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  1. #1

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    Default Damping factor values in Amplifiers

    I have a question regarding damping factor ratings on amps. You see the values listed in the specs of every amp.And they are all over the place for differant ss amps. But how important are they?
    As I understand, a high damping factor indicates that an amplifier will have greater control over the movement of the speaker cone especially at low frequencies (20Hz) and therfore a higher value you would think would be better. But the damping factor is also dependant on the resistance of the voice coil in the speaker and the output impedance of the amp itself. Maybe also if you have cheap speaker cable the resistance of the cables might also lower damping factor. So there are other factors.
    Here is my main question, do high damping values in solid state amps indicate high levels of negative feedback design(to control distortion) by lowering the output impedance of the amp? Is this a bad design? Some have disliked the high levels of negative feedback in amps (therefore higher damping factors).
    Here is the thing, I am looking at two amps. One having a damping factor of >150@20hz and the other having a value >1100@ 20 hz. Will I be able to tell the differance? Especially since the amps is only driving my fronts with everything above 80HZ (Everything below 80HZ is redirected to my subs) Is a damping factor of greater than 150 good enough? And maybe a better design?
    Thanks,Dave

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    It is nothing more (or less) than a measure of the output impedance of the amplifier; DF is the ratio of the nominal load impedance to the amp output impedance. A DF of 100 into an 8 ohm (nominal) load means the amplifier's output impedance is 8/100 = 0.08 ohms (80 milliOhms).

    It is essentially a useless specification for a couple of reasons: the nominal impedance of the load is just that (nominal) for most types of real-world loudspeakers (although there are some loads - most ribbons and some planar drivers - that behave essentially as purely resistive loads at audio frequencies) and low output impedance was (!) traditionally obtained using very high levels of global negative feedback.

    That said, it is possible to apply feedback carefully or indiscriminately; one cannot simply conclude "global negative feedback is bad". It is also possible to lower output impedance in other ways (e.g, paralleled output devices), so there's no easy blanket statement.

    Generally, though, DF per se -- like many hifi specs -- is "a great sound and fury signifying nothing" IMO.

    FWIW, I'd recommend that you stop "looking at two amps" and start "listening to two amps".
    Last edited by mhardy6647; 08-25-2011 at 08:29 AM.
    all the best,
    mrh

  3. #3
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    @dekuda..check this link out...it should help you understand more about amps ..Damping...of -/+ return of the current too and from you speakers..http://www.audioholics.com/education...dio-amplifiers...
    Last edited by ctank; 08-25-2011 at 09:06 AM.

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    FWIW - There are factual mistakes in that link (e.g., in number 7, the author confuses harmonic distortion spectra of single ended vs. push-pull topologies with vacuum tube vs. solid state distortion spectra)... so I'd recommend reading it carefully, critically, and amply cross-referenced.
    all the best,
    mrh

  5. #5
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    @mhardy6647..+1...@7 in the link...post read...check factual..where his input not fact..OP was asking about Damping..didn't Sony on there ES line..stop using that class amp..push/pull?..

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    Quote Originally Posted by mhardy6647 View Post
    It is nothing more (or less) than a measure of the output impedance of the amplifier; DF is the ratio of the nominal load impedance to the amp output impedance. A DF of 100 into an 8 ohm (nominal) load means the amplifier's output impedance is 8/100 = 0.08 ohms (80 milliOhms).

    It is essentially a useless specification for a couple of reasons: the nominal impedance of the load is just that (nominal) for most types of real-world loudspeakers (although there are some loads - most ribbons and some planar drivers - that behave essentially as purely resistive loads at audio frequencies) and low output impedance was (!) traditionally obtained using very high levels of global negative feedback.

    That said, it is possible to apply feedback carefully or indiscriminately; one cannot simply conclude "global negative feedback is bad". It is also possible to lower output impedance in other ways (e.g, paralleled output devices), so there's no easy blanket statement.

    Generally, though, DF per se -- like many hifi specs -- is "a great sound and fury signifying nothing" IMO.

    FWIW, I'd recommend that you stop "looking at two amps" and start "listening to two amps".
    Thanks for your feedback! If I could get both amps and compare them that would be the solution. But costs being what they are that is not possible at this time. One of them is available,Parsound 5250. The other one I missed my chance on,a Parasound 2205AT. Both good amps but huge differances in damping at 20hz. Do not know why unless the 2205at is that much better of a amp. But like you said if it not a important factor then I will not worry about it.
    Last edited by dekuda; 08-25-2011 at 11:19 AM. Reason: spelling

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    Damping factor is overrated. Tube amps tend to have lower damping factor than SS amps, the numbers the manufacturers give 1) aren't all measured by the same procedure 2) anything over 200 is good and the higher number has very minimal impact on the entire equation 3) these measurements aren't taken in real world use. ie; just looking at damping factor as criteria to purchase one amp over another is ludicris since there are many, many other more important factors.

    Sure a tube amp with a damping factor of say 25 and a SS amp with a damping factor of 300 might sound different, but there are many other factors that could be at work as well.

    Another term everyone gets wrapped around the axel about is slew rate, another pretty much meaningless measurement that people like to either quote or use as the basis for buying one amp over the other.
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

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    Quote Originally Posted by ctank View Post
    @dekuda..check this link out...it should help you understand more about amps ..Damping...of -/+ return of the current too and from you speakers..http://www.audioholics.com/education...dio-amplifiers...
    This link from the above one talks about damping factor specifically.
    http://www.audioholics.com/education...ystem-response

    Two point to throw in
    - once the DF is above 20-50, higher numbers result in increasingly vanishing differences in performance.
    - a DF of 1150 is > 150 and >1100, so it's possible that there might be no actual difference in the DF of the amps cited by the OP.
    cristo

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    Quote Originally Posted by heiney9 View Post
    Damping factor is overrated. Tube amps tend to have lower damping factor than SS amps, the numbers the manufacturers give 1) aren't all measured by the same procedure 2) anything over 200 is good and the higher number has very minimal impact on the entire equation 3) these measurements aren't taken in real world use. ie; just looking at damping factor as criteria to purchase one amp over another is ludicris since there are many, many other more important factors.

    Sure a tube amp with a damping factor of say 25 and a SS amp with a damping factor of 300 might sound different, but there are many other factors that could be at work as well.

    Another term everyone gets wrapped around the axel about is slew rate, another pretty much meaningless measurement that people like to either quote or use as the basis for buying one amp over the other.
    I agree that there are much more important considerations in buying a amp. But I was just wondering why the numbers varyied so greatly between two amps made by the same manufacturer. I basicly got my answer here and I thank all of you for responding. Notice, I was only refering to solid state amps.

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    I have amplifiers with adjustable damping, this is truly something that improves sound quality....as it tailoring the to the individual pair of speakers. Application improves speakers Sound Qualtiy across the board whether entry level or something more esoteric...so dampening in itself is important, just as current flow, however, I dont rush see what a manufacturer lists as there are problems with the spec as previously posted about.

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    Quote Originally Posted by reeltrouble1 View Post
    I have amplifiers with adjustable damping, this is truly something that improves sound quality....as it tailoring the to the individual pair of speakers. Application improves speakers Sound Qualtiy across the board whether entry level or something more esoteric...so dampening in itself is important, just as current flow, however, I dont rush see what a manufacturer lists as there are problems with the spec as previously posted about.

    RT1
    Is that on a modern amp? That's interesting.

    Adjustable damping on some of the better vacuum tube power amps wasn't uncommon in the late 1950s/early 1960s, but it pretty much disappeared thereafter. Didn't know it had made a comeback.

    Here, e.g., is a 1959 Knight (Allied Radio Corp.) EL37 push-pull mono power amp with variable damping (0.5 to 50).

    all the best,
    mrh

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    2001 model so "new" in comparison to the 40's-50's. I was actually a bit suprised at the difference in SQ heard at the Fest in 09 when we hooked them to some Tsi500. Micah and I were doing some listening and the tsi were bloating, a bit of adjustment and the bass tightened noticeable. The circuit was designed by Henry Wolcott, the Wolcott were built to run Roger West's speaker design which have impendance swings near short circuit. His designs present a diffulcult load and I had initially purchased and used them for the Sound Lab. I suppose another example of applying older proven techniques to a circuit.

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  13. #13
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    Quote Originally Posted by mhardy6647 View Post
    FWIW - There are factual mistakes in that link (e.g., in number 7, the author confuses harmonic distortion spectra of single ended vs. push-pull topologies with vacuum tube vs. solid state distortion spectra)... so I'd recommend reading it carefully, critically, and amply cross-referenced.
    I also have many issues with that article. It's an interesting read, but not gospel truth.

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    I would agree that it is far more important to listen than to read and compare specs.

    The two primary sollis state amps I use have wildly different damping factor "ratings".

    My old (1967-1979) solid state McIntosh MC-250 is 50 watts/channel and is listed as having a damping factor of only 38 at 8 ohms.

    My modern solid state Rotel RB-1080 is 200 watts/channel and is listed as having a damping factor of 1000 at 8 ohms.

    I prefer the bass response of the McIntosh over the Rotel in many cases with speakers that usually have "tight" (at least not flabby) bass response characteristics like A/D/S, Dahlquist, Canton, etc.

    Maybe in some situations a "loose" amp compliments a "tight" speaker, especially if you don't use a separate subwoofer, Also maybe since most of the preamps I use (Antique Sound Labs Line 1, Forte 44, Cayin TA-30 do not have any tone controls or loudness buttons that would let you boost the bass.
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    Some interesting info above. As for damping...those specs are all over the map. Some great amps have damping factors that aren't as good as some crappy amps and vice versa. Trust your ears first.

    But Ted's unit? The ability to match or adjust damping to a particular set of speakers...that is pretty cool!

    As per mhardy's post though, isn't almost all your stuff 'tube' gear, Ted? I guess what I mean is; does anyone know of any SS gear that allows for such adjustments?

    cnh
    Last edited by cnh; 08-25-2011 at 06:05 PM.

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    of course my gear glows...Tubes Rule.

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    Amen.
    In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence.

    "The best way to enjoy digital music reproduction is to never listen to good analogue reproduction". - Kenneth Swauger

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    The technical study by Pierce linked in #8 above illustrates that damping factor is rarely of audible significance in modern amplifiers. Factors anywhere in the double digits are sufficient to reduce any problem with a peak at the bass resonance frequency to insignificance and to maintain decay time at inaudibly low levels. Factors of 20, 200 or 2000 are all fine and only manufacturer hype lends imaginary special significance to the higher numbers.

    The only modern exceptions to the insignificance noted would be some tube amplifiers with output impedance of several ohms, resulting in damping factors around 1 or 2. With well-designed equipment this is another of the effects that can be measured but can't be heard.

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    Quote Originally Posted by John K. View Post
    The technical study by Pierce linked in #8 above illustrates that damping factor is rarely of audible significance in modern amplifiers. Factors anywhere in the double digits are sufficient to reduce any problem with a peak at the bass resonance frequency to insignificance and to maintain decay time at inaudibly low levels. Factors of 20, 200 or 2000 are all fine and only manufacturer hype lends imaginary special significance to the higher numbers.

    The only modern exceptions to the insignificance noted would be some tube amplifiers with output impedance of several ohms, resulting in damping factors around 1 or 2. With well-designed equipment this is another of the effects that can be measured but can't be heard.
    Thanks John K for a precise a definitive answer. It was not that I considered this a major reason in choosing a amp. Far from it. I just wanted a explanation on the wide varience of values given and what if any differance it would make to the sound. From the answers here it looks like it does not really matter that much.

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    another area where adjustable damping is important is your chimney flue,

    left it closed once after starting a fire, it was like a lucy episode.

    hope this info helps.
    humpty dumpty was pushed

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    [QUOTE=dekuda;1637899]I have a question regarding damping factor ratings on amps. You see the values listed in the specs of every amp.And they are all over the place for differant ss amps. But how important are they?
    As I understand, a high damping factor indicates that an amplifier will have greater control over the movement of the speaker cone especially at low frequencies (20Hz) and therfore a higher value you would think would be better. But the damping factor is also dependant on the resistance of the voice coil in the speaker and the output impedance of the amp itself. Maybe also if you have cheap speaker cable the resistance of the cables might also lower damping factor. So there are other factors.
    Here is my main question, do high damping values in solid state amps indicate high levels of negative feedback design(to control distortion) by lowering the output impedance of the amp? Is this a bad design? Some have disliked the high levels of negative feedback in amps (therefore higher damping factors).
    Here is the thing, I am looking at two amps. One having a damping factor of >150@20hz and the other having a value >1100@ 20 hz. Will I be able to tell the differance? Especially since the amps is only driving my fronts with everything above 80HZ (Everything below 80HZ is redirected to my subs) Is a damping factor of greater than 150 good enough? And maybe a better design?
    Thanks,Dave[/QUOTE




    You won't hear a difference caused by the damping factor. Yes a damping factor of 150 is good enough.
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    [QUOTE=DON73;1640106]
    Quote Originally Posted by dekuda View Post
    As I understand, a high damping factor indicates that an amplifier will have greater control over the movement of the speaker cone especially at low frequencies (20Hz) and therfore a higher value you would think would be better. Yes a damping factor of 150 is good enough.
    I was told dampening factor is only real important for a subwoofer amp , but a weak dampening factor is helped if your desired amp has more wattage than you need .
    I would think for your desired amp running above 80 hz you will hear a cold/weak sounding amp first .
    Amplifiers sound quality is a very personall thing , I think to make a good decision look for a largest majority of favorable votes .

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    [QUOTE=20hz;1640254]
    Quote Originally Posted by DON73 View Post

    I was told dampening factor is only real important for a subwoofer amp , but a weak dampening factor is helped if your desired amp has more wattage than you need .
    I would think for your desired amp running above 80 hz you will hear a cold/weak sounding amp first .
    Amplifiers sound quality is a very personall thing , I think to make a good decision look for a largest majority of favorable votes .
    I do not understand, why would the amp be weak/cold if I am driving the speakers above 80HZ. From most everyone's response, I should have no concerns.

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    What factors make an amp a "fast" amp? I guess I wrongly assumed that this was related to damping factor and slew rate.
    Stan
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    [QUOTE=dekuda;1640826]
    Quote Originally Posted by 20hz View Post

    I do not understand, why would the amp be weak/cold if I am driving the speakers above 80HZ. From most everyone's response, I should have no concerns.
    Just a bad sounding amp , like it has no warm midrange .
    For example I had a onkyo 501 it sounded bad compared to my adcom .
    I would play a cd for a whole side and than try the other amp adjusted to the same volume .
    Well some people base their decision completely on other peoples opinions
    ( I dont know if you do that ) but if you do look at it as a majority for example 90% of the people really liked this certain amp .

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