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

Garrincha

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I am aware that a state of the art amplifier should not have a specific sound, the mystical wire with a gain. Most important features to grant this are linear frequency response, low SINAD, IMD and crosstalk and a high SNR. But often the damping factor and the slew rate are discussed (mostly in subjectivist circles) . Could they have any significant influence on the sonic qualities?
 

MakeMineVinyl

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Slew rate is not much of an issue today, but if an amplifier has a too-low damping factor, this can cause frequency response irregularities and lack of control of the woofer. Most solid state amplifiers today have good damping factor. Tube amps are the most likely to be deficient if DF.
 

DonH56

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Yes.

Slew rate is rarely an issue unless bandwidth is very limited or leads to high levels of distortion through poor slew performance (e.g. TIM due to limited slew and feedback, or nonlinear behavior during heavy slew due to lack of current deliver capacity and so forth). All solved problems these days, and slew limitations will appear in things like distortion measurements.

Damping factor is inversely related to and amplifier's output impedance and thus a measure of how the frequency response and other system performance metrics like distortion change due to interaction with the speaker's impedance and current/voltage "kickback". See e.g. https://www.audiosciencereview.com/...amping-factor-and-speakers.23968/#post-807327 for a discussion of how frequency response changes. Dynamic transients can also be impacted by the amplifier's output impedance, affecting the distortion generated by the speaker.

And so forth.

No magic, science can explain the effects.

FWIWFM - Don
 
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Garrincha

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So to sum it up, any irregularities of slew rate or damping factor, even when not measured itself, would should up in the other, standard measurements, like FR and distortion and the like?
 

MakeMineVinyl

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So to sum it up, any irregularities of slew rate or damping factor, even when not measured itself, would should up in the other, standard measurements, like FR and distortion and the like?
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. Its still best to do slew rate and DF measurements specifically. At any rate, you can be reasonably confident that slew rate or DF limitations are not likely to show up in modern well made amplifiers.
 
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Garrincha

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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. Its still best to do slew rate and DF measurements specifically. At any rate, you can be reasonably confident that slew rate or DF limitations are not likely to show up in modern well made amplifiers.
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?
 

solderdude

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AFAIK Damping Factor (output resistance/load impedance) is not measured for speaker amps by Amir.
Also the effect it has is highly load and frequency dependent and DF needs to be really low to become audible < 25 or so.

If the slew rate becomes an issue (unlikely with modern SS amps) this is kind of shown in full power bandwidth measurements.
For bandwidth limited amps such as tube amps and class-D it is another matter.
 
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Prana Ferox

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As stated above, they're non-issues in remotely modern solid state amplifiers. In amps where they might be concerns (poorly designed tube amps, ancient iron) they take a back seat to other factors.
 

MakeMineVinyl

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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?
They are routinely so good in modern amplifiers that there's really no point in measuring them. Stereophile and some other magazines measure damping factor (really output impedance) but slew rate is rarely measured.
 
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HarmonicTHD

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For example Benchmark, Neurochrome Mod268, 686 and others have damping factors in the hundreds (I couldn’t find figures on the fly for Purifi, but most likely the same).

Slewrate dito (Bandwidth) no Problem.

As said above, these factors are a non-issue for modern well engineered amps. (Tube amps mostly differ).
 
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pma

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So to sum it up, any irregularities of slew rate or damping factor, even when not measured itself, would should up in the other, standard measurements, like FR and distortion and the like?
Very low damping factor ==> frequency response modulated by speaker complex impedance.
Do not forget that damping factor is frequency dependent, especially in class D amplifiers with no PFFB and typically 10uH output L.

Low slew rate ==> poor IMD 19kHz+20kHz distortion and poor high frequency THD (THD10kHz, THD20kHz).

Damping factor to be more than 50 and slew rate must not affect 19+20k IMD, slew rate to be about 5x higher than highest possible dv/dt of the amplifier output voltage.
For sine wave, dv/dt = 2 x pi x F x Vpeak, [Hz], [V].
 

dominikz

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pma

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Slewrate dito (Bandwidth) no Problem.
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.
 

DSJR

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my nearly half century old prosumer power amps made a big thing about damping factor. Looking back, I think the main reason they were so concerned was the thin 'bell wire' we routinely used as speaker cables back then and the 'high damping factor' promotion was their way to put a tech spin on the need for a good gauge speaker cable (they even provided a chart in their user and service manuals which weren't that different from each other really).. I also suspect that th etypical US home may well use longer speaker cable lengths than here in the UK (>10m?).
 

Mnyb

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Very low damping factor ==> frequency response modulated by speaker complex impedance.
Do not forget that damping factor is frequency dependent, especially in class D amplifiers with no PFFB and typically 10uH output L.

Low slew rate ==> poor IMD 19kHz+20kHz distortion and poor high frequency THD (THD10kHz, THD20kHz).

Damping factor to be more than 50 and slew rate must not affect 19+20k IMD, slew rate to be about 5x higher than highest possible dv/dt of the amplifier output voltage.
For sine wave, dv/dt = 2 x pi x F x Vpeak, [Hz], [V].
I forgot to mention that . Thanks .

“Old type “ or cheap class D can have to high output impedance in the treble , for a long time class D was only fit for subwoofers , nowadays with recent generation of designs it can be mitigated and the results are that it should not be a factor , but it would not hurt to check if theamp uses PFFB . In Purifi and Hypex modules it’s a given .
But it can be so that in some other cases it’s up to the designers to implement this feedback or not .
 

Mnyb

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Not really only in the bass some old class D exhibits quite a peak or dip in the treble with the "wrong" speaker , so the effekt on fr is there .
But i agree that its not much actual "damping" going on there .

Sidetrack . in active speakers where there is no series induktors or resistors to the drivers , the DF can be much better .
 
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