Benchmark AHB2 Review (Updated Measurements)

[new2hifi]

I think you've misunderstood what the AHB2 does. It applies feed forward correction to eliminate distortion. There's no high/low pass filtering going on. The measurements speak for themselves. Have a read of Stereophile's review (subjective and measurements). Kal Rubinson owns a handful of AHB2s, paid for out of his own pocket.

There's nothing to be measured that we haven't discovered yet, though that doesn't stop the die-hard audiophools from positing those theories.

John Siau talks about that in the video, at 10:15; you can go through him from 09:01 to 10:28 and help us all understand more clearly the point he is making there; yes I might have misunderstood him.

 

[SIY]

John Siau talks about that in the video, at 10:15; you can go through him from 09:01 to 10:28 and help us all understand more clearly the point he is making there; yes I might have misunderstood him.

He’s talking about altering the ratio of feedback and feedforward as a function of frequency.

 

[j_j]

He’s talking about altering the ratio of feedback and feedforward as a function of frequency.

Which is always the case in any design that does "feed forward". I'm curious as to how he keeps his loop gain stable enough to be able to know exactly how much feed-forward to use, at what frequency, and where the power to drive the feed-forward part comes from.

This almost sounds like having a second-order part in the feedback system. How about some pole/zero plots please?

 

[gfinlays]

The AHB2 applies feedback like any normal amplifier. At 1 kHz and above, feed forward starts to become the dominant mechanism. The output of the main amplifier is compared to the input signal and the output of the correction amplifier is just the distortion. There's no low pass or high pass filtering being applied. The feedback/feedforward application is frequency dependant, which is entirely different.

Edit: It seems I was beaten to it by @SIY and @j_j

 

[j_j]

The AHB2 applies feedback like any normal amplifier. At 1 kHz and above, feed forward starts to become the dominant mechanism. The output of the main amplifier is compared to the input signal and the output of the correction amplifier is just the distortion. There's no low pass or high pass filtering being applied. The feedback/feedforward application is frequency dependant, which is entirely different.

Well, taking the difference signal is normal behavior. So you're saying the inverted error signal goes through a different amplifier and is added back to the output?

How do things like transit time, storage time, etc, work into this?

 

[gfinlays]

So you're saying the inverted error signal goes through a different amplifier and is added back to the output?

Yes, if I'm interpreting correctly, that seems to be what John Siau said.

How do things like transit time, storage time, etc, work into this?

Perfectly it seems, given the AHB2's measured distortion levels. It's all in the analogue domain, so timing shouldn't be an issue.

 

[win]

here's some blasphemy: I have an ahb2 and I have a tube preamp before it

 

[gfinlays]

here's some blasphemy: I have an ahb2 and I have a tube preamp before it

A lot of people associate tubes with high 2nd order distortion, euphonic warmth etc. etc.

I have 2 tube headphone amps. If you held my feet to the fire, with the transformer tappings properly set according to the load impedance, I couldn't tell them apart from my HPA4.....

OK, granted, at full volume the HPA4 would make me deaf, but otherwise, indiscernible.

 

[misterdog]

Edit: There was a previous thread about the mediocre measurements

Wow that's some channel imbalance on the Gryphon Apex for the money.

 

[gfinlays]

Wow that's some channel imbalance on the Gryphon Apex for the money.

Truly shocking for a product in this price bracket.

"Probably one of the best power amplifiers ever built"

"Gryphon have always said that pure class A is the only way to achieve the best performance possible"

Right......

£95,000 worth of pure Class A can't hold a candle to the performance of the Benchmark AHB2. You could buy 27 AHB2s for the same money!

I have 2 AHB2s in dual mono and I'm about to add a third to switch to a three-way fully active setup. 300 perfect Watts per channel on tap for £10,500. The Gryphon can rustle up 210 crappy watts for 9 times the price.

Granted in H bias mode, the Gryphon also doubles as a 1 kW room heater. But, with the change from the AHB2s, I could insulate my home to Passivhaus standards, buy a multi-kiloWatt solar PV and battery storage system and add a ground-sourced heat pump installation that would provide free energy, heating and lighting for the rest of my lifetime.....

 

[Descartes]

When my 20 year old amplifiers die, I will purchase these for my speakers unless I go the Purifi route!

 

[Pearljam5000]

Truly shocking for a product in this price bracket.

"Probably one of the best power amplifiers ever built"

"Gryphon have always said that pure class A is the only way to achieve the best performance possible"

Right......

£95,000 worth of pure Class A can't hold a candle to the performance of the Benchmark AHB2. You could buy 27 AHB2s for the same money!

I have 2 AHB2s in dual mono and I'm about to add a third to switch to a three-way fully active setup. 300 perfect Watts per channel on tap for £10,500. The Gryphon can rustle up 210 crappy watts for 9 times the price.

Granted in H bias mode, the Gryphon also doubles as a 1 kW room heater. But, with the change from the AHB2s, I could insulate my home to Passivhaus standards, buy a multi-kiloWatt solar PV and battery storage system and add a ground-sourced heat pump installation that would provide free energy, heating and lighting for the rest of my lifetime.....

True audiophiles get the £195K
dual mono....

 

[j_j]

Truly shocking for a product in this price bracket.

"Probably one of the best power amplifiers ever built"

"Gryphon have always said that pure class A is the only way to achieve the best performance possible"

Right......

£95,000 worth of pure Class A can't hold a candle to the performance of the Benchmark AHB2. You could buy 27 AHB2s for the same money!

I have 2 AHB2s in dual mono and I'm about to add a third to switch to a three-way fully active setup. 300 perfect Watts per channel on tap for £10,500. The Gryphon can rustle up 210 crappy watts for 9 times the price.

Granted in H bias mode, the Gryphon also doubles as a 1 kW room heater. But, with the change from the AHB2s, I could insulate my home to Passivhaus standards, buy a multi-kiloWatt solar PV and battery storage system and add a ground-sourced heat pump installation that would provide free energy, heating and lighting for the rest of my lifetime.....

Compare it to a standard PASCAL switcher, just for grins.

 

[HappyCow]

At least the Apex looks mean.. always something. The stand for it costs more than 2x AHB2 - and it has perfect measurements!

 

[win]

it weighs 400 pounds and they recommend the spikes

Seems like a dangerous combo for your floors or whatever surface you are putting it on

 

[amirm]

I want to know who helps them handle these incredibly heavy pieces of audio gear! 400 pounds require 3 to 4 people! And then there is the job of packing it back up and giving it to a trucking company.

 

[Descartes]

True audiophiles get the £195K
dual mono....
View attachment 395286

Holy crap! The average price of a house in several states!

 

[Descartes]

I want to know who helps them handle these incredibly heavy pieces of audio gear! 400 pounds require 3 to 4 people! And then there is the job of packing it back up and giving it to a trucking company.

My back hurts just thinking about it!

 

[GXAlan]

I want to know who helps them handle these incredibly heavy pieces of audio gear! 400 pounds require 3 to 4 people! And then there is the job of packing it back up and giving it to a trucking company.

There is a Canadian audio retailer with a YouTube channel who has a mix of subjective reviews/marketing and fun “stories of the business.”

This is a great video about some delivery disasters. #3 is about some big Krell monoblocks. Fun even if you aren’t interested in their gear reviews.

 

[misterdog]

I want to know who helps them handle these incredibly heavy pieces of audio gear! 400 pounds require 3 to 4 people! And then there is the job of packing it back up and giving it to a trucking company.

I went to hear a system at a guys house where his listening room was upstairs with a Gryphon .

I'll stick with my Benchmark.