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I agree with all that's been written before. It's a very interesting intellectual challenge though. Brilliant piece of design. The claimed benefits are at least of second order. The test circuit they

In the light of chip shortages I would be really hesitant to add to the BOM of a product for marginal benefits. They are optimizing something that is really in the weeds here. Best Regards, Jules

I've seen this discussed elsewhere a few times and everyone seems to agree with you. In the current economic climate I don't see this product taking off, but who knows? You just need a few big names

Correction, I looked at the data sheet, it still uses the 6.81K resistors but looks to maintain a constant supply to them. Again, I still don't see a need. Jules [email protected]> wrote: -- Best

I am at AES in Europe (which is really fun) and a vendor approached me with a concept of their custom chip that supplies a constant current instead of using 48V and 6.81K resistors. It is here

What is the signal level (either input or output)? Distortion in a common-source JFET or triode is normally very sensitive to level. The 2nd harmonic at 46dB roughly (0.5%) below the 1KHz signal and

Hi! Just uploaded two THD Graphs, one for a Pat's Mic build and the other one for an OPA Alice build. I tried to use the same Input levels on both tests. Here are the graphs: Pat's Mic Build :

*1. Is the charge amp being accomplished through the Op Amps? * Yes, the first OPA (1C1A) is in a charge amp configuration. *2. Is it possible to use a Jfet with a built in diode for the triode

It is quite possible, but, as I wrote earlier, it wouldn't result in the "tube sound" the dicrete JFET is supposed to bring.

Homero - Thank you for the updates!??1. Is the charge amp being accomplished through the Op Amps??? 2. Is it possible to use a Jfet with a built in diode for the triode section?? Maybe something

Thank you Jerry Lee and Henry, @Jerry Lee Marcel <jerryleemarcel@...> I reduced the value of C8 to 1uf. Also there was an error on the C15 value, it should be 1000p instead of 0.1uf. @William

An additional RC filter would work, or simply adding a resistor between the BC549 and C14, and increasing C14 to push the RC time constant below audibility. The op-amps have good power supply noise

In terms of functionalities, it would certainly work. However, the subject here is getting the circuit to sound like a vacuum tube. An opamp could not do that. No. only singles, duals and quads.

May I suggest you decrease significantly C8. In combination with R15, its -3dB cut-off is at 0.015 Hz. ! Would think 100nF is largely enough there. It may not be the answer to your problem, though,

Hi all, Here's a quick update on the test build with the latest?PCB. I'm experiencing a weird low frequency noise below 1khz. It's?not too high, but can be perceived. At first I thought?it was only

Hello Homero, I hope all is well.? Has there been any further developments on this circuit, and have you had a chance to run any tests??? I am rather new with some of these concepts.? Could the

Here is the actual software: https://austrian.audio/polardesigner/

For ease of use and implementation, wouldn’t free software be a convenient solution? I realize physical interface is more satisfying and this is a DIY group, but I thought I’d mention this:

Here is a great implementation of Wurcer's chargeamp by forum member Zapnspark: /g/MicBuilders/files/Zapnspark/Occam-3b.pdf

Scott Wurcer used to be a member here and he did a thorough study of using a charge amp in a mic. As I recall it was very impressive, and probably about 6 or 7 years ago. The designs might still be in