Subject: Re: Driving headphones at high peak levels From: Steve Beet <stevebeet@xxxxxxxx> Date: Tue, 9 Dec 2014 13:27:55 +0000 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>Bob, that's a very interesting and thorough analysis, but the weak point of the sound card you recommend seems to be the low-frequency response. The 2 ohm output you refer to is labelled "line out" in your document, so doesn't that suggest that it's designed for driving high impedance loads? If so, there's probably a decoupling capacitor on the card's output, attenuating low frequencies, even when driving a normal (high) line impedance. This seems to be confirmed in your frequency response graphs. Driving a lower load impedance (e.g. headphones) will decrease the time constant associated with the capacitor and make this defect extend to higher frequencies. Or am I reading too much into the graphs? Steve Beet On Mon, 8 Dec 2014 08:58:13 -0500 Bob Masta <audio@xxxxxxxx> wrote: > > Choose a USB sound card with "better" specifications The > > USB sound cards that I have seen have output impedances > > of around 50 ohms or higher, making them unsuitable for > > driving low impedance phones, so a low-output-impedance > > USB sound card with decent maximum output would be one > > solution > > I have tested several USB sound cards. The hands-down > winner for low output impedance (2 ohms) can deliver nearly > 1.5 Vrms into 100 ohms. I especially like it because it > has no hardware controls on the unit that can get > accidentally changed in a lab setting. It has pretty good > specs in most other respects as well. See > the Comparison Table under "Sound Card Perfomance Tests" at > <http://www.daqarta.com/dw_gguu.htm>