Re: [linux-audio-dev] Writing a driver for this card: your thoughts?

New Message Reply About this list Date view Thread view Subject view Author view Other groups

Subject: Re: [linux-audio-dev] Writing a driver for this card: your thoughts?
From: Tim Orford (tim_AT_ipd50abcd9.speed.planet.nl)
Date: Wed May 29 2002 - 01:40:44 EEST


On Tue, May 28, 2002 at 04:19:48PM -0400, Lamar Owen wrote:
> [I may regret this... :-)]

:-) bring on the flames :-)

> > such insane amounts of compression as used by most radio stations are not
> > usually related to 'quality' as understood by most poeple.
>
> What happens is that lower quality audio is made to sound that much worse by
> that very compression.

and good quality audio sounds better?
this is a new one to me - i've never heard anyone
blame it on the source material before....hmmm...:-)

>Reverb is exaggerated, etc. As to the amounts being
> insane -- well, that is a big point of contention in the broadcast engineer
> and broadcast program director communities.

of course you have considerable commercial pressures on you,
but i was under the impression that it was
a) a cost saving thing so you dont have to constantly watch the level,
and
b) catering to the lowest-common-denominator listening environments
such as cars.
I do sympathise with you, but if that much compression was
desirable, then the tracks would be mixed like that in the first place.
But like you said, it has been a big point of contention for a long
time, and i dont think we will solve it here :-)

> > one of the most important aspects of analogue design is a good power
> > supply. Using a computer psu is going to severely limit what you are
> > going to achieve. Regulators are by no means perfect.
>
> If the output impedance of the output stage is low enough, and proper
> decoupling is done at the amplifier rails, along with 'sag' compensating caps
> (with low ESR! Tantalum only, and preferably sintered slug) in the proper
> places, DC rail regulation becomes moot. The key is a properly designed
> feedback network, with low net gain, using a high quality op amp with as high
> an open loop gain as possible, and operating the output well below rail
> voltage. If the output voltage goes over half rail, then all bets are off.

yes, this is one design philosophy (albeit a dominant one).

>
> > also, perhaps academic here, but using balanced
> > audio can actually degrade the sound by cancelling out even order
> > harmonics but leaving the odd order ones, or by increasing the component
> > count. Very high end stuff designed for non-hostile environments tends
> > to be unbalanced.
>
> Phase-linear balanced outputs won't cancel _any_ harmonics. Where did that
> concept come from?

i have seen this in balanced internal circuitry, for example
in valve compressors. Its been a few years since i did much
analogue stuff, so i'm gonna be deliberately vague here.
Not _so_ relevant to line drivers. My point being that balancing
solves one problem only; interference, and is no panacea.

>And the Carver Silver Seven sounds better than the old
> M400, too, right? :-) (audiophile humor)

ok, i can see that you think that i am some kind of audiophile
lunatic, which maybe i am to a certain extent. There have been
several things which have changed my life in a major way in the
last few years:
One was the discovery of the Free Software movement. One was the
discovery of class A, low feedback design (thereby shattering
most of what i was taught at college).

I'm not really disagreeing with you, but i think my
point was that there are more factors to take into
account that you appeared to be ignoring. There is a lot
more to analogue audio than just keeping impedances low,
wacking up the negative feedback, and measuring the noise
floor, as i'm sure you realise.

So to get back to the original point, i'm sure the cards
you mentioned are indeed fine cards, but if cost is no object
(ha ha!) and if quality is your objective, then you will put your
analogue converters in a separate box with a dedicated power
supply.

i think i'd better stop there :-)

best regards

--
Tim Orford

and no i dont have silver cable, but i would like some!


New Message Reply About this list Date view Thread view Subject view Author view Other groups

This archive was generated by hypermail 2b28 : Wed May 29 2002 - 01:35:18 EEST