The technology simply had to catch up with the format. Isn't that just about true with all things?
All the best,
Nonoise
All the best,
Nonoise
Did Redbook get it right?
Correct, I/V stages going back in the days of R2R Ladder Multibit dacs, were opamps with negative feedback, no matter how good the opamp was, the negative feedback couldn't handle the very high frequency glitches noise and other rubbish that came out of them. Today we now know to use active I/V stages that don't use feedback, and they then can make these old R2R Multibit dacs really come to life. Passive I/V resistors for R2R Multibit are ok, but they kill the output too much, so the next stage has be amplified too much to get anywhere near 2v, trouble is that the noise and crap gets boosted along with it and you end up with it on the output. The best Multibit dac with good I/V stage I've heard is the PCM1704 followed by the PCM1702 then the TDA1541 Cheers George |
Hi Clio, I use a Cary 303/200 which has the 24bit R2R Ladder PCM1704K chips, and it also has the PMD-200 HDCD filter as well as (switchable) copy of the DF1704 in DSP form. It also used OPA627 I/V which had feedback, but I completely gutted the I/V, filtering, buffer and XLR opamps. And now I use the I/V stage that I started a thread for over here (linked). It was also used earlier but I believe not fully exploited and slightly differently by Peja Rojic of Audial and Charles Hansen of Ayre. I also implemented a golden oldie for the output buffer, a BUF03 pure class A zero feedback unity gain stage. The whole setup is now dc coupled and feedback free from the PCM1704 dac's outputs to the output rca's of the cdp. http://www.diyaudio.com/forums/digital-source/227677-using-ad844-i-v.html Cheers George |