Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dude on January 29, 2011, 12:15:53 pm

Title: Advice on follow-up reducing gain on crate VC-20
Post by: dude on January 29, 2011, 12:15:53 pm

I'm going to take out the 3rd gain stage on this Crate VC-20 and add a cathode follower as per Hot Blues Plate's suggestion in another post. Similar to a early Fender Bassman type amp.

Someone brought up the issue of:

 "However, you've also raised a great point that the interstage voltage dividers may need to be adjusted after the 3rd stage becomes a cathode follower. They are like fixed volume controls, and could have too much loss after the extra gain is not there to offset the loss". (by Hot Blues Plates)

So, if I change the 3rd stage to a cathode follower, in the schematic where are the interstate voltage dividers and what values might they need to be?

  Are they R9, R10 the 475k's, maybe change to 270K ?


thanks in advance, This question is from this tread (http://www.el34world.com/Forum/index.php?topic=9454.msg86279#msg86279)

al

Title: Re: Advice on follow-up reducing gain on crate VC-20
Post by: jeff on January 29, 2011, 02:18:44 pm

 Maybe if you can move the tonestack between the 2nd and 3rd stage youd get a louder, cleaner signal. The tone stack has loss so you have to turn up the gain which causes distortion then loose part of that signal to the tone stack. If the tone stack came earlier with a gain stage after you could make up for that loss.