Subject: RE: [linux-audio-dev] audio card for linux (and audiality ?) + question about filtering
From: Benjamin GOLINVAUX (golinvaux_AT_benjamin.net)
Date: su elo 29 1999 - 14:00:29 EDT
>On Sun, 29 Aug 1999, Benjamin GOLINVAUX wrote:
>> The RME Hammerfall (http://www.rme-audio.com/english/digi96/hammer.htm)
>> card.
>Looks very nice... :-)
especially when the price is around 500€ ($500)... add a 250€ ADI-1 AD/DA
from the same companyt and you have a very serious system for... well... a
pretty amount of money but that's really a good card (and I have spared for
a linux audio card for 2 years now)
>I don't like the 1.5 ms minimum latency (which will result in a total
latency
>of at least 3 ms through a software engine - still good, though), but it's
>still a nice card, especially if it's *usable*! (That is; has Linux
drivers. :-)
I would say that a command->action of 3ms is beyond the perception of many
people except very good drummers... (that's the midi latency of a typical
synth)... Someone disagrees ?
However... something that has worried me for some time is that problem :
being given an audio fx engine for, let's say, vocals...
Someone sings : his/her voice has a direct path to the ears AND an indirect
path thru the fx box (be it hardware or audiality for that matter ;-)
So... the direct and indirect signals gets added with a delay of 3ms...
Let's compute the z-transform... you see what I mean ?
Every wave whose half period is 3ms (that is, T=6ms <-> f=166Hz) is delayed
by 180° which leads to total cancelling of these waves... So we get a huge
hole around 166Hz...
Am I correct ?
Furthermore, to move that hole out of the audible range, one has to have a
f=20KHz <-> T=50µs <-> latency = 25µs !!!!!!!!!
So... do we have to avoid mixing dry and wet or am I wrong somewhere ???
Thanks for some kind of explanation...
Benjamin-
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