Subject: Re: USB sound cards From: "Richard F. Lyon" <dicklyon@xxxxxxxx> Date: Sat, 13 Dec 2014 08:06:05 -0800 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>--089e0158b5c6c5a800050a1b2f09 Content-Type: text/plain; charset=UTF-8 Yes, adding a resistor will tend to increase, not decrease, frequency dependence of the voltage across the load. But that voltage may not be the key variable; power might be more important. Either way, it's hard to predict which will "sound better". Dick On Sat, Dec 13, 2014 at 4:35 AM, Anders Tornvig Christensen <atc@xxxxxxxx> wrote: > Interesting discussions. I would be curious to do the impedance test > Richard suggests, to dampen the headphone resonance. But if you consider > the setup 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 = 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 = 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 > reactive elements and resonances, such that some added resistance in the > driving circuit would lead to higher damping and a more even response. > Someone should do a test, starting with impedance measurements of various > headphones to see if they have identifiable resonances. It might turn out > that adding resistance is a good thing, for scientific perceptual > experiments or otherwise. I wouldn't be surprised either way. > > Dick > > > On Fri, Dec 12, 2014 at 3:36 PM, Steve Beet <stevebeet@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 >> why >> 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 On Behalf Of Bob Masta >> Sent: 11 December 2014 17:03 >> To: 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 >> for >> consumer use, where anyone can plug in most anything that fits the jack, >> manufacturer's typically add some output impedance. >> > > --089e0158b5c6c5a800050a1b2f09 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr">Yes, adding a resistor will tend to increase, not decrease= , frequency dependence of the voltage across the load.=C2=A0 But that volta= ge may not be the key variable; power might be more important.=C2=A0 Either= way, it's hard to predict which will "sound better".<br><br>= Dick<br><br></div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote"= >On Sat, Dec 13, 2014 at 4:35 AM, Anders Tornvig Christensen <span dir=3D"l= tr"><<a href=3D"mailto:atc@xxxxxxxx" target=3D"_blank">atc@xxxxxxxx</a= >></span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 = 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> <div> <div style=3D"direction:ltr;font-family:Tahoma;color:#000000;font-size:10pt= ">Interesting discussions. I would be curious to do the impedance test Rich= ard suggests, to dampen the headphone resonance. But if you consider the se= tup a simple voltage divider between source and load impedance, wouldn't you predict the opposite r= esult? That a relatively bigger source resistance RS increases voltage fluc= tuations 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> <div style=3D"direction:ltr"><font face=3D"Tahoma" color=3D"#000000"><b>Fro= m:</b> AUDITORY - Research in Auditory Perception [<a href=3D"mailto:AUDITO= RY@xxxxxxxx" target=3D"_blank">AUDITORY@xxxxxxxx</a>] on beha= lf of Richard F. Lyon [<a href=3D"mailto:dicklyon@xxxxxxxx" target=3D"_blank= ">dicklyon@xxxxxxxx</a>]<br> <b>Sent:</b> Saturday, December 13, 2014 7:09 AM<span class=3D""><br> <b>To:</b> <a href=3D"mailto:AUDITORY@xxxxxxxx" target=3D"_blank">AU= DITORY@xxxxxxxx</a><br> <b>Subject:</b> Re: USB sound cards<br> </span></font><br> </div> <div></div> <div><span class=3D""> <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.=C2=A0 Someone should do a test, starting with impedance measurements of various headphones to see if they have iden= tifiable resonances.=C2=A0 It might turn out that adding resistance is a go= od thing, for scientific perceptual experiments or otherwise.=C2=A0 I would= n't be surprised either way.<br> <br> Dick<br> <br> </div> </span><div><div class=3D"h5"><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:1p= x #ccc solid;padding-left:1ex"> This may be a red herring, but I've seen some self-proclaimed "aud= iophile"<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 sugges= t why<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 qua= lity.<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 increa= sing<br> the resistance.<br> <span><font color=3D"#888888"><br> Steve Beet<br> </font></span> <div> <div><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.=C2=A0 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.=C2=A0 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> </div> </div> </div> </blockquote></div><br></div> --089e0158b5c6c5a800050a1b2f09--