Holy mackeral, you're right.. what I'm speaking of makes absolutely no sense if IC is taken as integrated circuit...Spiny said:
Thanks, John
Afaik, Curl's preamp designs are bogus attempts of a neophyte designer to get over on the audio world by letting Mark Levinson put his name on the front panel of a design that has far far too few devices in it so that Curl could "make his name" in the audio world. A more self-serving, over publicising person I have never met. We all know that you can't make good sound with so few devices. It is absoolootly necessary to use far more devices, feedback, feedforward, bootstrapping and many ICs (integrated circuits), not to mention microprocessor digital controlled level setting and DSP in order to make a circut work properly. We all know these things... It is past time that Curl should stop trying to put this bit of tomfoolery over on us...
<takes blue pills...>
Ah, I feel much better now. Glad I could contribute and clear this up...
Joshua_G said:
Joshua_G said:
I do not have any guru.
In some way all possible candidates for my audio guru fail a bit.
---- some fail QUITE a bit
Can be attitude, can be some stains, can be some less good & sound audio ideas.
😉
I can agree this is a beautiful balanced JFET circuit by Curl.
It is great and good simplicity. Not as easy to get working perfectly as we may think ....
What I know and have read of John Curl in his posts and good information,
this is not how he would do the same balanced JFET preamp today 🙂
But maybe this is better for himself to comment on.
Lineup regards
bear said:
Afaik, Curl's preamp designs are bogus attempts of a neophyte designer to get over on the audio world by letting Mark Levinson put his name on the front panel of a design that has far far too few devices in it so that Curl could "make his name" in the audio world. A more self-serving, over publicising person I have never met. We all know that you can't make good sound with so few devices. It is absoolootly necessary to use far more devices, feedback, feedforward, bootstrapping and many ICs (integrated circuits), not to mention microprocessor digital controlled level setting and DSP in order to make a circut work properly. We all know these things... It is past time that Curl should stop trying to put this bit of tomfoolery over on us...
If I wouldn't think you are joking, I'd reply.
lineup said:
I'm glad we agree on this one.
lineup said:
Indeed. Next step of ingenuity would be to make it work. Agreed, it wouldn't be easy to make it work, nor inexpensive – yet possible, should proper JFETs and MOSFETs be available.
lineup said:
I have no clue how John Carl would do it today – and today also refers to some JFETs and MOSFETs out of production. All I can relate to is to the circuit I re-posted.
To my view, this circuit IS the work of a genius.
I challenge all to come up with a better one.
Criticism and cynicism I saw a lot in this thread. A better circuit I didn't see.
john curl said:
Thank you very much, John.
I intend to build a similar circuit as an I/V amp to a DAC kit I'm about to receive. In order for such circuit to work as a current amplifier, I believe the input shunt resistors (R1 and R17 in the above schematic) need be reduced. What value would you suggest?
Joshua_G said:
After swallowing a few of those blue pills, I got the balls to step again into the Temple and ask the Gods of Audio:
- A better circuit to do what?
- What exactly means "better"?
Actually, this is not necessarily the best circuit topology for I to V conversion. This is because this circuit is not intrinsically low impedance, and can only be made so by 'shorting' the input by either a very low value input resistor, or by negative feedback. The usual value for R9, and sometimes R17 (for balanced input) is 1 meg ohm.
It might be better to use a 1/2 circuit and drive through the 10 ohm bias resistors and eliminate the 268 ohm resistor. You can use only one side for a single drive, and both sides for a balanced input drive.
It might be better to use a 1/2 circuit and drive through the 10 ohm bias resistors and eliminate the 268 ohm resistor. You can use only one side for a single drive, and both sides for a balanced input drive.
You found me out, BEAR! And answer your phone, once in a while, so I can give you a real piece of my mind. 
john curl said:
Thank you very much.
The DAC's output is balanced, and so is the input of my pre-amp (or, rather, my future pre-amp).
What do you mean by 1/2 the circuit?
Joshua_G said:
I have posted quite a few circuits on this forum.
I would not have the daring ego to say they are better than John Curl best past designs.
However, I would not rule the chance out, that some one of my schematics would match some of John's amplifiers.
Even a blind chicken will occationally find a corn. 😉
I find it a bit sad
that John does not do ampifiers no more.And show us what he really can do for our DIY community.
With modern JFET and other devices I can only dream what this man could accomplish 🙂
Based on all the past exeperiences & knowledge stored in his brain memory.
I guess john Curl feel he is 'retired'. Have done what he should do in this life.
And who could blame him.
What he has done in one lifetime sure isnt bad.
By no standards! 😎
Regards
lineup said:
Please re-post and we'll see how good they may be.
lineup said:
What modern JFETs are you referring to?
Joshua_G said:
Do you think the noise performance has anything to do with this circuit topology/design? And why is noise so important if the circuit input/output metrics (input signal, gain, etc...) are not specified?
Joshua_G said:
Why is "without Global NFB" important? Are we still running around the "NFB bad" paradigm?
I do not post my circuits in this topic. I have several other small topics of my own. Check out my 4000 past posts and you will find quite a number of schematic ideas. Some unique and good and some not anything special.
Modern JFET for John Curl to use.
We have the Linear Integrated System Inc. They make very good low noise JFETs.
They have both single and dual matched JFETs in one package, capsule (monolithic)
http://www.linearsystems.com/
If you can find one distributor for private persons you can for example buy:
- LSK170 1nV / hz Low Noise, Low Capacitance, High Input Impedance, N-Channel JFET Amplifier
- LS846 Ultra Low Noise, N-Channel JFET
- LSK389 1nV/hz Low Noise, Monolithic Dual, N-Channel JFET
- J/SST/U308, 309, 310 High Gain N-Channel JFET Amplifier
- LS843, LS844, LS845 Ultra Low Noise, Low Drift, Monolithic Dual, N-Channel JFET
- LS830, LS831, LS832, LS833 Ultra Low Leakage, Low Capacitance, High Impedance, Monolithic Dual, N-Channel JFET
Other here can tell you some more good modern Audio JFET-s.
I am sure John Curl knows fairly well whats on the market today.
Joshua_G.
I sent you one email regarding John Curl stuff.
Regards 🙂
Modern JFET for John Curl to use.
We have the Linear Integrated System Inc. They make very good low noise JFETs.
They have both single and dual matched JFETs in one package, capsule (monolithic)
http://www.linearsystems.com/
If you can find one distributor for private persons you can for example buy:
- LSK170 1nV / hz Low Noise, Low Capacitance, High Input Impedance, N-Channel JFET Amplifier
- LS846 Ultra Low Noise, N-Channel JFET
- LSK389 1nV/hz Low Noise, Monolithic Dual, N-Channel JFET
- J/SST/U308, 309, 310 High Gain N-Channel JFET Amplifier
- LS843, LS844, LS845 Ultra Low Noise, Low Drift, Monolithic Dual, N-Channel JFET
- LS830, LS831, LS832, LS833 Ultra Low Leakage, Low Capacitance, High Impedance, Monolithic Dual, N-Channel JFET
Other here can tell you some more good modern Audio JFET-s.
I am sure John Curl knows fairly well whats on the market today.
Joshua_G.
I sent you one email regarding John Curl stuff.
Regards 🙂
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