A mic that never was (a thought-experiment circuit for the RK-12 capsule)

[micolas]

If you swap BOTH pairs of wires, it doesn't change anything.

You are absolutely right, the circuit works in both versions.
But...
In many years of working with transformers I have noticed some rather subtle details.
If I connect the beginning of the primary coil to the hot part of the audio signal, and the end of the primary coil to GND, the coil will behave as a kind of electromagnetic screen (especially the last layers of the winding) and we will have less hum. The secondary having low impedance will be less sensitive. That's why I chose the second variant of connecting the transformer.
Maybe that's why in many schemes we see the beginning of the coil marked, connected to the hot part of the signal.

 

[micolas]

OK, this is how I understand it so far, hopefully it's correct now:

View attachment 144758

Put C6=22uF though.
nte10-3 sounds a bit thin, has small magnetic core
I even increased C11 to 1.5...2.2uF.

 

[Jakub W]

Thanks a lot @micolas
That's the DCDC circuit I am most familiar with and would like to use:

 

[micolas]

View attachment 144756

I want to use a UTM0547 as OPT. I have used other ratios with a similat design in the past. J2 can be even be an BJT, but I'm just using parts I have laying around. Disregard R17, I forgot to pull it out, lol.

Many are of the opinion that J2 would be better off being a BJT.
But it's everyone's choice.
Is the schematic your design?

 

[Khron]

That's the DCDC circuit I am most familiar with and would like to use:

Are you 100% sure that schematic is drawn correctly?

 

[micolas]

Thanks a lot @micolas
That's the DCDC circuit I am most familiar with and would like to use:
View attachment 144762

DC/DC consumes very little current. C1=330uF is huge. 47uF is enough.
You will need to feed the DC/DC through a resistor so that you give the Zener 9.1 just a few extra volts to effectively stabilize, not "stealing" more current from the audio circuit.

 

[micolas]

Are you 100% sure that schematic is drawn correctly?

@Jakub W
Here is a proven scheme that I use in most situations.
At such low currents, I don't even use a zener diode, which can be noisy. The electrolytic capacitor behaves as a pseudo current reservoir.

 

[Drosselmeier]

Thanks a lot @micolas
That's the DCDC circuit I am most familiar with and would like to use:
View attachment 144762

To reduce the current consumption I've put a 1.6 meg resistor R9 for the 2n5551 transistor.
I selected it based on min current and max output voltage.

 

[micolas]

To reduce the current consumption I put a 1.6 meg resistor R9 for the 2n5551 transistor.
I selected it based on min current and max output voltage.

I often used between 1.2 ...1.5Mohm and obtained the higher polarization voltage, 90...100v
In addition, I made a tighter electromagnetic coupling between the inductors.

 

[analag]

Is the schematic your design?

Yes. I built the first version of it with BF245a in J1 and J2 position.
Here is a rap song with Rev 1 of that circuit. Mind you I mixing in
View attachment Make It.mp3
some grime to fit the track.

 

[micolas]

Yes. I built the first version of it with BF245a in J1 and J2 position.

I like the design, and I thought about something like that. Many years ago I was building guitar pedals with multiple jFETs, they behave closer to a tube than a BJT.
I'm really following @thor.zmt 's projects with MosFets very carefully. They have great potential.