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Review and Measurements of Benchmark AHB2 Amp

cany89

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Don't bother. The LA4 will presumably give you a better signal/noise ratio, but in a home environment, I doubt very much that you'll hear the difference.

Why should you have better sound by adding another pre to the system when you already have ADI2?

(Asking it bc I’m in the same situation btw :))
 

AudioExplorer

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I use a DAC going direct to AHB2 to speakers with either digital volume control in a DAC or software volume control. While using an analog preamp can theoretically preserve the signal to noise ratio as I reduce the volume it makes no difference practically at all since the noise floor is well below 0 dB SPL even at the highest volume. I can put my ear right at the drivers and I hear nothing. So when I reduce volume digitally I am still getting the best possible dynamic range as far as my listening is concerned at whatever volume I choose to listen to. And I have always preferred using digital volume control to an analog preamp in this set up.
 
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MC_RME

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While using an analog preamp can theoretically preserve the signal to noise ratio as I reduce the volume it makes no difference practically at all since the noise floor is well below 0 dB SPL even at the highest volume. I can put my ear right at the drivers and I hear nothing. So when I reduce volume digitally I am still getting the best possible dynamic range as far as my listening is concerned at whatever volume I choose to listen to.

This is so simple, yet so many people just don't get it. I pray this one over and over again, but every day someone is born who doesn't get the most simple thing I could think of. There is no mysterious listening into the noise when you don't hear noise in the first place. There is no darker background then none. There is no better low level resolution because the human ear is the limit. More SNR than no noise audible only serves a purpose in recording studios, but not in the fixed gain stages of a home user. Etc.
 

cany89

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Thanks @MC_RME ! I take it as there would be no improvement adding a pre-amp to the chain when I can use my beloved ADI-2. (Btw, thanks for making this amazing product. Now I own not one, but two ADI-2 FS!)
 

Manojrc

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I hear nothing, absolutely nothing from my speakers even if I keep my ears next to the driver. The sensitivity of it is 100 dB @8 ohm & being driven by RME/Yamaha A-S500 combo. The SNR of the Yamaha is 100 dB. Does it mean that I don’t get any benefit if I move to AHB2 from Yamaha other than an extra 15 watt ( Yamaha is 85 watt/Ch)..
 

MC_RME

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I can't really comment on that other than the Yamaha is a complete pre+Amp, so not directly comparable to the AHB2. Also the AHB2 surpasses the tech specs of that Yamaha amp so much (SNR 30 dB better, THD about 50 dB better etc.) that again it feels like comparing apples with oranges. Regarding SNR you are right - if the Amp's specced 100dB, your speakers and your typical listening volume match so that there is no audible noise, then at least SNR is nothing to worry about.
 

DonH56

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I use a DAC going direct to AHB2 to speakers with either digital volume control in a DAC or software volume control. While using an analog preamp can theoretically preserve the signal to noise ratio as I reduce the volume it makes no difference practically at all since the noise floor is well below 0 dB SPL even at the highest volume. I can put my ear right at the drivers and I hear nothing. So when I reduce volume digitally I am still getting the best possible dynamic range as far as my listening is concerned at whatever volume I choose to listen to. And I have always preferred using digital volume control to an analog preamp in this set up.

1. Anything in the signal path will add noise, albeit perhaps very little, and thus reduce the ultimate (maximum) SNR.
2. Reducing the volume digitally means reducing the number of bits representing the signal and thus will also reduce the SNR.

So indeed you may get SNR good enough for your system in a practical sense, but it is not "the best possible". That said, "the best possible" may not be at all suitable in practice, for example if the best possible from your system is at 140 dB SPL then you probably won't be comfortable listening at that volume. But as @MC_RME said, the best noise is no noise (even if not realizable in the real world). Yes, when can resolve below the noise floor, as long as the signal is within our ability to hear it (i.e. is loud enough), but if there were no noise then we could hear it all the better.
 

Vladimir_Kl

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Am I correctly understand that RME ADI-2 FS Pro with +24dbu output is a perfect match for AHB2 in low gain mode?
 

MC_RME

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IMHO yes. But even if set to +19 dBu (ADI) and Low Gain (AHB2) I bet you won't crank the ADI's volume fully up.
 

RPG

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IMHO yes. But even if set to +19 dBu (ADI) and Low Gain (AHB2) I bet you won't crank the ADI's volume fully up.

He's right.....AHB2 at low gain and the ADI-2 DAC at +19dbu cranked up to 0db feels like it would damage my hearing.
 

Olli

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I use an ADI-2 Pro R with 2 AHB2s in low gain mode. It is dead silent it and you can hardly crank up the voume to more than -20 dB in that setup.

I got the R as an upgrade to the previous ADI-2 Pro not because of the slightly improved performance, but because I thought I could apply volume dependent loudness via the remote control volume to my convoluted Roon MCH signal to Channels 1/2 (Mains) and Channels 3/4 (Subs) simultaneoulsy (BTW I know I could do all of this with JRIVER in the digital domain).

Unfortunately you can't sync the volume of Channel 1/2 and Channel 3/4 yet, but according to the RME support team as of March this will be included in a next firmware update. Any concrete plans when this is going to happen, @MC_RME ?
 

dearflight

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Hello there. I use RME ADI-2 FS DAC. I always use " auto dBu " as I do not know that is a good setting or not. By above posts, I check ADI-2 FS the max dBu I can set is +13 dBu. If XLR is 6 dBu more, does that means total + 19 dBu?

Because my space for listening music is not big, by auto dBu of ADI-2, the volume runs between -20 ~ -35 dBr.
As I know, auto dBu will change the value according to the volume. So auto dBu will stay at -5dBu on my volume. (-20 ~ -35 dBr)

@MC_RME Please help me to confirm which is the best setting?

1. +13 dBu (13+6 by XLR is 19) for AHB2 at low gain +22 dBu, but I need to turn the volume to -40 ~ -50 dBr?
2. use auto dBu and volume between -20 ~ -35dBr with -5 dBu.
 

MC_RME

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Your post is a bit unclear, but it doesn't matter. AutoRef On means the unit switches the hardware output reference levels correctly for you. You just choose the volume that you want (with the VOLUME knob), and can fully ignore the technical stuff behind it.
 

MC_RME

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Unfortunately you can't sync the volume of Channel 1/2 and Channel 3/4 yet

Sure you can. But it doesn't stay. It wasn't designed for 'continously active'.

but according to the RME support team as of March this will be included in a next firmware update. Any concrete plans when this is going to happen, @MC_RME ?

That is indeed planned for the next firmware update.

But (all) please take such posts to the ADI-2 Pro threads, this one here is about the AHB2.
 

dearflight

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Your post is a bit unclear, but it doesn't matter. AutoRef On means the unit switches the hardware output reference levels correctly for you. You just choose the volume that you want (with the VOLUME knob), and can fully ignore the technical stuff behind it.

@MC_RME

I try to clarify my question and need your opinion.
What would be the best dBu setting to use RME ADI-2 DAC with AHB2 low gain mode?
( Current status: ADI-2 AutoRef dBu, Volume knob -20 ~ -30 dBr)
Choice 1: remain current status, ADI-2 AutoRef dBu. So the dBu will change according to Volume knob.
Choice 2: by previous posts, set ADI-2 dBu to 13 (using XLR it will become 19 dBu, am I right?) to match AHB2 low gain.
When set to 13 dBu, the volume knob has to turn down to - 30 ~ -45 dBr because original -20 ~ -30 dBr will be too loud.

Due to previous discussion shows " dBu match " is important, that's why I wonder if the dBu need to be set on 13 dBu.
 

MC_RME

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dBr means dB relative. This value only makes sense (and therefore is only shown) when AutoRef is on. So when you use fixed 13 dBu as Ref Level Volume is set to -30 ~ 45 dB, not dBr.

As I said AutoRef On (Choice 1) is the best.
 

cichom

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1 minute ago
#128

What do you think about combo gustard x26 pro + benchmark ahb2 without analog preamp? Whould it works fine? I've tested gustard, but there is no benchmark distributor in my country so it's hard to test them both
 

Dgob

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Just bought two of these (AHB2's) to run a pair of Revel Performa3 F208 speakers. Absolutely amazing and very, VERY highly recommended.
 

Dgob

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1 minute ago
#128

What do you think about combo gustard x26 pro + benchmark ahb2 without analog preamp? Whould it works fine? I've tested gustard, but there is no benchmark distributor in my country so it's hard to test them both
I was toying with the same set-up. However, with me already having the Topping Pre90 and Ext90, I opted for the Topping D90 SE. Behind this, I have two Benchmark AHB2's running a pair of Revel's in bridged mono. Fabulous music. However, some do prefer the Gustard X26 Pro, although I think they tend to use the Gustard just as a DAC.
 

laidick

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I was toying with the same set-up. However, with me already having the Topping Pre90 and Ext90, I opted for the Topping D90 SE. Behind this, I have two Benchmark AHB2's running a pair of Revel's in bridged mono. Fabulous music. However, some do prefer the Gustard X26 Pro, although I think they tend to use the Gustard just as a DAC.

Snce you have 2 AHB2, I would suggest you try to biamp the F208 too, instead of bridge mono.

Not saying which one is better, just test it out yourself which one you like more.

I myself like biamp more than bridge.
I have 3 AHB2 , for LCR.
 
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