Review and Measurements of Benchmark AHB2 Amp

[MAB]

I have a pair of Tune Audio Anima horns which have a 109dB/watt spec, confirmed by measurement by a French magazine FWIW.
I was most concerned about noise but actually have driven them with Devialet D-Premier, Classic 16.0 40 wpc push-pull valve amplifier and a Job INTegrated and none gave audible noise at my listening distance of 4.5 m, and the Job, which is now its normal amp, has inaudible noise even with my ear against the mouth of either mid or treble horns.
I haven't tried a class-D amp but have been tempted to connect the headphone output of a portable player just to hear, but haven't bothered to make up a cable.

I've done the same with a JBL D2 compression driver. The only amp that I tried that is really disqualified is an old Aiwa A22 micro-amp.
The Bryston 3B ST and Marantz amps were acceptable, even if audible at close range.
The Hypex and PuriFi amps were all silent until I had my ear on the surface of the lens.
The pad and filter capacitor use in the passive part of the crossover practically eliminates the noise, except with the Aiwa which can still be heard.

Topping B100 Amplifier Review

Probably not. There's a calculation for that, but it typically degrades the worst component a dB or two (strictly speaking, that's just adding noise, but that's all there probably is to add). In your example, since it is 10dB better than the amp, you'll end up with maybe 84dB. I just ran the...

www.audiosciencereview.com

This is one of the very few applications where amps have a sound that is identifiable. Each amp has it's own noise spectra.

 

[Sal1950]

Those are nice speakers! I'd never go back to consumer level gear... pro-audio is the only way to go. I actively tri-amped my bed speakers, plus cross to 8 subs.

Be carefull of name tags.
Some pro-audio gear is junk.
Some consumer gear is SOTA TOTL.

 

[mdunjic]

A great tear-down video featuring John Saiu popped up on my YouTube feed:

Watched it few days ago

 

[SoupRKnowva]

I doubt you'd hear noise with the purifi module amps. I have the 6525 stereo amp and the 9040 module monos from Buckeye and I can put my head inside the horn of my 101db 4ohm JTR 212RTs in my theater and hear literally nothing. these amps are quiet

 

[Oniiz86]

I doubt you'd hear noise with the purifi module amps. I have the 6525 stereo amp and the 9040 module monos from Buckeye and I can put my head inside the horn of my 101db 4ohm JTR 212RTs in my theater and hear literally nothing. these amps are quiet

@SoupRKnowva That's pretty remarkable that your highly sensitive JTRs at 101dB have no hiss whatsoever with the Purifi 1ET6525SA amp, what Gain setting on the Buckeye is that set to? I too have a Purifi 1ET6525SA stereo amp (March Audio's P482) with the Gain set to 27db & unfortunately I have moderate hiss coming from my Klipsch RF-7 IIIs horns with 100dB (in reality measured to be 92.8dB), it must be Buckeye's combination of its lowest Gain setting of 15dB & very low noise input buffer?

 

[SoupRKnowva]

@SoupRKnowva That's pretty remarkable that your highly sensitive JTRs at 101dB have no hiss whatsoever with the Purifi 1ET6525SA amp, what Gain setting on the Buckeye is that set to? I too have a Purifi 1ET6525SA stereo amp (March Audio's P482) with the Gain set to 27db & unfortunately I have moderate hiss coming from my Klipsch RF-7 IIIs horns with 100dB (in reality measured to be 92.8dB), it must be Buckeye's combination of its lowest Gain setting of 15dB & very low noise input buffer?

I had only used them in low gain, but I just switched them to high gain, still zero hiss or anything else. silent with my head inside the horn, to try to get my ear as close to the compression driver as possible.

have you tried yours with nothing connected and the inputs shorted? Im wondering if the hiss is coming from your source? The 212RTs really are 101db, and thats at 2volts, its 104db at 2.83volts that most use(which is 2 watts into 4ohms, not 1)

 

[Oniiz86]

I had only used them in low gain, but I just switched them to high gain, still zero hiss or anything else. silent with my head inside the horn, to try to get my ear as close to the compression driver as possible.

have you tried yours with nothing connected and the inputs shorted? Im wondering if the hiss is coming from your source? The 212RTs really are 101db, and thats at 2volts, its 104db at 2.83volts that most use(which is 2 watts into 4ohms, not 1)

@SoupRKnowva I've tried with nothing connected, it makes no difference, I'm a bit concerned about shorting the inputs, don't want to risk that, the source is my Denon X8500H AVR which strangely does not exacerbate the hissing issue which is odd as the X8500H's pre-amp circuitry wouldn't be very clean, I should've mentioned that this hissing cannot be heard at my MLP which is approx. 3m but still there was no hissing at all when I just had the Denon X8500H connected which I believe has a slightly higher fixed Gain at 29dB.

 

[antcollinet]

@SoupRKnowva I've tried with nothing connected, it makes no difference, I'm a bit concerned about shorting the inputs, don't want to risk that, the source is my Denon X8500H AVR which strangely does not exacerbate the hissing issue which is odd as the X8500H's pre-amp circuitry wouldn't be very clean, I should've mentioned that this hissing cannot be heard at my MLP which is approx. 3m but still there was no hissing at all when I just had the Denon X8500H connected which I believe has a slightly higher fixed Gain at 29dB.

Shorting inputs is not a problem - and often needed to eliminate noise picked up on a high impedance input that largely doesn't exist when a low impedance source is connected.

 

[Sal1950]

@SoupRKnowva I've tried with nothing connected, it makes no difference, I'm a bit concerned about shorting the inputs, don't want to risk that,

As Ant said, shorting the inputs will never cause a problem.
Just never short the outputs, in some cases no problem, with others total disaster.

I curious if you ever tried using the X8500H AVR by itself using the internal amps, do you have any hiss then? Any since the hiss isn't audible at the MLP it's not really an issue, just more of a curiosity.
Cheers.

 

[Oniiz86]

I curious if you ever tried using the X8500H AVR by itself using the internal amps, do you have any hiss then? Any since the hiss isn't audible at the MLP it's not really an issue, just more of a curiosity.
Cheers.

@Sal1950 Yes that is my concern, the Denon X8500H AVR without the Purifi 1ET6525SA amp has no hiss at all despite the Gain being higher at 29dB & yes this hiss isn't audible at the MLP but I was still disappointed all the same to see the Purifi 1ET6525SA amp bringing out this moderate hissing noise when they are meant to exhibit a fairly low noise floor, I still don't quite understand how the Denon at 29dB has no hiss at all when I put my ear right up against the horn compression driver but the Purifi with 2dB less of Gain at 27dB is producing this hissing sound.

 

[Everett T]

@Sal1950 Yes that is my concern, the Denon X8500H AVR without the Purifi 1ET6525SA amp has no hiss at all despite the Gain being higher at 29dB & yes this hiss isn't audible at the MLP but I was still disappointed all the same to see the Purifi 1ET6525SA amp bringing out this moderate hissing noise when they are meant to exhibit a fairly low noise floor, I still don't quite understand how the Denon at 29dB has no hiss at all when I put my ear right up against the horn compression driver but the Purifi with 2dB less of Gain at 27dB is producing this hissing sound.

Maybe the pre out from the Denon is adding the noise?

 

[Oniiz86]

Maybe the pre out from the Denon is adding the noise?

@Everett T That seems to be entirely plausible & most likely the issue here, I just didn't realise how noisy the X8500H AVR's Pre-Out really is, even with using the Custom Amp-Assign mode disconnecting the amps from the Pre-Amp circuitry, anyway sorry for the OT discussion, I didn't mean to pollute this thread.

 

[Sal1950]

@Everett T That seems to be entirely plausible & most likely the issue here, I just didn't realise how noisy the X8500H AVR's Pre-Out really is, even with using the Custom Amp-Assign mode disconnecting the amps from the Pre-Amp circuitry, anyway sorry for the OT discussion, I didn't mean to pollute this thread.

No problem friend. I am also surprised that the Denon's pre-out should be that noisy but ???
Until just recently I was using a Denon X4700H pre-out to drive my 30 year old Adcom amp with fairly sensitive JBL speakers and had zero hiss with my head at the speakers, so ?
Neither of your components should be adding that noise but something is?
First test would be once again shorting the input to one channel on the amp, is the amp making noise.
If not, besides the Denon sending noise down the line, the last outside possibility would be the connecting cable having very poor shielding, do you have any other type innerconnects you can test with?
Good luck.
Back to our regularly scheduled programing.

 

[antcollinet]

No problem friend. I am also surprised that the Denon's pre-out should be that noisy but ???
Until just recently I was using a Denon X4700H pre-out to drive my 30 year old Adcom amp with fairly sensitive JBL speakers and had zero hiss with my head at the speakers, so ?
Neither of your components should be adding that noise but something is?
First test would be once again shorting the input to one channel on the amp, is the amp making noise.
If not, besides the Denon sending noise down the line, the last outside possibility would be the connecting cable having very poor shielding, do you have any other type innerconnects you can test with?
Good luck.
Back to our regularly scheduled programing.

Ground loop also quite possible.

@Oniiz86 what other components to you have connected upstream of the AVR? Can you try disconnecting everything from the AVR except the amp. Does the noise still exist.

 

[Everett T]

Ground loop also quite possible.

@Everett T what other components to you have connected upstream of the AVR? Can you try disconnecting everything from the AVR except the amp. Does the noise still exist.

My gear is good . Unless the Purifi has a power supply issue I don't see it being EMI but I've been known to be wrong.

@Oniiz86 I didn't notice you had mentioned you could hear the hiss with just the amp connected to the speakers (I'm assuming that includes the cables from the Denon.) Can you move the power to another circuit with an extension cord just to rule out EMI? Also and just for reference, what cables are you using for the connection between the Denon and the amp?

 

[antcollinet]

My gear is good . Unless the Purifi has a power supply issue I don't see it being EMI but I've been known to be wrong.

Sorry - I missattributed your post - Edited

 

[Oniiz86]

First test would be once again shorting the input to one channel on the amp, is the amp making noise.
If not, besides the Denon sending noise down the line, the last outside possibility would be the connecting cable having very poor shielding, do you have any other type innerconnects you can test with?

@Sal1950 I'm still a bit apprehensive to short one of the inputs on the amp, too risk-averse I don't think the cables are of poor quality it's Mogami's 2549 NEGLEX cable, they're the only ones I have which were purchased at the time of my Purifi amps.

what other components to you have connected upstream of the AVR? Can you try disconnecting everything from the AVR except the amp. Does the noise still exist.

@antcollinet I only have 3 components connected to the AVR, an OPPO UDP-205, OPPO BDP-105D & Sony Bravia 85Z8H, I haven't tried disconnecting them, something I should've done but a bit reluctant to do so as it's quite difficult to get behind the lowline but I will get around to it, thanks for the suggestion.

I didn't notice you had mentioned you could hear the hiss with just the amp connected to the speakers (I'm assuming that includes the cables from the Denon.) Can you move the power to another circuit with an extension cord just to rule out EMI? Also and just for reference, what cables are you using for the connection between the Denon and the amp?

@Everett T Yeah I've disconnected the XLR to RCA cables from the Denon, so only the RF-7 IIIs are connected to the Purifi amp. I could try another power circuit but I just thought that it may be the speaker cables behind the lowline that is contributing to this hissing issue, it could be that they aren't properly isolated from the mains power cables. The interconnect XLR to RCA cables are from the Purifi manufacturer/assembler based on Mogami's 2549 Low Noise NEGLEX cable with Neutrik XLR & Amphenol RCA connectors, I understand Canare's L-4E6S Star Quad cable is the ideal cable to use but would think Mogami's 2549 is more than sufficient for the job.

 

[nagster]

The safest way to handle input terminals is to connect a shorting plug.