Review and Measurements of Benchmark AHB2 Amp

[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.

 

[HarmonicTHD]

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.

Did you increase the input level or changed the sensitivity settings accordingly?

Audio Calculators

Audio Calculators. How loud will my stereo play? How much power do I need? Conversions from % to dB. Conversions between Volts and dBu, and much more.

benchmarkmedia.com

 

[DonH56]

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.

Measured how? And are you sure the Maggies are not compressing? I misdoubt a 1.7i will handle that sort of power without severe compression and distortion. Also, did the AHB2's clipping light ever come on?

 

[xaxxon]

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.

I have a 5.x system that used to have 3 ahb2's and I have put the stereo ones into protect before (center channel kept on playing). Now it has 5 ahb2s and it doesn't.

It definitely adds quite a bit more power, for sure.

 

[RichB]

I have a 5.x system that used to have 3 ahb2's and I have put the stereo ones into protect before (center channel kept on playing). Now it has 5 ahb2s and it doesn't.

It definitely adds quite a bit more power, for sure.

Just curious, what are your main speakers?

- Rich

 

[xaxxon]

Just curious, what are your main speakers?

- Rich

4x alexia 1 and a mezzo c/s center. I was sitting in another room messing with the volume when they protected . And there was a LOT of bass.

 

[RichB]

4x alexia 1 and a mezzo c/s center. I was sitting in another room messing with the volume when they protected

Efficient but they are no walk in the park to drive.

Wilson Audio Specialties Alexia loudspeaker Measurements

Sidebar 3: Measurements

www.stereophile.com

My estimate of the Alexia's voltage sensitivity was slightly higher than the specified 90dB/2.83V/m, at 91.3dB(B)/2.83V/m. This speaker will play loudly with just a few watts. However, it demands quite a lot of current from the partnering amplifier. The Alexia's electrical impedance and phase angle are shown in fig.1. (This graph was taken with the original, higher-value tweeter resistors.) The impedance magnitude stays between 2 and 6 ohms from 12Hz to 4kHz, with a gentle rise above that frequency. The minimum value is 1.96 ohms at 86Hz, and there is a demanding combination of 3.6 ohms and –43° phase angle at 54Hz.

- Rich

 

[xaxxon]

Efficient but they are no walk in the park to drive.

Wilson Audio Specialties Alexia loudspeaker Measurements

Sidebar 3: Measurements

www.stereophile.com

- Rich

Efficient but they are no walk in the park to drive.

Wilson Audio Specialties Alexia loudspeaker Measurements

Sidebar 3: Measurements

www.stereophile.com

- Rich

When the room suddenly got a lot quieter, my house was vibrating probably somewhere close to 54hz (and with no subs active at the time)

You have any links describing how phase angle impacts/relates-to how hard something is to drive? (or can you just tell me)

Thanks

 

[12Many]

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.

I believe there is a 3 position gain switch on the back of that amp. I understand you were just comparing, but if you wanted more and weren't already adjusting that switch, there may a bit more to give, if it works in mono mode.

 

[xaxxon]

I believe there is a 3 position gain switch on the back of that amp. I understand you were just comparing, but if you wanted more and weren't already adjusting that switch, there may a bit more to give, if it works in mono mode.

https://cdn.shopify.com/s/files/1/0321/7609/files/AHB2_Manual_-_Rev_H.pdf?v=1602610101 - page 9

> If this switch is set too low, you will not be able to drive the amplifier to its rated output.

 

[peng]

When the room suddenly got a lot quieter, my house was vibrating probably somewhere close to 54hz (and with no subs active at the time)

You have any links describing how phase angle impacts/relates-to how hard something is to drive? (or can you just tell me)

Thanks

I think the following is probably one of the best you can find on the topic.

Phase Angle Vs. Transistor Dissipation

Phase Angle Vs. Transistor Dissipation

sound-au.com

 

[xaxxon]

I think the following is probably one of the best you can find on the topic.

Phase Angle Vs. Transistor Dissipation

Phase Angle Vs. Transistor Dissipation

sound-au.com

Wow, at 45 degrees, the amp has to send 2 watts for the speaker to play at half-watt volume.

 

[peng]

View attachment 253129
Wow, at 45 degrees, the amp has to send 2 watts for the speaker to play at half-watt volume.

High phase angle such as 45 deg does not mean you need 2 W to produce the spl that 0.5 W would produce if it is 0 deg.

It just means at a given output voltage, more power will be dissipated in the amp's output devices if the phase angle is larger. Speakers spl output is proportional to the voltage applied, not the power dissipated in the crossover and the drivers.

 

[xaxxon]

High phase angle such as 45 deg does not mean you need 2 W to produce the spl that 0.5 W would produce if it is 0 deg.

It just means at a given output voltage, more power will be dissipated in the amp's output devices if the phase angle is larger. Speakers spl output is proportional to the voltage applied, not the power dissipated in the crossover and the drivers.

But it’s amperage that has to be available to maintain that voltage right?

 

[Itisawesome]

Did you increase the input level or changed the sensitivity settings accordingly?

Audio Calculators

Audio Calculators. How loud will my stereo play? How much power do I need? Conversions from % to dB. Conversions between Volts and dBu, and much more.

benchmarkmedia.com

Oh I see. I use a Mytek Brooklyn Bridge with balanced connections so it outputs 9.8V and I use low gain setting on AHB2. Using one of the calculators you mentioned I suppose the amp in mono mode is outputting less power? Maybe around 130W. If that is the case no wonder it doesn't sound louder. So should I be attenuating the gain on the Mytek to reduce to 4V so that the AHB2 can output more power by using middle gain setting on AHB2? Is this the correct way to use the calculators? But I didn't think the AHB2 could output 800W.

 

[HarmonicTHD]

Oh I see. I use a Mytek Brooklyn Bridge with balanced connections so it outputs 9.8V and I use low gain setting on AHB2. Using one of the calculators you mentioned I suppose the amp in mono mode is outputting less power? Maybe around 130W. If that is the case no wonder it doesn't sound louder. So should I be attenuating the gain on the Mytek to reduce to 4V so that the AHB2 can output more power by using middle gain setting on AHB2? Is this the correct way to use the calculators? But I didn't think the AHB2 could output 800W.

Just switching it to Bridge Mode doesn’t make it louder per se if you feed it the same input voltage. Either increase the input voltage or the sensitivity / gain (with the switch at the back of the amp).

One of the calcs from Benchmark illustrates this (as seen in your screenshots). In simple words: Output Voltage = Gain (sensitivity) x Input Voltage. With Bridge mode you have a higher max Output voltage available to you, but you need to utilize it so it plays louder.

 

[peng]

But it’s amperage that has to be available to maintain that voltage right?

It has nothing to do with that, the whole article is about the power dissipation in the output transistors versus that in the loudspeaker load. That values in the table you quoted is normalized to 1 watt.

Normalization Formula | Calculator (Examples With Excel Template)

Guide to Normalization Formula. Here we discuss how to calculate Normalization with examples, calculator and downloadable excel template.

www.educba.com

Regardless of the phase angle, if you apply say 2.83V to a loudspeaker at 1 kHz, and if the impedance at that frequency is 8 ohm, then current = 2.83/8 = 2.83/8 = 0.35375 A,
that is, whether the phase angle at that point is 0, 30, 45 or 60 degrees, the load current will still be 0.35735 A (assuming there are no other impedance in the circuit), but the power dissipation in the output devices will be higher at the larger phase angles. The math analysis involved are quite complicated, but it does appear to me the author knew what he's talking about so I trust those figures. At the same output voltage, large phase angles do not result in the amplifier having to supply higher current to the loudspeaker load, but it does mean the amplifier will be subject to more heat because as the load dissipate less power, the amplifier will have to dissipate more.

If you are keen on learning more on this, may as well read the following as well, I believe the author of the first article provided a link there (in the introduction) too:

Semiconductor Safe Operating Area

Semiconductor Safe Operating Area. The influences and problems faced with high power amplifiers using bipolar junction transistors (BJT).

sound-au.com

 

[dlaloum]

It has nothing to do with that, the whole article is about the power dissipation in the output transistors versus that in the loudspeaker load. That values in the table you quoted is normalized to 1 watt.

Normalization Formula | Calculator (Examples With Excel Template)

Guide to Normalization Formula. Here we discuss how to calculate Normalization with examples, calculator and downloadable excel template.

www.educba.com

Regardless of the phase angle, if you apply say 2.83V to a loudspeaker at 1 kHz, and if the impedance at that frequency is 8 ohm, then current = 2.83/8 = 2.83/8 = 0.35375 A,
that is, whether the phase angle at that point is 0, 30, 45 or 60 degrees, the load current will still be 0.35735 A (assuming there are no other impedance in the circuit), but the power dissipation in the output devices will be higher at the larger phase angles. The math analysis involved are quite complicated, but it does appear to me the author knew what he's talking about so I trust those figures. At the same output voltage, large phase angles do not result in the amplifier having to supply higher current to the loudspeaker load, but it does mean the amplifier will be subject to more heat because as the load dissipate less power, the amplifier will have to dissipate more.

If you are keen on learning more on this, may as well read the following as well, I believe the author of the first article provided a link there (in the introduction) too:

Semiconductor Safe Operating Area

Semiconductor Safe Operating Area. The influences and problems faced with high power amplifiers using bipolar junction transistors (BJT).

sound-au.com

Typically (and without going into maths - just from years of perusing speaker impedance/phase charts) - "difficult" speakers very often have "difficult" (ie: low) impedances, as well as "difficult" phase variations....

When you have a "difficult" speaker - you are going to need an amp that can supply more current, AND dissipate more heat.... the two tend to go hand in hand - although they are not the same thing, and in theory you could have each without the other. But in practice, they generally are found together.

 

[andrewngu]

I really wanted to like this amplifier. I ordered this and used my RME ADI-2 DAC straight into it to drive my KEF Reference 3's. The sound was cold, clinical and sibilant. I was hoping I could replace my Naim Uniti Nova, the big brother to the Atom, which was recently reviewed and trashed by Amir. End game amp for $3k? Hell yeah, I thought. Guess I'm one of those "euphonic distortion" guys.

 

[GXAlan]

I really wanted to like this amplifier. I ordered this and used my RME ADI-2 DAC straight into it to drive my KEF Reference 3's. The sound was cold, clinical and sibilant. I was hoping I could replace my Naim Uniti Nova, the big brother to the Atom, which was recently reviewed and trashed by Amir. End game amp for $3k? Hell yeah, I thought. Guess I'm one of those "euphonic distortion" guys.

It’s humbling to be a euphonic distortion person, but try listening to a few classical music pieces. I think you will appreciate the AHB2 and if that’s not your preferred genre of music, it will give you more confidence that you admittedly don’t want transparency in your music (which is perfectly OK).

I have been to three Michelin star restaurants, but I still like A1 with my steak…