Digital Drive

Posted by cooney (i) on January 08, 2001 at 17:48:23:

In Reply to: Re: P-3A doesn't convert to 24bit. posted by steve b on January 08, 2001 at 14:26:44:

I think you are still missing the point: .there is a difference in how the P-3A (as well as most other upsampling DACs) and the P-1A approach creating a 24-bit signal from 16-bit input.

While, as you indicate, the Crystal sample rate converter chip in the P-3A "maintains 24 bit precision in its calculations," it does this by adding dither to the signal, which is different from creating a 24-bit signal by interpolation using DSP, which can be done by the P-1A but not by the P-3A. .Please note, I'm not saying better, just different, as I've not heard this yet. .(I note, however, that Dan Wright and most of the others posting here who have listened to both feel that the P-1A's interpolated signal is preferable; .some users, as indicated earlier in this thread, are not so sure.)

In the recent review of the P-1A/P-3A in SoundStage!, Doug Blackburn quotes one of the P-Tech founders as follows, which is one of the most concise explanations I've seen of this distinction:

"Peter Madnick clarifies the operation of the P-3A and other so-called 24/96 DACs and 24/96 outboard processors this way: .The P-3A does not interpolate 16-20-bit data to 24-bit data -- nor does any 24/96 DAC (e.g., the Bel Canto DAC1) or add-on 24/96 external device (e.g., Assemblage D2D-1). .All of these products, so far, will output 24-bit data via dithering of the 16-bit input data. .This results in data that has roughly 17 bits of equivalent resolution within a 24-bit datastream. .The P-3A and other 24/96 products do upsample, for example, from 44.1kHz to 96kHz if you select that mode. .People tend to assume that 24/96 products that advertise upsampling and/or interpolation actually convert 16/44.1 data to full 24/96 resolution, which is not accurate. .To actually get 24-bit data in a 24-bit datastream, you must use digital signal processing (DSP), which is included in the P-1A and is referred to as "Resolution Enhancement" in the P-1A's user manual."

Hope this helps explain the distinction between the two processes, adding 8 bits of dither versus interpolation of 24-bit data by software running on DSP chips.

cooney