Gina, noise reduction (was: RE: AW: To earth, or not to earth ...)

[Fraser, Colin J]

> -----Original Message-----
> From:	Mikko Helin [SMTP:MHELIN at tne01.tele.nokia.fi]
> Sent:	Thursday, December 04, 1997 2:32 PM
> To:	synth-diy at mailhost.bpa.nl
> Cc:	MHELIN at tne01.tele.nokia.fi
> Subject:	Gina, noise reduction (was: RE: AW: To earth, or not to
> earth...)
> 
> I've got the Ensoniq AudioPCI (actually Shuttle Spacewalker HOT-255). 
> This is not quite over 90 dB snr sound card, but it seems to be
> possible to
> modify the card to use other ADC and DAC. I'm going to try Crystal's
> CS4222 codec, CS4330 & CS5330 could do as well (if anybody happens
> to know where to get these please tell me). With two EAPCI's synced
> together and with the new drivers coming soon it's possible to get 
> 4 inputs and 8 outputs for under $100 (AudioPCI is $44 at 
> www.carlind.com).
> 
Sounds like a bargain - anyone for PCI Soundcard-DIY ?
Does the Ensoniq card support spdif i/o ? 
Would it be possible to replace the ADC on a soundcard with a Crystal
spdif receiver  ?

> If the noise is problem there's another way to reduce it: the noise 
> reduction system. Analog Devices new HUSH(tm owned by Rocktron) chip 
> SSM2000 would be nice. I don't know much about it, but they promise 
> upto 26 db better dnr (or snr or whatever). It works like an envelope 
> controlled LPF, except that the envelope is not the straight amplitude
> 
> envelope, but more like a frequence envelope (filter follows the
> frequency
> content of the audio signal), and it's said to be very transparent, no
> pumping effetcs like with the usual amplitude controlled noise gates.
> 
I believe Maplin have the SSM Hush chips - I hadn't given them much
thought, but 26 db sounds like a very effective system !
Anyone have any experience with these, or know what the best case output
snr is ?
If it can take a signal with noise at about -70db, and lower that to
-96db it would cover a multitude of sins...

Colin f