Phantom Powered Tube Microphone (Frankentube) DONE!

[globalpurpose]

I use the mic as end address for live. +27v is plenty, having in mind proximity, plosives, and spl. It basically acts as a pad is engaged. Adding dc-dc converter would be best solution.

Hello , i know it is an old post , but what do You think of this pcb ??? it might help to polarize LDC , it s based on the shematic featured upper in the thread ... would it be "easy" to implement in the Frankebtube design ??? Hex Inverter Voltage Multiplier for Condenser Microphones - Share Project - PCBWay. today i m building it to make OPA Alice mic

 

[homero.leal]

Hello , i know it is an old post , but what do You think of this pcb ??? it might help to polarize LDC , it s based on the shematic featured upper in the thread ... would it be "easy" to implement in the Frankebtube design ??? Hex Inverter Voltage Multiplier for Condenser Microphones - Share Project - PCBWay. today i m building it to make OPA Alice mic

If you take the VCC for the DC-DC PCB from the 10V point (Zener Cathode) on the FrankenTube circuit, it may work. With 10V the DC-DC board should provide about 60+ volts for capsule polarization.

 

[Vac11]

Ive tried something similar few years back. No succes on my side....
No Franken tube mic circuit but slightly adapted 6418 tube di box circuit plus dc-dc converter for polarisation voltage. It was nice experience though

 

[kingkorg]

Ive tried something similar few years back. No succes on my side....
No Franken tube mic circuit but slightly adapted 6418 tube di box circuit plus dc-dc converter for polarisation voltage. It was nice experience though

Such a shame, looks great. What went wrong?

 

[Vac11]

Mic didnt work properly. Very low output between wall of noise....If i remember corectly only 19V on both xlr pins.... 19V on anode, 43V before plate resistor.... Heater was ok in spec. 56V on the output of schmidt dc converter.... Imho there wasnt propably enough juice from phantom...

But i have to say i spend not much time with debuging.

I have some boards. PM me if you want spend some time with this topology.... maybe its only something really stupid in otherwise nice circuit.

Best

M.

 

[jonathan9473]

hey guys! I just built a frankentube mic but there is a 9.8k to 10k hiss noise and I am not sure where does the noise came from. At first, I thought it is because of the tube, but I have tried like8 different 6418 tubes but the noise is still there. Maybe it's because of the opamp?
here's the file

 

[kingkorg]

hey guys! I just built a frankentube mic but there is a 9.8k to 10k hiss noise and I am not sure where does the noise came from. At first, I thought it is because of the tube, but I have tried like8 different 6418 tubes but the noise is still there. Maybe it's because of the opamp?
here's the file

Are you using the original opamp recommended for the build, from a reliable source? Also you can check if the noise comes from heater supply by replacing it temporarily with a 1.5v battery.

 

[jonathan9473]

Are you using the original opamp recommended for the build, from a reliable source? Also you can check if the noise comes from heater supply by replacing it temporarily with a 1.5v battery.

I am currently using opa134ua, is there any difference compared to the opa134pa? and about the heater I am going to try that, maybe there is something wrong with the heater supply.
thankyou

 

[Ricardus]

hey guys! I just built a frankentube mic but there is a 9.8k to 10k hiss noise and I am not sure where does the noise came from. At first, I thought it is because of the tube, but I have tried like8 different 6418 tubes but the noise is still there. Maybe it's because of the opamp?
here's the file

Pic?

 

[jonathan9473]

Pic?

This is a board that I have bought from a seller, and the op amp that he used is an opa134ua, maybe I should switch the opamp to opa134pa?

 

[jonathan9473]

Are you using the original opamp recommended for the build, from a reliable source? Also you can check if the noise comes from heater supply by replacing it temporarily with a 1.5v battery.

I used a 1.5v battery for the heater, the noise is still there but it does improve a lot, maybe there is something happening with the heater supply? what can I do to improve that?
here's the audio file:

 

[kingkorg]

This is a board that I have bought from a seller, and the op amp that he used is an opa134ua, maybe I should switch the opamp to opa134pa?

I asked before, how do you know it's a genuine opa134 at all?

 

[Khron]

This is a board that I have bought from a seller, and the op amp that he used is an opa134ua, maybe I should switch the opamp to opa134pa?

Good luck soldering a DIP8 package (through-hole, PA suffix) onto a SOIC8 (SMD, UA suffix) footprint...

 

[jonathan9473]

Good luck soldering a DIP8 package (through-hole, PA suffix) onto a SOIC8 (SMD, UA suffix) footprint...

true no way it will work, so maybe it's not the problem of soic8 version or dip8 version.

 

[jonathan9473]

ok, after some experiments with the circuit, I'm sure the noise that I'm hearing is from the lm2665, not the opamp. I use a 1.5v aaa battery straight to the filament and it works, the noise is gone( the reason why i can still hear the noise before is because i forgot to unsolder all the lm2665, which is why i am sure it is the lm2665 making the noise). Even that, I still want to know any ways that I could slove the noise problem without using a battery?