Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: mwelch55 on June 27, 2019, 10:00:39 am

Title: Input Stage Comparison
Post by: mwelch55 on June 27, 2019, 10:00:39 am

I noticed that the input stage for Epiphone Valve Junior is done slightly different than the input stage of a Fender Champ.  I was wondering about the 1M resistor.  On the Epiphone, the resistor is attached from the grid to ground, and the fender has the resistor attached before the 68K grid stopper resistor.

What is the advantage of one vs the other?  Why would you want to place the 1M resistor directly from the grid to ground instead of the way Fender does it?  How will it affect tone?

Title: Re: Input Stage Comparison
Post by: sluckey on June 27, 2019, 10:23:58 am

I think it's just a matter of choice. Either will work just fine. The Epiphone will have slightly less signal applied to the grid. I would not expect any difference in tone.

Title: Re: Input Stage Comparison
Post by: mwelch55 on June 27, 2019, 10:32:59 am

Thanks for the reply.  I have seen other amps that have that resistor from grid to ground.  I wasn't sure if one had an advantage over the other.

Title: Re: Input Stage Comparison
Post by: PRR on June 27, 2019, 06:34:59 pm

68k (should be 34k) in front cuts signal a half dB, not enough to care.