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Review and Measurements of Benchmark AHB2 Amp

RichB

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I bought a newer Fluke 115, good enough for my basic usage and level matching.
Level matching the AHB2 and ATI AT522NC, I noticed something odd.
The AHB2 measures 0 Volts with no signal and with the inputs removed.
The AT522NC measure consistently 0.08 volts with no signal and with the inputs removed.

It's not huge, but shouldn't the AT522NC be measuring 0 Volts?

- Rich
 

SIY

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Is that AC or DC?
 

SIY

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I don't know what the bandwidth of your meter is but it could certainly be some ultrasonic noise. If the meter's indication is correct, that's not enough to be concerned about for most situations. If your speakers are 8 ohms at the amp switching frequency, that represents less than a milliwatt.
 

RichB

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I don't know what the bandwidth of your meter is but it could certainly be some ultrasonic noise. If the meter's indication is correct, that's not enough to be concerned about for most situations. If your speakers are 8 ohms at the amp switching frequency, that represents less than a milliwatt.
The Meter is a Fluke 115. The speakers are 4 ohm.
Apparently, switching noise happens with no input or output connected.

- Rich
 

SIY

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The important thing is not the speakers' rated impedance, but what it is at the switching frequency. Now, even if it's 4 ohms, you're still at about a milliwatt (which is nothing), and since most speakers are inductive at the top end, the dissipation is far lower; the switching noise from the amp is causing them to dissipate 67 percent of f-all.

Short version- don't worry about it, it's meaningless.
 

Sal1950

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Each technology has its advantages.

OLED compensation cycles have more to do with residual images, banding in low APL areas.
It is not burn-in which is really uneven wear. If you watches stations with tickers, news most of the time, LCD is a better choice.

OLED is better than Plasma for IR and wear. For most, it is not an issue.
OLED's perfect black-levels and accurate color tracking provide an SOA viewing experience.
They are wonderful.

- Rich
No doubt.
I did experience bad screen burning on a expensive projection unit some years back from prolonged watching of network stations that constantly projected their logo in the bottom right corner of the screen. Ruined my ability to enjoy watching that set ever-after.
Once bitten twice shy the song goes. :(
 

DonH56

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A Fluke 115's AC frequency range is 5 Hz to 30 kHz, too low to pick up switching noise, but ACV is only specified to 1 kHz far as I can tell. Still might be integrating switching noise.

OLEDs do suffer burn-in, something I did not realize when I bought one. :confused: There are a number of articles and websites discussing it and showing the results.
 

maty

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Tonality is excellent with the AHB2.

You can hear three distinct depths. There is the main orchestra and soloist at the first level. Then there is a small group of strings at the next level- maybe 20-30 feet back. The echo chamber instruments were placed at the third level WAY in the back of the church (which has a lot of reverberant energy). The effect is really interesting, and the engineers captured it very well. You hear the main orchestra and when they are silent or only the violin soloist is playing, you sometimes here this island of strings much further back at the second level. And when Vivaldi whats the full echo, you hear the third layer very far away. Subjectively it sound like they are almost one hundred feet back. They may well have been...
Yesterday I tried to hear depth and sound plans. https://www.diyaudio.com/forums/music/6958-playing-listening-post5843226.html

Die Stereo Höertest - LP Volume II (2015), Vinyl x2, in-akustik, Germany

Die Stereo Hortest LP Volume II (Vinyl, LP, Sampler, Stereo) | Discogs



DR Peak RMS Filename
----------------------------------------------------------------------------------------------

DR13 -0.99 dB -17.20 dB A1 Aram Khatchaturian - Masquerade Suite - Galop
DR12 -2.22 dB -18.98 dB A2 Antonio Forcione, Sabina Sciubba - Visions
DR14 -1.26 dB -17.90 dB A3 Doug MacLeod - Rosa Lee
DR11 -1.09 dB -16.00 dB A4 Carolin No - Still Waters Run Deep
DR18 -0.60 dB -23.44 dB B1 Gregorio Paniagua, Atrium Musicae De Madrid - Principalis. Fermescens-Indica exacta
DR14 -0.42 dB -17.78 dB B2 CC Coletti - Whole Lotta Love
DR12 -1.24 dB -16.74 dB B3 Blues Company - If I Only Could
DR15 -3.40 dB -20.66 dB C1 Hanne Boel - Mad World
DR15 -0.52 dB -17.41 dB C2 Conga - Hands On Strings
DR13 -0.78 dB -16.52 dB C3 Lyn Stanley - A Summer Place
DR12 -0.22 dB -16.75 dB C4 Felix Hell - Prelude On B-A-C-H
DR12 -0.83 dB -14.99 dB C5 Wolfgang Bernreuther - For Ole
DR10 -1.02 dB -13.23 dB D1 Otis Taylor - If They Wore Blue
DR12 -0.65 dB -14.68 dB D2 Diana Panton - So Nice
DR13 -0.44 dB -20.17 dB D3 Maurice Ravel - Alborada Del Gracioso
----------------------------------------------------------------------------------------------

Number of files: 15
Official DR value: DR13

Depth: yes, near and far field. I would have liked more depth.

Sound plans: I was unable in either of the two situations.
 

zalive

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The important thing is not the speakers' rated impedance, but what it is at the switching frequency. Now, even if it's 4 ohms, you're still at about a milliwatt (which is nothing), and since most speakers are inductive at the top end, the dissipation is far lower; the switching noise from the amp is causing them to dissipate 67 percent of f-all.

Short version- don't worry about it, it's meaningless.
Short version, in your opinion it's meaningless.
You cannot guarantee it's not audible.
 

SIY

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I can't guarantee that you're not a Rigelian in low Earth orbit, either. But a bit of common sense suggests it's unlikely.
 

DonH56

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Bias voltage? Or is that only present at higher frequencies or not at all in a class D amp?
Bias voltage should not appear at the output of an amplifier -- that is an internal thing. Design and feedback should keep the output very near zero. I am not sure how much voltage can be harmful but significant (whatever that means) DC voltage at the output can degrade speaker performance in several ways.
 
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Bias voltage should not appear at the output of an amplifier -- that is an internal thing. Design and feedback should keep the output very near zero. I am not sure how much voltage can be harmful but significant (whatever that means) DC voltage at the output can degrade speaker performance in several ways.
Ok thanks for the clarification. I swear I learn more on this forum... high signal to noise ratio here.
 

RichB

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After 1/2 idling, the AHB2 measured 10 mV AC and the AT522NC 170mV AC with no input signal.
After an hour of use, the AT522NC does not change but the AHB2 dropped to 3.5 mV AC.

- Rich
 
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peng

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After 1/2 idling, the AHB2 measured 10 mV and the AT522NC 170mV with no input signal.
After an hour of use, the AT522NC does not change but the AHB2 dropped to 3.5 mV.

- Rich
For AC voltage, the Fluke 115's accuracy is:

Accuracy 1.0% + 3 (DC, 45 Hz to 500 Hz) and 2.0% + 3 (500 Hz to 1 kHz)

So a few mV means nothing, just pick up noises that should disappear if you short the leads, or connect them to the test points being measured.

If you are getting 170 mV at the AT522NC output terminals no input signal, something is not right. Even my cheap Denon AVR is able to output 0 AC in the mV range with no signal. I do get about 1 mV or less on the DC range, but that's extremely low offset. You wonder why I switched back from AVP to AVR.:D
 

RichB

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For AC voltage, the Fluke 115's accuracy is:

Accuracy 1.0% + 3 (DC, 45 Hz to 500 Hz) and 2.0% + 3 (500 Hz to 1 kHz)

So a few mV means nothing, just pick up noises that should disappear if you short the leads, or connect them to the test points being measured.

If you are getting 170 mV at the AT522NC output terminals no input signal, something is not right. Even my cheap Denon AVR is able to output 0 AC in the mV range with no signal. I do get about 1 mV or less on the DC range, but that's extremely low offset. You wonder why I switched back from AVP to AVR.:D
I am returning the Fluke 115 and ordered an 87V that is more accurate.

The Fluke 115 is not measuring any DC for either amp.
The AT522NC is consistently measuring about 170 mV on both outputs and no connections.

Should I contact ATI?
Every once and a while they respond to support requests.
However, adding Morris to the CC list is the only guarantee :p

- Rich
 

SIY

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Your multimeter accuracy is good enough for 99.9% of what you'll want to do. A scope across the output will tell all. If you don't have a nearby buddy with a scope, by all means contact the amp company. That seems unusually high.
 

RichB

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Your multimeter accuracy is good enough for 99.9% of what you'll want to do. A scope across the output will tell all. If you don't have a nearby buddy with a scope, by all means contact the amp company. That seems unusually high.
I have a friend (on vacation now) with an Oscium iPad spectrum analyzer.
I'll try that when he gets back.

- Rich
 

peng

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I am returning the Fluke 115 and ordered an 87V that is more accurate.

The Fluke 115 is not measuring any DC for either amp.
The AT522NC is consistently measuring about 170 mV on both outputs and no connections.

Should I contact ATI?
Every once and a while they respond to support requests.
However, adding Morris to the CC list is the only guarantee :p

- Rich
I have no experience with the 115 but the 87 V is excellent. A little pricey at over C$500, but it will definitely do a good job for you on audio stuff.
170 mV is crazy high if there is no inputs even connected. The 115 can measure frequency so I would suggest you do it and see what it shows. Switching frequencies are way too high for such multi-meters but that could be the reason for the crazy reading.
 
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