Review and Measurements of Benchmark AHB2 Amp

[restorer-john]

For folk who are not following the technical gibberish, this is a very rough quick sketch. Blue is the fundamental, a single tone (sine wave). When you notch out (remove) the fundamental, and amplify (greatly, typically 100x to 1000x) what is left, you can see the distortion waveform.

Here is a random little Rotel RA-930AX 30wpc integrated amplifier. 1kHz/1W@8R. Scope output from the distortion analyzer at -60dB (1000 times amplified for 1V FSD@-60dB). There is a hint of X/over buried in the noise on the rising zero cross, but to all intents and purposes there is none of significance.

My old CRO will show a cleaner looking residual. But now I have a new job. I have to dismantle the darned distortion meter and clean the interlocked range switch bank as it's getting touchy in its old age...

 

[DonH56]

Here is a random little Rotel RA-930AX 30wpc integrated amplifier. 1kHz/1W@8R. Scope output from the distortion analyzer at -60dB (1000 times amplified for 1V FSD@-60dB). There is a hint of X/over buried in the noise on the rising zero cross, but to all intents and purposes there is none of significance.

View attachment 67472

My old CRO will show a cleaner looking residual. But now I have a new job. I have to dismantle the darned distortion meter and clean the interlocked range switch bank as it's getting touchy in its old age...

Thanks John, trust you to have some pictures on hand. I've seen better, and much worse, as have you I am sure.

Touchy in its old age... Wish it was only a switch in my case! And I could switch it off.

 

[John_Siau]

Thanks John, trust you to have some pictures on hand.

https://benchmarkmedia.com/blogs/application_notes/135475655-crossover-distortion-video-clip

 

[RichB]

Here is a random little Rotel RA-930AX 30wpc integrated amplifier. 1kHz/1W@8R. Scope output from the distortion analyzer at -60dB (1000 times amplified for 1V FSD@-60dB). There is a hint of X/over buried in the noise on the rising zero cross, but to all intents and purposes there is none of significance.

View attachment 67472

My old CRO will show a cleaner looking residual. But now I have a new job. I have to dismantle the darned distortion meter and clean the interlocked range switch bank as it's getting touchy in its old age...

Trying to interpret these results, is 437mV = to .437 volts RMS of THD+N on a 2.81 volt RMS sine-wave?
What is the SINAD and frequency distribution?

- Rich

 

[DonH56]

https://benchmarkmedia.com/blogs/application_notes/135475655-crossover-distortion-video-clip

I'd expect any John to have pictures to share... Thanks!

 

[QMuse]

The issue has been heatsinks.

Honestly, relatively small housing which cannot house large heatsink(s) to me seems like a drawback with an amp which is otherwise SOTA design. Maybe long lead time of your supplier is a good excuse to redesign the housing and put larger heatsinks in it.

 

[RichB]

Honestly, relatively small housing which cannot house large heatsink(s) to me seems like a drawback with an amp which is otherwise SOTA design. Maybe long lead time of your supplier is a good excuse to redesign the housing and put larger heatsinks in it.

It has the heat sinks it need with a switching multi-rail power supply.
The thermal management is digitally controlled.

I have two stacked and the top one is 95 degrees and the top one is 103 degrees after being on all day.

I suppose you could house it an a full sized lead case for that full audiophile experience

- Rich

 

[QMuse]

It has the heat sinks it need with a switching multi-rail power supply.
The thermal management is digitally controlled.

I have two stacked and the top one is 95 degrees and the top one is 103 degrees after being on all day.

I suppose your could house it an a full sized lead case for that full audiophile experience

- Rich

Or you can provide a larger heatsinks so you don't have to worry how many hours it can play with 1/8 power.

With SOTA amplifiers I would like to see THX certified badge and with those heatsinks I doubt it would get it. Which is a pity, as everything else really seems to be top class.

 

[GXAlan]

It has the heat sinks it need with a switching multi-rail power supply.
The thermal management is digitally controlled.

I have two stacked and the top one is 95 degrees and the top one is 103 degrees after being on all day.

I suppose your could house it an a full sized lead case for that full audiophile experience

- Rich

If Benchmark has a home and studio version with the enclosure and heat sinks being different, then having two suppliers could alleviate the backlog problem. It’s a trade off between the aura/mystique of demand exceeding supply and the loss of a sale as people choose a Hypex nCore which may measure worse but be readily available.

 

[RichB]

Or you can provide a larger heatsinks so you don't have to worry how many hours it can play with 1/8 power.

With SOTA amplifiers I would like to see THX certified badge and with those heatsinks I doubt it would get it. Which is a pity, as everything else really seems to be top class.

I have driven theses hard and they do not overheat.

There will always be those who buy amps by the pound and claim it is SOTA.
It’s 2020 and technology has moved forward.

- Rich

 

[QMuse]

I have driven theses hard and they do not overheat.

There will always be those who buy amps by the pound and claim it is SOTA.
It’s 2020 and technology has moved forward.

- Rich

Large heatsinks have nothing to do with technology but with ammount of power you can deliver in time before overheating.

I like the way how @Sal1950 put it when commenting Linn AV5125, it cannot be put better.

"Power amps aren't supposed to be "cute".
They should reflect a muscular, beefy, mean look.
Something that will scare a speaker into submission. LOL "

 

[Frank Dernie]

If Benchmark has a home and studio version with the enclosure and heat sinks being different, then having two suppliers could alleviate the backlog problem. It’s a trade off between the aura/mystique of demand exceeding supply and the loss of a sale as people choose a Hypex nCore which may measure worse but be readily available.

Same design with 2 different enclosures would be quite a lot more expensive per unit, so poor engineering since the existing one does the job properly.

 

[RichB]

If Benchmark has a home and studio version with the enclosure and heat sinks being different, then having two suppliers could alleviate the backlog problem. It’s a trade off between the aura/mystique of demand exceeding supply and the loss of a sale as people choose a Hypex nCore which may measure worse but be readily available.

The demand for these amps has had them on short supply for years. Despite that, they have not raised the price.

There was a pandemic in the news, and reportedly, disrupted the supply chains. Word has it that even toilet paper was in short supply.

- Rich

 

[RichB]

Large heatsinks have nothing to do with technology but with ammount of power you can deliver in time before overheating.

I like the way how @Sal1950 put it when commenting Linn AV5125, it cannot be put better.

"Power amps aren't supposed to be "cute".
They should reflect a muscular, beefy, mean look.
Something that will scare a speaker into submission. LOL "

Large heat-sinks dissipate wasted power, converted to heat.
Reducing wasted power reduces the need for heat sinks.
Efficiency, does not reduce the perceived requirement.

Clearly, small-form factor amps also lack warmth, toe-tapping rhythm, and pace.
In the immortal words of Obi-wan, these are not the amps for you, move along.

- Rich

 

[QMuse]

I have driven theses hard and they do not overheat.

I am referring to what John said here:
"Amplifier RMS power ratings are based on the ability to run a 1/8th power continuously for one hour, before testing at full output. The 1/8th power preconditioning usually brings an amplifier up close to its thermal limits. "

From time to time, when I throw a party, I drive my amp (which is more powerful than AHB2, with speakers of 87dB/1m sensitivity) at more than 50% of the power for more than 2-3 hours, so reaching a thermal limit after 1 hour of driving amp at 1/8th of power wouldn't work for me. That is why I bought THX certified amp and that is why I would like to see larger heatsinks with AHB2, which is by all other means premium class amp. I am also very happy to see that in this era of D class amp somebody is still developing leading edge AB class amps.

 

[blueone]

I am referring to what John said here:
"Amplifier RMS power ratings are based on the ability to run a 1/8th power continuously for one hour, before testing at full output. The 1/8th power preconditioning usually brings an amplifier up close to its thermal limits. "

From time to time, when I throw a party, I drive my amp (which is more powerful than AHB2, with speakers of 87dB/1m sensitivity) at more than 50% of the power for more than 2-3 hours, so reaching a thermal limit after 1 hour of driving amp at 1/8th of power wouldn't work for me. That is why I bought THX certified amp and that is why I would like to see larger heatsinks with AHB2, which is by all other means premium class amp. I am also very happy to see that in this era of D class amp somebody is still developing leading edge AB class amps.

The pre-conditioning @John_Siau was referring to is run with 1KHz sine waves, if it resembles USA FTC audio power regulations. Does your music have a duty cycle similar to 1KHz sine waves?

 

[RichB]

I am referring to what John said here:
"Amplifier RMS power ratings are based on the ability to run a 1/8th power continuously for one hour, before testing at full output. The 1/8th power preconditioning usually brings an amplifier up close to its thermal limits. "

From time to time, when I throw a party, I drive my amp (which is more powerful than AHB2, with speakers of 87dB/1m sensitivity) at more than 50% of the power for more than 2-3 hours, so reaching a thermal limit after 1 hour of driving amp at 1/8th of power wouldn't work for me. That is why I bought THX certified amp and that is why I would like to see larger heatsinks with AHB2, which is by all other means premium class amp. I am also very happy to see that in this era of D class amp somebody is still developing leading edge AB class amps.

My 2 x ATI60002's idled at about 80 watts (if memory recalls) and the AT6006 (at 160 watts). My 4 AHB2's idle at 12 watts.
So 50 watts of wasted power replace 320 watts. These amps heated all components above them, necessitating fans. I was able to remove the excess heat, then the fans.

Music is not RMS, although with the loudness wars, it gets close
How do you know, your amps are running the equivalent of 50 watts RMS?

- Rich

 

[restorer-john]

I am referring to what John said here:
"Amplifier RMS power ratings are based on the ability to run a 1/8th power continuously for one hour, before testing at full output. The 1/8th power preconditioning usually brings an amplifier up close to its thermal limits. "

The AHB-2 is sold as a studio reference amplifier or an audiophile's domestic amplifier. It's not sold as a sound reinforcement amplifier intended to run at constant high power, a night-club, bar, or as a live music instrument/vocal amplifier. It's going to have a nice easy life in 99.9% of installations and will likely last for many decades.

Now you all know my views on the watering down of the FTCs 1/3 power preconditioning to a measly 1/8 power to appease the consumer electronics companies and save them money, but at the end of the day, if the playing field is level, things can be compared fairly. I don't have a problem with the Benchmark as long as it hits all its rated FTC specifications.

If you want an amplifier that can run an all weekend Bourbon fueled, AC/DC party in the backwoods someplace without overheating and going into "protection", either buy pro gear, or dig up some older big power amps built to different long term thermal standards.

 

[Billy Budapest]

The AHB-2 is sold as a studio reference amplifier or an audiophile's domestic amplifier. It's not sold as a sound reinforcement amplifier intended to run at constant high power, a night-club, bar, or as a live music instrument/vocal amplifier. It's going to have a nice easy life in 99.9% of installations and will likely last for many decades.

Now you all know my views on the watering down of the FTCs 1/3 power preconditioning to a measly 1/8 power to appease the consumer electronics companies and save them money, but at the end of the day, if the playing field is level, things can be compared fairly. I don't have a problem with the Benchmark as long as it hits all its rated FTC specifications.

If you want an amplifier that can run an all weekend Bourbon fueled, AC/DC party in the backwoods someplace without overheating and going into "protection", either buy pro gear, or dig up some older big power amps built to different long term thermal standards.

Buy a Crown or Behringer club amp from Sweetwater and call it a day.

 

[digitalfrost]

If you want an amplifier that can run an all weekend Bourbon fueled, AC/DC party in the backwoods someplace without overheating and going into "protection", either buy pro gear, or dig up some older big power amps built to different long term thermal standards.

Or keep the amplifier and use efficient horn speakers