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Level Matched Comparisson of the AT525NC and AHB2

RichB

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I have an ATI AT525NC (NCore) amp that will be deployed in the spring at another location and I need to test it before then.
My office and main system use AHB2 amplifiers.

I have edited this post since I changed the test configuration.

This provides an opportunity to perform some Single Blind Tests comparing the two.
Here is the configuration for the test.
  • The MiniDSP SHD is used as the source for both amplifiers. Its DSP permits level matching between .1 dB. In actuality, matching was 0.06 dB.
  • The MIniDSP outputs 1 and 3 are the left channel and 2 and 4 are the right channels.
  • Both amps were level matched to approximately 2.83 Volts measure with a Fluke 87V sinewave voltmeter.
  • Music selections are streamed by Roon to a Raspberry PI3 running DietPi and Roon endpoint to the MiniDSP USB DAC.
  • This passive A/B switch was used to switch instantaneously between sources: Amazon.com: Nobsound Stereo 2(1)-IN-1(2)-OUT Amplifier/Speaker Banana Female Audio Splitter/Switcher Passive Selector: Electronics
So the connections connection looks like this:
  • Roon -> RPI3 (DietPi Endpoint) -> MiniDSP USB Input
  • MiniDSP out 1 & 2 -> ATI525NC -> Nob switch Input A
  • MiniDSP out 3 & 4 -> AHB2 -> Nob switch Input B
  • Nob switch out -> Revel M123Be speakers
This configuration has nearly perfect level matching with 0.06 dB and instantaneous switching.
During the test, the MiniDSP channels were switched and no differences were found. This was done to make sure the MiniDSP was not affecting the test.

I have not yet done the single-blind-test (SBT) part so, for now, it is me listening and quick switching.

The AHB2 and AT522NC do sound different. These are most easily recognizable playing close-mic'ed female vocals, and percussive instruments, and recordings with good stereo imaging.

In all cases where they differed, I find the AHB2 to the cleaner sounding amp. The sound stage is more defined. The ATI sounds does not produce the sibilants as naturally and seemingly dulls the leading edge of drum hits and guitar strings. As a result the AHB2 sounds more lifelike and louder, though it is not.
This was surprising, so more than once, the outputs were re-measured with 1kHz 0 dBFS sinewaves. At 2.83 volts and the ATI is a just a hair louder, 0.02 volts which is insignificant. It was not a gain issue.

EDIT: I did find the AT525NC voltage varied during steady 1 kHz tone from 2.75 to 2.86 volts.
Whereas, the AHB2 was always 2.85 volts.


One album exemplified the differences more than the others, but all showed the same results.
Feist's "Metals" has excellent percussive sounds, up front female vocals, and wide imaging.
The AHB2 was exemplary and the ATI just did not excel.
To be fair, I am sure that if I walked in the room, I would not know which was playing but with the A/B switch it was not difficult.

Here are some images of the setup.
This was the original level match. I later changed it -3.0 dB and -8.5 dB to make sure that both channels were using the DSP processing. This made no difference.
AHB2MedLevelMatch.jpg


The setup.
SetupFront.jpg


AHB2_AT525NC_Voltage_Level_Match.jpg

I am actually surprised by these results. The expectation was the AT525NC would be indistiquishable.

- Rich
 

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RichB

RichB

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I have a Mapletree A/B speaker selector I'm not using, similar to the Nobsound (see here https://www.audiosciencereview.com/forum/index.php?threads/speaker-switch-diy.12671/page-2). I'm happy to send it to you if you want to borrow it. I don't know how folks will feel about having a speaker selector in the testing though.

I might take you up on that.
What do you think of this device?
2-way Speaker A/B Selector Amplifier Spiltter Home Stereo Audio Switcher Box Hub | eBay

Would it be transparent?

- Rich
 

pjug

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That looks like a nice device. I just wonder if it will be accepted to use switches or relays between amp and speakers, although I don't know how else you can do fast changes for comparison. Also, I wonder if Class D ultrasonic residuals sharing a switch with the AHB2 could degrade the AHB2 performance. I would suggest that you get some feedback from some people with weighty opinions before doing this (purpose of this thread). It would be a shame to go through the effort and have the procedure rejected here. Maybe @John_Siau would weigh in?

Anyway I am in NH so it will only take a day to get the switch box that I have down to you if you want it.
 
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RichB

RichB

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That looks like a nice device. I just wonder if it will be accepted to use switches or relays between amp and speakers, although I don't know how else you can do fast changes for comparison. Also, I wonder if Class D ultrasonic residuals sharing a switch with the AHB2 could degrade the AHB2 performance. I would suggest that you get some feedback from some people with weighty opinions before doing this (purpose of this thread). It would be a shame to go through the effort and have the procedure rejected here. Maybe @John_Siau would weigh in?

Anyway I am in NH so it will only take a day to get the switch box that I have down to you if you want it.

I'd like to take you up on that. Care to be on the panel ?

- Rich
 

pjug

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I'd like to take you up on that. Care to be on the panel ?

- Rich
Thanks, but I don't consider my ears to be expert quality! Also, if you are doing this anytime soon I'd probably have to quarantine at your house or office!

PM me with your address and I'll send the box to you.
 
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RichB

RichB

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I updated the fist post with my fast switching but sighted impressions of the AHB2 and AT525NC amps.
You would expect them to be indistiquishable given the measurements but I found them to be identifiable and the AHB2 proved to be an incredible amp.

This is my room, my ears, my gear, and these speakers. I don;t necessarily believe that this pertains to all speakers nor may be reflective of all Hypex implementations.

- Rich
 
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Thanks very much for that comparison. I bought a 525NC b/c I couldn't justify the cost of multiple AHB2s for my combined audio/video system. Glad to know the AHB2 effects a noticeable difference.
 

preload

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This is getting very interesting! Do you have a way to measure FR of the signal fed to the speaker terminals?
 

Whoareyou

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Hi Rich,
Very interesting post. I currently have that same ATI amp, but was looking at upgrade path for amplification. I was considering AHB2 as first step in upgrade path, for stereo only listening, but I would be blending that with remaining channels from the 525NC for multichannel.

In the post showing the original level match it looks as though the AHB2 level had to be reduced by 11.5db to properly match with the ATI volume?
I'm really not very good at this stuff :) Am I reading that correctly ?
 
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RichB

RichB

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Hi Rich,
Very interesting post. I currently have that same ATI amp, but was looking at upgrade path for amplification. I was considering AHB2 as first step in upgrade path, for stereo only listening, but I would be blending that with remaining channels from the 525NC for multichannel.

In the post showing the original level match it looks as though the AHB2 level had to be reduced by 11.5db to properly match with the ATI volume?
I'm really not very good at this stuff :) Am I reading that correctly ?

The AT525NC had to adjusted -5.5 DB initially and -5.4 later, after the SHD firmware update.
However, I don't think that may be the cause.
The AT525NC was not consistent, ranging from 2.75 to 2.86 volts while playing a 0 dBFS 1 kHz sinewave.
It was not warm-up because there were cases where it had been on for a while.
The AHB2 was always 2.85 volts and steady.
Perhaps, my power was sagging and affecting the AT525 where the AHB2 regulated supply was unaffected.

- Rich
 
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RichB

RichB

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Thanks very much for that comparison. I bought a 525NC b/c I couldn't justify the cost of multiple AHB2s for my combined audio/video system. Glad to know the AHB2 effects a noticeable difference.

It's sighted and I had no time to get participants for a blind.
But over many days, my impression remained the same.

- Rich
 
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RichB

RichB

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This is getting very interesting! Do you have a way to measure FR of the signal fed to the speaker terminals?

I do not have that capability.
I was able to use the Fluke 87V to level match at the speaker outputs without changing connections, using the A/B speaker switch.
This worked better because once I had a good connection, it was left alone.

On subsequent days, I checked the level match before and after listening for completeness.

- Rich
 

Whoareyou

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The AT525NC had to adjusted -5.5 DB initially and -5.4 later, after the SHD firmware update.
However, I don't think that may be the cause.
The AT525NC was not consistent, ranging from 2.75 to 2.86 volts while playing a 0 dBFS 1 kHz sinewave. ....
- Rich

That definitely gives me a better idea what to expect if I were to use ABH2 with AT525 in hybrid stereo/multichannel configuration .

Thanks Again
 
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RichB

RichB

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That definitely gives me a better idea what to expect if I were to use ABH2 with AT525 in hybrid stereo/multichannel configuration .

Thanks Again
To quantify it, I don't think I would know which amp was playing when walking in the room.

- Rich
 
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Whoareyou

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To quantify it, I don't think I would know which amp was playing when watching in the room.

- Rich
Well, no need to do so, since I picked one up today. FYI - Dirac (standalone with umik1) calibrated the system at 5.4 for other speakers on the AT525nc, so right in line with your measurements.

I know what I hear, and I like it very much. I believe the listening experience confirms everything you noted and also the measurements and comments in the 120+ page AHB2 thread. Don't want to get too subjective, but sometimes a product's measurements deserves the subjective response :)
 
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