Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Deric on September 27, 2023, 05:32:40 pm

Title: Gibson GA-20 RVT T-Filter Question
Post by: Deric on September 27, 2023, 05:32:40 pm
I was recently asked about removing the T filter in a Gibson GA-20 RVT.  I was referred to this video


https://www.youtube.com/watch?v=p2yFgikXrLo (https://www.youtube.com/watch?v=p2yFgikXrLo)


In the video he removes the filter network and replaces it with a .01u 600v cap and adds a 1M resistor from the following grid to ground.  Couldn't you just replace the filter with a piece of wire?  There is already a coupling cap between the first gain stage and tone controls/volume pot and the following grid would be referenced to ground via the volume pot.


Am I missing something? 


https://el34world.com/charts/Schematics/files/Gibson/Gibson_ga20rvt.pdf
Title: Re: Gibson GA-20 RVT T-Filter Question
Post by: PRR on September 27, 2023, 09:21:23 pm
You mean this section of the 7 minute video (https://youtu.be/p2yFgikXrLo?t=123)?

> Couldn't you just replace the filter with a piece of wire?

In this case, yes. For many hackers, and many mis-documented Gibsons, an R-C is a two-buck all-purpose safer solution.
Title: Re: Gibson GA-20 RVT T-Filter Question
Post by: Deric on September 27, 2023, 09:40:26 pm
Yes, that part of the video.  Thanks for confirming my thoughts.