That's a pretty good idea for MM phono using four 1644 channels in parallel, to cut e sub n down to about 2.5nV/sq rt Hz. I resorted to an 862 augmented source follower driving an OPA1612 section, which is still a bit better for voltage noise, although suboptimal compared to a common-source connection with stiff series feedback.
I'm an aggregator of (hopefully good) ideas: not sure who mentioned it first (jcx?), but should I ever build a phono preamp, that'll be my direction.
Scott showed a few clever bf862 diff pair -opamp topologies (bootstrapped in some fashion?) in his LA articles or something related to microphones. Would make for a good starting point/study, too.
Scott showed a few clever bf862 diff pair -opamp topologies (bootstrapped in some fashion?) in his LA articles or something related to microphones. Would make for a good starting point/study, too.
BF862 composite amps can go a long way. You can easily go sub 1nV with just a few parallel pairs even differential rather than single ended in.
Check out Home too.
EDIT - For some reason my laptop thinks Mr. Papa's site is my home.
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I almost felt sorry for him at one point with all the phono stages he built before he was happy. Also reminded me of that saying 'all amplifier projects can end up as power supply projects'.
The measurements page doesn't appear to be working, but assume the 5.1 version was spiffingly below the vinyl noise floor. EDIT: got there in the end from a different link. Very spiffingly low 🙂
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Yeah, syn08 and Samuel Groner (among so many others, remembering a very good preamp thread from iko) show some very good instrument preamp work, too. There's a lot of good stuff to steal. 🙂
I had to write a critical LTE about one of the guy's articles, and he still contended that he was correct about some of his declarations. I don't like to do this, but the article was in the nature of a tutorial, and when those are promulgating errors I find it hard to keep quiet. My letter was followed up by one from the sound of silence guy Burkhard Vogel, which apparently impressed a good deal more than my contribution even though it was a good deal harder on the author.
As the LTE took a couple of days of work, that quashed further ambitions for such publications for the moment.
As the LTE took a couple of days of work, that quashed further ambitions for such publications for the moment.
What if ...... ?
What can a cooler do to to help with noise for DIY projects? How cool could we get the jfet without resorting to LN etal?
Mount it in a vacuum box on a cooler;
http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-3450.pdf
THx-RNMarsh
What can a cooler do to to help with noise for DIY projects? How cool could we get the jfet without resorting to LN etal?
Mount it in a vacuum box on a cooler;
http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-3450.pdf
THx-RNMarsh
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Even at the fringes of esoterica wrt low noise, a thermoelectric block to cool your input transistors is way more than enough. As I wrote before, andor (among others) makes an emccd (electron multiplying, avalanche iirc) camera with a -100 C TE cooling system for single photon event counting (albeit noisy). I, ah, think low tenths of a nanovolt en is achievable without resorting to such measures.
That cooling/encapsulation (condensation!) budget is better spent on input transistors and pretty cases.
That cooling/encapsulation (condensation!) budget is better spent on input transistors and pretty cases.
If you read it the reduction in voltage noise is trivial. Virtually all CCD/charge amplifier amplifier cooling is to reduce leakage current where the current noise reduction is dramatic.
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Cooling has a dramatic effect on gate leakage. But for most audio apps the room-temp leakage of a moderately good-sized JFET is already small enough.
Which issue? I avoid ego bashing like the plague nothing good comes of it. An actual mistake should be clear to all parties and no one has anything to lose in correcting it. These LTE sessions are never clearly one way or the other in my experience.
It was an early issue, I have forgotten. And I wasn't doing any bashing, just pointing out errors. Of course some skins are thinner than others (the late Bob Pease's for example).
I used to hate being wrong, and although I don't enjoy making errors, some years ago I got to the point of appreciating being corrected. Most of my errors that now occur are caught by me before I blurt them out.
Vogel's letter said I was wrong too 🙂 but it turned out he just didn't appreciate the omission of noise expressions that included 1/f. My aim was to convey crucial concepts, not be comprehensive. His own contribution was extensively studded with equations, quite impressive, although his fundamental reference cited is in Germany a popular and lengthy general electronics textbook, according to Groner. I must say Vogel has come a long way, considering that his initial work was far afield from electronics. Popa believes him to possess an advanced degree which I don't believe is the case, but no matter. But he did get published by Springer!
I was just thinking of errors like, "you missed a factor of two in that equation" vs. if you change the architecture of your first stage to this you will get a different answer.
In terms of voltage noise, it'll be entirely recombination, so the excess 1/f noise will be where it's most affected.
One thing I remember was the belief that feedback resistor current noise would be reduced with feedback. I was even advised to run simulations to convince me that he was correct 😱. What I did do is show examples in extensive footnotes, that also in one case was a short exposition of the technique of "cooled" terminations. This still failed to connect, let alone persuade. I gave up.
keeping in line with cool and CCDs. They Came From Beyond Our Galaxy And Landed In The Ice! ? The Register
Another case of scientists being stoic beyond anything most of us can grasp. And plenty of readily available cold. Just not necessarily the 'right' cold 🙂
Another case of scientists being stoic beyond anything most of us can grasp. And plenty of readily available cold. Just not necessarily the 'right' cold 🙂
(nice of Mr. Vogel to include design approaches of Mr. Cordell, Mr. Gerhard, and Mr. Popa (5.1) in his latest publication on balanced phono stages of 2015)
Incredible! I am really upset now!
I reported an error in a TI data sheet (error in pinout) to the TI European HQ. Now some kid calls me to ask if I would please do it again but now using the proper procedure!! 'Scuse me, wft??
I told her I took my own time and reported out of courtesy an error, so I am not going to do it AGAIN.
Still she continues to lecture me about internal TI procedures, wtf??
Totally unfit for anything that resembles customer service!
Don't people THINK anymore these days!!
Jan
I reported an error in a TI data sheet (error in pinout) to the TI European HQ. Now some kid calls me to ask if I would please do it again but now using the proper procedure!! 'Scuse me, wft??
I told her I took my own time and reported out of courtesy an error, so I am not going to do it AGAIN.
Still she continues to lecture me about internal TI procedures, wtf??
Totally unfit for anything that resembles customer service!
Don't people THINK anymore these days!!
Jan
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