Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: shooter on November 10, 2016, 09:32:55 pm

Title: PI ?
Post by: shooter on November 10, 2016, 09:32:55 pm

Trying to figure out the results of the 100K in the thumbnail below.
My guess is  VERY? Unbalanced signals as PA drive.
thanks

Title: Re: PI ?
Post by: PRR on November 10, 2016, 11:11:35 pm

> My guess is  VERY? Unbalanced signals as PA drive.

Why??

The naked grid is >100MEG. Another 100K in front is not a big difference.

There's some Miller effect. Still flat to 16KHz. And the whole power section appears to have NFB which may pull it out a little more.

Williamsons often have 47K there.

Title: Re: PI ?
Post by: shooter on November 11, 2016, 08:37:28 am

Thank you!, As I was trying to sleep my brain came up with about that, 100k/1M isn't that much.  This is my 1st PI of this type.  I like trannies, less work :laugh:

Title: Re: PI ?
Post by: HotBluePlates on November 15, 2016, 11:59:55 am

Quote from: shooter on November 10, 2016, 09:32:55 pm

Trying to figure out the results of the 100K in the thumbnail below. ...

It is being used to smooth the distortion of the phase inverter during clipping.  See "The input coupling capacitors" section here (http://www.aikenamps.com/index.php/the-long-tail-pair).