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Review and Measurements of Benchmark AHB2 Amp

Sal1950

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Kal, I’m not sure what you mean? I’m asking if I’ll notice a difference between the
Proceed and the AHB2. I’d like to get some opinions before dropping 3k on an amp.
Just trying to get some feedback on
Before anyone could even take a wild guess at answering, you'd need to provide some solid info like the amp's exact model and the speakers your driving them with.
 

cbnbmore

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Before anyone could even take a wild guess at answering, you'd need to provide some solid info like the amp's exact model and the speakers your driving them with.
Absolutely agree, it is the Proceed Amp 2 made by Levinson and the speakers are the SMS1 by Benchmark also produced by Studio Electric as their M4 although there were claimed to be a few differences between the two models.
 
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amirm

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There's plenty of good reason to have user defeatable protection, not the least of which means the amplifier can be confirmed by third parties to actually hit its rated specification.
I have not seen a defeatable protection circuit before. The #1 reason to have protection circuit in an amp is to avoid warranty repair costs. As such, I can't imagine it being a good idea to have a defeat function for it.
 
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amirm

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Absolutely agree, it is the Proceed Amp 2 made by Levinson and the speakers are the SMS1 by Benchmark also produced by Studio Electric as their M4 although there were claimed to be a few differences between the two models.
I have the Proceed Amp 5 and it is and it is an excellent Amp. It powers my theater after all these years. It weighs so much that even if there is something better, I am not dragging it out of the rack to replace it. :)
 

Kal Rubinson

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Sorry it was asked incorrectly. I know you can’t say what I’ll notice but I’d like to hear your opinions on the two pieces of gear if you can.
I have heard the Proceed because my son-in-law still uses one in his HT system but with substantially different speakers, the original Revel Gems. I could swap in one of my AHB2 amps but the context is a complex, deeply embedded, centrally-controlled system and I am not sure it would be permitted. I can ask.

OTOH, I have reported on the AHB2 in Stereophile and made comparisons with other amps. As a result, I bought 3 of them.
 

March Audio

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There's plenty of good reason to have user defeatable protection, not the least of which means the amplifier can be confirmed by third parties to actually hit its rated specification.

Remember the standard is only 5 minutes, not 1 hour or continuously forever. If a power amplifier cannot achieve its rated power into specified rated loads for a measly 5 minutes, the ratings are false.

Plenty of you guys drive cars with top speed limiters that are not defeatable (easily). But the car makers do not advertise top speeds you cannot achieve, they just fit speedoes with numbers the dial pointer never quite reaches...

As for throwing out the FTC amplifier rule proposed a few pages back, it's the only thing keeping manufacturers partially honest. Without it, you'd be back to the Wild West of amplifier ratings in the early 70s.

Hopefully we'll get to see an AHB-2 properly tested into all its rated loads, stock standard, as per the long standing rules. If I had money to burn, I'd buy one because I think it's a fabulous amplifier and I'd test it, report the results and put the whole thing to bed.

Just a post commenting on the FTC testing.

For the record I think the AHB kicks ass from a technical performance POV. Aiming to hear it soon. It would be a nice reference / comparison component for the listening / test room.

Anyway, the problem with the FTC test is that it bears no resemble to real world usage. The most demanding musical conditions just won't come close to being as taxing as a sine test. So the POV of some manufacturers, that conforming to it increases cost for no real world benefit, is quite valid.

The other issue is that the FTC test is not enforced, so it's not delivering the objective of protecting/informing the consumer.

Consumers require accurate information and manufacturers should not be able to publish any old misleading marketing guff. Whilst the intent of the FTC test is 100% correct, I don't think it is entirely fit for purpose in its current form.

So, what to do? Not sure I have a comprehensive answer, but I don't think the FTC test tells me much about how an amp will perform in the real world.

Independant publications such as ASR are extremely valuable for informing the consumer, we just need to improve the reach for it to have a real impact on manufacturer behaviour.
 
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amirm

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Our testing here is an excellent replacement for any standard. So I am not worried about companies cheating. As long as you go by what we test here, you have level playing field.
 

cbnbmore

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No doubt, the Proceed 5 was the 5 channel version of the Proceed 2. It was a beast and if I had one it would be in my home theater without question. I’m just getting the feeling the AHB2 is something special and no need to do any amp swapping. Thanks.
 

March Audio

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Our testing here is an excellent replacement for any standard. So I am not worried about companies cheating. As long as you go by what we test here, you have level playing field.
Just need a power cube ;)

I think the wider issue is that the general consumer doesn't know about ASR which in any case can only ever have a finite number of components tested. How do you protect consumers wandering into a hifi shop?
 
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amirm

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Just need a power cube ;)
I need to win the lottery. :D

I am thinking about building one. Can't imagine paying $25,000 for a bunch of resistors, inductors and capacitors.
 

Sal1950

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Absolutely agree, it is the Proceed Amp 2 made by Levinson and the speakers are the SMS1 by Benchmark also produced by Studio Electric as their M4 although there were claimed to be a few differences between the two models.

I’m just getting the feeling the AHB2 is something special and no need to do any amp swapping. Thanks.
Special yes, SOTA in the extreme when it comes to measurements, but audibly superior to what you have now, debatable. Couldn't come up with any in depth measurements of the Proceed and the published ones sure aren't awe inspiring. (the S/N?) Nothing about the SMS1 would suggest it to be a difficult load, only it's low efficiency suggests reasonable power be supplied..
Without any glaring measurement issues to go buy all I can do is put my personal feelings forward. I doubt you would be able to tell one from the other in a bias controlled DBT. But seeing as you look to be a Benchmark guy, it's very possible it will sound superior to you. ;)

Proceed Amp2
Power output: 150 watts per channel into 8Ω (stereo)
Frequency response: 20Hz to 20kHz
Total harmonic distortion: 0.1%
Gain: 29 dB
Input sensitivity: 1.2V
Signal to noise ratio: 80dB
Speaker load impedance: 4Ω (minimum)
 

restorer-john

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I'm sure we can figure out building one for low cost. A community project? Start a thread to thrash out a design?

I've been working on a possible design myself. We should all collaborate on this. I know SIY wants one too.
 

pjug

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I'd like to follow up on this, hope it's not OT in this thread.

Would you like to chime in on this, @John_Siau ? I noticed that you wrote this in an application note:


Class-D amplifier switching noise can create problems in a loudspeaker measurement system. More importantly, this ultrasonic noise may become audible when it is demodulated by the non-linearities that occur in all loudspeakers. This potential source of distortion may detract from our musical enjoyment. Class-D amplifiers are compact and cheap, but are not necessarily a good choice for a high-end Hi-Fi system.

What I wonder is if this a purely theoretical worry, or whether you have been able measure it? Or heard it in a blind test?
@John_Siau I am hoping that you would respond to the above. In the video too, Class D seems to be dismissed out of hand. I don't like the idea of having ultrasonic noise, but on the other hand I think I can be convinced that it is completely harmless if the best engineers in the business are not providing good reason to believe otherwise.
 

RichB

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@John_Siau I am hoping that you would respond to the above. In the video too, Class D seems to be dismissed out of hand. I don't like the idea of having ultrasonic noise, but on the other hand I think I can be convinced that it is completely harmless if the best engineers in the business are not providing good reason to believe otherwise.

Manufacturers of Class-D amps say it is not a problem, manufactures of other types say it is.
Both may be correct because it may depend on the frequency, level, and the speaker.
I'd rather not have it, but not to the point that I would rule out class-D. I have one.

- Rich
 

Digital_Thor

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I played on a small set of speakers, with a Maratnz PM-80 MKII SE wit ha few friends, while trying out different equipment. We then tried the AHB2 with an old high end Denon pre amp - cant remember the details of it. But the Benchmark started clipping easily, before we found out that you need to adjust the load on the rear. But still, there was no real improvement in sound. Maybe the Denon was not up to the job. But maybe, sometimes even good specs, does not equal better sound.
 

FrantzM

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I played on a small set of speakers, with a Maratnz PM-80 MKII SE wit ha few friends, while trying out different equipment. We then tried the AHB2 with an old high end Denon pre amp - cant remember the details of it. But the Benchmark started clipping easily, before we found out that you need to adjust the load on the rear. But still, there was no real improvement in sound. Maybe the Denon was not up to the job. But maybe, sometimes even good specs, does not equal better sound.
We need more ...

What speakers?
What Preamp?
How loud?
etc...
 
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headshake

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pm-80 mkii
https://www.hifiengine.com/manual_library/marantz/pm-80.shtml

Power output: 100 watts per channel into 8Ω (stereo)

Frequency response: 10Hz to 100kHz

Total harmonic distortion: 0.006%

Damping factor: 120

Input sensitivity: 0.22mV (MC), 2.8mV (MM), 170mV (line)

Signal to noise ratio: 70dB (MC), 89dB (MM), 111dB (line)

Channel separation: 65dB (line)

Dimensions: 420 x 146 x 334mm

Weight: 13kg
 

Digital_Thor

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We nee more ...

What speakers?
What Preamp?
How loud?
etc...
2 way home made - SB drivers
DAP 2500
Fairly loud, but clipping started early. Never heard it like this before on any amp.

I know it's not a fair test. I just noted that rather old analog gear sounded fine in comparison with the Benchmark. We have no measurements to prove anything and I myself is a firm believer in specs and good theoretical corrects designs. But for some reason I expected something magical from the AHB2 - from all the reviews - even though I know they are mostly flawed. Maybe the old DAP 2500 is inferior in this situation.
 
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