Yamaha RX-A820 amps versus ATI AT522 for two-channel system

[RichB]

Many have asked if adding an amplifier would improve the sound of their AVR.
You can compute the power but and that may look good but it may also be that a particular speaker is not well driven by an AVR.

In pursuit of the answer for my particular system, I have decided to compare the ATI AT522C (arriving soon) to the Yamaha RX-820 driving my Revel M20 bookshelf speakers.
Will there be any improvement driving the speakers when neither amp should be clipping?

The Yamaha RX=A820 specs can be found here:
https://europe.yamaha.com/en/products/audio_visual/av_receivers_amps/rx-a820/specs.html

The ATI AT522NC specs can be found here:
http://ati-amp.com/manuals/AT500NC Manual Oct 2017 SM.pdf

The A820 is rated 100 WPC 2-channels driven into 8 Ohms 20Hz to 20kHz.
The AT522C is rated 200 WPC 2-channels driven into 8 Ohms 20Hz to 20kHz.

The Oppo 105D is the source will also be used for volume control. I’ll play some pure tones and adjust the A820 volume as close as possible (should be within .5 DB) comparing the voltage. Once matched, I can listen to both components (the Yamaha in Pure Direct mode) by swapping the speaker cables.

The M20s are wall- mounted on OmniMounts and their placement is less than ideal. I have always been bothered by the noticeable degradation in sound quality when using the A820 HDMI input. I prefer listening to the 105 analog outs in the A820’s Pure Direct mode.

One might think that bookshelf speakers are easier to drive but this is not always the case. The M20’s measurements can be found on Stereophile:

https://www.stereophile.com/content/revel-performa-m20-loudspeaker-measurements

My estimate of the Revels' voltage sensitivity was a little lower than specified, at 84.5dB(B)/2.83V/m. Given the sophistication of Revel's measurement facilities and the agreement I had obtained between my figure and their figure for the Performa F30, I was surprised by this disparity. I rechecked my figures; no change.
The speaker's impedance was assessed using an Audio Precision System One; the results are shown in fig.1, with the tweeter-level control set to its maximum and minimum positions. The lowest impedance is with the control set to "+1," in which case the minimum magnitude is 4 ohms between 2 and 3kHz. The electrical phase angle varies quite considerably, with a worst-case combination of 5.9 ohms and 42 degrees capacitive angle occurring at 100Hz. Good 4-ohm-rated amplifiers will work best with this speaker.

The M20s drop below 4 Ohms between 80 and 90Hz. So, they are inefficient and a somewhat complex load. I may also arrange a SBT.

- Rich

 

[KEW]

Many have asked if adding an amplifier would improve the sound of their AVR.
You can compute the power but and that may look good but it may also be that a particular speaker is not well driven by an AVR.

In pursuit of the answer for my particular system, I have decided to compare the ATI AT522C (arriving soon) to the Yamaha RX-820 driving my Revel M20 bookshelf speakers.
Will there be any improvement driving the speakers when neither amp should be clipping?

The Yamaha RX=A820 specs can be found here:
https://europe.yamaha.com/en/products/audio_visual/av_receivers_amps/rx-a820/specs.html

The ATI AT522NC specs can be found here:
http://ati-amp.com/manuals/AT500NC Manual Oct 2017 SM.pdf

The A820 is rated 100 WPC 2-channels driven into 8 Ohms 20Hz to 20kHz.
The AT522C is rated 200 WPC 2-channels driven into 8 Ohms 20Hz to 20kHz.

The Oppo 105D is the source will also be used for volume control. I’ll play some pure tones and adjust the A820 volume as close as possible (should be within .5 DB) comparing the voltage. Once matched, I can listen to both components (the Yamaha in Pure Direct mode) by swapping the speaker cables.

The M20s are wall- mounted on OmniMounts and their placement is less than ideal. I have always been bothered by the noticeable degradation in sound quality when using the A820 HDMI input. I prefer listening to the 105 analog outs in the A820’s Pure Direct mode.

One might think that bookshelf speakers are easier to drive but this is not always the case. The M20’s measurements can be found on Stereophile:

https://www.stereophile.com/content/revel-performa-m20-loudspeaker-measurements

My estimate of the Revels' voltage sensitivity was a little lower than specified, at 84.5dB(B)/2.83V/m. Given the sophistication of Revel's measurement facilities and the agreement I had obtained between my figure and their figure for the Performa F30, I was surprised by this disparity. I rechecked my figures; no change.
The speaker's impedance was assessed using an Audio Precision System One; the results are shown in fig.1, with the tweeter-level control set to its maximum and minimum positions. The lowest impedance is with the control set to "+1," in which case the minimum magnitude is 4 ohms between 2 and 3kHz. The electrical phase angle varies quite considerably, with a worst-case combination of 5.9 ohms and 42 degrees capacitive angle occurring at 100Hz. Good 4-ohm-rated amplifiers will work best with this speaker.

The M20s drop below 4 Ohms between 80 and 90Hz. So, they are inefficient and a somewhat complex load. I may also arrange a SBT.

- Rich

It would be nice if you could get someone to change (or not) the connections so you don't know which you are hearing when and also for you to do the same with him as the subject!
Also, my audio memory may be worse than most, but any change I perceive after a 30 second delay seems more like a notion than a certain difference.
Of course, if you can run double (or single) blind, multiple trials with consistent results achieve confidence in the result.
Do you have power specifications on either unit at 4 or 6 Ohms?
It sounds like Stereophile believes 100Hz @ 6 Ohms is the most demanding load.

 

[KEW]

Also, I would assume the Yamaha RX-A820 is closely related to the A860 which is known to have a rather anemic amp section!
From Gene's review:

While the RX-A860 is fine driving small bass-managed 8 ohm speakers, this is the first time I'd actually caution people against using 4 ohm speakers or even running 8 ohm tower speakers on the “large” setting. I’ve never said this about a Yamaha before. It's sad that a $400 predecessor from the very same company offered a more robust amp and power section than this product, which has AVENTAGE moniker stamped on it. To pour further salt on the power wound, the preamp out section of this receiver is a bit weak, making it critical to match with a high gain amplifier to ensure the preamp itself doesn't clip while driving external amplification. I'd like to see Yamaha beef up the amp section so the current limiting could be a little less restrictive and for God's sake, please give us a clean 2Vrms output from the pre-outs of ALL your AV receivers!

https://www.audioholics.com/av-receiver-reviews/yamaha-rx-a860/conclusion

Should be an interesting test!
I look forward to reading the results!

 

[PENG]

Hey Rich, how far will you be sitting from the M20s?

 

[RichB]

Hey Rich, how far will you be sitting from the M20s?

The room is my basement game room so there is lots of walking around. Especially, when playing pool.

When working out, about 15 feet. The room is over 35 feet.
I really don't push the system very often.

I am also considering replacing the speakers with Revel M126Be's.

- Rich

 

[RichB]

It would be nice if you could get someone to change (or not) the connections so you don't know which you are hearing when and also for you to do the same with him as the subject!
Also, my audio memory may be worse than most, but any change I perceive after a 30 second delay seems more like a notion than a certain difference.
Of course, if you can run double (or single) blind, multiple trials with consistent results achieve confidence in the result.
Do you have power specifications on either unit at 4 or 6 Ohms?
It sounds like Stereophile believes 100Hz @ 6 Ohms is the most demanding load.

I'll arrange to place the units on top of one another to make the switching fast and blind. Is there an inexpensive speaker switch that does not cause too much loss?

- Rich

 

[PENG]

The room is my basement game room so there is lots of walking around. Especially, when playing pool.

When working out, about 15 feet. The room is over 35 feet.
I really don't push the system very often.

I am also considering replacing the speakers with Revel M126Be's.

- Rich

In that case the 820 will likely run out of gas.

 

[KEW]

I'll arrange to place the units on top of one another to make the switching fast and blind. Is there an inexpensive speaker switch that does not cause too much loss?

- Rich

I have no experience with speaker switches. I always do my speakers comparisons using two AVRs fed a common source (like using Toslink and HDMI outputs from Oppo.

@WaynePflughaupt has, on occasion, been knowledgeable about non-mainstream gear, but I have no idea if he knows a unit to switch between two amps feeding the same speaker.

 

[RichB]

In that case the 820 will likely run out of gas.

I can measure the voltage and SPL at 12 feet to compute the approximate power usage and some tests performed that should be kept within range where both amps are not clipping, chasing the illusive "operating within its limits".

- Rich

 

[RichB]

I have no experience with speaker switches. I always do my speakers comparisons using two AVRs fed a common source (like using Toslink and HDMI outputs from Oppo.

@WaynePflughaupt has, on occasion, been knowledgeable about non-mainstream gear, but I have no idea if he knows a unit to switch between two amps feeding the same speaker.

I found this one:

https://www.amazon.com/Nobsound-Audio-Crossover-Speakers-Amplifiers/dp/B077Z4ZKG5/ref=sr_1_10?ie=UTF8&qid=1520988951&sr=8-10&keywords=ab+speaker+selector+switch

- Rich

 

[RichB]

I found this one:

https://www.amazon.com/Nobsound-Audio-Crossover-Speakers-Amplifiers/dp/B077Z4ZKG5/ref=sr_1_10?ie=UTF8&qid=1520988951&sr=8-10&keywords=ab+speaker+selector+switch

- Rich

I don't think I will use this switch, the risk of a relay or momentary dual connection is too great. I don't want to blow up my amps.

- Rich

 

[PENG]

I don't think I will use this switch, the risk of a relay or momentary dual connection is too great. I don't want to blow up my amps.

- Rich

I think the Adcom GFS-4 should be good. It claims audiophile grade, affordable and relay free (as far as I can tell). No protection either (price to pay for audiophile gear), so you can connect and actually select 4 pairs of 4 ohm speakers if you wanted to try out your amp's protective system.

https://www.usahifi.com/sites/default/files/product/500/manuals/Adcom GFS-3 GFS-6 GFS-4 Speaker Selector Brochure.pdf

 

[RichB]

^ These are speaker selectors designed to allow multiple speaker to be active.
Multiple amps active would be a good test of the protection circuitry.

- Rich

 

[PENG]

^ These are speaker selectors designed to allow multiple speaker to be active.
Multiple amps active would be a good test of the protection circuitry.

- Rich

Oh, sorry, I forgot you are comparing amplifiers.

 

[RichB]

According to the AVS AT500NC thread, the AT522NC included break-in recommendation but that was removed. It does make sense for caps and there are a couple of large 80 volt caps. So, I will revisit this testing.

I brought the AT522NC up to see how it compared to the AT6000 driving the Salon2s.
Prior to measuring the voltage I did some listening and my impression was the AT500NC was doing an amazing job driving the Salon2's bass section, both single and bi-amped. The AT500NC could not match to crystal clear highs of the AT6000. The NC added just a bit edginess to the treble.

I can definitely see putting together a system with the AT500NC in the single or bridged model driving the woofers and the AT4000 driving the upper end.
The measurements taken comparing the voltages driving the upper and lower half of the Salon2’ are attached.

I got the math from Gene DellaSala (Audioholics); ATI/Par SPLdB diff: =10*LOG(r3/r4), where r is the row.
The AT5000NC is the denominator so a negative number means the AT6000 is softer, and positive louder.
So from 50 to 250Hz, there isan almost 1 DB tilt. The AT500NC has more bass a less treble with sine-wave signals requiring about 2 watts.

I think there is evidence that these amps are performing differently with this load a very low power.

- Rich
Attached Thumbnails

 

[RichB]

I ordered this switch, which in the comments states that connections are break-then-make.

https://www.amazon.com/gp/product/B0796KGVXT/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

- Rich

 

[PENG]

I did some checking, and would suggest you do your comparison at 75 dB average maximum, if you sit 10 ft from the M20's. If you sit 15 ft and still go with 75 dB average or higher, then you don't need to tell me the result.

 

[RichB]

I've done some testing in the game room today. Using a 60 Hz tone, the Oppo BDP-105 at 33 produced 2.7 volts. With the Oppo at 33, the Rx-A820 +8 also produced 2.7 volts.

The bass produced by the 522 is impressive. The highs brighter on the A820 but the 522 is cleaner. I'll do more listening after the switch arrives.

- Rich

 

[lovinthehd]

What does "at 33" mean?

 

[RichB]

What does "at 33" mean?

The Oppo Volume setting which uses a scale from 0 to 100.

- Rich