5.3v on 6SN7 filament?

[G]

What are the liabilities of running 5.3 volts DC on 6SN7 filaments?

 

[Fuling]

Lower gm, higher rp and shorter lifespan

 

[SpreadSpectrum]

If you don't run them very conservatively, you can deplete the space charge and damage the cathode.

See:
http://www.diyaudio.com/forums/showthread.php?postid=1441880#post1441880

 

[G]

Thanks for the answers. I was just curious.

 

[gingertube]

Let me guess - you are rectifying a 5V winding originally intended to supply the tube rectifier heater/cathode.

I've done this myself BUT using schottky diodes. In the amp concerned, a 5V 2A winding with schottky diode bridge and 10,000uF/25V electrolytic pushed 5.95V DC into a 12AX7 heater (0.3 Amps draw) very nicely.
I used 4 off 1N5822 (40 Volt 3 Amp) schottky diodes for the bridge.
These things aren't real cheap but when I looked at replacing 2 of them with a MBR20100CT (dual 100V 20A with common cathode in a TO-220 pack) to save some bucks I found that the voltage drop was significantly higher.
Looking at the heater supply with a CRO (in circuit with the whole amp running) I did see a few small spikes projecting out of the ripple which went away when I sat the whole supply on a +60V DC supply derived from the main HT.

Heater Voltage Specification is +/- 5%. 6.3 - 5% is 5.97V. As far as I'm concerned the 5.95 is "in spec" (ish) whereas 5.3 is not.

Cheers,
Ian