Review and Measurements of Benchmark AHB2 Amp

[Music1969]

Truly sad that no recording studio I've been in used ESLs or ribbons for monitoring and so all of the their recordings are flawed.

Minor side note but Adam Audio monitors have been quite popular for some years.

 

[Kyle / MrHeeHo]

Since the AAA technology performs so well I have to wonder if or when we will see it used in pro and commercial settings if there is a place for it

 

[DonH56]

Sansui loved their "super feedforward" AU-Dxxx series in the early 1980s.

AUD-11 block diagram:

View attachment 26730

AUD-11 implementation:

View attachment 26729

Denon, Yamaha etc used various "direct distortion cancelling" systems too.

I think the most famous would be the Quad 405 from the 1970s.

Attached Quad prepared leaflet (as PDFs below) compiled with two test reports from HFN and Studio Sound, April and March 1976.

Sansui is the one I had in mind but couldn't quite place. Trust @restorer-john to know the answer!

 

[direstraitsfan98]

Measures better then rated specs
It's about 150wpc into 8ohm and 290wpc into 4ohms.
Class A. Personally I could not identify this amp sounding any different then several other amps, and this sounds a lot better then a Pioneer M-22 which is hilariously under powered comapred to the DA-A10, and much larger.
They just don't make them like they used to.

 

[phoenixdogfan]

IMO:
1. It will handle ESLs just fine.
2. Too many unknowns; it will have a lower noise floor and lower distortion but whether that is audible to you I could not say. I suspect it would not be audible to me. The AHB2's lower output impedance might make the bass a bit better, and lower noise floor means less hiss in the treble.

Frankly I am not sure I would be able to tell the difference between the AHB2 and my Emotiva XPA-2, but I am anxious to find out. Just not sure I can justify the money outlay right now.

In the past I have been surprised by the times I could and could not tell the difference among power amplifiers. Back then I had many more resources for finding the technical reasons (there always was one or more). The white paper on the Benchmark site about hearing low-level crossover distortion was interesting. That is one of those things you'd think would never be a problem these days, but previously I have noticed crossover distortion and found it much more audible than I expected. I think the trend the past few years (actually, many years) has been toward lower bias levels and that leads to higher levels of crossover distortion. Less power at idle, so less heat, and easier on AVRs with their limited power supply and output capacity as well as limited ability to dissipate heat when crammed into a console, but greater amounts of low-level "grunge" in the sound. I have a bias toward high-power amplifiers and, aside from the obvious headroom advantage with my low-sensitivity speakers, I think the higher idle bias many have and lower output impedance is a player in that.

https://benchmarkmedia.com/blogs/application_notes/power-amplifiers-the-importance-of-the-first-watt

I am starting to really hate the AHB2; it is not something I can really afford, but it is pushing all my buttons.

It's one of those product you feel like you could almost afford if you skipped lunch for a year, and one of those you really, really want because even if you probably can't hear the difference between it and some other competent amp, you still want it for the technical tour de force it is anyway. I know reading this thread is making me crazy and I have stereo NCore parts on the way. Yet I still want this one.

 

[Purité Audio]

I wouldn’t worry you will not hear any difference between the two.
Keith

 

[D700]

How much heat does this unit put off at moderate volume, running for 4-5 hours? Does it require good amount of clear space on top or just the sides?

 

[Manbeard]

How much heat does this unit put off at moderate volume, running for 4-5 hours? Does it require good amount of clear space on top or just the sides?

Not much at all. Heatsinks aren't noticeably warm after a few hours of use. Don't think there would be an issue using it in a somewhat confined space.

 

[dkfan9]

Measurements for the a31 are at the following.
A31 measurements.
Anyone have any ideas?

OK I've skipped 4 pages so I may have missed other discussion on the matter.

One idea: Output impedance (damping factor) differences

Below are the frequency response differences between the A31 and the AHB driving Kal's Monitor Audio Silver 8's. AHB as monoblock in green, AHB in stereo in blue.

Derived by tracing JA's SPL and Impedance Measurements of the Monitor Audio Silver 8's from Kal's review in Stereophile using VirtuixCAD's built in tool. Imported these as a driver into VirtuixCAD, put a .01 ohm resistor inline to approximate the A31's output impedance (from SSN review), a .09 for the AHB, and a .14 for the AHB monoblock (from Stereophile review). Divided A31's FR by the AHB's and AHB Monoblock's in VirtuixCAD, then imported to REW for viewing.

 

[Soniclife]

OK I've skipped 4 pages so I may have missed other discussion on the matter.

One idea: Output impedance (damping factor) differences

Below are the frequency response differences between the A31 and the AHB driving Kal's Monitor Audio Silver 8's. AHB as monoblock in green, AHB in stereo in blue.

Derived by tracing JA's SPL and Impedance Measurements of the Monitor Audio Silver 8's from Kal's review in Stereophile using VirtuixCAD's built in tool. Imported these as a driver into VirtuixCAD, put a .01 ohm resistor inline to approximate the A31's output impedance (from SSN review), a .09 for the AHB, and a .14 for the AHB monoblock (from Stereophile review). Divided A31's FR by the AHB's and AHB Monoblock's in VirtuixCAD, then imported to REW for viewing.

View attachment 26767

What's the scale on that graph?

 

[dkfan9]

What's the scale on that graph?

.3db is the top line (300m) and -.1 is the bottom (-100m)

 

[Aibo]

Perfect little amp. I really like the idea of compact sized high end amp. Not a fan of huge mono blocks needing a team to move them around. Actually, know some guys exchanging some seriously heavy artillery with AHB2 and not looking back.

 

[Soniclife]

.3db is the top line (300m) and -.1 is the bottom (-100m)

Thanks. So the A31 gives a subtle amount more output in the 40-50 & 100 to 200 Hz ranges. Enough to give the impression of more grunt possibly.

 

[Kal Rubinson]

Below are the frequency response differences between the A31 and the AHB driving Kal's Monitor Audio Silver 8's. AHB as monoblock in green, AHB in stereo in blue.

Thanks. So the A31 gives a subtle amount more output in the 40-50 & 100 to 200 Hz ranges. Enough to give the impression of more grunt possibly.

Interesting even though I never made such a comparison on the MA Silver8s. OTOH, I did make it on the Revel Performa3 F228BE speakers and the curves you have created are similar to what I would expect. https://www.stereophile.com/content/revel-performa-f228be-loudspeaker-page-2

 

[Blake Klondike]

This is very cool to see-- $3000 dollars is a big investment, but as a guitar store owner I know used to say: "You can buy one $1000 guitar and play it forever, or buy several $300 guitars over the years and then a $1000 guitar. At that point, your $1000 guitar has cost you $2200."

 

[Tks]

So if you sit in the studio while the musician plays with no equipment between you will the lack of added distortion strip away the emotion of the performance?

 

[yummy]

secret: no transducer can do better than -60db thd+n in audio BW, please don't chase the sun, I know it's sad, but brutal

 

[dkfan9]

Interesting even though I never made such a comparison on the MA Silver8s. OTOH, I did make it on the Revel Performa3 F228BE speakers and the curves you have created are similar to what I would expect. https://www.stereophile.com/content/revel-performa-f228be-loudspeaker-page-2

Ah, I managed to conflate what I read in this thread with what I read in the "Listening in the Country" section of the AHB review without double checking... In the meantime I realized I made another mistake in comparing the SSN and Stereophile measurements, when they don't match for the AHB2. I'm not sure what causes the differences (.06-.09 ohms, and the difference is consistent across two other post-2007 measurement sets I compared). With the SSN numbers for the AHB2 the profile will be similar but less dramatic... I'll update the graph later today if i get time.

 

[Kal Rubinson]

Ah, I managed to conflate what I read in this thread with what I read in the "Listening in the Country" section of the AHB review without double checking... In the meantime I realized I made another mistake in comparing the SSN and Stereophile measurements, when they don't match for the AHB2. I'm not sure what causes the differences (.06-.09 ohms, and the difference is consistent across two other post-2007 measurement sets I compared). With the SSN numbers for the AHB2 the profile will be similar but less dramatic... I'll update the graph later today if i get time.

Thanks. Your analysis, although extracted from disparate sources, fascinates me because it provides a potential explanation for what I hear as a difference between two excellent (but unequal) amplifiers with a single speaker. I'd be really happy if you based the re-analysis on the F228Be because that is where I heard it most clearly.

 

[RichB]

Sometimes a bare wire just won't work.

As everyone already knows, I use (now defunct) BellCore approved power cable (we are delivering power, aren't we), terminations, and antioxidant...

It's a bit OT, but does it make sense to treat cables with antioxidant before making screw contact connections?
I am currently using these locking banana plugs:

https://www.parts-express.com/angle...crews-poly-carbonate-shell-and-insu--091-3608

I am considering switching the amp side to these NEUTRIK NL2FX SpeakON 2-Pole Female Cable Connectors:

https://www.amazon.com/dp/B01BFD8XM...olid=2JTHQ49ZVS4K6&psc=0&ref_=lv_ov_lig_dp_it

- Rich