Comparison of JFETs for mic applications

[JohnRoberts]

If you are still working in the Audio field, they are not. Trust me on that.

I'm not, trust me on that.

That's terrible Latin. If you MUST be trite, please use:

NOLI PATI A SCELESTIS OPPRIMI

Thor

Quid agis hodie?

My apologies for dog latin, but I studied it 60 years ago....

JR

 

[thor.zmt]

Quid agis hodie?

litore habitantis
potator cervisie
persequens puellarum
excogitatoris singulari soni apparatu

My latin lessons are also long time ago.

Thor

 

[k brown]

k brown, you are right that the IBM/Lenovo ThinkPads are by far the most reliable. That's what I've been using so far but the last one died about a year ago. The T61 is the most powerful that had XP drivers. The later Lenovo TP series are not as reliable.

Which model ThinkPads have you got? If you can spare one from the early 90s, dis beach bum would be eternally grateful. Do any have XP?

Not sure how I can re-compense you unless you are making a Tetrahedral Ambisonic mike. If so, I can do a full alignment and calibration that you can compare with da 'general purpose' programmes .. or perhaps even Thors SupaDupa one

Something a mystery here; I had three, and the only one I can find now is an A31. It won't boot up because the mem batt is dead; I used to be able to manually put in the date and it would boot, but now I cen't get it do that.

The other two I can't find anywhere; my wife may have taken them to electronics recycling without my knowledge.

 

[k brown]

No, the J-Fet Library posted at the LT-Spice group of course. The one you need to sign up to access.



In the 2sk660 pdf.

View attachment 143448
As you can see, once we have > 2V across the FET, we are in saturation.



But we are not operation at 1V, are we?

View attachment 143449

I ran BAV99 in the sim, the results match @MicUlli 's test results, good enough for me.



Can do. If you insist. Not that it will change things.



There is nothing here not reasonably well understood for at least 5 decades. I'm still puzzled why we even have a debate.



Other than the Brownian motion noise of the capsule, which I will tackle once my office is set back up, I have confidence in my sims. The kind of confidence that comes from having simmed many dozens of circuits, taken them onto a PCB for mass production and having tested the result with AP2.

So thank you for concern, but it's misplaced.

Meanwhile, please post the circuits you want me to use for the "SimpleP48" and the "SimpleP48RCA" clfor a build in diode J-FET with Id(ss) = 370uA @ 10V.

I was digging around at the io group but gave up. Very poor SNR.

Thor

I purposely retain a certain amount of noise in my gear because recorded music is only emotionally moving because of Brownian Motion.

 

[Khron]

I purposely retain a certain amount of noise in my gear because recorded music is only emotionally moving because of Brownian Motion.

This one / this kind, right?

 

[micolas]

This one / this kind, right?

 

[JohnRoberts]

litore habitantis
potator cervisie
persequens puellarum
excogitatoris singulari soni apparatu

My latin lessons are also long time ago.

Thor

but still teaching vocabulary...

I only recognize about half those words. None of them are JFET.

JR

 

[thor.zmt]

I only recognize about half those words. None of them are JFET.

You asked what I am doing...

Thor

 

[ricardo]

No, the J-Fet Library posted at the LT-Spice group of course. The one you need to sign up to access.

In the 2sk660 pdf.

View attachment 143448

Thanks Thor. I've already got this. But this isn't ... build in diode J-FET with Id(ss) = 370uA @ 10V.

Please post your model with Idss = 370uA @ 10V

I'll have a look at the model in the LTspice JFET library

---

It display can be customized a lot, but it displays either input or output noise density in V|/Hz .. across an arbitrary bandwidth.

Can it plot this against log frequency?

V/rt(Hz) is OK if we have log frequency scale like moamps B&K curve (which is Constant Relative Bandwidth .. but we'll pass on that if it's too difficult for TINA )

Or are you saying we have to do V/rt(Hz) in a bunch of separate 'bandwidths' and plot them ourselves???

After all, the noise advantage is my 'only' claim for both Zephyr's circuit and SimpleP48. I've already conceded da THD battle to Thor's SupaDupa circuit though I'd like another go with SimpleP48RCA .. which is in SimpleP48.pdf as one of the two recommended versions.

 

[ricardo]

Something a mystery here; I had three, and the only one I can find now is an A31. It won't boot up because the mem batt is dead; I used to be able to manually put in the date and it would boot, but now I cen't get it do that.

The other two I can't find anywhere; my wife may have taken them to electronics recycling without my knowledge.

Thanks for taking the trouble to have a look k brown

 

[thor.zmt]

I purposely retain a certain amount of noise in my gear because recorded music is only emotionally moving because of Brownian Motion.

This an interesting topic.

Easy experiment. Take a super clean acoustic recording, with very little noise.

Now add pink noise, violet noise and white noise at -60dB based on signal envelope, to make separate "noisy" tracks, meaning the noise will always be 60dB below the signal peak level and in principle mased by the signal.

Do a blind listening comparison.

Not ABX, but preference based.

And try to find descriptive terminology for each file without knowing the spectrum of the added noise.

Similar fun can be had with HD, compare a classic even order distortion dominant "picket fence" at -60dB added to an (overly?) "clean" track, to a distortion spectrum at -60dB without the even order harmonics (odd order only).

These levels are not that far from what many classic microphones produce.

Thor

 

[JohnRoberts]

You asked what I am doing...

Thor

The words I did recognize appear on brand for you... I do not need to feed this veer.

JR

 

[JohnRoberts]

This an interesting topic.

Easy experiment. Take a super clean acoustic recording, with very little noise.

Now add pink noise, violet noise and white noise at -60dB based on signal envelope, to make separate "noisy" tracks, meaning the noise will always be 60dB below the signal peak level and in principle mased by the signal.

Do a blind listening comparison.

Not ABX, but preference based.

And try to find descriptive terminology for each file without knowing the spectrum of the added noise.

Similar fun can be had with HD, compare a classic even order distortion dominant "picket fence" at -60dB added to an (overly?) "clean" track, to a distortion spectrum at -60dB without the even order harmonics (odd order only).

These levels are not that far from what many classic microphones produce.

Thor

I vaguely recall some old psychoacoustic research that suggested a high noise floor can create the impression of extended HF response .

Human audition is not exactly linear.

JR

 

[rogs]

This one / this kind, right?

Trouble is, once you've seen this you cant 'unsee' it!... I shall now have this picture in my head every time I hear the word 'Brownian' -- probably forever!

 

[micolas]

I vaguely recall some old psychoacoustic research that suggested a high noise floor can create the impression of extended HF response .

Human audition is not exactly linear.

JR

Some intentionally introduce noise into the music or mix, for artistic/psychoacoustic or technical purposes. When mastering, for example, we apply dithering (we add intentional noise to a signal in order to reduce quantization distortion when reducing the bit depth of a file, when bouncing from 24 or 32-bit down to 16-bits)