Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: hiegdk on January 24, 2024, 06:37:31 pm

Title: 100R vs 1K screen grid resistors in DR103?
Post by: hiegdk on January 24, 2024, 06:37:31 pm

Anyone have any thoughts on using the original spec 100R screen grid resistors (old Hiwatts) vs 1K (a la Ceriatone Hey What)?

Title: Re: 100R vs 1K screen grid resistors in DR103?
Post by: pdf64 on January 25, 2024, 03:23:35 am

The DR103 has combination of 100R individual plus 470R shared.
That type of arrangement introduces some local negative feedback, tends to improve linearity in the linear area, and smooth out the overdriven response.
https://el34world.com/charts/Schematics/files/Hiwatt/Hiwatt_100w_dr103.pdf

Title: Re: 100R vs 1K screen grid resistors in DR103?
Post by: hiegdk on January 26, 2024, 04:59:36 pm

From what I've seen the newer takes on the circuit (like the Ceriatone version) keep the 470R shared and just increase the 100R individual resistors to 1K - just wondering what the implications of this change might be, ie: is it really just a change to better accommodate modern EL34s? Would it have any meaningful impact on the sound of the amp? Any obvious reason to choose one value over the other?