Ok you taking about the delta time between the converter samples. Yea you could put a parallel to parallel shift register between the DACs to get rid to the bit delay. I really don't believe that it's really worth the effort to equilize or align 1/2 bit of offset between the DACs.
I use to use serial DAC's by Micro Networks and Hybrid Systems, I see that Micro Networks is still in business. There parts or true high performance R2R ladder dacs, Industrial and Military grade components. They do offer an 18bit part.
I not sure what you saying Bernhard
I completely understand, what I said was that one of the dac has an offset. The offset is a offset in time, of a 1/2 the period of a sample. So I don't see that being an problem, music stereo all about psycho acoustics and the phase and groups delay through a digital filter is greater than that 1.1usec data offset between the converters.
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The real advantage is not in parallel dac but in complimentary dacs. Or we can call them differential dacs.
How does the offset constitute a phase or group delay?
While the two DACs (for each channel) are offset in time by ½ sample, each DAC outputs for a full sample time. The result is a displaced overlap. Consider samples numbered A, B, C, D, etc. The output of the two DACs, examined at half-sample intervals, looks like this:
DAC1: A B B C C D D E E F F
DAC2: B B C C D D E E F F G
The outputs are summed resulting in ½ sample time where both DACs are outputting the same sample and ½ sample time where the DACs are outputting adjacent samples. The effect is similar to 2x oversampling.
SUM: A+B B+B B+C C+C C+D D+D D+E E+E E+F F+F F+G
Offset, parallel, and differential DACs are different techniques used to achieve different goals. They are not interchangeable and they certainly are not comparable.
I was talking about an over sampling digital filter with some kind of FIR.
While it is possible to take the outputs of two converters in the same channel and sum the outputs signals at a summing amp. I would be hard pressed to call this a true 2X over sampling circuit.
Also, for me it better to discuss converters in bit values. Maybe I am just too old but I just have not seen converters that output the alphabet. I’ll have to think about that.
0, 1, 2,4,16, 32 ,64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384 and so on.
Back to your subject, not only are we getting a change in amplitude we also get a small shift in time. The act of over sampling sticks more bits between the original samples. When summing, we are doing something a little bit different. So now we have one wave form that offset by 1/2 bit in time. Maybe we could give one suming channel a different gain value at the amp.
This thread was about paralleling DAC’s not trying to over sampling in the analog domain there is a difference. My statement stands; I would rather implement differential converters. Whether the analog summing buy’s us anything I do believe it does, also I have not tried it and don’t believe that I am going to…
there or just to may other way to skin this beast. I need a beer.......
jewilson said:
rfbrw
I am starting to wonder if you read these posting. It obvious that the minuscule, dam small, insignificant, offset between channels is not, very very dough full, meaningless to the importance sound, audio, music and stereo reproduction.
That is where i stand on this.
I don't doubt that whatever you are going on about is extremely obvious but it is also obvious that it is not what fumihiko or I were referring to.
Originally posted by jbokelman
konnichiwa
offset-DAC, I called Staggered-DAC before yesterday .
I read old MJ magagine(japanese audioDIY magagine)
they called shifted-pallareling DAC.
I think,different techniques used to achieve same goal.
goal is Good Sound and Low Price!
WADAI and Accuphase considered that at $1000 are low price .
konnichiwa
offset-DAC, I called Staggered-DAC before yesterday .
I read old MJ magagine(japanese audioDIY magagine)
they called shifted-pallareling DAC.
different goals?
I think,different techniques used to achieve same goal.
goal is Good Sound and Low Price!
WADAI and Accuphase considered that at $1000 are low price .
Offset is just another way of paralleling DACs. It has most of the advantages of plain paralleling: increased output and the averaging errors between DACs. Additionally, it gives the benefits of oversampling. With recent improvements in digital filters and low-cost delta-sigma converters, offset DACs have fallen out of favor.
Differential is yet another way. It gives increased output, the averaging of errors, suppression of common-mode sampling noise, and differential output. It also requires a two’s-complement data stream.
MJ had 2 or 3 articles in the 'Sidewinder' section. The only one I could find quickly was a weird one , that took I2S off of SAA7220 and fed 4 PCM56 per channel, through an array of 6 - 74HC164. This is in the March 1993 issue, page 200. I've tried some of the schemes years back (not this particular one as I didn't need the I2S conversion) and it was interesting. These are attempts at discrete versions of what Wadia was likely doing in DSP. French Curve / Digital Spline... what ever the marketing terms were 12 to 14 years ago
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