Re: [ARSCLIST] circuit noise

[Tom Fine <tflists@xxxxxxxxxxxxxxxxxxx>]

Hi:

I've been lurking on this list for a while. You sure have a nice collection
of experts here.

Regarding the listmember with the noisy/hashy computer soundcard, I can
offer a few thoughts from personal experience in my own studio.

1. most unbalanced computer soundcards seem to have grounding issues where
they don't interface well with other gear, producing noise or hash or even
hum. I think it's either lousy ground plane on the card, lousy grounding in
the computer or strange ground issues being created by the computer's
switching power supply. Even though it is a veritable interference/radiation
factory inside a computer box, there's no reason why a quiet sound card
cannot be built. Indeed, my old trusty Ensoniq unbalanced cards run very
quiet and do not create hash/noise problems when interfaced with other gear.
My card of choice on my DAW is a CardDeluxe, which is balanced +4dB
pro-grade audio and runs dead silent. So I must disagree with the theory
that an internal card _can't_ do pro-grade silent performance. I think many
card makers don't build the consumer cards to that level of grounding and
isolation.

2. a good example of a problematic card is the Soundblaster Live Digital
card I use in my video-editing computer. It runs pretty quiet in and of
itself but has issues when its shield is tied to the shield of most balanced
gear in the studio. I'm guessing that's because the Dell computer's
ground/shield plane that this card is using is not really greenwire ground
and/or it's polluted or susceptible to pollution from within the machine. My
solution, which works perfectly, is to bring the Soundblaster's outputs to
tip and ring of balanced TRS connectors and leave the shield unconnected on
the receiving end (opposite MO for sending signal to the Soundblaster).
Problem solved. The card runs very quietly and actually produces credibly
decent audio, particularly for video transfers of VHS and U-Matic tapes
(which have lousy sound for the most part anyway). BTW, the digital part of
the card has no issues. SPDIF in and out work fine with everything SPDIF in
my studio (CD players, DAT machine, audio DAW, DVD player, etc). Thinking
about this now, perhaps the soundblaster's DSP chip is the source of issues.
I think SPDIF stuff may not move thru any or most of the DSP chip.

3. In the case of the gentleman who posed the question to this list, as I
understand it he has unbalanced external equipment and unbalanced
connections on the soundcard. I would suggest his best solution is a Jensen
IsoMax box or an upgrade to a better card. I will again put in a plug for
the CardDeluxe from Digital Audio Labs. I've used mine for hundreds of
transfers and it's never let me down. Never lets me down for playback
either; I route most digital sources in the studio through its SPDIF
connection and use it for D-A because it's so honest. DAL sells an add-on
AES and optical digital input daughterboard for it. Plus you can sync up to
4 cards (8 channels) for multi-track. End of plug.

4. The situation I described above with the Soundblaster card was also true
with my old Dell 4100 box I used to use for video, so it seems to be a
standard problem with that card, either all of them or my specific unit. As
I said, no problems with an older/cheaper Ensoniq card in my workshop
computer, which is a homebrew amalgam of castoff parts and is probably very
noisy and hashy inside since it's in tight quarters and has two extra
cooling fans, a separate IDE card, 4 hard drives and a CD burner. That
Ensoniq problem has no issues going unbalanced out to the unbalanced in of
my preamp in the workshop. Since the speakers for that system are right over
my workbench, I hear hum and hash loud and clear if there is any. So, again,
I'd say it's bad manufacturing practice on the part of some or many card
makers that lead to this assertion that quiet audio _can't_ come from an
internal card.

-- Tom Fine