LTP question

[C Moore]

http://www.valvewizard.co.uk/acltp.html
Merlin may have explained it, but the explanation might be beyond my Basic Understanding of electronics.
What is the cap to ground doing.? I guess it is Cg2...from the second grid to ground.
Thank You

[martin manning]

The second triode is arranged as a grounded grid stage. The input to that stage is at its cathode, coming directly from the cathode of the first triode, and the cap is there to AC ground the grid.

[C Moore]

OK...so the signal is driving the cat of V2...that cap keeps the bias steady.? So no AC will effect the grid bais.?

Thank You

[martin manning]

Yes, correct.

[C Moore]

OK...Thank You

[David Root]

Is there a good reason to use the traditional Cg2 value of 0.1uF or is it simply higher than it needs to be in a modern high gain design where blocking distortion might become a problem?

I have never seen a .01uF in this position.

[deeder]

You can also read ‘Cathode coupled inverters’ section in this site, very helpful to understand how LTP works: http://lenardaudio.com/education/14_valve_amps_3.html

Find this instructive ‘teaching blackboard’ in TGP technical discussion, p.43 if I remember well.

[martin manning]

Is there a good reason to use the traditional Cg2 value of 0.1uF or is it simply higher than it needs to be in a modern high gain design where blocking distortion might become a problem? I have never seen a .01uF in this position.

Blencowe discusses this, and suggests that 10nf might be a better choice than the traditional 100nF for a guitar amp to avoid blocking distortion. The difference would be decoupling to 1.6Hz rather than 0.8. Now, if one were to reduce the grid leak resistors to 470k at the same time, the decoupling frequency would be back down to 0.8Hz, and the tendency for blocking distortion would be even further reduced. Lowering the value of the grid leak resistors has been suggested as a way to reduce noise as well. This all sounds good, but as you say, you don't see anybody doing it.

[C Moore]

You can also read ‘Cathode coupled inverters’ section in this site, very helpful to understand how LTP works: http://lenardaudio.com/education/14_valve_amps_3.html

Find this instructive ‘teaching blackboard’ in TGP technical discussion, p.43 if I remember well.

THAT is quite a sight.....
Thank You