Subject: Re: USB sound cards From: Anders Tornvig Christensen <atc@xxxxxxxx> Date: Sat, 13 Dec 2014 12:35:52 +0000 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>--_000_2DC307A9A8F2AA4F9051AD6874B268B59879D4A1ADEXCHMBX21aaud_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Interesting discussions. I would be curious to do the impedance test Richar= d suggests, to dampen the headphone resonance. But if you consider the setu= p a simple voltage divider between source and load impedance, wouldn't you = predict the opposite result? That a relatively bigger source resistance RS = increases voltage fluctuations across the load impedance ZL (and decreases = the overall voltage). VL/VS =3D ZL/(ZL+RS) The electroacoustic transfer function from V to Pa is unchanged. The situation is different if you have a current source VL/IS =3D ZL*RS/(ZL+RS) I guess, in this case, you would aim for just one but either one of ZL and = RS to be large relative to the other. Best, Anders ________________________________ From: AUDITORY - Research in Auditory Perception [AUDITORY@xxxxxxxx= on behalf of Richard F. Lyon [dicklyon@xxxxxxxx Sent: Saturday, December 13, 2014 7:09 AM To: AUDITORY@xxxxxxxx Subject: Re: USB sound cards It seems not unlikely that headphones (or speakers) might have some reactiv= e elements and resonances, such that some added resistance in the driving c= ircuit would lead to higher damping and a more even response. Someone shou= ld do a test, starting with impedance measurements of various headphones to= see if they have identifiable resonances. It might turn out that adding r= esistance is a good thing, for scientific perceptual experiments or otherwi= se. I wouldn't be surprised either way. Dick On Fri, Dec 12, 2014 at 3:36 PM, Steve Beet <stevebeet@xxxxxxxx<mailto:ste= vebeet@xxxxxxxx>> wrote: This may be a red herring, but I've seen some self-proclaimed "audiophile" publications which claim that when headphones are driven from a resistive source impedance of a few tens of Ohms, they "sound better" than when they are driven from an ideal (very low impedance) voltage source. As far as I recall, these statements were referring to listening tests of professional-quality headphones with nominal impedances of 200 Ohms. These publications didn't present any analytical measurements to suggest wh= y this might be the case, but the output resistance added to many headphone amps might not be there solely to prevent damage or distortion - it might also be to persuade audiophiles that they're getting the best sound quality= . For music produced and mixed to be listened to via loudspeakers, it may be that adding a series resistor might indeed make the headphones sound more like the original mixing engineer or producer intended, but for scientific perceptual experiments I can't see any advantage in artificially increasing the resistance. Steve Beet -----Original Message----- From: AUDITORY - Research in Auditory Perception [mailto:AUDITORY@xxxxxxxx<mailto:AUDITORY@xxxxxxxx>] On Behal= f Of Bob Masta Sent: 11 December 2014 17:03 To: AUDITORY@xxxxxxxx<mailto:AUDITORY@xxxxxxxx> Subject: Re: USB sound cards However, there *is* a problem getting low output impedance as well. The native design of modern amplifier stages has essentially zero output impedance due to negative feedback (milliohms or less). That means that if you connect such an amp to a low-impedance load, the current draw can be high... high enough to damage the output stages, or at least cause massive distortion as they go into protective current limiting. Since these are fo= r consumer use, where anyone can plug in most anything that fits the jack, manufacturer's typically add some output impedance. --_000_2DC307A9A8F2AA4F9051AD6874B268B59879D4A1ADEXCHMBX21aaud_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <html dir=3D"ltr"> <head> <meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3Diso-8859-= 1"> <style id=3D"owaParaStyle" type=3D"text/css">P {margin-top:0;margin-bottom:= 0;}</style> </head> <body ocsi=3D"0" fpstyle=3D"1"> <div style=3D"direction: ltr;font-family: Tahoma;color: #000000;font-size: = 10pt;">Interesting discussions. I would be curious to do the impedance test= Richard suggests, to dampen the headphone resonance. But if you consider t= he setup a simple voltage divider between source and load impedance, wouldn't you predict the opposite resul= t? That a relatively bigger source resistance RS increases voltage fluctuat= ions across the load impedance ZL (and decreases the overall voltage). <br> <br> VL/VS =3D ZL/(ZL+RS) <br> <br> The electroacoustic transfer function from V to Pa is unchanged.<br> <br> The situation is different if you have a current source<br> <br> VL/IS =3D ZL*RS/(ZL+RS)<br> <br> I guess, in this case, you would aim for just one but either one of ZL and = RS to be large relative to the other.<br> <br> Best, Anders<br> <br> <div style=3D"font-family: Times New Roman; color: #000000; font-size: 16px= "> <hr tabindex=3D"-1"> <div style=3D"direction: ltr;" id=3D"divRpF972204"><font face=3D"Tahoma" si= ze=3D"2" color=3D"#000000"><b>From:</b> AUDITORY - Research in Auditory Per= ception [AUDITORY@xxxxxxxx on behalf of Richard F. Lyon [dicklyon@xxxxxxxx= CM.ORG]<br> <b>Sent:</b> Saturday, December 13, 2014 7:09 AM<br> <b>To:</b> AUDITORY@xxxxxxxx<br> <b>Subject:</b> Re: USB sound cards<br> </font><br> </div> <div></div> <div> <div dir=3D"ltr">It seems not unlikely that headphones (or speakers) might = have some reactive elements and resonances, such that some added resistance= in the driving circuit would lead to higher damping and a more even respon= se. Someone should do a test, starting with impedance measurements of various headphones to see if they have iden= tifiable resonances. It might turn out that adding resistance is a go= od thing, for scientific perceptual experiments or otherwise. I would= n't be surprised either way.<br> <br> Dick<br> <br> </div> <div class=3D"gmail_extra"><br> <div class=3D"gmail_quote">On Fri, Dec 12, 2014 at 3:36 PM, Steve Beet <spa= n dir=3D"ltr"> <<a href=3D"mailto:stevebeet@xxxxxxxx" target=3D"_blank">stevebeet@xxxxxxxx= o.com</a>></span> wrote:<br> <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex; border-left:1= px #ccc solid; padding-left:1ex"> This may be a red herring, but I've seen some self-proclaimed "audioph= ile"<br> publications which claim that when headphones are driven from a resistive<b= r> source impedance of a few tens of Ohms, they "sound better" than = when they<br> are driven from an ideal (very low impedance) voltage source. As far as I<b= r> recall, these statements were referring to listening tests of<br> professional-quality headphones with nominal impedances of 200 Ohms.<br> <br> These publications didn't present any analytical measurements to suggest wh= y<br> this might be the case, but the output resistance added to many headphone<b= r> amps might not be there solely to prevent damage or distortion - it might<b= r> also be to persuade audiophiles that they're getting the best sound quality= .<br> <br> For music produced and mixed to be listened to via loudspeakers, it may be<= br> that adding a series resistor might indeed make the headphones sound more<b= r> like the original mixing engineer or producer intended, but for scientific<= br> perceptual experiments I can't see any advantage in artificially increasing= <br> the resistance.<br> <span class=3D"HOEnZb"><font color=3D"#888888"><br> Steve Beet<br> </font></span> <div class=3D"HOEnZb"> <div class=3D"h5"><br> <br> -----Original Message-----<br> From: AUDITORY - Research in Auditory Perception<br> [mailto:<a href=3D"mailto:AUDITORY@xxxxxxxx" target=3D"_blank">AUDIT= ORY@xxxxxxxx</a>] On Behalf Of Bob Masta<br> Sent: 11 December 2014 17:03<br> To: <a href=3D"mailto:AUDITORY@xxxxxxxx" target=3D"_blank">AUDITORY@xxxxxxxx= LISTS.MCGILL.CA</a><br> Subject: Re: USB sound cards<br> <br> However, there *is* a problem getting low output impedance as well. T= he<br> native design of modern amplifier stages has essentially zero output<br> impedance due to negative feedback (milliohms or less). That means that if<= br> you connect such an amp to a low-impedance load, the current draw can be<br= > high... high enough to damage the output stages, or at least cause massive<= br> distortion as they go into protective current limiting. Since these a= re for<br> consumer use, where anyone can plug in most anything that fits the jack,<br= > manufacturer's typically add some output impedance.<br> </div> </div> </blockquote> </div> <br> </div> </div> </div> </div> </body> </html> --_000_2DC307A9A8F2AA4F9051AD6874B268B59879D4A1ADEXCHMBX21aaud_--