Review and Measurements of Benchmark AHB2 Amp

[misterdog]

the possibility that the Benchmark will sound better than the NCore in practice.

Hmmmm.

Why did Amir include all the out of hearing range data ?

 

[Jimbob54]

Hmmmm.

Why did Amir include all the out of hearing range data ?

Did you read the commentary before and after this graph?

 

[tmtomh]

Hmmmm.

Why did Amir include all the out of hearing range data ?

What do you think this graph says about the comment of mine that you quoted?

(And you do realize that the Benchmark is not a Class D amp, yes?)

 

[PGAMiami]

What do you think this graph says about the comment of mine that you quoted?

(And you do realize that the Benchmark is not a Class D amp, yes?)

Not class d, but it does have a regulated switching power supply, which for most audiophiles is a no no. I would think Amir wanted to see whether this was generating noise. You may not hear it but it can damage your tweeters. In my estimation the benefits of a regulated supply far exceed and negatives from it not being a linear power supply. Very very few amplifiers have regulated power supply. I recall some huge Levinsons, 33 and 33H, had regulated power supplies, but not many at all.

 

[misterdog]

Did you read the commentary before and after this graph?

It is like a restaurant scrubbing their parking lot with soap and pad as well as their dishes.

Yes.

 

[misterdog]

(And you do realize that the Benchmark is not a Class D amp, yes?)

Yes.

Built my own N-Cores before building Neurochrome mono's, before owning AHB2.

 

[PGAMiami]

I can understand how some can describe the accuracy of near zero, added distortion, as cold and clinical.

Sibilance however, suggests something else.
I have Quad 989 ESL's with supertweeters and there is no sibilance, through either analogue or digital source.

No sibilance on TAD R1s that have beryllium drivers that are very prone to sibilance. This is the first amp on these that truly had a totally clean top end.

 

[tmtomh]

Not class d, but it does have a regulated switching power supply, which for most audiophiles is a no no. I would think Amir wanted to see whether this was generating noise. You may not hear it but it can damage your tweeters. In my estimation the benefits of a regulated supply far exceed and negatives from it not being a linear power supply. Very very few amplifiers have regulated power supply. I recall some huge Levinsons, 33 and 33H, had regulated power supplies, but not many at all.

Understood RE the PSU - I too appreciate a regulated supply and I too don't feel anything is lost with a properly implemented switching supply instead of a linear one. But RE the NCore, how is a spike at -75dB at 450kHz, or one at -97dB at 100kHz, going to hurt a tweeter?

 

[Doodski]

Understood RE the PSU - I too appreciate a regulated supply and I too don't feel anything is lost with a properly implemented switching supply instead of a linear one. But RE the NCore, how is a spike at -75dB at 450kHz, or one at -97dB at 100kHz, going to hurt a tweeter?

Even if there where enough energy to harm a tweeter what is the frequency response of various tweeters at the upper frequency? I guess they mechanically roll-off.

 

[tmtomh]

Even if there where enough energy to harm a tweeter what is the frequency response of various tweeters at the upper frequency? I guess they mechanically roll-off.

Yes, that's the thinking behind the question I posed to PGAMiami.

 

[PGAMiami]

Even if there where enough energy to harm a tweeter what is the frequency response of various tweeters at the upper frequency? I guess they mechanically roll-off.

I believe Amir’s point is exactly that the AHB2 is clean even at ultrasonic frequencies, and so is the Ncore. Neither will cause a problem with your tweeter. Back in the days of Spectral high bandwidth amplifiers, they could oscillate at ultrasonic frequencies under certain loads. You wouldn’t hear anything and either the amp would destroy itself or destroy your tweeter or both. That was one of the excuses for requiring MIT cables. So even though the tweeters are not able to reproduce these very high frequencies, they can cause problems.

Think of it this way, imagine hooking up a tweeter to a professional radio transmitter. It will fry the tweeter. The test shows these amps do not have this problem.

 

[Jukka]

Rising impedance of coiled drivers usually dwarf the current going through the tweeter at those frequencies. It's better without for sure, but a non-issue.

 

[fpitas]

Rising impedance of coiled drivers usually dwarf the current going through the tweeter at those frequencies. It's better without for sure, but a non-issue.

Yes; unless there's several volts of supersonic stuff, the tweeter will just ignore it.

 

[PGAMiami]

Yes; unless there's several volts of supersonic stuff, the tweeter will just ignore it.

The high frequency oscillation on Spectral amps had a very different genesis than the leakage from a power supply or digital amp. First of all, it was unpredictable and it was not low energy. Certain cable, speaker combinations were more prone to problems. First symptom was the amps would run hot, even with no music playing. Sometimes you could hear lower harmonics on the tweeters. Sometimes the amps burnt first, but other times they fried the tweeters.

This is surely not what we see in modern state of the art amps

 

[fpitas]

The high frequency oscillation on Spectral amps had a very different genesis than the leakage from a power supply or digital amp. First of all, it was unpredictable and it was not low energy. Certain cable, speaker combinations were more prone to problems. First symptom was the amps would run hot, even with no music playing. Sometimes you could hear lower harmonics on the tweeters. Sometimes the amps burnt first, but other times they fried the tweeters.

This is surely not what we see in modern state of the art amps

I think Amir would notice that.

 

[tmtomh]

I think Amir would notice that.

Indeed he would. I honestly don't understand the stubborn persistence some members have when it comes to trying to find every different which way to claim that high-frequency ultrasonic noise from amps can somehow become lower-frequency ultrasonic noise that will damage speakers or compromise frequency response in ways that don't show up in Amir's measurements. I feel like we've been over this repeatedly, and every time the outcome is the same - an endless parade of "but this could theoretically happen" and "this used to happen in the old days" and "this can happen if an amp breaks or is designed in a certain way" that the modern amps we're discussing are not designed. At some point it just seems to become FUD.

 

[fpitas]

Indeed he would. I honestly don't understand the stubborn persistence some members have when it comes to trying to find every different which way to claim that high-frequency ultrasonic noise from amps can somehow become lower-frequency ultrasonic noise that will damage speakers or compromise frequency response in ways that don't show up in Amir's measurements. I feel like we've been over this repeatedly, and every time the outcome is the same - an endless parade of "but this could theoretically happen" and "this used to happen in the old days" and "this can happen if an amp breaks or is designed in a certain way" that the modern amps we're discussing are not designed. At some point it just seems to become FUD.

Some people just distrust class D. I was deeply skeptical until we hooked a friend's UcD180s directly to his horns and listened extensively.

 

[RichB]

Indeed he would. I honestly don't understand the stubborn persistence some members have when it comes to trying to find every different which way to claim that high-frequency ultrasonic noise from amps can somehow become lower-frequency ultrasonic noise that will damage speakers or compromise frequency response in ways that don't show up in Amir's measurements. I feel like we've been over this repeatedly, and every time the outcome is the same - an endless parade of "but this could theoretically happen" and "this used to happen in the old days" and "this can happen if an amp breaks or is designed in a certain way" that the modern amps we're discussing are not designed. At some point it just seems to become FUD.

I don't expect the AP instruments to modulate ultrasonic noise.
If this is to be tested, it would have to involve a variety of tweeters.

IMO, amps should be measured with a bandwidth with no ultrasonic filters applied.

- Rich

 

[tmtomh]

I don't expect the AP instruments to modulate ultrasonic noise.
If this is to be tested, it would have to involve a variety of tweeters.

IMO, amps should be measured with a bandwidth with no ultrasonic filters applied.

- Rich

That’s not how Class D amps are designed to work.

 

[RichB]

That’s not how Class D amps are designed to work.

I am not referring to the amplifier implementation filtering, but the AP filters often used to measure them, so they don't look noisy.

- Rich