Brauner Phantom V, I need a schematic!

[Gus]

One simple thing to try is powering the bigger board with the top board disconnected to see if the voltage goes up at the zener and if they do measure the BC246D drain and source voltages

The next thing to try is, lift one end of the 10k that goes to the DC to DC section (the one that goes to the 22uF) and checking the voltages again

I have a schematic drawn that I am going to check again

The circuit looks like it is sensitive to the JFETs used and phantom power

 

[Gus]

You might want to clean the top PCB. I don't understand why the capsule wires go direct to PCB without insulated turrets in the high resistance section.

If I was to build a circuit like this(the microphones do cost some money) I would have a CC not a resistor to the Zener and also take into account Zener noise at the SF part(or I might use something else besides a Zener). There are a few others things I would change.

Thanks for the puzzle it was fun to trace this. I am thinking about the whys in the design process.

I have a trace, had some help. Would it be bad form to post it?

 

[Nollman]

If it would help someone who is trying to repair a microphone or open a discussion about the unique circuitry choices in this mic then posting it would be beneficial to this community. The down side is that the manufacturer would not prefer having their carefully guarded design shared. I'm not sure what the rules of this forum dictate.

 

[GeorgeToledo]

At least in the US, a trace of a circuit is not the official manufacturer circuit diagram, there is no copyright on it except the one that belongs to the person who traced it.

That said, I remember the puzzling incident where the trace of the Distressor circuit was taken down, so who knows.

 

[RuudNL]

Did you measure the transformer?

Some time ago I had a Brauner Phantom Classic in for repair.
I measured the (very small!) transformer and to my surprise it was a 1:1 one.

 

[Gus]

That is interesting about the transformer ratio I was guessing 5:1 or lower.


Elliott Sound Products has a good JFET article link on the first page of the site. For anyone that finds it look at diagram 7.1 and the paragraph and the distortion measured

 

[RuudNL]

Speaking about distortion: the distortion of the Brauner Phantom Classic measured pretty high.
I injected a test signal with very low distortion (<0.01%) on the gate of the first FET and even at moderate levels the distortion at the output of the Classic was around 0.5%, mainly second harmonic.

 

[Gus]

Nollman
Did you get the gain stage power supply voltage to increase?

 

[Gus]

If traced the circuit correctly, it is very dependent on the jfet specs or resistors used to set up the two stages If the drain currents are too great there might not be enough current to Zener and keep the voltage at about 15VDC.

I am GUESSING the gain stage part of the sound is most likely the output source follower into the transformer(RuudNL's post is interesting). I have not worked on or tried a phantom C or V.

 

[Gus]

Has anyone else traced this circuit?
RuudNL post about the distortion in the classic is interesting

 

[steffenaa]

hello, what kind of transformer is this?

 

[steffenaa]

can I buy it somewhere?

 

[mic test]

I have a brown one here, how can I measure the transformer behavior? would like to recreate it

 

[mic test]

this