D-Noizator: a magic active noise canceller to retrofit & upgrade any 317-based VReg

There's a moving coil phonostage here on the Forums called "Pearl3".

Moving . Coil . Phonostage .

With 100 microvolts to 400 microvolts of input signal and 70dB of voltage gain (3160X).

Pearl3's power supply is just a MC7815 voltage regulator IC for +15V plus a MC7915 voltage regulator IC for -15V. That's all. Yet those old and forlorn IC regulators manage to attend the needs of a moving coil phonostage. Many dozens of diyAudio members have built Pearl3 and LOVE its sound. LOVE its sound. Measured performance is extremely good too. Search the Forums, you'll find Pearl3 easily.

If there's anything even remotely exotic about Pearl3's power supply, it could be the fact that the transformer and rectifiers and power supply filter capacitors are located in a separate chassis. Two meters away. The high gain amplifier (with decrepit old 7815 / 7915 regulators) is 2 meters away from the transformer's magnetic field, and there are two metal boxes separating them.
 
  • Thank You
Reactions: triode_al
It doesn't bring anything compared to stock application with R1/R2. It does seem to offer more LF PSRR with a bypass cap though. But that is also valid with higher value R1 (2.7K-3.3K).

LM317.png
 
Then I will use it with no denoisator.
There might be a middle term: you can blunt the denoisator by reducing the gain of the correction. The simplest way to do it would be the addition of an emitter resistor to the transistor.
If the correction is reduced from 30dB to 15~20dB, it will still make useful job, but it should be more stable.
I didn't test it, but it should be done in the real world, because sims are useless for this kind of tweak.
Start with 150 ohm, and see what happens
 
  • Like
Reactions: diegomj1973
L1 most likely won't be required, but footprint might be useful to correct C4 ESR in case you have only low ESR caps. C4 should be around 0.2R ESR. You can also use 100uF-470uF depending on what you can find with that ESR, but have at least 100uF.
You could also add a 22uF-47uF cap between your TP1 and GND for some extra PSRR.
If you want the full 1.5Aout of LM317 you need around 13.5-14VAC transformer secondary voltage, and at least 2200uF for each C1 and C2 in your schematic. Bridge should also be up to par. Bellow schematic is for 12Vout.

View attachment 1436932
I'm going to substitute in BC327 to keep it THT.

Regards,
Dan
 
There might be a middle term: you can blunt the denoisator by reducing the gain of the correction. The simplest way to do it would be the addition of an emitter resistor to the transistor.
If the correction is reduced from 30dB to 15~20dB, it will still make useful job, but it should be more stable.
I didn't test it, but it should be done in the real world, because sims are useless for this kind of tweak.
Start with 150 ohm, and see what happens
The same trick can be used with dantwomey's regulator?

Pity it can't be seen on LTspice sim. How will this modified circuit, with the emitter resistor, show it's stable?