Benchmark AHB2 Power Amp: The Quietest and Cleanest Amp on Planet Earth?

[ddude003]

@Sonnie How do your amps react to those Martin Logans dipping down to less than 1 ohm somewhere between 10kHz and 20kHz???

 

[Sonnie Parker]

You analysis is way off. Too lengthy to correct this evening.

That really wouldn't be my analysis... it would be the manufacturer/engineer analysis. I was basically repeating what I was told. One guy wouldn't even sell me his amp.

 

[Sonnie Parker]

@Sonnie How do your amps react to those Martin Logans dipping down to less than 1 ohm somewhere between 10kHz and 20kHz???

From all I can tell is it is pushing them to their limits with the warning LEDs flashing regularly at moderate volumes. I ignore them, as it sounds fine, but I'd probably like a little more volume on some songs from time to time.

It's actually .52 ohms at 20kHz. I think everything else is nominal 4 ohms.

 

[AJ Soundfield]

It was interesting and your opinion was anticipated but not the tactless delivery

Shame on you for not anticipating my tactless delivery .
Not sure who asked, but none anticipated the same type analysis/critique of a sighted test???
Not clear how this would support Sonnie either, he's determined to dump the amps based on flashing light...not sound.
Clearly that spooked the Ncore amp builders. Despite a 1200 being more than capable of driving his speakers transparently.

After a few listening session today, the two amps were closer

How do you reconcile this with you initial sighted AB test? No question you are matching levels.

cheers

 

[AJ Soundfield]

That really wouldn't be my analysis... it would be the manufacturer/engineer analysis. I was basically repeating what I was told. One guy wouldn't even sell me his amp.

Yeah you very publicly dumping the Benchmark spooked them pretty good
Worries about an amp that can deliver 1Kw clean into your MLs

 

[Sonnie Parker]

I don't think the Ncore amp builder has any idea I have spoken of the Benchmarks publicly, just simply that the lights were flashing and I was afraid I was reaching the limits a bit too soon and wanted more power.

So the AHB2 indeed only does the 500 watts bridged into 4 ohms per ASR, as Rich pointed out. Amir states: You get 500 watts of stunningly clean power. Protection circuit shut the unit down after that so it is quite safe to try. With a THD essentially matching the non-bridged mode, there is no reason to be afraid of trying this.

Then a couple of charts on the Nord NC1200...

I would be better off with the NC2000 to be assured of sufficient power. Amir states: Seems like there is an intermediate non-linearity that shows up between 10 and 100 watts and then stabilizes until we start to saturate the amp/power supply. I didn't dare letting it go to full clipping.

 

[Sonnie Parker]

A pair of the Apollon NC2000 are about 5K with shipping.

 

[Sonnie Parker]

Yeah you very publicly dumping the Benchmark spooked them pretty good
Worries about an amp that can deliver 1Kw clean into your MLs
View attachment 41540

Isn't that equal to 500 watts clean into 4ohm... I've got that now.

 

[AJ Soundfield]

Isn't that equal to 500 watts clean into 4ohm... I've got that now.

No sir, its like nearly 1kw into 2 ohms as shown. Your speakers impedance varies, its not constant 4 ohm. We know it droops towards HFT, thus it is important to view power vs load when assessing real life "performance" as Amir likes to say. Did I mention I've been designing active speakers for 20+ yrs? Not an "amp" guy. I need to know about the whole kit and caboodle, end to end. Then there is perception. You're probably not going to hear 1%, much less 0.1% THD, as THD is very poorly correlated to perception. Worse, at those extremely high output levels, your ears are starting to compress/distort, further clouding perception/non-linearity detection.
The NC1200 will deliver more indiscernible power, not less into your ML than the bridged AHB...which you already can't "hear" clipping.
It doesn't have clip lights either, so...
Anyway, you clearly scared the amp assembler guys..and the NC2000 is available to destroy either your hearing and/or speakers, so party on Garth.

 

[Sonnie Parker]

Who listens to Garth? That's young girl stuff, or at least use to be.

Not at all arguing that it's 1000 watts into 2 ohms... that much is pretty clear. However, that would equate to considerably less power into 4 ohms, pretty sure of that too. No reason to wiggle around it.

I still like to compare apples to apples with ratings, and the 15A's are nominally rated at 4 ohms. So comparing 1000 watts 2 ohms (NC1200) to 500 watts 4 ohms (AHB2) is not really apples to apples is it?

You are probably right about not hearing the 1%, but then there is perception... and 1% THD destroys me mentally, whether it affects my hearing or not... you should know that by now.

 

[RichB]

A pair of the Apollon NC2000 are about 5K with shipping.

If it is 500 to 800 WPC, then that is less than 3 dB.
I trust the protection mechanisms in the AHB2 over any kit amp.

I agree with @AJ Soundfield, you ears will be compressing. Most speakers will be compressing but I think many correlate compression and distortion with "loud".

- Rich

 

[Sonnie Parker]

With reasonable distortions number it will be considerably more than 800 watts. Although I don't consider 1% reasonable, that number is upwards of 2000 watts.

But I won't be going to a kit amp. I'm going back to the Magtechs with regulated power supply. They don't need a protection circuit... so I won't have to worry about plenty of power and/or flashing lights. I think the Benchmarks would be fine for most setups, but my OCD is definitely kicking in while using them. I've always admired Roger's amp design and should have stuck with them several years back when I had them in my room, but the timing was not right financially.

 

[AJ Soundfield]

However, that would equate to considerably less power into 4 ohms, pretty sure of that too. No reason to wiggle around it.
I still like to compare apples to apples with ratings, and the 15A's are nominally rated at 4 ohms. So comparing 1000 watts 2 ohms (NC1200) to 500 watts 4 ohms (AHB2) is not really apples to apples is it?

You're not understanding how voltage sources work. The amp sees the entire load, NOT "4 ohms".

 

[Sonnie Parker]

You're not understanding how voltage sources work. The amp sees the entire load, NOT "4 ohms".

I understand... but still each amp is going to see the same load, so compare the wattage at what each one sees, not one at 4 ohms and another at 2 ohms. Those 15A's are somewhere around 100 ohms in the midrange, right? Either way, they are rated at 4 ohms, so that is the nominal rating we use to compare them in general.

 

[AJ Soundfield]

You should spend $100 and see what you're missing...the actual impedance curve that the amp drives

 

[RichB]

I may snag me up a couple of the Magtechs from Sanders... they have regulated power supplies. I've had those before and can get a very good deal. I've emailed him about them.

Yeah... I don't know... two different amp manufacturers, one I know is an electrical engineer, said that .52 ohms can cause amps issues, although it would require very moderate levels to do so, which apparently I'm reaching.

Both LEDs flash at the max volume I can reach.

I'm not familiar with how to measure them as you are referencing... volt meter? What settings, how to proceed... I'll try it.

By both LEDs, do you mean the left and right Clip or Temp on a channel?

The Temp indicates current clipping, which means the amplifier could not supply cannot supply the power required to maintain the voltage.

Even thought the 15As have low impedance, I have read that they have resistive behavior, so should the load is not going to have a lower effective resistance found in speaker with high-phase angles.

The Stereophile review for these speakers is not detailed and even the efficiency claims are suspect, given they are based on measurements with an iPhone 6. Nobody thought the bring a $150 mic.

- Rich

 

[AJ Soundfield]

The Magtech get as minus for no measurements, but a plus for the cat picture, so its a wash.
Like the NC1200, 2000...and most likely AHB2, not going to be "audible".
Just pick the nicest looking one without clip indicator

 

[RichB]

The Magtech get as minus for no measurements, but a plus for the cat picture, so its a wash.
Like the NC1200, 2000...and most likely AHB2, not going to be "audible".
Just pick the nicest looking one without clip indicator

ATI amps have peak indicators but do not illuminate when my voltage measurements indicate they are clearly clipping. I suppose that is why ATI called them peak indicators, they have their design and quality goals and have always stood by them.

- Rich

 

[RichB]

@Sonnie, if you are running your 15As full range, those built in 500 WPC amps driving the bass units and drivers will be running out of gas where a great deal of energy lies.

It could be the a clean amp is allowing the upper section to remain unobjectionable while the bass units are compressing. An amp with more distortion may dissuade you from turning up the volume.

- Rich

 

[Sonnie Parker]

I believe the Temp lights flash first... then the clip lights at the loudest volume.

Wayne and Dennis listen louder than I do when testing (hurts my ears)... but we've had more powerful amps during those evaluations/tests in previous years.

I thought I had a link to the 15A's impedance measurement... can't seem to find it... gotta start bookmarking stuff. Thought it was Stereophile, but not seeing it there.

The 15A's are self powered on the subs, and those crossed over at 50Hz to my 4 SB16-Ultras, so there's barely a load there I would think. It's all happening up top.

 

[ddude003]

The Martin Logan spec for those 15A's are: "Impedance Nominal: 4 ohms, 0.5 ohms @ 20 kHz"... I don't think they go from 4 to 0.5 in a spike... All the Graphs I have seen, all the ESLs roll from ~4 ohms to ~0.5 ohms on down from ~10kHz to ~20kHz...

 

[AJ Soundfield]

I thought I had a link to the 15A's impedance measurement... can't seem to find it... gotta start bookmarking stuff. Thought it was Stereophile, but not seeing it there.

Hence my PE link.
It probably looks something like this other "4 ohm" ML

As I've tried to explain to you, the amp sees that entire load, including 2ohms at 8k where there is plenty content.
Get whatever allays your audiophic-psychosis, just beware that it helps to have, oh say 1Kw at 2ohm capability when you drive a real load.

cheers

 

[ddude003]

Who listens to Garth? That's young girl stuff, or at least use to be.

I didn't know that young girls liked balding old men with pot bellies... I guess I still stand a chance after all...

And if your playing MQA content there will be lots of noise at 20kHz and above...

 

[Sonnie Parker]

Hence my PE link.
It probably looks something like this other "4 ohm" ML
View attachment 41574

As I've tried to explain to you, the amp sees that entire load, including 2ohms at 8k where there is plenty content.
Get whatever allays your audiophic-psychosis, just beware that it helps to have, oh say 1Kw at 2ohm capability when you drive a real load.

cheers

I should be well north of 1000 watts at 2 ohms using the Magtech. If I can't find the chart for the 15A, then I'll order that PE gizmo. But I suspect it's similar.

I didn't know that young girls liked balding old men with pot bellies... I guess I still stand a chance after all...

And if your playing MQA content there will be lots of noise at 20kHz and above...

You ain't right, but in Garth's defense, when he was singing back in the day, he was slimmer... can't say as to the bald part, but the girls couldn't see it for the cap.

The next question is can you sing like Garth... it matters.

No MQA here.... nope! Very funny though... very funny indeed.

 

[ddude003]

The next question is can you sing like Garth... it matters.

Raised on the west coast... No twang or drawl to my singing voice... And I drive fast, ride hard and shoot straight... Redneck enough for here in Missouri...