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In the Forum: Didital Things
In the Thread: Metaxas-Wolfson ADC with Sound Devices SD744T
Post Subject: Metaxas-Wolfson ADC with Sound Devices SD744TPosted by Romy the Cat on: 2/11/2007
An email that I got from Kostas Metaxas, (posted with Kostas’ permission):

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I wanted to share some of my preliminary findings using my newly developed A-D [Wolfson chip] to bypass the SD744T inputs/ADC.

This is very early days as I've just started playing with this external ADC, but you can already easily hear  the WOLFSON's "potential".

Here is the SM8 dubbed to the analogue inputs [1&2] of the Sound Devices 744T, using it's internal amps/ADCs
http://www.reel2reel.tv/samplers/_SM8_744Tanalogue_in_Benaud.wav
[170Mb 5min sample 24bit/96k]

Here is the SM8 dubbed to the Metaxas - WOLFSON ADC - SPDIF output to Sound Devices 744T SPDIF in
http://www.reel2reel.tv/samplers/_SM8_MAS-ADC_744T_SPDIFin_Benaud.wav
[170Mb 5min sample 24bit/96k]

Here is the SM8 dubbed to the SONY DSR11 DVCAM VTR, using it's internal ADCs
http://www.reel2reel.tv/samplers/_SM8_SONYDSR11_BenaudA.wav
[88Mb 5min sample 16bit/48k]

You can view a track from this concert to see how the mics/musicians were lined up. I was using Neumann M150s in AB and TLM50s in XY:

http://www.reel2reel.tv/SCREENERS_WMV/__benaud_stairway-1a.wmv

The background noise is the "airconditioning"....the blight of location recordists!

The Metaxas-WOLFSON - I'm using the WOLFSON chip since it has recently been favourably reviewed in the audiophile press [mostly as a DAC actually]. I'm not using any input buffers, and have removed all the goofy big ceramic caps from the signal path to the differential ADC inputs. Then, I've added my own ultra-low noise discrete regulators - isolating the clock with it's own regulator from the rest of the board. All driven by 8 AA batteries which will run it for over a day.

Listen to the huge "weight" in the sound. To me this is the key. And this is the problem with all the location recorders I've tried so far [including Nagra V, Aaton Cantar and Sound Devices]. So I'm hoping that by using my ADC with the SD744T, I should be able to recover the rich, huge, "blooming" bottom that the Neumann's easily record onto the Stellavox. Of course this ADC can be used with NAGRA etc as well...

I'll be using it in the field to record a few upcoming festivals, so will keep you posted with how things turn out.

Rgds,
Kostas

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