Heating only one half of a double triode

[bequerel]

Is it OK to let a current source (LM317) heat only one half of a double triode (provided that I only need one single triode in each channel)? Eg. heater current from pin 4 to 9 in the left channel tube and current from 5 to 9 in the right channel tube.
This way I could swap tubes after some time, and get double milage out of the tubes.

 

[kooltubes]

Hi,
Which tube are you using?

 

[EC8010]

Is it OK to let a current source (LM317) heat only one half of a double triode (provided that I only need one single triode in each channel)? Eg. heater current from pin 4 to 9 in the left channel tube and current from 5 to 9 in the right channel tube.
This way I could swap tubes after some time, and get double milage out of the tubes.

Don't see why not. Mind you, I'd simply use both of the valves in the one envelope and not worry about the tiny amount of crosstalk due to the capacitances.

 

[bequerel]

Thank you EC8010. It still looks a little bit cooler with two tubes, one per channel, than charing one single tube for both channels

RE: kooltubes
It was a general question, however I was thinking about ECC99 or 5687.

 

[kooltubes]

Hi Bequerel,

I have tried both the ECC99 and 5687 with AC and DC heaters; I have found that AC sounds best, there is no hum providing that your grounding is good.

 

[bequerel]

Re: kooltubes
Was this in a linestage or as poweramp driver stage?

I will be using it in a linestage with output transformers.

 

[kooltubes]

Bequerel,

It's a linestage with output TX

I have tried ECC99 was biased at 18 ma 155 V on the TX input and 18ma without output TX (plate voltage:150V). No hum with AC heaters!

I am still having some difficulties trying to bias the 5687 and the 7044.

However the 5687 and 7044 at 14~15ma are interesting. The 5687 is on the warm side (not my cup of tea); the 7044 is brighter and has more kick than the ECC99....so I am still undecided on which tube to use for the linestage.

 

[bequerel]

"It's a linestage with output TX
I have tried ECC99 was biased at 18 ma 155 V on the TX input and 18ma without output TX (plate voltage:150V). No hum with AC heaters!"

Exactly what I am working on too! Think I will try AC first, since this probably sounds best, too

 

[DigitalJunkie]

Or you could parallel both halves. I've heard this can help reduce noise.

 

[Colt45]

you could just use similar tubes with only one triode too.

6AV6 = 1/2 12AX7 + 2 diodes
6C4 = 1/2 12AU7
etc..