How do I get power amps with wildly different power outputs to play nicely together in a single system?

[smk267]

Hi, ASR, I'm hoping some of you can offer guidance/advice on mixing amps that have different power outputs (80W, 200W, 500W) in a single system. Please forgive me for not using technical terminology correctly -- or if I've overlooked a guide in the forum/other posts. Please also forgive the length. I tried to keep it short while also providing enough context and information to enable knowledgeable people to correct/teach or suggest something I hadn't considered.

Thanks in advance!

My surround-sound system is 11.4 -- eleven-speaker surround sound + four subwoofers -- via a Denon X3800H AVR in preamp mode. My current amp configuration:

• 80W of power go to L/R via a Cary SLI80 HS tube preamp/amp.
• 200W of power go to center via a Topping B200 power amp
• 500W go to remaining channels via two Buckeye Amps hypex power amps (a six channel and a two channel). (I can lower the output via the gain switch/jumpers, but for the purpose of this post let's assume the output will be 500W.)

The problem I need to solve: what's the best way to equalize loudness across all channels without replacing any of these amps? The Cary obviously produces much less power than the B200 or 500w amps, and my Denon X3800H can adjust individual channels' output by +/- 12 db, but this isn't remotely enough, particularly considering that the L/R are Monitor Audio Gold 200 5G floorstanding speakers (receiving just 80W) and the rest of the speakers are less-power-hungry bookshelf speakers (receiving a ridiculous, unnecessary 500W. Yes, I should have gotten the 250W versions. Too late now.) Note: the Cary powers my L/R because I find it much funner than the class-d amps for music, so powering surrounds with the Cary isn't an option.

My questions:

1. If I want to mix these amps in a single system, while continuing to use the Cary for L/R, should I just add preamps between the Denon and amps so that I can attentuate/amplify individual channels and match volumes?
2. Let's say I do that and then set my Denon X3800H's volume to -50 db. Let's also say I proceed to find that surround L and surround R need attentuation of -30 db, compared to L and R, so that L, R, SL, and SR have equivalent loudness. When I increase the Denon volume to -40 db, will the required attentuation still be -30 db? Or might it change to, say, -25 or -35? If the required attentuation is a moving target, how do I calculate the appropriate attentuation/amplification, channel by channel, when mixing 80W, 200W, and 500W amps?
3. I have a Lundahl Sound Systems VC2316, which can attenuate the six-channel hypex 500W amp. What other preamps would be good candidates for the remaining channels (center, surround left and right, and L + R)? My requirements: balanced in/out; 12v trigger. Fosi ZP3 would be the obvious choice, if not for the volume/volume display issue that Amir's review points out, but maybe I can make my peace with it if there's no better choice.

Related question:

1. Is there any reason why I shouldn't get a separate preamp to boost the volume before it reaches the Cary SLI80, so that, at a given AVR volume level, my L/R will be louder?
   1. Why I ask: the preamp signal sent to L/R by my X3800H has weirdly, confusingly low volume.
      1. I have a second stereo, just two channels, in which another Cary SLI80 powers a pair of Monitor Audio Gold 300 5Gs.
      2. The Gold 300s (in my two-channel system) have higher power requirements than the Gold 200s (in my surround system). Neverthlesss, the Cary SLI80 in my surround-sound system needs to be turned up much, much higher than the Cary SLI80 in my two-channel to be even adequately loud, even when I set the AVR volume at -0 db. In my two-channel system I barely need to turn up the Cary for the volume to become uncomfortably loud.
         1. (Just in case it's helpful, here are other parts in the two-channel system: Rega P10 with Benz Micro Ruby 3; EAR 834P phono pre; Cary DMS-600 streamer/DAC)
      3. The amp isn't defective. I've already taken it to the shop where I bought it (authorized Cary distributor/servicer). The owner examined it and tested it. It's working as expected and has no issues (other than the tube-amp inaccuracies, which I happen to love).
      4. I've also just recently replaced all of my tubes, so that's not the issue either.
   2. I can turn up the volume on the Cary SLI80 to compensate for the quietness, but I'd prefer to avoid that, because it causes two problems:
      1. Tubes and amp burn hotter at higher volumes, shortening their lifespan.
      2. A buzz/hum becomes audible at higher volumes. This isn't a ground loop. Jensen isolation transformers don't fix it. I think it's the result of an electrical issue in my house/room, requiring a probably expensive fix.

 

[Mort]

Note: the Cary powers my L/R because I find it much funner than the class-d amps for music, so powering surrounds with the Cary isn't an option.

Funner?


Have you tried Audyssey? It should level match your speakers.

 

[smk267]

Have you tried Audyssey? It should level match your speakers.

That's a good idea. I'll try it tomorrow. Even with Audyssey, though, I think the Denon will amplify/attenuate individual channels a maximum of +/-12 db.

Funner?

Funner. Better, too, as far as my ear is concerned, but I wanted to use neutral language so as to avoid arguments about tube vs solid-state.

 

[klettermann]

I'm struggling to see how all this fits together. Maybe post a diagram?

 

[Everett T]

You don't want to hear it, but the Cary is only eye candy and is dragging your system down. Aside the fact that it is an integrated amp not a power amp, the measurements are brutal. If you still want to use it for two channel only, that would be the only option I see.

Cary Audio SLI-80HS integrated amplifier Measurements | Stereophile.com

Sidebar 3: Measurements I measured the Cary SLI-80HS using my Audio Precision SYS2722 system (see the January 2008 As We See It"). Both the small-signal and output tubes—all Electro-Harmonix—are numbered or marked L or R, and I installed them as instructed in the manual. Cary recommends checking...

www.stereophile.com

 

[MAB]

Hi, ASR, I'm hoping some of you can offer guidance/advice on mixing amps that have different power outputs (80W, 200W, 500W) in a single system. Please forgive me for not using technical terminology correctly -- or if I've overlooked a guide in the forum/other posts. Please also forgive the length. I tried to keep it short while also providing enough context and information to enable knowledgeable people to correct/teach or suggest something I hadn't considered.

All you need to worry about is the gain, the concerns about power are distracting you. Unless you have dramatically different sensitivity speakers and/or amps with dramatically different gain, +/- 12 dB is going to be fine, the 24 dB range is 250x change in power.

I can turn up the volume on the Cary SLI80 to compensate for the quietness, but I'd prefer to avoid that, because it causes two problems:

1. Tubes and amp burn hotter at higher volumes, shortening their lifespan.
2. A buzz/hum becomes audible at higher volumes. This isn't a ground loop. Jensen isolation transformers don't fix it. I think it's the result of an electrical issue in my house/room, requiring a probably expensive fix.

I'm sorry, but this is totally self-inflicted. Your Denon AVR has a more competent internal-amp, and despite the poor performance of the Cary the two are indistinguishable from each other. That is of course so long as you don't hook the Cary up to a high sensitivity driver, or try to integrate it into a complex AVR, drive a low-impedance speaker, etc.

 

[DVDdoug]

Like, MAB says, it's the gain (including any attenuation) that's important. If the gain is matched, an 80W amp will match a 500W amp until you go over 80W, clipping/distorting the 80W amp while the 500W watt amp goes "louder".

If the lower power amp has more gain it will be louder (up to the point of clipping).

The bass generally requires more power and the surround channels may require less power than the left, right, and center.

If you can't get enough attenuation you can get inline attenuators:
Fixed Attenuator
Variable Attenuator

If the required attentuation is a moving target

It's not a "moving target". A 3dB change is a 3dB change... If the volumes are matched they will will stay matched and if Amp A is 6dB louder than amp B, that 6dB difference exists as long as they are driven/adjusted by the same source.

1. Tubes and amp burn hotter at higher volumes, shortening their lifespan.

That's a different issue. And it's going to be related to the actual wattage coming-out, regardless of the gain/attenuation settings. It seems silly to listen quieter than you'd prefer just to save the tubes.

Tubes should normally last several years, if not decades, if they are "correct" for the particular amplifier design and if the amp is properly designed.

You probably don't need the higher-power amps (depending on different speaker sensitivity/efficiency) if the loudness without distortion is limited by the 80W amp, especially if you are avoiding pushing the 80W amp to its maximum.

IMO - Tubes are dumb. This isn't 1955. But if you like the distortion/inaccuracies of your amp I guess you should keep it. A good tube amp will sound exactly like a good solid state amp with no particular sound of its own. A different "imperfect" tube amp will sound different from the one you have.

 

[smk267]

You don't want to hear it, but the Cary is only eye candy and is dragging your system down. Aside the fact that it is an integrated amp not a power amp, the measurements are brutal. If you still want to use it for two channel only, that would be the only option I see.

Cary Audio SLI-80HS integrated amplifier Measurements | Stereophile.com

Sidebar 3: Measurements I measured the Cary SLI-80HS using my Audio Precision SYS2722 system (see the January 2008 As We See It"). Both the small-signal and output tubes—all Electro-Harmonix—are numbered or marked L or R, and I installed them as instructed in the manual. Cary recommends checking...

www.stereophile.com

Hah, I appreciate the reality check, but I have no delusions! I'm well aware that tube amps (including the SLI80) are, pretty much by definition, inaccurate, distorted, and can't hold a candle to my class-d amps! They're also fussier, more expensive to maintain, more power hungry, and include pitfalls that class-d don't: if you turn a tube amp on, off, and on again in quick succession, you can easily blow a fuse (at best) or the transformer (at worst); if you run a tube amp too hot, you can kill both the amp and the tubes. Technically and objectively, my Buckeye amps are better. There's no contest.

 

[smk267]

All you need to worry about is the gain, the concerns about power are distracting you. Unless you have dramatically different sensitivity speakers and/or amps with dramatically different gain, +/- 12 dB is going to be fine, the 24 dB range is 250x change in power.

As far as I'm aware, that's exactly the problem: the speakers differ in sensitivity (I think?), and the amps do have different gain/power outputs. But maybe I'm confused.

 

[smk267]

IMO - Tubes are dumb. This isn't 1955. But if you like the distortion/inaccuracies of your amp I guess you should keep it. A good tube amp will sound exactly like a good solid state amp with no particular sound of its own. A different "imperfect" tube amp will sound different from the one you have.

Hah, yep, that makes perfect sense. I'm well aware of the objective inferiority. I think of my tube amp as a kind of ASP (analog sound processor) or the psychoacoustic equivalent of room treatment: I use it to modify the sound in a manner that I like. In that sense, the 'goodness' of the amp is, for me, somewhat subjective, and a solid-state amp, in order to be equally 'good' for my purposes, would need to be equally fun/enjoyable, not equally measurably accurate.

But, really, I don't mean to start an argument about this or claim my tastes are correct; objectively/technically, my tastes are are demonstrably wrong and outdated.

 

[smk267]

I'm struggling to see how all this fits together. Maybe post a diagram?

Good idea, I'll try to do that today. Thanks for making the effort to fit everything together without it.

 

[antcollinet]

As far as I'm aware, that's exactly the problem: the speakers differ in sensitivity (I think?), and the amps do have different gain/power outputs. But maybe I'm confused.

So you need to understand the gain/sensitivity calculation from each output of the AVR to SPL level out of the speaker.

Just to pluck figures out of the air as an example.

Front LR - Amp, 25dB gain, speakers 85 dB sensitivity (use the sensitivity figure, not the efficiency figure)
Surround Speakers - Amp 30dB gain, Speakers 88dB sensitivity.

So surround have +8dB SPL output for the same input voltage (output from AVR) compared to front LR.

You would need to turn down the AVR channels for the surrounds by 8dB compared to the FLR to get levels more or less matched (Assuming same listening distance - but that is another step)


If that 8dB were larger, and exceeded the 12dB available as adjustment in the AVR, you could install in line attenuators at the input to the higher gain amp.

 

[MAB]

As far as I'm aware, that's exactly the problem: the speakers differ in sensitivity (I think?), and the amps do have different gain/power outputs. But maybe I'm confused.

Not likely, unless your surround speakers are massively low sensitivity. Your mains are ~87dB(B)/2.83V/m per Stereophile's measurements, which are right in the middle of typical speakers, and not likely a problem.

The problem you are having is too many amps to accomplish the same thing. Introduce lots of concepts, with lots of gain switches that help to match but also deepen the confusion. If you systematically hooked the gear up and tested the various gain, you would be able to prove to yourself that you can get the Denon to level match all of the amps' output despite the mismatched pieces. If you did this while also systematically listening for differences you would also come to the conclusion that this is a big effort for no gain. In fact, your tube amp is already humming away and causing tube-wearout-anxiety. Tubes are fun, I have a classic McIntosh MC-30 that I am refurbishing. They aren't fun when asked to integrate into a modern system, as you are demonstrating.

You add lots of complexity with the external amps, and introduce new issues with the tube amp. If you want to play around, try using the Buckeye amps to drive the mains, receiver driving the rest. At least then you will have more power, avoid clipping where perhaps you will get some advantage. But with so many speakers that's loud unless you have a cavernous room... At overwhelming volume it is pretty hard for us to hear differences.

 

[antcollinet]

You add lots of complexity with the external amps, and introduce new issues with the tube amp. If you want to play around, try using the Buckeye amps to drive the mains, receiver driving the rest. At least then you will have more power, avoid clipping where perhaps you will get some advantage. But with so many speakers that's loud unless you have a cavernous room... At overwhelming volume it is pretty hard for us to hear differences.

This is good advice.

 

[smk267]

So you need to understand the gain/sensitivity calculation from each output of the AVR to SPL level out of the speaker.

Just to pluck figures out of the air as an example.

Front LR - Amp, 25dB gain, speakers 85 dB sensitivity (use the sensitivity figure, not the efficiency figure)
Surround Speakers - Amp 30dB gain, Speakers 88dB sensitivity.

So surround have +8dB SPL output for the same input voltage (output from AVR) compared to front LR.

You would need to turn down the AVR channels for the surrounds by 8dB compared to the FLR to get levels more or less matched (Assuming same listening distance - but that is another step)


If that 8dB were larger, and exceeded the 12dB available as adjustment in the AVR, you could install in line attenuators at the input to the higher gain amp.

Thanks very, very much for explaining this. The arithmetic makes perfect sense to me now.

 

[smk267]

Tubes are fun, I have a classic McIntosh MC-30 that I am refurbishing. They aren't fun when asked to integrate into a modern system, as you are demonstrating.

Oy, definitely a headache.

Not likely, unless your surround speakers are massively low sensitivity. Your mains are ~87dB(B)/2.83V/m per Stereophile's measurements, which are right in the middle of typical speakers, and not likely a problem.

The problem you are having is too many amps to accomplish the same thing. Introduce lots of concepts, with lots of gain switches that help to match but also deepen the confusion. If you systematically hooked the gear up and tested the various gain, you would be able to prove to yourself that you can get the Denon to level match all of the amps' output despite the mismatched pieces. If you did this while also systematically listening for differences you would also come to the conclusion that this is a big effort for no gain.

I use the Denon primarily with desktop computer, and I've found that Windows frequently changes the AVR's output configuration. When that happens, the internal amps turn on/off, resulting in a loud mechanical "click"/"thunk". It's infuriating and there seems to be no non-annoying, non-labor-intensive way to prevent it, other than to disable the internal amps entirely.

Moreover, I do prefer the sound of my external amps to the Denon's built-in amps. The difference isn't night and day, but it's audible (so far I can't prove that; I don't have any objective data).

I'd also like eventually to replace the Denon with an amp-less processor that has balanced outs, something like the Marantz AV10 (though I'm not sure I can justify the cost). The external amps are a step in that direction.

Thanks very much for the write up. I'm going to do some more testing, armed with your and @antcollinet's guidance.