Tube Mic - How precise should the power supply be?

Hello everyone,

quick question about Tube microphone power supply. How precise should the power supply be?

I have a mic that needs 120v for B+ and 6.3v for the Heater. The chinese made psu that came with it gives 124.1v and 6.71v.

Will this affect the performance of the mic? or as long as the voltage is stable and filtered everything will be fine?

Also I see a lot of post on various forum talking about replacing everything in the chinese made PSU (caps + diodes) to lower the noise floor... to me what's inside the PSU look just fine  :-\

Thanks

you might want to lower the heater voltage

Gus said:

you might want to lower the heater voltage

Click to expand...

It's all by design; Chinese cable drops around 0.5v over 7.5 meters, for 6.2-6.3 at tube.

Change the crappy cable for something better, and you'll get the full 6.7v inside the mic. Best then to pull diode on ground pin of 7806 (D11?) and replace with jumper for 6v.

Are those voltages measured with the microphone connected or not? And where was the measurement made?

In general, don't worry about mic supplies if they're within 10%..

Jakob E.

Khron said:

Are those voltages measured with the microphone connected or not? And where was the measurement made?

Click to expand...

The measurements were taken directly at the tube pins with the 15 feet cable.

My concern was more about the heater. The tube is rated for a maximum of 6.3v but it's not mentioned if there's a tolerance %...

elskardio said:

The measurements were taken directly at the tube pins with the 15 feet cable.

My concern was more about the heater. The tube is rated for a maximum of 6.3v but it's not mentioned if there's a tolerance %...

Click to expand...

If you have the standard Chinese cable, yours is too short for the proper voltage drop (rated for 25' minimum).

You can add a 1 ohm resistor, or remove the diode.

I added a 1 ohm resistor in series and now have exactly 6.3v

thank you all for your input

Banzai said:

Change the crappy cable for something better, and you'll get the full 6.7v inside the mic.

Click to expand...

Besides getting better voltage at the end of the cable, does a high quality cable improve the sound of the microphone? (lower noise floor)

I'm about to order some Gotham cables and I wanna make sure it's a good investment 

Thanks