Do damping factor, slew rate and the like have possibly any influence on the "sound" of an amplifier?

[pma]

'damping factor' only matters at woofer frequencies and any number well above 10 is good enough.

This is oversimplified statement. Damping factor is a ratio between load impedance and output impedance. Both are complex functions and frequency response is modulated according to this complex impedance divider. This is physics, electrical engineering and electrical circuits rule. No subjective opinion matters. I have shown numerous measurements here that show influence of output impedance to various speakers frequency response. I will not make a search job, I expect that any qualified reader understands.

 

[rwortman]

Please take into account that slew rate and bandwidth are not directly related. Bandwidth is often defined as a small signal parameter, especially in opamp datasheets. But slew rate is a large signal related parameter. You may have very wide bandwidth and low slew rate at the same moment with the same component.

But not power bandwidth which more of interest in a power amplifier.

 

[Alexanderc]

Some good DF discussion here: https://www.audiosciencereview.com/...tor-benchmark-myth-busting-white-paper.13826/

 

[Mnyb]

Some good DF discussion here: https://www.audiosciencereview.com/...tor-benchmark-myth-busting-white-paper.13826/

Thanks this modifies a bit on Tooles findings from the 70’s

Audio Myth - "Damping Factor Isn't Much of a Factor"

Myth - "Damping Factor Isn't Much of a Factor" Myth - "A Damping Factor of 10 is High Enough" Myth - "All Amplifiers Have a High-Enough Damping Factor" Where did these Myths Originate? These myths seem to trace back to a well-known paper (PDF) written by Dick Pierce. His analysis shows that a...

benchmarkmedia.com

 

[Mnyb]

Are not >100 routinely achieved so this is still not a big issue ( but still an existing issue )

Avoid some tube amps and some simple class D amps and your probably never “hear” about this issue again ? Is that fair.

 

[ebslo]

Ok, but as far as I know, Amir never measures these, right? So it would be better he should or it is just too unlikey anythink noteworthy showing up?

Damping factor: He does usually provide a "Load Dependency" plot which shows frequency response for both 4 and 8 Ohm loads. Damping factor as a function of frequency can be inferred from the difference in responses for 4 and 8 Ohm loads.

Slew rate: He also provides a "Power vs. Distortion" plot at several frequencies. A slew-rate limited amplifier would show much higher high-power distortion in the highest frequency plot than in the lower frequency plots.

 

[pma]

Slew rate: He also provides a "Power vs. Distortion" plot at several frequencies. A slew-rate limited amplifier would show much higher high-power distortion in the highest frequency plot than in the lower frequency plots.

You think so? Like this one, right? No.

Regardless of opinion of armchair debaters, the only method to reveal slew limited issue is to measure full swing step response with a wideband oscilloscope. Low frequency instruments like AP limited to 1.5MHz cannot tell it, every real amplifier designer knows this.
What you see has a different reason.

High frequency distortion is a potential secondary effect of the slew rate limitation. It may have different roots.

 

[KSTR]

Slew rate: He also provides a "Power vs. Distortion" plot at several frequencies. A slew-rate limited amplifier would show much higher high-power distortion in the highest frequency plot than in the lower frequency plots.

No. Sometimes there is an increased distortion at high frequencies and high levels, sometimes there isn't.
Slew-limiting is like clipping of any kind, the amp completely leaves stable operation region and any present feedback loop goes open. And just like some amps don't show any distortion increase right before clipping they may or may not show distortion rise before slewing.

 

[restorer-john]

Not as such. They would effect other measurements, but you can't really separate out how much is the influence of slew rate or DF verses what comes from other mechanisms of distortion/frequency response error.

Both a loaded and unloaded frequency repsonse plot gives enough data to derive an accurate DF vs frequency plot.

 

[MakeMineVinyl]

Both a loaded and unloaded frequency repsonse plot gives enough data to derive an accurate DF vs frequency plot.

Yes true, but to do so requires some level of skill in intrepretation. Its far simpler to just have the relevant measurement there in the first place. I always strive to present data which I generate so that it can be plainly and simply used by the least skilled person that would likely be looking at the data.

 

[Davide]

I'd like to ask a completely ignorant question.
Can't the concept of slew rate also apply to current and / or delivered power?

 

[HarmonicTHD]

I'd like to ask a completely ignorant question.
Can't the concept of slew rate also apply to current and / or delivered power?

Correct me if I am wrong, most simply put

U = R x I

And

P = U squared / R

 

[restorer-john]

I'd like to ask a completely ignorant question.
Can't the concept of slew rate also apply to current and / or delivered power?

Slew rate is voltage vs time. It has no relationship to power delivered.

An amplifier with a rated 400V/uS slew rate does not actually swing 400V in 1us. It may only swing 40VRMS over an 8R load. It is usually referenced to microseconds (uS) or perhaps nanoseconds (nS) for ease of comparison.

 

[conman]

If your damping factor is the minimum necessary of say 10, and then you use DSP to tailor the measured frequency response to whatever curve takes your fancy, does it even matter?

 

[CrustyToad]

Check out this test showing the different frequency response of an amp with a low dumping factor

SUMMER MUSINGS: No... Not all amplifiers sound the same (but many do! ;-).

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

 

[wwenze]

If your damping factor is the minimum necessary of say 10, and then you use DSP to tailor the measured frequency response to whatever curve takes your fancy, does it even matter?

That would be like using EQ to fix room reflections vs having a good room to begin with.

 

[HarmonicTHD]

Check out this test showing the different frequency response of an amp with a low du ping factor

SUMMER MUSINGS: No... Not all amplifiers sound the same (but many do! ;-).

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

It just confirms what was said previously: a SOTA amp with a damping factor larger than 10 to 20 will be fine. Keep in mind SOTA amps have damping factors in the order of 100 (200 to 400) across the frequency band. The Pass Amp is ages away from SOTA ( there is a review somewhere on this site - the Pass has many problems, not just damping factor).

 

[restorer-john]

an amp with a low du ping factor

A low duping factor? Most audiophiles seem to go for the highest duping factor they can.

Or that new Chinese brand- Du Ping who make amplifiers?

 

[dominikz]

If your damping factor is the minimum necessary of say 10, and then you use DSP to tailor the measured frequency response to whatever curve takes your fancy, does it even matter?

Given that the result of low damping factor / high output impedance is just a (small) change in frequency response, it is completely fixable by EQ.
However, to do a precise EQ correction you would first need to measure the amplifier output when driving a specific loudspeaker load - and I suspect this would not be trivial for most (non-technical) people. Also, the required EQ correction changes with any new set of loudspeakers you connect to the amp.

Of course, given that the change in FR due to low damping factor / high output impedance is normally small, and variability is mainly located in the LF range, it is usually swamped by room effects, and consequently implicitly taken care of by room EQ.

While I personally like to see amps that have very low output impedance, in my experience this is a relatively secondary issue in most cases - it is more important to have enough clean power. Thankfully these days you don't really have to choose one or the other, as most good amps also have low output impedance.

 

[CrustyToad]

A low duping factor? Most audiophiles seem to go for the highest duping factor they can.

Or that new Chinese brand- Du Ping who make amplifiers?

The former of course xD