Fig 29? What is the reason to specify tantalum? Does that have better HF performance?
Jan
Interesting thoughts from many sources - thank you, one and all.
Jacco, that circuit was published in 1990 or '91. I don't know which work of Walt Jung you refer to, what I've seen from him didn't have a RIAA circuit, so I don't know about it, but as ever with Walt Jung, I would very much like to see it. So, if you have a link, I'd be grateful for it.
If it is, as you suggest, a rip off, then the need to see the original is all the greater. I honestly don't remember if WJ was mentioned, it has been 23 years at least, and the text was unfortunately spread over a very big number of pages, too big to scan and keep it all.
For myself, I have seen and heard it only twice, but I do remember that it sounded way better than most other similar circuits I have heard, even in very expensive audio gear. It did manage to transform very hunble gear into quite decent gear, and that's not very easy.
The imposed +/-15V limit can be bypassed by using dual supply lines, by feeding the second op amp from higher voltage lines. Of course, that complicates matters, and once one goes down that road, one might as well add a discrete outout current stage, it's not too complicated and adds very little to the manufacturing price. Besides, I'm sure Analog Devices will have something nice for me, haven't looked at their product lists for a long time, something I need to do pronto.
Scott, a little help info, please. How is AD fixed for higher supply line linear op amps? Is there any you would recommend for further investigation? I have ready vesrions of shunt power supplies for +/- 16.5, 22. 24 and 30 V. Specifically, I refer to the second op amp, which does the grunt work, current is of no great concern because the supply difference will eat up only a small voltage.
Unfortunately for this purpose, my stock curretly has only OPA 37, AD 826, AD 818 and AD 828.
Jacco, that circuit was published in 1990 or '91. I don't know which work of Walt Jung you refer to, what I've seen from him didn't have a RIAA circuit, so I don't know about it, but as ever with Walt Jung, I would very much like to see it. So, if you have a link, I'd be grateful for it.
If it is, as you suggest, a rip off, then the need to see the original is all the greater. I honestly don't remember if WJ was mentioned, it has been 23 years at least, and the text was unfortunately spread over a very big number of pages, too big to scan and keep it all.
For myself, I have seen and heard it only twice, but I do remember that it sounded way better than most other similar circuits I have heard, even in very expensive audio gear. It did manage to transform very hunble gear into quite decent gear, and that's not very easy.
The imposed +/-15V limit can be bypassed by using dual supply lines, by feeding the second op amp from higher voltage lines. Of course, that complicates matters, and once one goes down that road, one might as well add a discrete outout current stage, it's not too complicated and adds very little to the manufacturing price. Besides, I'm sure Analog Devices will have something nice for me, haven't looked at their product lists for a long time, something I need to do pronto.
Scott, a little help info, please. How is AD fixed for higher supply line linear op amps? Is there any you would recommend for further investigation? I have ready vesrions of shunt power supplies for +/- 16.5, 22. 24 and 30 V. Specifically, I refer to the second op amp, which does the grunt work, current is of no great concern because the supply difference will eat up only a small voltage.
Unfortunately for this purpose, my stock curretly has only OPA 37, AD 826, AD 818 and AD 828.
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http://waltjung.org/PDFs/Topology_Considerations_for_RIAA_Phono_Preamps.pdf
OPA606 datasheet, page 9, figure 10
(I would have expected someone interested in phono stages, to recognise that circuit)
That is cos subjective hearing is perception and like trying to judge white balance by eye can be easily fooled......
But then I'm just a blind deaf and dumb kid....
OH! NOOOo.
They'd only go and irritate on other threads!
Seriously though, there are some valuable insights still being given….it's a shame that finding them can be like the old needle in haystack search.
Frankly I don't remember, others might work too. I do remember no arrangement of normal bypassing and ground connection of the displacement current return was as good (which included cutting leads to a mm or so and pulling pins into the air, etc.).
Thank you for the lnk, Jacco.
I am bad at recognizing things I've never seen before.
Also, I am not particularly interested in phono circuits. My interest has been boosted by this thread. and by the fact that I shall soon be moving into a bigger room, where I can once more put the whole system together (at this time, the TT is disconnected, as is my Sony TC-K 808 ESD; as a matter of fact, there's way more audio gear in my cupboards than in the room itself).
I may be coming to your part of the world soonish...some customers want to see me in person and do some on site work!!!!!! Delft is where I will be going, rather looking forward to it and getting away from not so sunny Blackburn. its ok if you like rugged countryside round here (i.e. rain, hills, more rain, more hills, sheep)
First, I meant high current supply, not Class-A; the preamp circuitry is Class-A biased .
Anyway, if the supply is stable you can run it with no output cap and the dynamics and low frequencies are stunning. Bob Pease mentioned that there were lab supplies designed this way once so I felt my approach was valid after that. I've been slowly refining this for more than 10 years and can hear the the effect of the cap readily.
Not sure what you mean by master/slave with regards to supplies. I'll have to give it some thought.
Mike
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