john curl said:
John, I'm sure you are familiar with the sampling theorem. I say with the greatest respect, but I hope you see how wrong that statement is.
Sampling theorem requires sampled signal to be frequency limited at Fs/2, there must be no spectral component above Fs/2. The music is not limited to 22kHz, signal is brickwalled, reconstruction is right for the wrong (frequency cutted) signal; so in fact John is right.
Please see amended circuit attached below.
This particular IC can accept capacitive load.
There is no need for it, since the input is well regulated.
Originally posted by dimitri
also your opamp has 2.5uV/sqrtHz, while 2SK170 has 1uV/sqrtHz, I'll replace opamp with AD797
This opamp has 2.7nV/sqrtHz, not 2.5uV/sqrtHz – it looks quiet enough.
Please see amended circuit attached below.
This IC has 2.7nV/sqrtHz, so it looks quiet enough.
Attachments
Thank you – this is how I intended doing it, following my past experience and reading this thread from post #1 onward.
What's the reason for it?
Thank you.
It's looking better, Joshua, but you really don't need R3 or C3. If you want to make a really effective bypass circuit, you might replace R1 with a LOW Gm low noise jfet and wire it as a current source. Then, you will have a Vendetta phono power supply buffer reference.
Did you buy GR or BL or V grade?
I think that GR has lower noise -anyone know more about this?
I am curious:
What was the statistical noise data of your 300 JFET measurements?
Sigurd
I think that GR has lower noise -anyone know more about this?
I am curious:
What was the statistical noise data of your 300 JFET measurements?
Sigurd
syn08 said:
scott wurcer said:
Let me change my white hat to black one and say, "square waves are not music". I could not find a non-anecdotal reference to the audibility of a 24kHz anti-aliasing filter. Apogee was modifying Sony PCM-F1's with ANALOG filters to produce "square" waves (their words) almost 25yrs ago.
Anyway Happy New Year.
G.Theile did a research about the audibility of anti-aliasing filters. (He compared 20kHz to 40kHz)
http://www.hauptmikrofon.de/theile/HD-Audio_TMT1998_.PDF
Unfortunately written in german, only the abstract is translated.
I would not put too much faith in any 'objective' test of anti-aliasing filters, as many early ones were pushed by Sony, and KNOW what do they recommend? (think SACD) They are just a necessary evil with low bandwidth audio systems.
Apogee did make some effort to advance the anti-aliasing filters, in fact a good friend of mine, Richard Steiger, car pool mate for about 1 year, and worked at Ampex on a digital project in 1968-69, worked at Apogee I am pretty sure. Very sharp guy. I learned most of my early digital info from him, but I also heard the the first prototype, and heard the problems as well, with digital, that for me, have not completely gone away.
Apogee did make some effort to advance the anti-aliasing filters, in fact a good friend of mine, Richard Steiger, car pool mate for about 1 year, and worked at Ampex on a digital project in 1968-69, worked at Apogee I am pretty sure. Very sharp guy. I learned most of my early digital info from him, but I also heard the the first prototype, and heard the problems as well, with digital, that for me, have not completely gone away.
john curl said:
What objective testing would you put faith in ?
Presumably nothing published by Sony.
Noting your signature then, why the condemnation ?
Vendetta data, courtesy of John Curl.
http://farm4.static.flickr.com/3263/3156456221_7883d94038_b.jpg
http://farm4.static.flickr.com/3268/3157291270_70073dd2c2_b.jpg
http://farm4.static.flickr.com/3263/3156456221_7883d94038_b.jpg
http://farm4.static.flickr.com/3268/3157291270_70073dd2c2_b.jpg
Sony has been shown to be self-serving, over the years with audio standards. Now, they promote a more ideal bandwidth, because it is now easier for them to do so, but 25 years ago, they were forcing us to use a 44.1KHz sampling rate, so that it would be compatible with their video recorder, NOT for the highest audio standard, OR compatibility with existing standards at the time. They just forced the AES to accept it.
SY said:
Ok, so this set of measurements shows 0.28nV/rtHz 20Hz-20KHz which is very impressive and also consistent with the reported number (8) and Idss of the input JFETs. Amazing result and once again, I am dissapointed by the quality of the Stereophile measurements (Halcro was the other example). BTW, Xono and HPS2.0 are both 0.4-0.45nV/rtHz and use 4xJFET. HPS 3.0 will try to reach the same numbers as the Vendetta, I can parallel more JFETs myself 😀
Which leaves my last question open: how is this thing built to stay stable with 8xJFET at the input? The only thing that I can think of is ferrite beads on the gates, but somehow I don't believe John went this path.
john curl said:
Interestingly, if they had also specified the anti-aliasing and anti-imaging filter, the system could have been made much more phase correct without the need for all the fancy upsampling bandaids (which only take care of one end of things) and oddball filtering schemes. Less fun for the marketeers, though.
I do note that the top subjective reviewer at that time, J. Gordon Holt, went ape-$#@! with both the first CD player and the F1 recorder, declaring them as close to perfection as anything he'd ever heard. Hmmmm.
Gordon Holt could hear well, but he liked digital better than many of us did. It might be interesting that Dr. Diamond also bought a Sony digital recorder for live recording. It was just more practical at the time for him. I asked him about it, and he would roll off the very high response to make it easier listening.
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