Re: USB sound cards ("Richard F. Lyon" )

Subject: Re: USB sound cards From: "Richard F. Lyon" <dicklyon@xxxxxxxx> Date: Thu, 18 Dec 2014 07:33:38 -0800 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY> --001a11398536ed93c9050a7f5072 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable And Jont and JJ and I are EEs, too, I think. Dick On Thu, Dec 18, 2014 at 1:40 AM, Zlatan Ribic <zlatan@xxxxxxxx> wrote: > I think no one in this discussion (except Bob) is "electrical engineer" > Zlatan > > > *From:* Oberfeld-Twistel, Daniel <oberfeld@xxxxxxxx> > *Sent:* Thursday, December 18, 2014 9:43 AM > *To:* AUDITORY@xxxxxxxx > *Subject:* Re: USB sound cards > > Series resistors are often put in for reasons of stability, for example > when driving capacitive loads. An example is shown in figure 2 of the > attached PDF. > > > > I also always believed that a low output impedance is optimal for > precisely controlling a "reactive" load like a loudspeaker, although this > is of course not the most power-efficient design (-> see impendance > -matched transmission lines). At least that is what most texts on amplifi= er > design suggest - but anyway, that might be wrong and hey, I'm only a > psychologist, not an electrical engineer ;-) > > > > [Although I actually had to build a low-noise headphone amplifier for my > PhD experiments, because back then my lab wanted to save the money for > something like a TDT device=E2=80=A6 Interesting experience.] > > > > Best > > > > Daniel > > > > > > PD Dr. Daniel Oberfeld-Twistel > > Johannes Gutenberg - Universitaet Mainz > > Department of Psychology > > Experimental Psychology > > Wallstrasse 3 > > 55122 Mainz > > Germany > > > > Phone ++49 (0) 6131 39 39274 > > Fax ++49 (0) 6131 39 39268 > > http://www.staff.uni-mainz.de/oberfeld/ > > https://www.facebook.com/WahrnehmungUndPsychophysikUniMainz > > > > *From:* AUDITORY - Research in Auditory Perception [mailto: > AUDITORY@xxxxxxxx *On Behalf Of *James Johnston > *Sent:* Thursday, December 18, 2014 6:16 AM > *To:* AUDITORY@xxxxxxxx > *Subject:* Re: USB sound cards > > > > Not sure of your point, Jont. Of course it is the current through the > voice coil that actually moves the diaphragm and thus makes the pressure. > > None the less, the back EMF is key, especially for low-frequency system > designs, and the back EMF is converted to current by both the internal an= d > external resistance. This is a key part of the filter design problem tha= t > makes the system something approximating flat at low frequencies. > > I'm not sure who you think is putting resistors in series, one generally > avoids that, except for the obligatory resistance of a crossover if one i= s > using a passive crossover system. > > > > On Wed, Dec 17, 2014 at 3:51 AM, Jont Allen <jontalle@xxxxxxxx> wrote= : > > Jim + Auditory-list > > While it is true that speakers are "designed" to be driven by the voltage= , > our detailed research has shown that it is the > current that controls the pressure (i.e., force on the cone). If you want > the details I already sent the links, but I'll send them once > more, just in case you missed it. > > The theory of how the current drives the force is given by our ASA > presentation from last month, at the special session on historic > transducers: > > http://hear.ai.uiuc.edu/public/Allen/NK_ASA_Indianapolis.pdf > * Kim and Allen (2014) *Historic transducers: Balanced Armature Receiver > (BAR),* ASA meeting INDY, IN, Oct 30, 2014 pdf > <http://hear.ai.uiuc.edu/public/Allen/NK_ASA_Indianapolis.pdf> > > > The full theory is in a Hearing Research article: > > http://hear.ai.uiuc.edu/public/KimAllenMar20.13.pdf > * Kim, Noori and Allen, J.B. (2013). "Two-port network Analysis and > Modeling of a Balanced Armature Receiver, "Hearing Research, special MEMR= O > 2013 issue (pdf <http://hear.ai.uiuc.edu/public/KimAllenMar20.13.pdf>) > > Ms Kim's (i.e., Noori's) PhD thesis has the most complete story, and is > available directly from her (noorimail@xxxxxxxx). > > Because it is the current that determines the pressure, via the electrica= l > input impedance, and because this impedance can be (i.e., is) reactive > (have inductance), it can be tricky to figure out what is going on. One > must know (i.e., measure) the load impedance, or at least the current. Al= so > the distortion is mostly determined by the nonlinear flux vs current (i.e= ., > B-H curve), as described by Hunt, for example. > Hunt mostly quotes Mott and Minor's BSTJ Jan 1951 article, adding little > new material to their story. > > In the interesting case of the Etymotic ER-3 (insert headphone), they > place a 10 ohm resistor across the input terminals. > So if you try to beat this with a series resistor, you will not be > successful in changing anything, because all the current is going into th= at > 10 ohm resistor. > I opened up one of my ER-3 and cut out the resistor, and then I could see > what was really going on. It worked better too. > > When that ER-3 went back for repairs once, they were shocked to see the > resistor was missing. I had to admit I cut it out, and wanted it left tha= t > way. > > In general, adding a series resistor to your circuit, is working blind. > You will likely get a random result, and random is never better. > Thus I dont advise it unless you are willing to measure the input > impedance and the resulting frequency response of the headphone. While th= ere > are some interesting things you can do with a series impedance, a series > resistor is not one of them. > > Jont Allen > > > > On 12/16/2014 06:12 PM, James W. Beauchamp wrote: > > I agree with Bob. Most loudspeakers are designed to be driven by > > an ideal voltage source. Under this criterion they attempt to get > > the flattest possible response overall. This is not necessarily > > the most efficient response. In fact, some loudspeaker designs, > > like the Small-Thiele closed-box non-vented design, are very > > inefficient. > > > > Jim > > > > Bob Masta wrote: > > From: Bob Masta <audio@xxxxxxxx> <audio@xxxxxxxx> > > Date: Sun, 14 Dec 2014 09:15:19 -0500 > > To: AUDITORY@xxxxxxxx > > Subject: Re: USB sound cards > > > > On 13 Dec 2014 at 21:59, Richard F. Lyon wrote: > > On Sat, Dec 13, 2014 at 5:52 AM, Bob Masta <audio@xxxxxxxx> <audio@xxxxxxxx= arta.com> wrote: > > > > It's the other way around: Adding resistance in the > > driving circuit gives poorer damping. "Damping Factor" for > > a power amplifier is the reciprocal of output impedance. > > > > Bob, I wasn't aware of that definition. > > I was thinking of http://en.wikipedia.org/wiki/Damping_ratio > > rather than http://en.wikipedia.org/wiki/Damping_factor > > Oops, you are correct... I should have said it is > > *proportional* to the reciprocal. > > > > Is there an understanding of why high "damping factor" would be good? > > Jont's findings suggest otherwise (I believe he's saying the current is > > typically more relevant than the volage). > > The second reference you cited covers it under > > "Explanation". Basically, a conventional electrodynamic > > speaker is both a motor and a generator. Imagine that the > > speaker receives a momentary voltage pulse, after which is > > is instantly disconnected from the source. The speaker > > would ring at its resonant frequency, damped only by > > friction. The generator would be creating a voltage, but > > no current, so no load to add damping. > > > > However, if instead of disconnection the leads were > > *shorted* after the pulse, the generator would be driving > > all its current into the zero-ohm load, giving a maximum > > damping effect. > > > > Conventional loudspeakers are designed to be driven by > > voltage sources, not current sources. The current may be > > more "relevant" (in the sense of force generation), but not > > for getting a flat frequency response from a conventional > > speaker design. (Although there have been occasional > > attempts at current drive, the ones I recall required > > special dedicated amplifiers.) > > > > Best regards, > > > > Bob Masta > > > > D A Q A R T A > > Data AcQuisition And Real-Time Analysis > > www.daqarta.com > > Scope, Spectrum, Spectrogram, Signal Generator > > Science with your sound card! > > > > > > -- > > James D. (jj) Johnston > > Independent Audio and Electroacoustics Consultant > --001a11398536ed93c9050a7f5072 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr">And Jont and JJ and I are EEs, too, I think. Dick<b= r> </div><div class=3D"gmail_extra"> <div class=3D"gmail_quote">On Th= u, Dec 18, 2014 at 1:40 AM, Zlatan Ribic <<a href=3D"m= ailto:zlatan@xxxxxxxx" target=3D"_blank">zlatan@xxxxxxxx</a>></spa= n> wrote: <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;b= order-left:1px #ccc solid;padding-left:1ex"> <div style=3D"PADDING-TOP:15px;PADDING-LEFT:10px;PADDING-RIGHT:10px" link= =3D"blue" vlink=3D"purple" name=3D"Compose message area" lang=3D"DE"> <div>I think no one in this discussion (except Bob) = is=20 "electrical engineer"</div> <div>Zlatan</div> <div>=C2=A0</div> <div style=3D"FONT:10pt Tahoma"> <div> </div> <div style=3D"BACKGROUND:#f5f5f5"> <div>From: <a title=3D"mailto:oberfeld@xxxxxxxx STRG + Klicken, um Verkn=C3=BCpfung zu folgen" href=3D"mailto:oberfeld@xxxxxxxx= MAINZ.DE" target=3D"_blank">Oberfeld-Twistel, Daniel</a> </div> <div>Sent: Thursday, December 18, 2014 9:43 AM</div><div><div class= =3D"h5"> <div>To: <a title=3D"mailto:AUDITORY@xxxxxxxx STRG + Klicken, um Verkn=C3=BCpfung zu folgen" href=3D"mailto:AUDITORY@xxxxxxxx= S.MCGILL.CA" target=3D"_blank">AUDITORY@xxxxxxxx</a> </div> <div>Subject: Re: USB sound cards</div></div></div></div></div><div>= <div class=3D"h5"> <div> </div> <div> Series=20 resistors are often put in for reasons of stability, for example when drivi= ng=20 capacitive loads. An example is shown in figure 2 of the attached=20 PDF. =C2=A0 I=20 also always believed that a low output impedance is optimal for precisely= =20 controlling a "reactive" load like a loudspeaker, although this i= s of course not=20 the most power-efficient design (-> see impendance -matched transmission= =20 lines). At least that is what most texts on amplifier design suggest - but= =20 anyway, that might be wrong and hey, I'm only a psychologist, not an el= ectrical=20 engineer ;-) =C2=A0 [Although=20 I actually had to build a low-noise headphone amplifier for my PhD experime= nts,=20 because back then my lab wanted to save the money for something like a TDT= =20 device=E2=80=A6 Interesting experience.] =C2=A0 Best =C2=A0 Daniel =C2=A0 <div style=3D"BORDER-TOP:medium none;BORDER-RIGHT:medium none;BORDER-BOTTOM= :windowtext 1pt solid;PADDING-BOTTOM:1pt;PADDING-TOP:0cm;PADDING-LEFT:0cm;B= ORDER-LEFT:medium none;PADDING-RIGHT:0cm"> <p class=3D"MsoNormal" style=3D"BORDER-TOP:medium none;BORDER-RIGHT:medium = none;BORDER-BOTTOM:medium none;PADDING-BOTTOM:0cm;PADDING-TOP:0cm;PADDING-L= EFT:0cm;BORDER-LEFT:medium none;PADDING-RIGHT:0cm">=C2=A0</= u></div> PD=20 Dr. Daniel Oberfeld-Twistel Johannes=20 Gutenberg - Universitaet Mainz Department=20 of Psychology Experimental=20 Psychology Wallstrasse=20 3 55122=20 Mainz Germany =C2=A0 Phone=20 <a href=3D"tel:%2B%2B49%20%280%29%206131%2039%2039274" value=3D"+4961313939= 274" target=3D"_blank">++49 (0) 6131 39 39274</a> </fo= nt> Fax=C2=A0=C2=A0=20 <a href=3D"tel:%2B%2B49%20%280%29%206131%2039%2039268" value=3D"+4961313939= 268" target=3D"_blank">++49 (0) 6131 39 39268</a></fon= t> <a href=3D"http://www.staff.uni-mainz.de/oberf= eld/" target=3D"_blank">http://www.staff.uni-mainz.de/oberfeld/</a><= u> <a href=3D"https://www.facebook.com/WahrnehmungUndPsychophysi= kUniMainz" target=3D"_blank">https://www.facebook.com/WahrnehmungUndPsychop= hysikUniMainz</a> =C2=A0 <div style=3D"BORDER-TOP:medium none;BORDER-RIGHT:medium none;BORDER-BOTTOM= :medium none;PADDING-BOTTOM:0cm;PADDING-TOP:0cm;PADDING-LEFT:4pt;BORDER-LEF= T:blue 1.5pt solid;PADDING-RIGHT:0cm"> <div> <div style=3D"BORDER-TOP:#b5c4df 1pt solid;BORDER-RIGHT:medium none;BORDER-= BOTTOM:medium none;PADDING-BOTTOM:0cm;PADDING-TOP:3pt;PADDING-LEFT:0cm;BORD= ER-LEFT:medium none;PADDING-RIGHT:0cm"> = From: AUDITORY - Research= =20 in Auditory Perception [mailto:<a href=3D"mailto:AUDITORY@xxxxxxxx" = target=3D"_blank">AUDITORY@xxxxxxxx</a>] On Behalf Of James Johnston Sent: Thursday, December 18, 2014 6:16=20 AM To:=20 <a href=3D"mailto:AUDITORY@xxxxxxxx" target=3D"_blank">AUDITORY@xxxxxxxx= S.MCGILL.CA</a> Subject: = Re: USB sound=20 cards</div></div> =C2=A0 <div> <div> <div> Not sure of your point,= =20 Jont. Of course it is the current through the voice coil that actually move= s the=20 diaphragm and thus makes the pressure.</div= > None the less, the back E= MF=20 is key, especially for low-frequency system designs, and the back EMF is=20 converted to current by both the internal and external resistance.=C2=A0 Th= is is=20 a key part of the filter design problem that makes the system something=20 approximating flat at low frequencies.</div= > I'm not sure who you think is putting resistors in= =20 series, one generally avoids that, except for the obligatory resistance of = a=20 crossover if one is using a passive crossover=20 system.</div> <div> =C2=A0 <div> On Wed, Dec 17, 2014 at 3:51 AM, Jont Allen <<a hre= f=3D"mailto:jontalle@xxxxxxxx" target=3D"_blank">jontalle@xxxxxxxx<= /a>>=20 wrote: <div> Jim + Auditory-list While it is true that=20 speakers are "designed" to be driven by the voltage, our detailed= research has=20 shown that it is the current that controls the pressure (i.e., force on = the=20 cone). If you want the details I already sent the links, but I'll send = them=20 once more, just in case you missed it. The theory of how the curr= ent=20 drives the force is given by our ASA presentation from last month, at the= =20 special session on historic transducers: <a href=3D"http://hear.ai.u= iuc.edu/public/Allen/NK_ASA_Indianapolis.pdf" target=3D"_blank">http://hear= .ai.uiuc.edu/public/Allen/NK_ASA_Indianapolis.pdf</a> *=20 Kim and Allen (2014) Historic transdu= cers:=20 Balanced Armature Receiver (BAR), ASA meeting INDY, IN, Oct= 30,=20 2014 <a href=3D"http://hear.ai.uiuc.edu/public/Allen/NK_ASA_Indianapolis.pd= f" target=3D"_blank">pdf</a> <div> The full theory is in a Hearing Research=20 article: <a href=3D"http://hear.ai.uiuc.edu/public/KimAllenMar20.13.= pdf" target=3D"_blank">http://hear.ai.uiuc.edu/public/KimAllenMar20.13.pdf<= /a> * Kim,=20 Noori and Allen, J.B. (2013). "Two-port network Analysis and Modeling = of a=20 Balanced Armature Receiver, "Hearing Research, special MEMRO 2013 issu= e (<a href=3D"http://hear.ai.uiuc.edu/public/KimAllenMar20.13.pdf" target= =3D"_blank">pdf</a>) Ms Kim's (i.e., Noori's) PhD thesis ha= s the most=20 complete story, and is available directly from her (<a href=3D"mailto:noori= mail@xxxxxxxx" target=3D"_blank">noorimail@xxxxxxxx</a>). Because = it is the current that=20 determines the pressure, via the electrical input impedance, and because th= is=20 impedance can be (i.e., is) reactive (have inductance), it can be tricky to= =20 figure out what is going on. One must know (i.e., measure) the load impedan= ce,=20 or at least the current. Also the distortion is mostly determined by the=20 nonlinear flux vs current (i.e., B-H curve), as described by Hunt, for=20 example. Hunt mostly quotes Mott and Minor's BSTJ Jan 1951 article, = adding=20 little new material to their story. In the interesting case of the= =20 Etymotic ER-3 (insert headphone), they place a 10 ohm resistor across the i= nput=20 terminals. So if you try to beat this with a series resistor, you will = not=20 be successful in changing anything, because all the current is going into t= hat=20 10 ohm resistor. I opened up one of my ER-3 and cut out the resistor, an= d=20 then I could see what was really going on. It worked better too. Whe= n=20 that ER-3 went back for repairs once, they were shocked to see the resistor= was=20 missing. I had to admit I cut it out, and wanted it left that way. I= n=20 general, adding a series resistor to your circuit, is working blind. You wi= ll=20 likely get a random result, and random is never better. Thus I dont advi= se it=20 unless you are willing to measure the input impedance and the resulting=20 frequency response of the headphone. While there are some interesting th= ings=20 you can do with a series impedance, a series resistor is not one of=20 them. Jont Allen <div> <div> On 12/16/2014 06:12 PM, James W. Beauchamp=20 wrote:</div></div></div> <blockquote style=3D"MARGIN-BOTTOM:5pt;MARGIN-TOP:5pt"> <div> <div><pre>I agr= ee with Bob. Most loudspeakers are designed to be driven by</= span></pre><pre>an ideal voltage source. Under this criterion they attempt to get = </pre><pre>the flattest possible response overall. This is not nec= essarily </pre><pre>= the most efficient response. In fact, some l= oudspeaker designs, </pre><pre>like the Small-Thiele closed-box = non-vented design, are very </pre><pre>inefficient.</u= ></pre><pre>=C2=A0</pre><pre>Jim</pre><= pre>=C2=A0= </pre><pre>Bob Masta wrote:</pre></div></di= v> <blockquote style=3D"MARGIN-BOTTOM:5pt;MARGIN-TOP:5pt"> <div> <div><pre>Fro= m: Bob Masta <a href=3D"mailto:audio@xxxxxxxx" target=3D"_blank"><aud= io@xxxxxxxx></a></pre><pre>Date: Sun, 14 Dec 2014 09:15:19= -0500</pre><pre><sp= an style=3D"FONT-SIZE:10pt">To: <a href=3D"mailto:AUDITORY@xxxxxxxx"= target=3D"_blank">AUDITORY@xxxxxxxx</a>= </pre><pre>Subjec= t: Re: USB sound cards</pre><pre>=C2=A0</fo= nt></pre><pre>On = 13 Dec 2014 at 21:59, Richard F. Lyon wrote:</p= re> <blockquote style=3D"MARGIN-BOTTOM:5pt;MARGIN-TOP:5pt"><pre>On Sat, Dec 13, 2014 at 5:5= 2 AM, Bob Masta <a href=3D"mailto:audio@xxxxxxxx" target=3D"_blank"><= audio@xxxxxxxx></a> wrote:</pre><pre><fon= t face=3D"Courier New">=C2=A0<= /span></pre> <blockquote style=3D"MARGIN-BOTTOM:5pt;MARGIN-TOP:5pt"><pre>It's the other way aro= und:=C2=A0 Adding resistance in the</pre><pre><= font face=3D"Courier New">driving circuit gi= ves poorer damping.=C2=A0 "Damping Factor" for</spa= n></pre><pre>a power amplifier is the reciprocal of output impedance.</= span></pre><pre>=C2=A0</pre></blockquote><pre>Bob, I wasn't aware of = that definition.</pre><pre>I was thinking of <a href=3D"http://e= n.wikipedia.org/wiki/Damping_ratio" target=3D"_blank">http://en.wikipedia.o= rg/wiki/Damping_ratio</a></pre><pre>rather than <a href=3D"http= ://en.wikipedia.org/wiki/Damping_factor" target=3D"_blank">http://en.wikipe= dia.org/wiki/Damping_factor</a></pre></blockquo= te><pre>Oops, you= are correct... I should have said it is </pre>= <pre>*proportiona= l* to the reciprocal.</pre><pre>=C2=A0</fon= t></pre> <blockquote style=3D"MARGIN-BOTTOM:5pt;MARGIN-TOP:5pt"><pre>Is there an understanding o= f why high "damping factor" would be good?</= font></pre><pre>J= ont's findings suggest otherwise (I believe he's saying the current= is</pre><pre>typically more relevant than the volage).<u= ></pre></blockquote></div></div><pre>The second reference you cited covers= it under </pre><pre>"Explanation".=C2=A0 Basically, a= conventional electrodynamic </pre><pre>speaker is both a motor = and a generator.=C2=A0 Imagine that the </pre><= pre>speaker recei= ves a momentary voltage pulse, after which is <= /pre><pre>is inst= antly disconnected from the source.=C2=A0 The speaker = </pre><pre>would ring at its resonant frequency, damped only by = </pre><pre>friction.=C2=A0 The generator would be creating a voltage, but <= /u></pre><pre>no current, so no load to add damping.</fon= t></pre><pre><= /u>=C2=A0</pre><pre>However, if instead of disconnection the leads were= </pre><pre>*shorted* after the pulse, the generator would be dr= iving </pre><pre><sp= an style=3D"FONT-SIZE:10pt">all its current into the zero-ohm load, giving = a maximum </pre><pre>damping effect.=C2=A0 = </pre><pre>=C2=A0</pre><pre><s= pan style=3D"FONT-SIZE:10pt">Conventional loudspeakers are designed to be d= riven by </pre><pre>= voltage sources, not current sources. The cu= rrent may be </pre><pre>more "relevant" (in the sense = of force generation), but not </pre><pre>for getting a flat freq= uency response from a conventional </pre><pre><= font face=3D"Courier New">speaker design.=C2= =A0 (Although there have been occasional </pre>= <pre>attempts at = current drive, the ones I recall required </pre= ><pre>special ded= icated amplifiers.)</pre><pre>=C2=A0= </pre><pre>Best r= egards,</pre><pre><s= pan style=3D"FONT-SIZE:10pt">=C2=A0</pre><pre><= font face=3D"Courier New">Bob Masta<u= ></pre><pre>=C2=A0</pre><pre>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0 D A Q A R T A</pre>= <pre>Data AcQuisi= tion And Real-Time Analysis</pre><pre>=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 <a href=3D"http://www.daqarta.com" target=3D= "_blank">www.daqarta.com</a></pre><pre>Scope, Spectrum, Spectrog= ram, Signal Generator</pre><pre>=C2=A0=C2=A0 Science with your s= ound card!</pre></blockquote></blockquote> =C2=A0</div></div> -- <= /p> <div> <div> James D. (jj)=20 Johnston</div> <div> Independent Audio and Electroacoustics=20 Consultant</div></div></div></div></div></d= iv></div></div> </blockquote></div> </div> --001a11398536ed93c9050a7f5072--

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