Overdriving the 6C45 tube

[swich401]

As in the subject, is it possible to overdrive the 6C45's in the my mainline (e.g. running them biased at 160-180V)?

Benefits (I assume none... maybe a bit more output power)? Negatives (exploding tubes and a dead mainline?) ?

What's the relationship between bias voltage and current applied to the tube? Does increasing voltage drop the current? Does decreasing bias voltage increase the current?

Not that I need to overdrive the tube... I'm just wondering is all...

[Paul Birkeland]

You could overdrive the tube by putting a lot of signal into the Mainline and leaving the level control all the way up.

Negatives:
1.  It will be too loud to listen to.
2.  There will be a lot of distortion.
3.  It won't sound good.

Positives:
I can't think of any.

In the Mainline, the current through the tube is independent of the bias, as a constant current source is used as the load.  The bias voltage is set to obtain the perfect plate voltage, which allows for maximum power output of the amplifier.

If you rebiased the amp to take more input voltage, it would actually end up making less power. 

-PB

[Doc B.]

Overdrive is the onset of distortion. That's for guitar amps, not headphone amps.

[swich401]

Why I was asking is because I saw some DIY builders on the net running the 6C45's with plate voltages as high as 200V and was wondering why.

So if I read you correctly, setting the bias to anything higher or lower than 145V will lead to less output power, and setting the bias higher than 145V can lead to more output distortion?

Thanks for your replies,

-Mischa

[Paul Birkeland]

Why I was asking is because I saw some DIY builders on the net running the 6C45's with plate voltages as high as 200V and was wondering why.

Different designs will call for different implementations. 

So if I read you correctly, setting the bias to anything higher or lower than 145V will lead to less output power, and setting the bias higher than 145V can lead to more output distortion?

The bias is actually the voltage applied to the cathode, which will move around the plate voltage.  In the case of the Mainline circuit, your statement is true.