Is the regular 6s6b tube ok?

[elskardio]

Hi guys,
I’m working on a M49 style microphone and bought a couple of 6s6b tubes. It's the regular version (no -v in the product code).
Will it give similar results or do I absolutely need the 6s6b-v for the lowest noise?
Thanks

 

[bremusound]

The -v variant is a bit more rugged, maybe slightly less microphonic. Noise level should be the same.

 

[elskardio]

Thanks for the reply
While I was testing the tube the psu 7806 regulator for the heater died and the tube received 12v for 1-2 minutes…
Can this damage the tube?

 

[RuudNL]

I would say it is a miracle if it is still alive...

 

[LevinGuitar]

Well, that's a good reason to install a fuse in the psu

And I thought Ruud was too cautious
https://groupdiy.com/threads/cheap-power-supply-for-ac701-tube-microphones.67924/

 

[gyraf]

..could also current-limit the PSU, that would protect at startup (cold filament) as well..

 

[elskardio]

..could also current-limit the PSU, that would protect at startup (cold filament) as well..

The 6s6b’s heater draws 200mA at 6.3v
Would a 250mA fuse on the psu 6.3v output suffice?

 

[gyraf]

What does it draw when cold? That's what you'd need to dimension for..

Perhaps a 300mA PTC "reset-able fuse" could make sense e.g. https://www.aliexpress.com/item/1005005334886883.html - although it's hard to estimate if it gets triggered by turn-on-cold-current

 

[aazaa]

I like the first suggestion of gyraf, to go for a simple current limiter.
You could use for R1 6R8 parallel with 68R, the result is a current limitation of 202mA.

 

[GussyLoveridge]

This is a question, not a suggestion, but could you use a Thermistor in this case to limit the inrush current?

 

[gyraf]

Yes, I think television s did that for many-heater- series strings