AKG C3000 TO Tube Mic Mod..

[commanderberti]

sounds great, the T47 (Behringer) tube circuit are perfekt für the AKG C3000 Capsule.. see the steps..

 

[micolas]

@commanderberti
That's an interesting idea!
What can you say about the self-noise?
With the C3000b capsule, the SNR will improve a bit, but the stock T-47 had maybe over 20dB of noise with the original small electret.

 

[k brown]

@commanderberti
That's an interesting idea!
What can you say about the self-noise?
With the C3000b capsule, the SNR will improve a bit, but the stock T-47 had maybe over 20dB of noise with the original small electret.

With the AKG capsule SNR will improve a LOT!

 

[micolas]

With the AKG capsule SNR will improve a LOT!

That's exactly what I thought, but the headroom will decrease.

 

[commanderberti]

That's exactly what I thought, but the headroom will decrease.

exact , i will test it on weekend.. with the c3000 capsule the output is much higher.. i will test the headroom.. and test it with lower gain tubes.. results i post here.. cu

 

[commanderberti]

here you can see how i mecanical fit them together..

 

[commanderberti]

here the schematic .. T1 is near by T47 ..

 

[micolas]

exact , i will test it on weekend.. with the c3000 capsule the output is much higher.. i will test the headroom.. and test it with lower gain tubes.. results i post here.. cu

ECC83/12AX7 is a high-gain valve
(μ approximately 100) and has an anode impedance of 62,000 Ω.
ECC81/12AT7 is a medium to high gain valve (μ approximately 60) and has an anode impedance of 10,000 Ω
ECC82/12AU7 is a low-gain valve
(μ approximately 17) and has an anode impedance of 7,700 Ω.

 

[micolas]

@commanderberti
In another discussion group about tubes the following remark is made:
12AT7 has more focus on mids
12AU7 is pretty flat

 

[k brown]

ECC83/12AX7 is a high-gain valve
(μ approximately 100) and has an anode impedance of 62,000 Ω.
ECC81/12AT7 is a medium to high gain valve (μ approximately 60) and has an anode impedance of 10,000 Ω
ECC82/12AU7 is a low-gain valve
(μ approximately 17) and has an anode impedance of 7,700 Ω.

Though it's frequently done, the 12A_7 types are not fully interchangeable in most circuits; they really should be optimized for a specific one.

Probably best to reduce gain some other way.

 

[micolas]

Though it's frequently done, the 12A_7 types are not fully interchangeable in most circuits; they really should be optimized for a specific one.

Everyone agrees with that.

* But the 12ax7 is not a very good tube for a microphone.
Some useful information can be found in the thread:

https://groupdiy.com/threads/sct700-mods.66307/#post-854985

I changed the 12AX7 into an SCT-700 with ECC81 Tungsram NOS, although the tube pins were soldered to the pcb and the small space did not allow me to add a socket. I mounted a socket with additional wires and tested several ECC83,81,12a... from Tesla, Telefunken, EH,etc.
I kept the stock transformer that sounded good to me and the stock power supply, I don't remember what else I tweaked, it's been many years since then. Yes, the original capsule sounded good but too bright, even sibilant, I tested several.
* I used the 12AX7 successfully in guitar amplifiers, especially if I wanted the clean sound to be more crunch on guitars with humbuckers (if what I'm saying makes sense)

 

[ZHOUJUN]

Many years ago, a friend gave me a T47, which I almost threw away as garbage. I am going to try to replace the sound capsule according to your method.