Why didn't they choose an AVR?

[AcuDefTechGuy]

Me too, if the slew rate is in fact too low for comfort. The 16 V per microsecond of the AHB2 is, as RichB pointed out, still very good with 100 kHz bandwidth for the rated 100 W. My only little concern is that it may not be great for speakers that have high impedance peaks well above 8 ohms especially if that happens in the lower bass frequencies. In that case it may not perform so perfectly if pushed near the 100 W mark on transient peaks.

Wow, a $200 Harman Kardon 70W receiver has a slew rate of 40 V/micro sec, and this $3,000 Benchmark amp has a slew rate of only 16 V/micro sec ?

Perhaps that's why Stereophile experienced the loss of that bell-like richness!

I just looked up the slew rate on my ATI 3005 & 2005 amps and they are 50 V/micro sec. So at least they are higher than a $200 receiver.


Conclusion: This $3K Benchmark amp

1. Clips at 108W/8 ohms (less power output than many AVR - the Denon X4000 AVR - which you can buy on sale for $799 on Amazon - can output 149W x 2 ch into 8 ohms)

2. Has a Slew Rate of 16 V/uS (2.5 times lower than a $200 HK receiver)

3. Will only sound good with some speakers. For other speakers, please use a Receiver or other amps.

 

[highfigh]

Wow, a $200 Harman Kardon 70W receiver has a slew rate of 40 V/micro sec, and this $3,000 Benchmark amp has a slew rate of only 16 V/micro sec ?

Perhaps that's why Stereophile experienced the loss of that bell-like richness!

I just looked up the slew rate on my ATI 3005 & 2005 amps and they are 50 V/micro sec. So at least they are higher than a $200 receiver.

Any data on the slew rates of other AVRs from Denon, Yamaha, etc. ?

50V/uS used to be the number people looked for, to see if the amp designer was serious about this. 16? Kinda weak, IMO.

This article from AH states that 32V/uS relates to flat bandwidth of 100KHz.

********EDIT*******

I guess it would have been more informative if I had included the link.

http://www.audioholics.com/audio-amplifier/amplifier-slew-rate

 

[Mikado463]

My only little concern is that it may not be great for speakers that have high impedance peaks well above 8 ohms especially if that happens in the lower bass frequencies. .

Peng, that would be well outside the norm wouldn't it ? with the exception of electrostatics most dynamic speakers imp falls in the lower octaves.

 

[3db]

Just out of curiosity, does slew rate even matter so long as an amplifier can achieve at least 50khz flat?

Sent from my LM-X210(G) using Tapatalk

Frequency response and slew rate are both important but slightly different. Slew rate indicates the amp's ability to follow the rising edge of a fast rising signal (dv/dt) all the way to its peak. Amps with low slew rates will not be able to follow this signal causing a skewed signal output and introducing distortion into the signal chain. A lot manufacturers advertise very low distortion rates, far below audibilty (which in itself is totally dumb) and fail to mention the more important spec of slew rate.

 

[highfigh]

Frequency response and slew rate are both important but slightly different. Slew rate indicates the amp's ability to follow the rising edge of a fast rising signal (dv/dt) all the way to its peak. Amps with low slew rates will not be able to follow this signal causing a skewed signal output and introducing distortion into the signal chain. A lot manufacturers advertise very low distortion rates, far below audibilty (which in itself is totally dumb) and fail to mention the more important spec of slew rate.

Which begs the question- if this amp's THD is in the .0032% range, how is it possible that the slew rate is only 16V/uS? Low slew rate (and the associated rise time spec that nobody talks about) means the amp reacts and follows the signal quickly and as long as it doesn't ring, it doesn't add much distortion.

Some friends had a band in the early-'80s, called 'dv/dt'. I asked and he confirmed that it was the time derivative for acceleration- he had gone back to school as a Theoretical Mathematics major and it was a pretty appropos name for the band.

 

[AcuDefTechGuy]

A lot manufacturers advertise very low distortion rates, far below audibilty (which in itself is totally dumb) and fail to mention the more important spec of slew rate.

Benchmark has Slew Rate of 16V/uS.

HK receiver has a slew rate of 40V/uS.

Parasound Halo has a slew rate of 130V/uS.

http://www.parasound.com/a23.php


Mark Levinson did not list any slew rate either, although it's probably the same as ATI (50-60V/uS) - also Monolith, Outlaw, Cary Audio, etc.


Bryston listed the slew rate at 60V/uS.


Anthem amps' slew rate is 30V/uS.

https://www.anthemav.com/products-current/type=amplifier/model=mca-225/page=specs

Krell - slew rate = 40V/uS.

http://www.krellonline.com/stereo-amps.html#Duo125


McIntosh, PASS, NAD, Rotel, ADCOM, Emotiva, Crown, QSC, Yamaha, Marantz, Denon - no slew rate listed.

 

[RichB]

Why would one use the "4 ohm" setting? Receiver amp vs an external power amp was always a compromise based on needs....has that particularly changed over the years?

Amps clip differently, some more gracefully than others. A common view is that distortion continues to increase to level and the amp sounds bad. This is certainly true but some amps have limiters that reduce clipping artifacts but change the balance of the sound (clipping does this as well); bass may simply not be produced at the same level as the rest of the signal.

Some AVRs have limiters that are engaged when the amps is set to 4 Ohms. For those who are curious and want to hear what less power or limiting sounds like, this setting can be used for direct comparison.

For those who are not curious, simply leave it a the higher 6 or 8 ohms setting as recommended by AH.

- Rich

 

[3db]

Which begs the question- if this amp's THD is in the .0032% range, how is it possible that the slew rate is only 16V/uS? Low slew rate (and the associated rise time spec that nobody talks about) means the amp reacts and follows the signal quickly and as long as it doesn't ring, it doesn't add much distortion.

All this means that the slew rate is high enough to follow the leading edge of the signal.. ie rise time like you said. I was talking about if the slew rates were low and couldn't keep up with the rise time.

QUOTE="highfigh, post: 1231773, member: 36433"]Some friends had a band in the early-'80s, called 'dv/dt'. I asked and he confirmed that it was the time derivative for acceleration- he had gone back to school as a Theoretical Mathematics major and it was a pretty appropos name for the band.[/QUOTE]

 

[Verdinut]

The question is: "Can someone hear the difference between a low voltage and a higher voltage slew rate?"
I read somewhere that a SS amplifier slew rate was irrelevant for practical purposes.

Another question: How does the slew rate of a tube amp compare with that of a typical SS amp?

 

[Verdinut]

While we're at it, another question:
What about an amplifier which would have a very fast slew rate but a poor output damping factor? Would the advantage of that fast slew rate be killed?

 

[AcuDefTechGuy]

The question is: "Can someone hear the difference between a low voltage and a higher voltage slew rate?"

It depends on whether they have golden ears or not.

If they can hear the difference between every single amp, DAC, and every different SNR and THD, then they can hear the difference between slew rates and damping factors too.

 

[PENG]

Peng, that would be well outside the norm wouldn't it ? with the exception of electrostatics most dynamic speakers imp falls in the lower octaves.

Sort of, but not totally true, take a look of the graphs below. They all have some relatively high impedance peaks below 100 Hz, but I forgot what I was thinking at the time as I really meant to say impedance peaks in the high frequencies. For low frequency, even 8 V/micro sec is plenty, obviously.

 

[PENG]

Just out of curiosity, does slew rate even matter so long as an amplifier can achieve at least 50khz flat?

Sent from my LM-X210(G) using Tapatalk

Yes and no, no because it also depends on the output power/voltage. The higher the voltage the faster the dv/dt rate needs to be. Again, no one is saying 16 V/micro second is not good enough for a 100 V amp as the reviewer (forgot which one) did say it would still be good for 100 kHz bandwidth, that's way pass the 20 kHz many of us cannot hear anyway. My added minor concern is for some speakers that have unusually higher impedance in some the audible high frequencies, that would cause need the output voltage to be higher, so I would feel better with 32 V/micro second even for a 100 W rated amp.

 

[PENG]

While we're at it, another question:
What about an amplifier which would have a very fast slew rate but a poor output damping factor? Would the advantage of that fast slew rate be killed?

No, slew rate affects the very high frequencies not the bass frequencies unless it is ridiculously low.

 

[PENG]

Which begs the question- if this amp's THD is in the .0032% range, how is it possible that the slew rate is only 16V/uS? Low slew rate (and the associated rise time spec that nobody talks about) means the amp reacts and follows the signal quickly and as long as it doesn't ring, it doesn't add much distortion.

Some friends had a band in the early-'80s, called 'dv/dt'. I asked and he confirmed that it was the time derivative for acceleration- he had gone back to school as a Theoretical Mathematics major and it was a pretty appropos name for the band.

Great point, they typically measured THD up to 20,000 Hz. As indicated in the review RichB linked, even at that relatively low slew rate, the AHB2 would have a bandwidth of 100 kHz. I have never seen anyone measured THD at even 25 kHz. Of course slew rate is measured as dv/dt it is stated as volt per second afterall, obviously dv/dt (v=velocity) for a car is acceleration. That why the reviewer also mentioned the rated power. At 200 W into 8 ohms, the AHB2's output voltage would have to be higher, so at the same dv/dt, it would take longer to reach the peak voltage required for the particular load it is driving.

 

[Mikado463]

I forgot what I was thinking at the time as I really meant to say impedance peaks in the high frequencies.

OK, that's what I thought you meant. Again though, keep in mind electrostatics behave in the opposite , their impedance dips in the upper octaves. So where that would be of greater concern with a dynamic driver (amplifier clipping distortion destroying the fragile tweeter driver) it is not the issue with an electrostatic.

 

[PENG]

OK, that's what I thought you meant. Again though, keep in mind electrostatics behave in the opposite , their impedance dips in the upper octaves. So where that would be of greater concern with a dynamic driver (amplifier clipping distortion destroying the fragile tweeter driver) it is not the issue with an electrostatic.

Thank you for bring up electrosatic speakers. I have to agree, you can say the same about THD+N, SNR, frequency response etc. etc., and at the end of the day it is more about marketing and bragging right. To say 16 V/microsecond being too low is like saying 0.05% THD+N is too high, or damping factor 50 too low and yet people seems so forgiving on loudspeakers relatively much uglier measured performance.

 

[AcuDefTechGuy]

Thank you for bring up electrosatic speakers. I have to agree, you can say the same about THD+N, SNR, frequency response etc. etc., and at the end of the day it is more about marketing and bragging right. To say 16 V/microsecond being too low is like saying 0.05% THD+N is too high, or damping factor 50 too low and yet people seems so forgiving on loudspeakers relative much uglier measured performance.

Oh, no, it doesn’t matter how much distortion and noise the speakers cause or anything else (like Room Acoustics), as long as the amps have the lowest possible THD and highest SNR, the amp will sound better than other amps.

You think eargiant will say, “Slew Rates and Damping Factors don’t matter - only 130dB SNR and 0.0000001% THD matter.”?

 

[AcuDefTechGuy]

No, slew rate affects the very high frequencies not the bass frequencies unless it is ridiculously low.

I think most audiophiles equate slew rate to the treble and damping factor to the bass, right?

 

[highfigh]

The question is: "Can someone hear the difference between a low voltage and a higher voltage slew rate?"
I read somewhere that a SS amplifier slew rate was irrelevant for practical purposes.

Another question: How does the slew rate of a tube amp compare with that of a typical SS amp?

A lot of the performance in a tube amp depends on the output transformer(s). They do just fine at high frequencies with transformers that are capable- Allen Bradley used McIntosh MC-75 amps for data transfer but I don't know what the baud rate was- I suspect it was pretty low, since this amp came out in 1961.