In his mailing-
'Re: Need help: My .asoundrc no longer works.'
On Friday 26 January 2007 01:28, Tim wrote:
> ---------------------------------
> There is one more important issue:
> What happened to all the input gain controls (IPGA) in the ice1712 driver?
> With alsa-1.0.14rc2 they are gone! They don't show up in envy24control,
> or any other mixer I try which shows ALL alsa controls.
> If this is an attempt to unify the IPGA and ADC controls, I agree. Carry
> on. Anyone who has used the envy24control knows it is a bit strange.
> If you operate the ADC controls, the IPGA controls are forced to zero,
> likewise if you operate the IPGA controls, the ADC controls are forced
> to max. Unification of the two controls would make a lot of sense.
> But I could not seem to get them to work properly with this alsa-1.0.14rc2
>
> Tim.
I was intending to raise this matter myself. In the changelog 1.0.12 to
1.0.13 I noticed this:-
+ AK4XXX AD/DA converters
- ak4xxx - Remove bogus IPGA controls
Remove IPGA volume controls and merge the IPGA range to ADC volume
controls. These two volumes are not really independent but connected
simply in different ranges 0-0x7f and 0x80-max. It doesn't make sense
to provide two controls.
Since both 0x7f and 0x80 specify 0dB, a hack is needed for IPGA range
to skip 0x80 (increment one) for such controls.
But I could not find the changeset on Hg and was intending to ask about it.
>From an analogue electronics POV this may not be a wise change. Adding gain
usually worsens singal-to-noise ratio and other signal parameters, and
attenuation may mean avoidable gain elsewhere. So the best operating point in
general is with no gain or attenuation at the converter. Then the minimum of
either would be used if necessary, in conjuction with controls on the source
equipment.
Thus to achieve best performance I would think it is important to be aware of
both these controls separately. That is what the Terratec 'Windows' driver
for my ice1712 sound card does. If gain is needed, for example, it may be
better to add it elsewhere than at the converter. The 'strange' behaviour of
the two controls in 1.0.12 is in fact entirely correct and neccessary when
the underlying electronics is considered -it is vitally important to avoid
gain and attenuation together even though the effect seems the same.
Remember that the ice1712 creates essentially a semi-pro sound system, so the
users should be aware of technical and signal performance tradeoffs
throughout their equipment (eg mixing desk, effects units), and be able to
make intelligent decisions about the best settings of them all. User
friendliness should not override technical quality issues in this case. It
is not really a domestic piece of kit (eg delta 1010, ews88, dsp24).
Alan
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