Driving headphones at high peak levels (Bob Carlyon )

Subject: Driving headphones at high peak levels From: Bob Carlyon <Bob.Carlyon@xxxxxxxx> Date: Sun, 7 Dec 2014 13:29:15 +0000 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY> --_000_9A9432BC31857848B97F53CEAE8386C4938872A3wsrex101mrccbsu_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Dear list, I am involved in a project where we are play some pulsatile stimuli to list= eners who may have a hearing loss. To do so we need to produce high peak le= vels in order to obtain sufficient loudness. The test will be run in differ= ent clinics worldwide, which means both that we can't choose an expensive s= olution, and that, at least preferably, we should be using USB devices - al= though I realise that the voltage provided by the USB will impose some limi= tations. I would be grateful for suggestions on how to maximise the audio output, an= d list below the general options & limitations as I see it Choose a sensitive transducer At present we are using Sennheiser HD650s which produce about 106 dB SPL/V = for a 1-kHz sinusoid. In a recent post Mike Stone mentioned the HDA200 whic= h produces 117 dB SPL/V, but that is very expensive; does anyone know of ch= eaper headphones that are also very sensitive? Another option is to use ins= ert earphones such as the Etymotic ER 5. However the highest input impedanc= e these come in is 50 ohms, which is similar to the output impedance of the= USB sound cards I have tried (see below) Choose a USB sound card with "better" specifications The USB sound cards that I have seen have output impedances of around 50 oh= ms or higher, making them unsuitable for driving low impedance phones, so a= low-output-impedance USB sound card with decent maximum output would be on= e solution The two cards that I have been calibrating differ by more than 8 dB in the = maximum output they can produce into a 300-ohm load without clipping - the = winner being the Roland Quad capture at a peak value of approx.. 2.6V. If = anyone knows of a USB sound card that would exceed this, or even match it a= t a cheaper price (The Roland is about UK=A3150, so say US$225) I would be= glad to hear of it Use a separate headphone amplifier Does anyone have experience of relatively inexpensive(say < US$150) headph= one amps? As mentioned above something USB driven would be ideal, but maybe= at a pinch we could use something driven by a 12V power supply using a mai= ns adaptor. One option (just gleaned from the internet) is the ART headamp = 4, but I have no experience with this and so if anyone has calibrated any s= uch device and has suggestions again I'd be grateful I'd be happy to collate responses and post them to the list Cheers Bob Dr. Bob Carlyon Deputy Director MRC Cognition & Brain Sciences Unit 15 Chaucer Rd. Cambridge CB2 7EF England Tel: +44 (0)1223 355294 Fax: +44 (0)1223 359062 www.mrc-cbu.cam.ac.uk<http://www.mrc-cbu.cam.ac.uk/> See also the Cambridge Hearing Group<www-hearing-research.eng.cam.ac.uk/Main/WebHome> --_000_9A9432BC31857848B97F53CEAE8386C4938872A3wsrex101mrccbsu_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <html xmlns:v=3D"urn:schemas-microsoft-com:vml" xmlns:o=3D"urn:schemas-micr= osoft-com:office:office" xmlns:w=3D"urn:schemas-microsoft-com:office:word" = xmlns:m=3D"http://schemas.microsoft.com/office/2004/12/omml" xmlns=3D"http:= //www.w3.org/TR/REC-html40"> <head> <meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3Diso-8859-= 1"> <meta name=3D"Generator" content=3D"Microsoft Word 14 (filtered medium)"> <style></style> </head> <body lang=3D"EN-GB" link=3D"blue" vlink=3D"purple"> <div class=3D"WordSection1"> Dear list,<o:p></o:p> I am involved in a project where we are play some pu= lsatile stimuli to listeners who may have a hearing loss. To do so we need = to produce high peak levels in order to obtain sufficient loudness. The tes= t will be run in different clinics worldwide, which means both that we can’t choose an expensive soluti= on, and that, at least preferably, we should be using USB devices – a= lthough I realise that the voltage provided by the USB will impose some lim= itations.<o:p></o:p> <o:p> </o:p> I would be grateful for suggestions on how to maximi= se the audio output, and list below the general options & limitations a= s I see it<o:p></o:p> <o:p> </o:p> Choose a sensitive transducer<o:p></o:p> At present we are using Sennheiser HD650s which prod= uce about 106 dB SPL/V for a 1-kHz sinusoid. In a recent post Mike Stone me= ntioned the HDA200 which produces 117 dB SPL/V, but that is very expensive;= does anyone know of cheaper headphones that are also very sensitive? Another option is to use insert earphones su= ch as the Etymotic ER 5. However the highest input impedance these come in = is 50 ohms, which is similar to the output impedance of the USB sound cards= I have tried (see below)<o:p></o:p> <o:p> </o:p> Choose a USB sound card with “better”= specifications<o:p></o:p> The USB sound cards that I have seen have output imp= edances of around 50 ohms or higher, making them unsuitable for driving low= impedance phones, so a low-output-impedance USB sound card with decent max= imum output would be one solution<o:p></o:p> The two cards that I have been calibrating differ by= more than 8 dB in the maximum output they can produce into a 300-ohm load = without clipping – the winner being the Roland Quad capture at a peak= value of approx.. 2.6V.  If anyone knows of a USB sound card that would exceed this, or even match it at a cheaper = price (The Roland is about  UK=A3150, so say US$225) I would be glad t= o hear of it<o:p></o:p> <o:p> </o:p> Use a separate headphone amplifier<o:p></o:p>= Does anyone have experience of relatively inexpensiv= e(say < US$150)  headphone amps? As mentioned above something USB d= riven would be ideal, but maybe at a pinch we could use something driven by= a 12V power supply using a mains adaptor. One option (just gleaned from the internet) is the ART headamp 4, but I ha= ve no experience with this and so if anyone has calibrated any such device = and has suggestions again I’d be grateful<o:p></o:p> <o:p> </o:p> <o:p> </o:p> I’d be happy to collate responses and post the= m to the list<o:p></o:p> <o:p> </o:p> <o:p> </o:p> Cheers<o:p></o:p> <o:p> </o:p> Bob<o:p></o:p> <o:p> </o:p> <o:p> </o:p> Dr. Bob C= arlyon<o:p></o:p> Deputy Di= rector<o:p></o:p> MRC Cogni= tion & Brain Sciences Unit<o:p></o:p> 15 Chauce= r Rd.<o:p></o:p> Cambridge= CB2 7EF<o:p></o:p> England<o= :p></o:p> Tel: &#43= ;44 (0)1223 355294<o:p></o:p> Fax: &#43= ;44 (0)1223 359062<o:p></o:p> <a href= =3D"http://www.mrc-cbu.cam.ac.uk/">www.mrc-cbu.cam.ac.uk</a><o:p></o:p></sp= an> See also = the<o:p></o:p> <a href= =3D"www-hearing-research.eng.cam.ac.uk/Main/WebHome">Cambridge Hearing Grou= p</a><o:p></o:p> <o:p> </o:p> </div> </body> </html> --_000_9A9432BC31857848B97F53CEAE8386C4938872A3wsrex101mrccbsu_--

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