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Review and Measurements of Benchmark AHB2 Amp

RichB

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I came across this article from AH that measured a traditional linear power supply amplifier with 15 and 20 amp service.
https://www.audioholics.com/audio-amplifier/ac-power-home-theater-system

Anthem STR Output 0.1%, 2CH, 4 ohms
15 Amp Line: 536 watts/channel
20Amp Line: 671 watts/channel
% Increase: About 25%

This appears to be another area where regulated power supplies perform to specification when line-power sags and linear supplies do not.
This may be a consideration when living in a brown-out towns (or states - I'm looking at you CA. :p)

- Rich
 

Matias

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scociu

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What gain setting should i set the ahb2 to when connected to the balanced outputs of a cambridge audio cxn v2? I can't find any info on the output levels for it.
 

John_Siau

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Most consumer products with balanced outputs deliver 4 Vrms and you will want to use the mid-gain position on the AHB2.

The high-gain position is for 2 Vrms unbalanced outputs.

The low-gain position is for +22 dBu (9.76 Vrms) professional balanced outputs, such as those produced by Benchmark DACs.
 

F1308

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What gain setting should i set the ahb2 to when connected to the balanced outputs of a cambridge audio cxn v2? I can't find any info on the output levels for it.

The manual gives some clues....

Input Sensitivity
Low-Gain = 22 dBu (9.8 Vrms)
Mid-Gain = 14.2 dBu (4 Vrms)
High-Gain = 8.2 dBu (2 Vrms)
Use Mid-Gain or High-Gain settings for unbalanced inputs
Unbalanced inputs require RCA to XLRM adapter cables
 

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  • AHB2_Manual_-_Rev_G.pdf
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etc6849

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This is a real concern. In my theater with 5 powered subs and 10 AHB2 amps, I ended up using 4 separate circuits.

This is a short video clip I made a few years back. What was happening was the excessive instantaneous current draw of all the equipment in my home theater would cause the voltage to drop.

I could have hooked up an oscilloscope to capture it, but figured an incandescent light bulb would work just fine. Of course, the breaker eventually trips in extreme listening.

Once I added four separate AC circuits, I did have to re-level match the five powered subs! No BS, the subs had much more power.


Some more technical information:
A breaker has a characteristic trip curve (multiples of rated current vs time). So a 15A breaker can handle much more than 15 amps, if and only if the time period is very short. For example, check out this document:
https://www.eaton.com/content/dam/e...elboards/br-family-trip-curves-tc003002en.pdf

Believe it or not, 200%, 1000% and even 4000% above rated current are possible without tripping if the time period is short enough.... But, what happens to voltage? Well, imagine the voltage drop down a 14 gauge wire (typically used for a 15 amp 120V circuit in the US) when 60 amps of instaneous current are demanded over a short period time period. I didn't measure or calculate it, but it is measurable. You can see the light bulb dim in the video so we know voltage is sagging.

I came across this article from AH that measured a traditional linear power supply amplifier with 15 and 20 amp service.
 
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Pjetrof

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I used to have a pair of DIY class D (Tripath based) that power my pair of Pioneer's. One of them was damaged when I was tinkering with the circuit.

I switched to Benchmark AHB2 last year after reading review from this forum. Budget was tight and I only bought one AHB2.
Now I have a pair to drive my speakers... I am doing vertical bi-amp.

First Impression is that I get better imaging. Bass is tighter.. Treble is clearer. I think its worth the upgrade..
( I am using 17db gain setting)

Now I also have the option to go bridging too..
AHB2's max gain is 23db and after bridging its 29db.

I have an integrated Accuphase E-480 which has gain fixed at 28db. (I think 1db is not much of a difference.)
I may try mix and match and use that to bi-amp with 2x bridged AHB2.

how do they compare benchmark vs accuphase
 

Mikechw

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how do they compare benchmark vs accuphase

My current set up, signal path is as follows:
Roon + HQPlayer (PC)(USB) -> Topping D90 (Balanced out) -> Accuphase E480 (preout) -> 2 x Benchmark AHB

I prefered the AHBs. The sound is much clearer and I can listen to them longer..
One problem I found with Accuphase E-480 is that the sound is better when the amp is cool. May be first 30 mins.
E-480 use power MOS-FETs at the power amplification stage and it seems it sounds better when the unit is cool.

I only use my Accuphase E-480 as the pre-amp now..
 

Pjetrof

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My current set up, signal path is as follows:
Roon + HQPlayer (PC)(USB) -> Topping D90 (Balanced out) -> Accuphase E480 (preout) -> 2 x Benchmark AHB

I prefered the AHBs. The sound is much clearer and I can listen to them longer..
One problem I found with Accuphase E-480 is that the sound is better when the amp is cool. May be first 30 mins.
E-480 use power MOS-FETs at the power amplification stage and it seems it sounds better when the unit is cool.

I only use my Accuphase E-480 as the pre-amp now..
Thx for reply
why i asked i m thinking of buying Benchmark AHB2 just not sure about the power.
its for harbeth 30.2 in a 40 square meters room its open plan kitchen dining living room 10 by 4 speakers on long wall
2 meters apart and 2.7 meters seating position music singer songwriter.
if i need 2 for me they are to expensive then, then i would go d class. What do you think?
 

RichB

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Thx for reply
why i asked i m thinking of buying Benchmark AHB2 just not sure about the power.
its for harbeth 30.2 in a 40 square meters room its open plan kitchen dining living room 10 by 4 speakers on long wall
2 meters apart and 2.7 meters seating position music singer songwriter.
if i need 2 for me they are to expensive then, then i would go d class. What do you think?

I use the AHB2's bi-amped and can achieve 104 dB (stereo) in a 5400 cu. ft. (42 sq. meters) room driving the Salon2s at 11 feet (3.3 meters).
You can measure 2.,83 volts playing a full scale sine wav at the speakers and measure the SPL at your listening position.
Then, plug those into a spreadsheet. I played the tone in stereo since that is a typical use case.

- Rich
 

Pjetrof

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I use the AHB2's bi-amped and can achieve 104 dB (stereo) in a 5400 cu. ft. (42 sq. meters) room driving the Salon2s at 11 feet (3.3 meters).
You can measure 2.,83 volts playing a full scale sine wav at the speakers and measure the SPL at your listening position.
Then, plug those into a spreadsheet. I played the tone in stereo since that is a typical use case.

- Rich

I was a bookkeeper it took me a whole day to make my own speakercable, i mean to put banana plugs on the end.
I wouldn't know how to start. After reading al the threads about benchmark I am certain! Just budget wise, if i need two then i would buy Something diffrent. My speaker Harbeth 30.2 is not high efficient but easy load never drop below 6 ohm. That is what people tell me anyway.
 

RichB

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I was a bookkeeper it took me a whole day to make my own speakercable, i mean to put banana plugs on the end.
I wouldn't know how to start. After reading al the threads about benchmark I am certain! Just budget wise, if i need two then i would buy Something diffrent. My speaker Harbeth 30.2 is not high efficient but easy load never drop below 6 ohm. That is what people tell me anyway.

You'd need a multi-meter, SPL meter, and a source wav file. So, it may be a too far, but the spreadsheet part, you should be all over that :p

Here are the measurements for the Harbeths:
https://www.stereophile.com/content...-anniversary-edition-loudspeaker-measurements

My estimate of the Harbeth's sensitivity was 87.3dB(B)/2.83V/m, which is usefully higher than the specified 85dB. The Monitor 30.2's nominal impedance is specified as 6 ohms, and its impedance magnitude (fig.1, solid trace) actually remains at or above 6 ohms throughout the audioband. I would have specified this speaker as an 8 ohm design; it should be an easy load for amplifiers to drive.

- Rich
 

Pjetrof

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RichB

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The difference is 3 dB but it depends on your listening level. If the AHB2 provides all the power you need, then above that does not matter.
There are accurate clip indicators so you will know if you are overdriving them.

I don't think you can get better information than this post by @John_Siau:
https://www.audiosciencereview.com/...era-vs-hypex-class-d.14131/page-4#post-434713

It's technical but, it boils down to you should be fine.
What type of music and volume are you listening to?

- Rich
 

Pjetrof

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The difference is 3 dB but it depends on your listening level. If the AHB2 provides all the power you need, then above that does not matter.
There are accurate clip indicators so you will know if you are overdriving them.

I don't think you can get better information than this post by @John_Siau:
https://www.audiosciencereview.com/...era-vs-hypex-class-d.14131/page-4#post-434713

It's technical but, it boils down to you should be fine.
What type of music and volume are you listening to?

- Rich

thx Rich that was to technical for me didn’t understand it.
I listen to singer songwriter, all types of good music, no hard rock.but streaming tidal and qobuz no vinyl or cd anymore
sit 2.7 meters from my speakers and they are 2 meters apart. I downloaded ones an app spl meter never came above 80 db but how accurate dont know just put it on my ipad and put it on the table in front of me.
 

RPG

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thx Rich that was to technical for me didn’t understand it.
I listen to singer songwriter, all types of good music, no hard rock.but streaming tidal and qobuz no vinyl or cd anymore
sit 2.7 meters from my speakers and they are 2 meters apart. I downloaded ones an app spl meter never came above 80 db but how accurate dont know just put it on my ipad and put it on the table in front of me.

My Revel F208 speakers have a sensitivity of 88.5 and one AHB2 is more than ample for these (at least for me!). I generally listen at 75-80 db but, for fun, have listened to a few tracks that peak above 90 db. I kept an eye on the AHB2 during the 90+ peaks and never saw a clipping indicator.
 

Pjetrof

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My Revel F208 speakers have a sensitivity of 88.5 and one AHB2 is more than ample for these (at least for me!). I generally listen at 75-80 db but, for fun, have listened to a few tracks that peak above 90 db. I kept an eye on the AHB2 during the 90+ peaks and never saw a clipping indicator.
Thx
 

RichB

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thx Rich that was to technical for me didn’t understand it.
I listen to singer songwriter, all types of good music, no hard rock.but streaming tidal and qobuz no vinyl or cd anymore
sit 2.7 meters from my speakers and they are 2 meters apart. I downloaded ones an app spl meter never came above 80 db but how accurate dont know just put it on my ipad and put it on the table in front of me.

Generally, these device are slow and will not measure peaks.
Based on your music and backup up by @RPG's experience, you should be fine with 1 AHB2.
It's a wonderful amp.

- Rich
 

John_Siau

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I used to have a pair of DIY class D (Tripath based) that power my pair of Pioneer's. One of them was damaged when I was tinkering with the circuit.

I switched to Benchmark AHB2 last year after reading review from this forum. Budget was tight and I only bought one AHB2.
Now I have a pair to drive my speakers... I am doing vertical bi-amp.

First Impression is that I get better imaging. Bass is tighter.. Treble is clearer. I think its worth the upgrade..
( I am using 17db gain setting)

Now I also have the option to go bridging too..
AHB2's max gain is 23db and after bridging its 29db.

I have an integrated Accuphase E-480 which has gain fixed at 28db. (I think 1db is not much of a difference.)
I may try mix and match and use that to bi-amp with 2x bridged AHB2.
Mikechw,
I just noticed this post.

I would not recommend using different amplifier models in any biamp configuration. Amplifier delays must match exactly.

The delay through the AHB2 and the E-480 will not be the same. This means that you will have phase issues at the crossover frequency. Also, the 1 dB difference in gain is problematic.

Furthermore, there is no need to run amplifiers at a gain of 23 to 29 dB if you have a good preamplifier or DAC. In your case you would be forced to run the AHB2 at high gain just to match the excessively high gain of the E-480.

Operating at high gain will almost always increase the noise in your system because you will be amplifying the output noise of the preamplifier or DAC. With Benchmark DACs (DAC1, DAC2 or DAC3) or preamplifiers (LA4 or HPA4), you will want to run your AHB2 amplifiers at minimum gain (9.2 dB stereo or 15.2 dB mono). These benchmark products support the studio-level XLR connections where 0 dBFS is typically calibrated to 22 or 24 dBu.
 
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