Review and Measurements of Benchmark AHB2 Amp

[gfinlays]

Would this amp pair up well with a RME ADI-2 DAC FS https://www.audiosciencereview.com/...version-2-dac-and-headphone-amp-review.13379/ or do I also need a pre-amp?

Yes. The ADI-2 goes up to about 7 Vrms via the balanced outputs, which will allow you to switch to a lower gain setting on the AHB2 and let you maximise the ADI-2's SINAD.

 

[xaxxon]

Yes. The ADI-2 goes up to about 7 Vrms via the balanced outputs, which will allow you to switch to a lower gain setting on the AHB2 and let you maximise the ADI-2's SINAD.

I like to set the gain on my ahb2s for hearing comfort. Far too many devices let you easily set max volume. So I set my voltages and gain settings such that max is loud but not painful.

 

[gfinlays]

T

I like to set the gain on my ahb2s for hearing comfort. Far too many devices let you easily set max volume. So I set my voltages and gain settings such that max is loud but not painful

The AHB2's gain settings are about allowing it to reach maximum output at minimum noise and also about preventing the inputs from clipping. They should be set appropriately to the output voltage of your preamp. If you're using a Benchmark front end, then you want them at lowest gain. If you're using a lower output preamp, you want a higher gain setting.

 

[xaxxon]

T

The AHB2's gain settings are about allowing it to reach maximum output at minimum noise and also about preventing the inputs from clipping. They should be set appropriately to the output voltage of your preamp. If you're using a Benchmark front end, then you want them at lowest gain. If you're using a lower output preamp, you want a higher gain setting.

Yep, but I find it much more useful for stopping them from accidentally hurting my ears.

Benchmark preamp isn't easy to accidentally jam up to max level, but a lot of bluetooth streamers allow for very easily setting to 100% volume with short unintentional presses on phone volume buttons

So that's how I use them

 

[pablolie]

The AHB2 has no hiss - I pulled a -120 dBFS 1kHz test tone into audibility with a DAC3/HPA4/dual mono AHB2s.The HPA4 was at +4dB.

Agreed entirely - any hiss is down to some upstream component in the chain. I have a friend who drives his super-sensitive 100k horn speakers with AHB2, you can put your ear to the horn and there is complete and total silence. So it is either a defective unit (and Benchmark is pretty good at customer support, just email them) or a source device that has an issue.

 

[Wino]

The efficacy of using the AHB2 in mono mode driving a speaker with a 4ohm impedance was not clear to me from this review. The review briefly discussed this configuration and the low distortion associated with it, and continued to note that the speaker protection switched in and shut the output off. I am interested in using two AHB2's in bridged mode, driving a pair of 4ohm (minimum) speakers. I queried Benchmark about why they do not list specifications for bridged operation into a 4ohm load, and they replied to the effect that they do not list output specifications unless the output has been preconditioned, if memory serves me correctly, at 1/3 output for 1 hour. Under these conditions, the protection mode would be asserted, which seems to be supported by the review here. Benchmark further assured me that this pre-condition did not represent actual conditions when playing music, so I should be fine. In any case, my speakers will be protected. In fact, Benchmark said, the AHB2 can perform reliably at lower impedances than 4 ohms. So, my question is, can two of these in mono mode drive 4ohm speakers witih a sensitivity of 87 dB/1W/1m minimum?

Driving a pair of Dynaudio Focus 360s with LA4 and 2 x AHB2. Have not had a problem, never clipped and sound great.

 

[xaxxon]

Driving a pair of Dynaudio Focus 360s with LA4 and 2 x AHB2. Have not had a problem, never clipped and sound great.

I’m driving Wilson alexia 1s on monos. I managed to protect the amp while running one in stereo but that took me being in another room to crank it up loud enough.

Benchmark told me the same thing which is in artificial conditions it will protect so they don’t list 4ohm but in practice it works great.

When I did protect my alexia’s on one ahb2 in stereo I also had a full range center (mezzo c/s) on mono block and that kept on thumping out the bass.

So now I have 5 amps one for each speaker in my HT system. 4xalexia and 1xmezzo

 

[cheapsoundguy]

Agreed entirely - any hiss is down to some upstream component in the chain. I have a friend who drives his super-sensitive 100k horn speakers with AHB2, you can put your ear to the horn and there is complete and total silence. So it is either a defective unit (and Benchmark is pretty good at customer support, just email them) or a source device that has an issue.

Sorry again. I think my post caused some confusion. I found that the hiss was in the *actual music file* and very obviously NOT caused by the AHB2. It is absolutely dead silent.

My Outlaw 2200 amps however DID have hiss from the tweeters even when everything else was on "mute" or silent.

 

[k900733]

I bought ome more ahb2 three weeks ago at $2999 for mono-mono. The price goes up to $3299 now. Oh boy

 

[cheapsoundguy]

I am absolutely loving mine. Best HiFI purchase I've made.

 

[Deleted member 4708]

I am absolutely loving mine. Best HiFI purchase I've made.

Same here. Probably many others will say the same.
In contrast with Benchmark I bought a miniDSP SHD. What a piece of crap!!! And Kafkaesque support. Replacing it with an Okto DAC 8 but I am digressing.

 

[misterdog]

I bought ome more ahb2 three weeks ago at $2999 for mono-mono. The price goes up to $3299 now. Oh boy

Though my mother's care home fees have gone up by £ 130............... Per week.

 

[misterdog]

Sorry again. I think my post caused some confusion. I found that the hiss was in the *actual music file* and very obviously NOT caused by the AHB2. It is absolutely dead silent.

Plenty of music has very high levels of noise and distortion unfortunately.

 

[misterdog]

The second paragraph is a disgrace.

Compared to the amplifier which is a masterpiece.

Both in our opinions obviously.

 

[cheapsoundguy]

Same here. Probably many others will say the same.
In contrast with Benchmark I bought a miniDSP SHD. What a piece of crap!!! And Kafkaesque support. Replacing it with an Okto DAC 8 but I am digressing.

Interesting. I am using the MiniDSP SHD and I love it. (Although I use a different DAC for final D>A conversion).

What don't you like about yours?

 

[Deleted member 4708]

Interesting. I am using the MiniDSP SHD and I love it. (Although I use a different DAC for final D>A conversion).

What don't you like about yours?

Arrived with a dead Ethernet and had to deal with their anti-customer care for dozen emails and 2 weeks. The streamer interface skips to the next song randomly for Qobuz and in general pony streamer interface.

 

[pogo]

After the STEREO team has confirmed that the DF was measured properly at a 4ohms load and not bridged ((63Hz/1kHz/14kHz): 48/45/19), I still wonder how the reduced control of the chassis and especially in bridge mode should not have an effect?

According to the new issue of STEREO, such measurements are performed with a 1m long cable with a gauge of 1.5 square millimeters, i.e. close to reality, which should also take into account longer cables with higher gauges.

 

[RichB]

According to the new issue of STEREO, such measurements are performed with a 1m long cable with a gauge of 1.5 square millimeters, i.e. close to reality, which should also take into account longer cables with higher gauges.

They do there own thing, that does not seem to resemble others.
Here (again) is the Soudnstage measurement for damping factor:

SoundStageNetwork.com | SoundStage.com - BHK Labs Measurements: Benchmark Media Systems AHB2 Stereo/Mono Amplifier

www.soundstagenetwork.com

Would it be nice if the AHB2 had higher Damping Factor to compete with high-feedback amps? Sure.
Does it matter, there is no reason to believe that it does, and Benchmark provides a spreadsheet for those interested in the math.

- Rich

 

[peng]

Does it matter, there is no reason to believe that it does, and Benchmark provides a spreadsheet for those interested in the math.

- Rich

Others have tried that route but if I remember right, no one succeeded in convincing Pogo on the damping factor/output impedance thing.

 

[Itisawesome]

One other thing:

The output level of the AHB2 is exactly 6.02 dB higher for a given input voltage when running in bridged mono (4 times the available power and exactly twice the voltage gain). If the input level is not turned down by 6 dB when running mono, the stereo to mono A/B comparison is not valid.

The mono mode can play 6 dB louder before clipping, but must be turned down to match the listening level that was used for the stereo mode if you are attempting to run a valid A/B test.

I compared my single ahb2 running in stereo vs mono mode connected to a single magnepan 1.7i speaker and I couldn’t measure 6db extra gain. Maybe 1db at most. So I don’t think a pair of bridged ahb2 amps will give me the extra loudness I was looking for. I suppose I will need to consider a different amp in the future.