Subject: RE: [linux-audio-dev] Writing a driver for this card: your thoughts?
From: Bob Colwell (bob.colwell_AT_attbi.com)
Date: Fri May 31 2002 - 00:59:01 EEST
Somehow I feel the need to get even more specific.
Voltage sags for two reasons: DC resistance and AC impedance.
DC resistance is just plain old ohms law -- no perfect conductors
exist (until the folks in the labs give us high-temp superconductors),
so a current flow will always cause a voltage drop, as in E=IR.
AC impedance matters because conductors also exhibit inductance and
capacitance. Capacitance causes signal leakage and cross-coupling.
But inductance causes AC-induced voltage spikes, because coils
convert electrical energy into a magnetic field, and if you try to
collapse that magnetic field quickly (as a fast-changing electrical
signal does) it reconverts back into an electrical potential that
acts to oppose the change in current. If one distributes capacitors
of the appropriate size and speed, one can effectively decouple
the downstream inductances from the current spike.
Lamar knows all this but I thought it might benefit others who might
not. -BobC
-----Original Message-----
From: linux-audio-dev-admin_AT_music.columbia.edu
[mailto:linux-audio-dev-admin_AT_music.columbia.edu]On Behalf Of Lamar Owen
Sent: Tuesday, May 28, 2002 4:49 PM
To: linux-audio-dev_AT_music.columbia.edu
Subject: Re: [linux-audio-dev] Writing a driver for this card: your
thoughts?
On Tuesday 28 May 2002 07:20 pm, Tobias Ulbricht wrote:
> one question:
> could you do this for the unsophisticated audiophile with less Acronyms?
> > > supply. Using a computer psu is going to severely limit what you are
> ^^^ = power supply unit?
Yes.
> > decoupling is done at the amplifier rails, along with 'sag' compensating
> > caps
> ^^^
Voltage sag due to current draw.
> > (with low ESR! Tantalum only, and preferably sintered slug) in the
proper
> ^^^ ? electron spin resonance :)?
Equivalent series resistance. The higher the ESR, the slower the cap will
discharge, and the less effective it is as a 'voltage flywheel'.
> > But again, the hardware must be able to cancel out the enevitable RFI
> > that is
> ^^^
Radio Frequency Interference.
Sorry.
-- Lamar Owen WGCR Internet Radio 1 Peter 4:11
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