Gain matching different external amplifiers with AVR - Recommended approach?

[Spennis]

Hi,

I have been running my 7.2.6 system with a Denon AVR-X6700H (link to ASR review) and two external amplifiers (XTZ Edge A2-300, link to ASR review, link to the manual with specs) for the LCRs. I've used these amps with the gain set to its highest setting without thinking about whether it is the optimal setting or not (the concept of gain matching is new to me).

Now, I've decided to upgrade the amplification for the LCRs with the Purifi-based three channel amplifier Audiophonics HPA-T450ET (link to manufacturers specs) and use the two XTZ Edge A2-300 to power the surround and back surround speakers instead.

Now to the question: how would you recommend I gain match these two (three including the Denon AVR) amplifiers?

Given that the Denon can easily output 2 Vrms (up to 4.4 Vrms @ 92 dB SINAD), my thinking was that I start by setting the Audiophonics HPA-T450ET to its second lowest gain setting of 20dB whereby it reaches its max power output at 2.12Vrms (RCA input). My 4 Ohm speakers can't handle the 300 W that the amplifier can output, but my understanding is that I shouldn't think about that, but rather the match between the pre-out voltage and the voltage needed to drive the amplifier to its maximum power (?).

But then what?

The XTZ Edge A2-300 has a gain potentiometer and I have no idea what the gain span is (the manual does not say, it just says gain 28.15 dB, while the ASR review suggests it can go higher than that). I was thinking that I could measure the SPL output of a given speaker at a given AVR volume level with the Audiophonics HPA-T450ET powering the speaker, then switch the amplification of that speaker to the XTZ Edge A2-300 and adjust the gain potentiometer until it matches the previously recorded SPL output as closely as possible.

Is this a sensible approach, or do you have a better suggestion? Obviously, I want to find the gain setting that gives me the lowest noise and highest dynamic range possible.

Thanks in advance!

 

[Anton S]

This article may be helpful for determining the best gain setting on the Audiophonics with respect to system SNR:

Your proposed approach to matching the gain on the XTZ sounds logical to me, after optimizing the gain of your Audiophonics.

Amplifier Sensitivity – Is Yours Optimized?

 

[Spennis]

This article may be helpful for determining the best gain setting on the Audiophonics with respect to system SNR:

Your proposed approach to matching the gain on the XTZ sounds logical to me, after optimizing the gain of your Audiophonics.

Amplifier Sensitivity – Is Yours Optimized?

Thank you. I read the article, and my understanding is that the recommendation is to keep the amplifier gain as low as possible while making sure that you can reach the maximum output or target SPL.

I just checked the AVR trim levels needed to reach 75 dB at the MLP using the internal pink noise (see picture). With the Audiophonics gain set to 20 dB, the AVR trim is around +0.5 dB for the fronts and -2 dB for the center speaker. I've heard people say that the AVR trim shoule be in the -8 to -6 dB range (see e.g.

), but following the logic in the article you shared it seems to me that 20 dB gain should be preferable to let's say 25 dB gain (i.e. higher AVR trim in exchange for lower amplifier gain)?

Looking at the trim levels for the surrounds and back surrounds, it does seem that I can lower the gain on the XTZs to achive a better balance?

 

[jsrtheta]

Yet another reason I stick to a 2.1 setup.

 

[Oddball]

I think this one is for @peng to respond. From what I understand you would want external amps to be happy with 1.4V or so output as ideal case as you would still be driving internal amps. Where is the point of clipping is fluid - so yes 2.0V could still make sense.

But then again, never dealt with the issue as used 6700H in pre-amp mode.

As far as picking nits between your amp gain I would just use the ear - the setting that gives you power but not noise would be the right one and I would not obsess over it. I lived happily ever after with this approach and Parasound amp.

I might have not really read your post as it seems complicated - but let me know if that is the case.

 

[Anton S]

The reference I linked is correct with respect to maximizing your overall system SNR.

I strongly disagree with the trim level approach advocated by the individual doing the presentation in that video (but not with everything he had to say). Your LCR speaker trims look fine to me, and I'm reasonably certain that the the manufacturer of your AVR would agree.

Aside: I'm hearing/seeing many people these days, including the presenter in the video, referring to input saturation as input "clipping". Clipping is an output phenomenon. Overdriving an input has traditionally been referred to as "saturating" the input, which results in an audibly identifiable form of distortion. The amp's input signal isn't clipped, but it is exceeding the input's maximum voltage capability.

Addendum: I would recommend reducing the gains on your surrounds and sub amps (but not your heights, if possible) and rerunning your calibration.

 

[peng]

Thank you. I read the article, and my understanding is that the recommendation is to keep the amplifier gain as low as possible while making sure that you can reach the maximum output or target SPL.

I just checked the AVR trim levels needed to reach 75 dB at the MLP using the internal pink noise (see picture). With the Audiophonics gain set to 20 dB, the AVR trim is around +0.5 dB for the fronts and -2 dB for the center speaker. I've heard people say that the AVR trim shoule be in the -8 to -6 dB range (see e.g.

), but following the logic in the article you shared it seems to me that 20 dB gain should be preferable to let's say 25 dB gain (i.e. higher AVR trim in exchange for lower amplifier gain)?

It is fine to leave thing alone based on those numbers. Or, set the Audiophonics gain to 25 dB, that's what I would do if those were my gear.

The Denon, especially if your unit has the AK4458 dac IC, like the one Amir measured.

Take a look of the SINAD vs level graph.

You are getting about 96 dB SINAD at 0.5 V and didn't fall below 90 dB at the lowest limit of the X-axis, that means it will be virtually silent in a typical room with noise floor at least 10-20 dB!!

I prefer 25 dB gain because to me a few dB lower in SINAD overall would make no audible difference whatsoever, but psychologically, having to turn volume up higher would bother me, but that's just me.

Looking at the trim levels for the surrounds and back surrounds, it does seem that I can lower the gain on the XTZs to achive a better balance?

Agreed, you can do that, but why even bother. "better balance" would be for the look, no performance issues there at all, you have a very nice setup.

 

[Spennis]

The reference I linked is correct with respect to maximizing your overall system SNR.

I strongly disagree with the trim level approach advocated by the individual doing the presentation in that video (but not with everything he had to say). Your LCR speaker trims look fine to me, and I'm reasonably certain that the the manufacturer of your AVR would agree.

Aside: I'm hearing/seeing many people these days, including the presenter in the video, referring to input saturation as input "clipping". Clipping is an output phenomenon. Overdriving an input has traditionally been referred to as "saturating" the input, which results in an audibly identifiable form of distortion. The amp's input signal isn't clipped, but it is exceeding the input's maximum voltage capability.

Addendum: I would recommend reducing the gains on your surrounds and sub amps (but not your heights, if possible) and rerunning your calibration.

Thank you. I think what he (and others I've heard) is saying is that you can run into output clipping on the Denon in case you have high trim levels and crank the volume. I don't know if that's true, but if I were Denon, I would make sure you could have the highest trim sand the highest volume without running into want issues. Why allow for a volume level that high otherwise?

Yes, that's what I will do.

 

[Spennis]

It is fine to leave thing alone based on those numbers. Or, set the Audiophonics gain to 25 dB, that's what I would do if those were my gear.

The Denon, especially if your unit has the AK4458 dac IC, like the one Amir measured.

Take a look of the SINAD vs level graph.

You are getting about 96 dB SINAD at 0.5 V and didn't fall below 90 dB at the lowest limit of the X-axis, that means it will be virtually silent in a typical room with noise floor at least 10-20 dB!!

I prefer 25 dB gain because to me a few dB lower in SINAD overall would make no audible difference whatsoever, but psychologically having turning my volume up higher would bother me, but that's just me.


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Agreed, you can do that, but why even bother. "better balance" would be for the look, no performance issues there at all, you have a very nice setup.

Thank you. I've decided to stick with the 20 dB gain on the Audiophonics amp as I can easily hit the volume levels I need. I've also decided to lower the gain on the XTZs, mostly because I am getting a very low volume buzz from the speakers that disappears when I lower the gain.

Side note: I'm very happy with the Audiophonics amp. Amazing build quality, fantastic sound. Highly recommended!