In summary, you can see that base on your speaker's characteristics (being similar to the S2), and the fact that it really can' take more than 300 W continuously anyway, even if you leave it on BTL mode, there is no need to lose sleep over it. Our (assuming others agreed) suggestion of selecting "normal", or "Biamp", is just cautionary, as Gene alluded to, he would have no issue doing it, but wouldn't tell others to do it.

If and when you are ready to upgrade to speakers such as the KEF reference, and/or B&W's 800 diamond series, then you do need to pay more attention the impedance/phase angle curves, versus you Amp 10's capability. For the 702 series, just sit back and enjoy, as you alluded to, you never push the volume thing too hard anyway so do whatever you like, any mode selection should work safely (just that normal mode is even safer) for your application/speakers.

I hope this long post clarifies things enough for you.


Bowers & Wilkins 702 S2 loudspeaker Measurements | Stereophile.com

1715085527437.png
 
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everettT

everettT

Audioholic Spartan
As Peng just noted the 702 S2 plot, note the similarities between the 802D2 and the 603S3
1000003288.jpg

1000003289.jpg


This is definitely part of their design philosophy as I've seen it since the introduction of the 800 Nautilus series.
 
Verdinut

Verdinut

Audioholic Spartan
As noted, you have very nice flagship class AVP and power amplifier, so it may be worth for you to understand the impedance and phase angle curves so that when you are ready to upgrade your speakers, you know what to look for, in order not to put your very nice but expensive equipment at risk unnecessarily.

Below is such a graph, but they are for the S2, so your S3 will have different characteristics, that could be very similar. So, let's assume they are similar enough and you can see the following potential concerns:

The solid curve is impedance versus frequency, and the dotted one is phase angle versus frequency.

- If you draw a line at 4 ohm, it is obvious that at between around:
85 and 195 Hz, 510 and 880 Hz, 1200 and 40,000 Hz, impedance dip below 4 ohms

- For much wider bands, impedance drops below 6 ohms

- At around 88 Hz, the phase angle is about 88 Hz, such large phase angle would cause much more heat dissipation in the output stage of class AB amplifiers, but likely much less so in class D amplifiers.

So, that's why John Akinson noted the following:



Gene, and some of us are suggesting that when using BTL, at the same output power, the current would be 2X that for "normal" connections, and that's why it is not advisable to use such configuration with 4 ohm nominal speakers.

Your speakers, if the curves are the same or similar enough to that of the S2, then it is not really 4 ohm nominal, but it does dip below 4 ohms in the range mentioned above.

That really isn't a huge concern because music contents and movie sound tracks don't play pure tones, so the chance for contents to demand the amplifier to play at those frequency dips will mot likely be for very short duration. Any decently designed power amplifiers can sustain much higher current for short durations.

The phase angle is also not a huge concern because it does not really result in higher current, that lots of internet forum members might think it would, because of Stereophile's undue (imo only) emphasize on their term know as EPDR (equivalent peak dissipation resistance). That term, while useful as it can be used conveniently to assess the effects of phase angle effects on power amplifiers, it also tend to mislead forum members who may not have deep enough understanding of electrical principles.

Regardless, in this case the "DPDR" will not be much lower than the 3.1 ohm dip anyway so let's not worry it. I just want to mention it, because sooner or later someone may throw that term of you and might care you (just ignore them if and when they do, take it as a cautionary note but not more than that).

In summary, you can see that base on your speaker's characteristics (being similar to the S2), and the fact that it really can' take more than 300 W continuously anyway, even if you leave it on BTL mode, there is no need to lose sleep over it. Our (assuming others agreed) suggestion of selecting "normal", or "Biamp", is just cautionary, as Gene alluded to, he would have no issue doing it, but wouldn't tell others to do it.

If and when you are ready to upgrade to speakers such as the KEF reference, and/or B&W's 800 diamond series, then you do need to pay more attention the impedance/phase angle curves, versus you Amp 10's capability. For the 702 series, just sit back and enjoy, as you alluded to, you never push the volume thing too hard anyway so do whatever you like, any mode selection should work safely (just that normal mode is even safer) for your application/speakers.

I hope this long post clarifies things enough for you.


Bowers & Wilkins 702 S2 loudspeaker Measurements | Stereophile.com

View attachment 67421
You meant about -58 degrees for the phase angle at 88 Hz?
 
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