Review and Measurements of Benchmark AHB2 Amp

[maty]

https://www.audiosciencereview.com/...-of-purifi-1et400a-amplifier.7984/post-195556

There is something wrong with your kit then as that voltage is within specification, and generally amps prefer more rather than less juice.
More likely it's purely in your head, but for some reason audiophiles never want to admit that they have emotions that we cannot control.

The amp is old. It was probably designed to work at 220 Vac. Then 238 Vac is too much. One of my modifications, the first, was to increase the bias.

Audiophiles and others who can not control their emotions are the ones who spend a lot of money, believing it to be the solution to their audio problems.

 

[DonH56]

So, how might this AHB2 run a pair of Magnepan 3.7i?
They are a 4 Ohm, current-hungry, mostly non-reactive load.

This is for the 3.6R, but you get the idea.

Just fine. Magnepan speakers in general are a low but otherwise pretty benign load for any amp. They are also insensitive (low dB/W/m) so often benefit from higher-power amplifiers (that are available in abundance these days).

Frankly I am a lot more excited about the possibility of AHB2's driving my Salon2's than my old Maggies; the Salon2's are a much more difficult load, as are many conventional speakers. The AHB2's ability to shrug off varying reactive loads is appealing.

 

[tensor9]

Just fine. Magnepan speakers in general are a low but otherwise pretty benign load for any amp. They are also insensitive (low dB/W/m) so often benefit from higher-power amplifiers (that are available in abundance these days).

Frankly I am a lot more excited about the possibility of AHB2's driving my Salon2's than my old Maggies; the Salon2's are a much more difficult load, as are many conventional speakers. The AHB2's ability to shrug off varying reactive loads is appealing.

Yeah, I currently have a pair of PS Audio Stellar M700 monoblocks, 700W/ch into 4 Ohms.
I've been considering a variety of different amps, but I just don'w want to let go of that power.

 

[DonH56]

What's wrong with your current amps? If you just have extra money in your pocket, send it to me, or give it to Amir to test more gear.

 

[tensor9]

What's wrong with your current amps? If you just have extra money in your pocket, send it to me, or give it to Amir to test more gear.

They are fine, but I want an amp that measure better. I am also having some sonic issues, mainly really forward vocals and shrill highs. The ribbon tweeters on the Magnepans are very, very revealing, but they are also shrill to my ears. Partly because my room is extremely live, with lots of slap echo. I'm moving soon, so I'll probably reevaluate after I move the speakers to a different room.

Mostly, I just want to try some other stuff out.

 

[DonH56]

Ah, would we all had the funds to play like that...

Installing the tweeter resistor, or increasing its value if it is already installed, will help a lot with shrill highs especially in a live room.

 

[SIY]

Even better, put the funds into fixing what you identified as your most likely actual problem- the room.

 

[tensor9]

Ah, would we all had the funds to play like that...

Installing the tweeter resistor, or increasing its value if it is already installed, will help a lot with shrill highs especially in a live room.

Yep, I have tried a few. Currently I have 2 Ohm Mills for the tweeter and 1 Ohm for the mid. I might try playing around a bit more.

Even better, put the funds into fixing what you identified as your most likely actual problem- the room.

As I said, I'm moving soon. I'll have a different room to try out in a few weeks... we'll see how it goes.

 

[zalive]

Yeah, I currently have a pair of PS Audio Stellar M700 monoblocks, 700W/ch into 4 Ohms.
I've been considering a variety of different amps, but I just don'w want to let go of that power.

Keep those amps.

 

[RichB]

They are fine, but I want an amp that measure better. I am also having some sonic issues, mainly really forward vocals and shrill highs. The ribbon tweeters on the Magnepans are very, very revealing, but they are also shrill to my ears. Partly because my room is extremely live, with lots of slap echo. I'm moving soon, so I'll probably reevaluate after I move the speakers to a different room.

Mostly, I just want to try some other stuff out.

It will cost about $100 (in U.S. shipping costs) to try a single AHB2.
This allows obeying the first rule of wing-walking: Never let go with one hand before having a firm grip with the other.

It's not hard to do some SBT (single blind test) level matched comparisons with the assistance of a patient friend.
That wont satisfy many here but it's a good for making better informed purchasing decisions.

- Rich

 

[Sal1950]

They are fine, but I want an amp that measure better. I am also having some sonic issues, mainly really forward vocals and shrill highs. The ribbon tweeters on the Magnepans are very, very revealing, but they are also shrill to my ears. Partly because my room is extremely live, with lots of slap echo. I'm moving soon, so I'll probably reevaluate after I move the speakers to a different room.

Mostly, I just want to try some other stuff out.

Some room dampening and possibly DSP would be a much more effective improvements. DSP will give you endless tweaking joy.
I doubt a new amp would change the situation in any meaning manner. (except for that imagained).

 

[tensor9]

Some room dampening and possibly DSP would be a much more effective improvements. DSP will give you endless tweaking joy.
I doubt a new amp would change the situation in any meaning manner. (except for that imagained).

I hate to derail this thread. Maybe I'll start a new one about Magnepans.

I just wanted to update on something I tried today. I had my Maggies (3.7i) with the tweeters on the outside (because I preferred my 1.7i this way--got a better soundstage this way). But, I JUST tried to switching the speakers so that the tweeters are on the inside, and EVERYTHING settled down. In fact, I might remove some attenuation from the tweeter now! It's something about how the highs fire out of that ribbon, given the different angles of the two configurations.

Since Magnepan suggests the tweeter ALWAYS be just a tad farther away from the listener that the rest of the panel, with the tweeters on the inside, you tend to toe the speakers in quite a bit. Interesting. Maggies are fickle, but I LOVE them!

 

[DonH56]

I have almost always preferred tweeters inside. IIRC the need for the extra distance is primarily due to their crossover network which causes the bass signal to lag the tweeter signal.

 

[Blumlein 88]

When I had them I tried them both ways in several rooms. Outside could be made to sound alright. But everything just fit together much more nicely in all aspects with tweeter ribbons on the inside and toed in the right amount.

 

[typericey]

I'm just going to put this here:

Hi-Fi news review of the XPA-DR2 amp states that "...Emotiva has still achieved cool-running efficiency by blending a Class AB output stage with a Class H stepped-rail PSU architecture on each amplifier card. This switches up to a higher voltage PSU rail only when signal conditions demand it, minimising waste heat. It’s not dissimilar to the ‘Achromatic Audio Amplifier’ used in Benchmark’s AHB2 power amp. Like the AHB2, the XPA-DR2 also features a similarly compact and efficient switch-mode PSU..."

 

[DonH56]

I strongly suspect the XPA-DR2 comes nowhere near the Benchmark's performance in terms of distortion or load tolerance. And I own a bunch of their XPA series amps.

 

[amirm]

I strongly suspect the XPA-DR2 comes nowhere near the Benchmark's performance in terms of distortion or load tolerance.

Indeed. Their spec at 100 watts is 0.008% which translates into a SINAD of just 89 dB. The Benchmark AHB2 clocks at 117 dB at the same power level:

 

[anmpr1]

They are fine, but I want an amp that measure better. I am also having some sonic issues, mainly really forward vocals and shrill highs. The ribbon tweeters on the Magnepans are very, very revealing, but they are also shrill to my ears. Partly because my room is extremely live, with lots of slap echo. I'm moving soon, so I'll probably reevaluate after I move the speakers to a different room.

Mostly, I just want to try some other stuff out.

1) it will be difficult to find a better production amplifier that measures better than Benchmark. Whether that is a good enough reason to change what you have is up to you.

2) 'really forward vocals' sounds like a problem in a particular recording. Unless everything in the upper register sounds shrill to you. Then, the problem will not likely be solved by a new amplifier, but rather new speakers. Possibly moving the speakers around, however a speaker's basic 'sonic signature' remains, no matter about placement. Especially the highs, which tend to be directional. What can mostly be changed by moving speakers around are LF stuff, imaging, directionality, and things like that. No matter where you put it, a Magneplanar speaker will always sound like a Magneplanar.

3) FWIW, my speakers have often been criticized for having 'aggressive highs', but I find that in almost all cases of that sort of thing, it's the recording. Good speakers are hell on bad recordings. Moving them around did solidify the bass a lot, though. Going to the Benchmark amp did nothing about the overall sound of the speakers, but subjectively I thought the sound was 'cleaner', and that I could play program material louder without 'aural fatigue'. At least that was my impression.

 

[headshake]

Going to the Benchmark am

What was the old amp? Do you EQ?

 

[John_Siau]

Just fine. Magnepan speakers in general are a low but otherwise pretty benign load for any amp. They are also insensitive (low dB/W/m) so often benefit from higher-power amplifiers (that are available in abundance these days).

Frankly I am a lot more excited about the possibility of AHB2's driving my Salon2's than my old Maggies; the Salon2's are a much more difficult load, as are many conventional speakers. The AHB2's ability to shrug off varying reactive loads is appealing.

We ran a surround system at two trade shows where we had 5 AHB2 amplifiers driving 5 Salon 2 speakers. Each amplifier was running in bridged mono. We have many customers who are using the AHB2 to drive the Salon2. They can be driven in stereo or bridged mono mode.