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good driver tube with 150mA heater?

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SemperFi

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Joined 2002
I need a decent driver (for PP triode output stage) and I only have 150mA for the heater so 12AY7 can work, but are there any 12V versions of tubes like 6EJ7? 12AU7 looks like a good driver tube, but from what others report it's not a very good tube. ?
I'd love to use a cheapo pentode triode strapped and prefer 6EJ7, but in this case I must have a 150mA heater.
Any suggestions?
 
soulmerchant

soulmerchant

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Joined 2006
SemperFi said:
I need a decent driver (for PP triode output stage) and I only have 150mA for the heater so 12AY7 can work, but are there any 12V versions of tubes like 6EJ7? 12AU7 looks like a good driver tube, but from what others report it's not a very good tube. ?
I'd love to use a cheapo pentode triode strapped and prefer 6EJ7, but in this case I must have a 150mA heater.
Any suggestions?
Click to expand...

6EJ7 triode strapped has an a gain of around 45 right? Why do you need so much gain for a driver stage?

ok.. maybe I don't want to know, but from my experience, all great drivers need some current, and that needs some heat. 150mA just won't get you much heat. No other way to design around getting some more filament current for your driver?

Too bad you don't have a bit more filament current. If you did, you could use the 12B4.... but the heater needs 300mA.
 
soulmerchant

soulmerchant

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Joined 2006
It would help to know what you are trying to drive. If miller capacitance is not an issue then I guess there is a lot of choice out there and wimpier tubes will do it well enough.

edit: if you are driving 6AS7 then 12AU7 is a fine choice - but you won't get a gain of 45 out of it. I think it has a gain of 15-17. I still prefer 12B4 though... ;)
 
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SemperFi

Member
Joined 2002
Youre right Soulmerch! I hope I would have caught that if I had 300mA and about to wire them in. They are an example of cheap pentodes that triode well. I use a pair to transformer drive a pair 6V6 in a guitar amp.
The 6AS7 amp is also for guitar and they overdrive nicer with some gate drive. I think Shoog's suggestion are worth trying.
 
Shoog

Shoog

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Joined 2002
My personal experience is that the xAU6 series has a tendency to generate a reasonable amount of 2nd harmonic distortion where other pentodes do not. No harsh edge to this little valve. It makes an excellent, capable and cheap all purpose small signal pentode with no real downsides ( I have yet to hear a microphonic one despite their reputation for been microphonic.

Shoog
 
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