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    Moderated By: Maxxwire
    Agoraquest Forum Index Ľ Ľ Amp/Receiver/Speakers/Connections/Cables
      
    Damping Factor,what does it mean? Dashboard
    Replies: 37 | Views: 23,644
    Last Reply: October 12, 2005, 3:21 pm

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    Craig_Nike | Keithant | Maxxwire | AaronB | SPCOOLIN | jttar | jehill | DocVijay | mykyll2727 | Navmaster | yuriv |
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    Author Damping Factor,what does it mean?
    Keithant

    Rank: Sony Addict


    Joined: Aug 06, 2002
    Posts: 179
    From: Rome NY

      Posted: 2005-10-01 17:52

    Hello,could someone explain to me what Damping factor is in a power amp.I am looking at a Sony 150 watt/channel power amp on ebay that has a Damping factor of 40 but my 100 watt/channel HK power amp has a Damping Factor of 80.What does this factor mean and does it affect sound or have anything to do with the quality of the amp?I have even seen some amps as high as 200.Thanks for any info,Keith.

    [ This message was edited by: Keithant on 2005-10-01 19:04 ]


       


    SPCOOLIN
    Premium Member

    Rank: Ultimate Sony Reviewer


    Joined: Jan 20, 2003
    Posts: 3627
    From: Tampa Bay FL.

      Posted: 2005-10-01 18:49

    Keith,

    Damping factor is a measurement indicating an amps ability to control the speakers cone....The higher the value the better it controls the cones movement for things like fast bass.....

    That's my understanding.

    Is this the same Sony amp you asked about in your previous thread?

    Steve~

    -----------------
    Spcoolin's Web Site:

    http://marine-ac.com/




       
    Keithant

    Rank: Sony Addict


    Joined: Aug 06, 2002
    Posts: 179
    From: Rome NY

      Posted: 2005-10-01 19:02

    SPCOOLIN,yes it is the Sony TA-N611 Power Amp..Thanks,Keith.


       
    Maxxwire
    Moderator
    Premium Member

    Rank: Sony Adept


    Joined: Aug 29, 2002
    Posts: 26057
    From: Portland, Oregon - USA

      Posted: 2005-10-02 01:03

    Definitions for damping factor-

    (1) A factor defined as the rated load divided by the amplifier output impedance.

    (2) The ability of an amplifier to control the motion of a loudspeaker cone after a signal disappears, ie, its ability to defeat the natural ringing tendency of the body (cone) in motion.

    An amplifier with a high damping factor looks more like a kind of short circuit to the speaker, reducing its vibration when the signal stops.

    ~Maxx~


    -----------------
    A Satisfied Sony Fan Since 1974!



    The OCCC Furu-Charged Sony DB 930


         
    yuriv

    Rank: Sony Devotee


    Joined: Jul 07, 2005
    Posts: 80
    From: Coral Springs, FL

      Posted: 2005-10-02 07:58

    To make the info in Maxxís post more explicit, try this neat experiment: disconnect your speakers and (gently!) tap on the woofer cone. You might hear a tubby sound because the bass overhang is longer, i.e., it takes a while for the sound to decay. Now short the speaker terminals and try it again. The sound should be tighter this time. This effect is a direct consequence of Faradayís law and Lenzís law. A short circuit or an amp with a high DF doesnít block back EMF, which stops the speakerís ringing.

    Because a speaker's impedance is a function of frequency, so is the effective DF. Reading the specs that jehill posted in your other thread, we can see that the TA-N611ís damping factor at 1 kHz into an 8-ohm load is 40. That means that the TA-N611ís output impedance at 1 kHz is about 0.2 ohms. (8 / 0.2 = 40). If you have long runs of thin speaker wire, the effective speaker damping might go down. A damping factor of 40 is low for a solid-state amp, but you should be fine with most 8-ohm speakers. The DF might even go up at lower frequencies. Hereís a comparison with some amps that I own or have played with:

    Adcom GFA-535L: 130 (20 Hz Ė 20 kHz)
    Alesis RA300: 200 (no frequency given)
    Bryston 2B LP Pro: >500 at 20 Hz.
    Bryston 3B SST: >300 at 20 Hz.
    Crown K1: >3000 (10 Hz Ė 400 Hz)
    Hafler P3000: 400 at 1 kHz, 200 at 10 kHz, 18 at 100 kHz.
    Hafler TA1600: 350 at 1 kHz, 150 at 10 kHz, 18 at 100 kHz.
    Mackie M1400/M1400i: >350 from 0 to 400 Hz
    QSC RMX 1450: >300 at 1 kHz and below

    Thereís a lot of interesting information (and debate) on amplifier damping factor online. Itís a good thing the TA-N611 specs donít list the slew rate and the CMRR so you donít have to worry about them.

    I hope youíve heard the TA-N611 in action before. If not, youíre doing the same thing I did with the GFA-535LóI bought one on e-bay without listening to it first. But I got lucky because I liked what I got; that amp is in a bedroom system now. So, good luck with your auction.


    [ This message was edited by: yuriv on 2005-10-02 08:01 ]


       
    mykyll2727

    Rank: Sony Pro


    Joined: Apr 30, 2004
    Posts: 4171
    From: Las Vegas

      Posted: 2005-10-02 13:52

     Does anyone know the damping factors of the 5k, 9k, and 7100ES receivers? I can't seem to find them. _9.6/9kS.W.Mike


       
    jehill
    Premium Member

    Rank: Sony Senior Advisor


    Joined: Mar 13, 2003
    Posts: 14278
    From: Sewell, NJ

      Posted: 2005-10-02 15:36

    The damping factors are not listed.  That fact suggests that they are low.  A contributing factor to a low damping factor in the digital amps is the low pass filters required to filter out the switching frequency.  As frequency increases, the impedance of the series inductors increases, effectively increasing the output impedance of the amp and reducing the damping factor.  True, the impedance of the capacitance across the speaker decreases, but how effective would two 0.27 uF capacitors in series (0.135 uF total, the value in an STR-DA5000ES) be in damping a speaker?  Yet, many people rave about the tube like sound of the amps and enjoy them immensely!  I suspect that a low damping factor is a contributing factor to the tube like sound.  Lets face it.  There is no way that the output impedance of a tube amp can be as low as a conventional solid state amp.  I used to have an amp that had a DF or 1000.  I could tell the difference between that amp and another with a DF of 200 when driving my Bose 901s.  I didn't imagine the difference.  The bass was noticeably tighter.

    -----------------
    -John

    Sony A/V System: KDL-55XBR8, BDP-S550 and AVD-LA2500PKG, consisting of AVD-C70ES Super Audio CD/DVD Receiver, 4 SS-LA500ED surround speakers, 1 SS-LAC505ED center channel speaker and 1 SA-WD200 Active Subwoofer


       
    Maxxwire
    Moderator
    Premium Member

    Rank: Sony Adept


    Joined: Aug 29, 2002
    Posts: 26057
    From: Portland, Oregon - USA

      Posted: 2005-10-03 00:28







    • Member Quote

    On 2005-10-02 15:36, jehill wrote: Yet, many people rave about the tube like sound of the (Digital) amps and enjoy them immensely!††









    I suspect that†a low damping factor is a contributing factor to the tube like sound.† Lets face it.† There is no way that the output impedance of a tube amp can be as low as a conventional solid state amp.



    When I auditioned the DA5000ES thought that it sounded Tubelike in the sense that that it had a smooth and detailed delivery, but the other distinctive qualities of Tube amplification such as a lush liquid midrange, abundant instrumental bloom and the ability to recreate an ultracomplex harmonic structure in a magically lifelike manner is strictly in the domain of Tube amplification.

    If low damping factor were a root cause of this performance then any Amp with a low damping factor would have these traits which does not appear to be the case.

    What is the case for many Audiophiles who crave huge amounts of tight bass is that they bi-amp their speakers by using a high powered Solid State Amp with a very high damping factor to power the woofer and Tube amplification to power the midrange and tweeter.


    Audio is full of trade-offs, but if you use the strengths of each type of amplification a very listenable compromise can be made where you end up with the best of both worlds.


    As the owner of a Conrad-Johnson MV-52 Tube Power Amp which has Push-Pull 6CA7 Fatboys wired in low impedance Ultralinear Mode I wanted to inclue a note about this particular type of Tube output configuration where each channel has-


    A push-pull pair of 6CA7's operating in "enhanced" class-A/B, with screen grids tied to the output transformer's primary so the tubes can deliver more power than if they were used in triode modeóyet also sound sweeter and exhibit a 750% lower output impedance than if they were used in pure pentode mode.


    Tube-amp enthusiasts will recognize that as an Ultralinear output circuit, which was first patented in 1937.


    ......................


    ~Maxx~




    -----------------
    A Satisfied Sony Fan Since 1974!



    The OCCC Furu-Charged Sony DB 930

    [ This message was edited by: Maxxwire on 2005-10-04 23:26 ]


         
    yuriv

    Rank: Sony Devotee


    Joined: Jul 07, 2005
    Posts: 80
    From: Coral Springs, FL

      Posted: 2005-10-03 06:48

    Even though Sony doesnít make the damping factor specs available, we can compute an upper bound if we know the values of some of the components on the board. Iím imagining that the scenario looks like the ones for the Tripath and TI Equibit designs:

    Switching transistors --> Inductor --> (0.135 uF in parallel with the speakers)

    For comparison, see the sample application schematic on page 6 of the Tripath TA3020 data sheet.

    At low frequencies, where high DF makes for tighter bass, the 0.135 uF capacitance in parallel with the speaker shouldnít negatively affect speaker damping. Let see, at 20 Hz 100 Hz, and 1 kHz, the reactance should be around 59 k ohms, 12 k ohms, and 1.2 k ohms, respectivelyómuch higher than the speaker impedance if Iím doing my calculations properly (Z = -jXc = 1/(j (omega) C) = 1/ (j 2 pi f C)).

    The Tripath and TI designs use something around 10 uH for the inductor, effectively a 0.001-ohm, 0.006-ohm, 0.06-ohm series impedance at 20 Hz, 100 Hz, and 1 kHz, respectively using Z = jXl = j(omega)L = j 2 pi f L. If the S-Master Pro amps also use a 10 uH inductor, then the DF at 1 kHz is at best 8 ohms / 0.06 ohms = 15.9. Ouch.

    Using the same reasoning, for 100 Hz DF = 159 at best. At 20 Hz, DF = 796 at best (the impedance of the transistors might come into play, so actual DF might be much lower). At these bass frequencies, these figures for DF are pretty good. In fact, they shouldnít cause a switching amp to produce flabby bass. My experience with my amps seems to agree with these numbers; the T-amp (Tripath TA2024) and Panasonic SA-XR50 (TI Equibit TAS5182) switching amps produce tight bass; kick drums have a crisp slam on these amps. Thereís no reason the S-Master Pro receivers should be any different.

    In fact, my Alesis RA300 does worse in this regard despite having a damping factor of 200 (no frequency referenced). Thatís the problem with specs; itís sometimes hard to tell whatís really going on. For example, my Adcom has a minimum DF of only 130 from 20 Hz to 20 kHz. But I suspect that itís much higher at low frequencies because bass sounds more controlled on the Adcom than on the Alesis. If the TA-N611 has DF = 40 at 1 kHz for an 8-ohm load, and it doesnít get better at low frequencies, then DF = 20 for Keithís 4-ohm speakers might not be satisfactory, depending on how picky we are.

    Methinks the problem with these digital switching amps isnít the bass, but the other end of the spectrum. At 20 kHz, the 0.135 uF capacitance is 59 ohms in parallel with the speakers (harmless?). The bigger problem is the 10 uH inductor which now has a series impedance of 1.25 ohms. If the speakerís impedance is low at 20 kHz, say 3 ohms, then the response wonít be flat. (JVC claims to have fixed this problem. Iíd like to see how they did it without upping the switching frequency.)

    Furthermore, we have to worry about how well the LPF rejects the switching PWM noise. This depends on the switching frequency. For the TI Equibit, itís 8 Fs = 8 * 44.1 kHz = 352.8 kHz. For the Tripath chips itís variable between 200 kHz and 1.2 MHz depending on the level of the input signal. I havenít heard the Sharp 1-bit amps, which switch at 2.8 MHz or 5.6 MHz. Those should sound good because they can have an LPF with a higher cutoff frequency, and so should be more transparent at 20 kHz. Does anybody here know what the switching frequency is for the S-Master amps?

    Anyway, at 352.8 kHz, 0.22 uF becomes 2 ohms. 10 uH becomes 22 ohms. If these values were used for L and C, how well does it attenuate a 352.8 kHz signal? Assuming an 8-ohm purely resistive speaker load, the voltage divider looks like (8 || -j2) / (j22 + (8 || -2)). This is roughly 2/20 = 1/10 = 0.1 = -20 dB. Iím sure thereís something wrong with my math, because it sounds a little too high, even if I am off by a factor of 10.

    Someone please find a flaw in these arguments and calculations, which were made in haste. Jehill? Maxx?


    [ This message was edited by: yuriv on 2005-10-03 06:51 ]


       
    Craig_Nike

    Rank: Ultimate Sony Reviewer


    Joined: Apr 05, 2002
    Posts: 2262
    From: Australia

      Posted: 2005-10-03 08:21

    I have to stop coming here, you guys are too smart.

    I dont understand a single word of this thread.
    Somebody else please say they are confused so that I am not on my own here.....

    -----------------
    This is the last thing I need for my HT - now i'm finished!

    AVR: STR-DA9000ES & STR-DA5300ES
    AMP: TA-N9000ES
    BLU: PS3
    DVD: 999ES & 777ES
    SPKR: SS-X70ED, SS-XCN70ED, SS-LA500ED
    SUB: SAW-X700M


         
    AaronB

    Rank: Sonyphile


    Joined: Nov 26, 2002
    Posts: 624
    From: Ottawa, Canada

      Posted: 2005-10-03 09:15

    Quote:
    8 ohms / 0.06 ohms = 15.9



    You'd best double check your calculations. The result is a respectable 133, not a paltry 15.9.


    [ This message was edited by: AaronB on 2005-10-03 14:17 ]


       
    yuriv

    Rank: Sony Devotee


    Joined: Jul 07, 2005
    Posts: 80
    From: Coral Springs, FL

      Posted: 2005-10-03 12:10


    • Member Quote

    On 2005-10-03 09:15, AaronB wrote:
    Quote:
    8 ohms / 0.06 ohms = 15.9



    jehill,

    You'd best double check your calculations. The result is a respectable 133, not a paltry 15.9.


    Aaron,
    The error is not jehill's. It is mine. Thank you. I need to get some more sleep. . I'm off by a factor of 8. At 100 Hz, DF is at best 1333. So there you go, but that doesn't change my conclusion that the LPF should not be a problem at the low end and that the bigger problem is in the other end of the spectrum. My digital amps seem to have authoritative bass. DF < 133 (maybe much less) also confirms jehill's suspicion that the DF at 1 kHz might be low enough that Sony doesn't publish a spec. Well, they could "cheat" and do what Crown and Mackie do, which is to give a minimum number up to 400 Hz, which sounds kinda arbitrary. That's one problem with specs. I'd like to know the value of L in the S-Master amps so we can make a comparison.


    Craig,
    As you can see, I'm not that smart. Try Jehill and Maxx. We just want to know if we can figure out what's going on. All of this stuff you can look up online if you're interested.



       
    jehill
    Premium Member

    Rank: Sony Senior Advisor


    Joined: Mar 13, 2003
    Posts: 14278
    From: Sewell, NJ

      Posted: 2005-10-03 14:26

    Not that anyone really needs to know this, but there are actually two LPFs, one in series with each speaker lead.  This is necessary because each amp is actually two amps in a bridge circuit.  Each LPF is two stages, i.e. a second inductor and capacitor is across the first capacitor.  The two capacitors are connected to ground.  The values are L1 = 10 uH, C1 = 0.75 uF, L2 = 10 uF, C2 = 0.27 uF.  In addition, there is another 0.75 uF capacitor, call it C3, connected between the hot sides of the two C1s.  Interestingly enough, each of the two filters in the STR-DA7100ES is only a single stage.  L1 = 10 uH and C1 = 1 uF.  L2, C2 and C3 are omitted.  If you like to do calculations, have a ball!  I'm not about to!

    -----------------
    -John

    Sony A/V System: KDL-55XBR8, BDP-S550 and AVD-LA2500PKG, consisting of AVD-C70ES Super Audio CD/DVD Receiver, 4 SS-LA500ED surround speakers, 1 SS-LAC505ED center channel speaker and 1 SA-WD200 Active Subwoofer


       
    jttar
    Moderator
    Premium Member

    Rank: Sony Master


    Joined: Feb 28, 2003
    Posts: 9228
    From: Chicago,IL, USA

      Posted: 2005-10-03 22:50






    On 2005-10-03 08:21, Craig_Nike wrote:
    I have to stop coming here, you guys are too smart.

    I dont understand a single word of this thread.
    Somebody else please say they are confused so that I am not on my own here.....


    Craig,

    I'm in the same boat as you. I was following along pretty good until yuriv started speaking Latin.   Still, that's what I like about coming here, always something to learn.

    Joe


         
    Keithant

    Rank: Sony Addict


    Joined: Aug 06, 2002
    Posts: 179
    From: Rome NY

      Posted: 2005-10-03 22:56

     Thanks Guy's,very informative.My brain is OOZING with knowledge now.Peace,Keith.


       
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