Benchmark ahb2 power amplifier

[Kal Rubinson]

2 hours ago, blue2 said:

............................., and more here by Stereophile who found a flaw with one recording.

But the reviewer just bought three of them.  😎

[Kal Rubinson]

5 hours ago, Ralf11 said:

6 channels?  I thought you were a 5 channel guy?

Three channels, L/C/R, driven by the Benchmark monoblocs.

[Kal Rubinson]

44 minutes ago, Ralf11 said:

ok, are there other channels?  or is this a 2nd system, or am I wrong ini thinking you have ~~5 channels in your system...

Sure.  The two surround channel speaker are driven by a different stereo amp.  I may get another Benchmark or two for them but there are other changes afoot and that decision will wait until that dust settles.

[Kal Rubinson]

33 minutes ago, sandyk said:

Kal

 Do you know how they manage to increase S/N to such a degree given limitations due to Johnson noise in resistors etc ?

 Signal/noise (A-weighted): 132dB (stereo) is much higher than most amplifiers are capable of .

Was this measured at the low gain setting ?

I cannot directly answer that.  However, Benchmark is pretty demonstrative of their measurement philosophy and results.  You can also read John Atkinson's efforts to measure the amp as part of my subjective review.

[Kal Rubinson]

2 hours ago, arcman said:

I'm thinking this would be a great, super quiet amp for my 101 db Zu Speakers. I can add "flavor" by tube rolling my Rogue preamp. Plus, the gain settings will allow me to ditch the passive pre between my RP-5 and amp. My current Nuforce STA200 has higher gain than normal thus making my preamp tube hiss a bit too loud. 

It should do this well.  I was originally attracted to the AHB2 by the low gain settings which complemented the very high output of my AR MP1 preamp. 

[Kal Rubinson]

23 minutes ago, barrows said:

As i recall this is a low gain amp (I need to go back and look at the Stereophile measures), low gain is a sure way to reduce noise.  I suspect the rest of the engineering is good as well

IIRC, the three gain settings measured at 23dB, 17dB and 9.2db.

 

23 minutes ago, barrows said:

Of course nothing comes for free, with this low gain one will have to have higher gain in the source to reach the same levels in a given system context, higher gain in the source means higher noise there, so no free lunch.

Agreed.  In my case, I have a preamp with lots of output but with a bothersome noise floor that is unaffected by its volume setting and sources that are very quiet.  Turning down the gain in the AHB2 is easily compensated by the preamp but the result is greatly reduced noise at the end of the chain.

[Kal Rubinson]

1 hour ago, Ralf11 said:

I think running their DAC straight to their power amp is what Benchmark would like you to do.

Indeed, I did run three DAC3s into three AHB2s very successfully except for the inability to use the volume knobs.

[Kal Rubinson]

5 hours ago, Miska said:

But with that combination you probably get very good performance thanks to good gain matching and then it should be within bounds of safely relying on software digital volume...

I am not sure what you are suggesting but I when I said........

11 hours ago, Kal Rubinson said:

Indeed, I did run three DAC3s into three AHB2s very successfully except for the inability to use the volume knobs.

I was referring to a temporary situation but it reveals my personal preference for a physical knob control.  AFAIK, the only multichannel DACs that have a physical volume knob are the Merging (NADAC and Hapi) and the upcoming OKTO.  Do you know of any others?

[Kal Rubinson]

1 hour ago, psjug said:

It is not too clear, but it seems that JA's noise testing in Stereophile was done using the highest gain setting, and he also said the noise difference at different settings was only 3dB.

The value of the lower gain settings is not that it reduces the noise contribution of the amp but it, effectively, attenuates the noise contribution from its sources.

[Kal Rubinson]

5 hours ago, barrows said:

Kal, a more clear way of stating the above might be to say: the lower gain setting in my system reduces the amplification of the source noise (as it does not really attenuate it) such that it is no longer audible.  Or something to that effect.

Not just to that effect but exactly.

 

5 hours ago, barrows said:

Suffice it to say, proper gain matching in a system to where the user does not have to apply high levels of attenuation (using the volume control) can result in improved system performance, and it is likely that a lot of audiophiles are leaving some performance on the table in this regard.  If one's volume control never goes above -20 dB, then one could benefit from changing the gain structure/relationships between their components.

Most users think that most standard equipment will be compatible unless something ugly pops up.  It would actually be best if one took this into account, consciously, when choosing and installing equipment.  Suffice it to say that I did know about this for most of my life but only actively pursued it when it became necessary. 

 

I am checking with JA about the precise conditions of his tests on the AHB2.

[Kal Rubinson]

10 minutes ago, Panelhead said:

  How many channels do you need? One of the reasons I use my Clarett 4Pre is it can be configured for 4 channel balanced out. Has a single knob. 

  There are other good reasons, but Hooking up active subs is a goal.

  Four channel dacs are just not very popular.

I need 6-8 channels.

[Kal Rubinson]

44 minutes ago, Miska said:

 

If it doesn't need to have DSD support (well, I think OKTO doesn't do high rate DSD multichannel anyway), I think there are number of such around in pro-audio. Like RME UFX+, or pretty much anything you can control with ARC USB. And then Prism Titan and Prism Atlas. Then Apogee Control works with number of their products. Then Universal Audio Apollo x8 and Apollo x16. And then Focusrite Red 16Line. Probably there are many many others.

 

I will look into those but there are other requirements. 6-8 channels, PCM/DSD, physical volume knob, wireless remote control.

[Kal Rubinson]

3 minutes ago, barrows said:

Bricasti.

It's only 2 channels.

[Kal Rubinson]

34 minutes ago, Miska said:

I can control HQPlayer with wireless remote control, but your requirements are becoming complex enough that there's probably not much left. Rules out also Hapi (AFAIK it doesn't have wireless remote control). Focusrite can be controlled also with iPhone/iPad.

 

I personally don't want a DAC with digital volume control, because I'm not happy with the implementations. If a DAC has volume control, for me it must be analog, like motorized pot in Marantz, or even better a switched resistor ladder like in T+A (my preamp also has switched resistor ladder). For computers you can get all kinds of knobs, bells and whistles to control the software volume.

 

The remote controls I referred to in the earlier post are specifically ones with a knob, I assume that is also what you want with a remote control. There are quite a bunch of such for studios/mastering use. You can usually also switch function of the knob between volume/seek/whatever with simple press of a function key. A bit like my DSLR that has two programmable rotary controls and couple of programmable function buttons.

Thanks again.  I have been looking for something suitable for quite a while and I am less insistent on the mode of the solution than I am to achieve something with which I will be comfortable.  Unfortunately, I am less technically competent than I used to be. 

 

Is there a wireless RC volume control (knob or not) that will work with HQP? 

[Kal Rubinson]

Let me add that an advantage of having adjustable gain is that having more gain than is necessary for full output means that you are unnecessarily amplifying the noise in the input signal.  The AHB2 allows one to choose a lower gain in such a situation and enjoy lower output noise.