R/E/P > Bruno Putzeys (Designer) - Dave Hecht (Master Tech)

Delta-Sigma A/D converter design.

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Evalon:
Hello Prosoundweb & Bruno,

Wow, surprising to find that the forum had "gone" before realizing that there was a "new" and "previous" version ...

As you may remember you helped with some questions related to designing a delta-sigma a/d converter in the previous forum. Things are somewhat progressing & being considered (multibit/singlebit) and I hope it's ok to ask you some more questions:

1. Assuming loop filter calculations & circuit works how long will you say it takes to make a high-speed D/S converter work "flawlessly"? Adjustments etc.

2. Understanding that 1-bit signals are not directly editable - have you experience with what are the audible losses when converting 1 bit signals to 24 bit signals? And do you know if there is software available that can do this in a "gentle" way, also converting to higher than 192 kHz/24 bits?

3. I noticed that in one of your threads in the "previous" Prosoundweb forum you mentioned that feeding single-ended signals to an A/D with a differential input makes the A/D distort heavily (if I remember correctly). Can this be amended e.g. by using a pseudo-differential topology?

Hope you can help with this ...

Greetings from Denmark,

Jesper Mønsted

Bruno Putzeys:
1. Depends on how good you are at pre-empting problems (that is, not have to discover them the hard way). I believe I did about 4 rounds of prototypes before the performance was robust.
2. Doing it right is more effective than doing it gently. To give an example, Weiss' Saracon is almost perfectly transparent even at 44.1kHz/24 bit. It accepts DSD.
3. Most converter IC's have this problem. Make sure your front end delivers nicely symmetrical signals centered around the common mode reference that you can find on most ADC's.

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