I have a question about these micro tube mic ?

[pasarski]

Usually, the heat generation of an electronic tube mainly comes from the energy released by its filament (like an incandescent light bulb). Compared to this, the heat generated by the anode voltage is still negligible. Therefore, if a voltage conversion component is not placed inside the microphone, a lower filament power means lower heat generation. Considering that many commercial products nowadays excel in placing electronic tubes such as ECC88 in such small microphone housings, I believe this will not be a problem

I think we are talking about powering the whole tube with P48 and I believe that's what done with Kinkgorgs mic.

 

[mmadu]

I think we are talking about powering the whole tube with P48 and I believe that's what done with Kinkgorgs mic.

Oh, what I mean is that if heating doesn't become a problem in ECC88 and other electronic tube microphones, then microtubes won't either, that's all

 

[mmadu]

By the way, some electronic tubes are designed to operate at extremely low voltages and currents, but those are likely to have significant distortion issues. It is best to refer to the data sheet to confirm this. Electronic tube microphones have been around for nearly a hundred years, and many engineers have conducted research on them. There is a reason why phantom powered electronic tube microphones have not appeared. If they cannot bring better performance than FET, they will be meaningless:（

 

[mmadu]

I think this one you posted in another thread is even more intriguing. Wonder what the device is? Maybe a nuvistor? Also doesn't seem to be connected.

Oh, and also, this electronic tube comes from China/Soviet Union, starting with 1z8 and with a maximum of 1z11. It is a high back pressure pulse rectifier tube, usually used for high-voltage pulse rectification in televisions, and can provide approximately a few mA of current. As you can see, the metal cap on the top of this electronic tube is designed to pass high voltage.

Correction: The maximum current of 1z11 is 300 μA

 

[pasarski]

By the way, some electronic tubes are designed to operate at extremely low voltages and currents, but those are likely to have significant distortion issues. It is best to refer to the data sheet to confirm this. Electronic tube microphones have been around for nearly a hundred years, and many engineers have conducted research on them. There is a reason why phantom powered electronic tube microphones have not appeared. If they cannot bring better performance than FET, they will be meaningless:（

Yes. The datasheet of the 6418 tube I posted here earlier states 12% total distortion. What ever that means, it doesn't imply very hi-fi performance. (Though the spec is for using it as a power tube in a hearing aid device I think.)

 

[mmadu]

Oh, that makes sense. Deaf people usually only need to amplify the sound in the frequency band where the human voice is located, so reducing design difficulty in this way is economical (just like radio)

Yes. The datasheet of the 6418 tube I posted here earlier states 12% total distortion. What ever that means, it doesn't imply very hi-fi performance. (Though the spec is for using it as a power tube in a hearing aid device I think.)

 

[kingkorg]

There is a reason why phantom powered electronic tube microphones have not appeared.

https://www.audio-technica.com/en-us/at3060

https://shop.funky-junk.com/shop/re...e/microtech-gefell-um-900-tube-condenser-mic/

https://naiant.com/2016/02/16/x-v-tube-kit-microphone/

I've had no issues with these tubes. Neither distortion, or any other aspect. They have to be suspended carefully to avoid microphonics. They are fun to play with.

 

[mmadu]

https://www.audio-technica.com/en-us/at3060

https://shop.funky-junk.com/shop/re...e/microtech-gefell-um-900-tube-condenser-mic/

https://naiant.com/2016/02/16/x-v-tube-kit-microphone/

I've had no issues with these tubes. Neither distortion, or any other aspect. They have to be suspended carefully to avoid microphonics. They are fun to play with.

The reason why a large number of microphones used miniature tubes in the early days was stability and microphone effect - the tube contained a rather unstable filament structure, and if it was subjected to vibration, it would produce strange sounds or even be damaged. However, microphones such as the AKG C61 use Nuvistor, a specially designed tube used in the aerospace field. It should be pointed out that these tubes still require filaments and high voltage power supply - this is due to the principle of the tube. Without filament heating and high voltage, electrons cannot be emitted to the anode normally.

Correction：its C61

 

[MagnetoSound]

C61 is nuvistor, C60 is AC701(k).

 

[mmadu]

C61 is nuvistor, C60 is AC701(k).

Sorry, I remembered it wrong.

 

[Wavelength]

Yes. The datasheet of the 6418 tube I posted here earlier states 12% total distortion. What ever that means, it doesn't imply very hi-fi performance. (Though the spec is for using it as a power tube in a hearing aid device I think.)

That's driving headphones, which I think is silly for that tube.
~~~
Distortion depends on a number variables, my audio 6418 preamp is at 0.5% at 2Vac rms at 20Hz.

 

[pasarski]

That's driving headphones, which I think is silly for that tube.
~~~
Distortion depends on a number variables, my audio 6418 preamp is at 0.5% at 2Vac rms at 20Hz.

Yes of course. That's not bad at all. @mic test you should check the Naiant schematic posted here earlier. 20% underheated, a good P48 and voilà.

 

[Emmathom]

Usually, the heat generation of an electronic tube mainly comes from the energy released by its filament (like an incandescent light bulb). Compared to this, the heat generated by the anode voltage is still negligible.

I don't really agree... The electrons hiting the plate generate ~90% of the heat of the tube.
Touch an EL84 of an amplifier with your fingers 1) just heater on 2) HV fed (and audio signal) and you'll notice that (finger burn !) Speaking about a power tube not a pre tube...
Best Regards

 

[rankot]

FWIW i have made a phantom powered version of C12 with russian 1J24B (1Ж24Б) with 1.1v filament, and like it a lot.

Do you intend to share a schematic for that, or sell PCB perhaps?

 

[rankot]

Gang,
The 6088,6418 and other tubes like this are directly heated. I use these all the time and have like 2K of the 6418 here. The 6088 draws 20ma at 1.25V and the smaller 6418 draws 10ma on the filament. BUT here is where it becomes tricky. Unlike an indirectly heated cathode, a directly heated bias point is in the center and it also needs to float bias and for these tubes best to use a current source for that. I use a LM317L with a 121 ohm resistor into pin 5 with a capacitor to ground and bias off pin 3 with a pot. The big problem with these tubes is that they are microphonic if mounted wrong. Put them on a 1/2" of foam. Digikey sells 1/2" foam double tape that works great.
So in triode mode the max gain I have ever gotten is 8. In pentode mode you can get up to 30. The Rp is really high either way so I use typically a 0.33ma current source then use an LSK189 as a source follower to drive the signal.
Here's is one of my clean boost pedals using the 6418 or the 6088. Both do triode strapping of pins 1 & 2 together. These tubes get a little funky in pentode mode. I am working on a 500 series DI and tried to use pentode mode and it's not being consistent across a lot of tubes.

So you actually just limit current for filaments? But how do you drop voltage to 1.25V, if you use phantom powered mic?

 

[kingkorg]

Do you intend to share a schematic for that, or sell PCB perhaps?

I just built it on the spot. No schematic unfortunately. It is just the typical c12 cardioid only arrangement where i just adjusted plate and cathode resistors to get appropriate operating point for the tube, and ran the filament straight from the battery. Probably went from xlr 2 and 3 through two 6k range resistors to the plate resistor. If you take the battery route, make sure battery voltage doesn't get too low so that the filament doesn't underheat, and possibly eventually damage the tube.

 

[rankot]

I just built it on the spot. No schematic unfortunately. It is just the typical c12 cardioid only arrangement where i just adjusted plate and cathode resistors to get appropriate operating point for the tube, and ran the filament straight from the battery. Probably went from xlr 2 and 3 through two 6k range resistors to the plate resistor. If you take the battery route, make sure battery voltage doesn't get too low so that the filament doesn't underheat, and possibly eventually damage the tube.

Thanks!