Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jordane on June 15, 2025, 10:42:53 am
-
I have built a Plexi SE that sounds good as is, but my question is about the VW (edit: Valve Wizard) cathode follower tweaks, from here:
https://www.valvewizard.co.uk/dccf.html
Merlin shows two versions of a resistor-diode in series between the grid of the second triode in the cathode follower (V2b, not noted on my schematic but I modified the design in my build) and cathode of V2b. Forgive me if this has been discussed, I can’t find much through searching.
The first schematic shows a 10k into the diode, and the second shows a 47k into the diode. I’m wondering whether there’s a functional difference between the two. The one I built uses the 10k->diode… but possibly the 47k->diode would suit me better?
Schematics included.
-
...... the VW cathode follower tweaks
There's a reason we use words, not just a letter for a word.
What is 'VW' mean?
If you would at least spell out the words the 1st time, then you can use letters further on.
-
Apologies, will edit the first post. VW=Valve Wizard.
-
I was over-cautious when I started using that mod, I didn't want the diode to overwrite the tube clipping, so I used a generous 47k resistor. Later I dropped down to 10k as that also seemed fine. Finally, I'm now satisfied the resistor isn't necessary at all, the tube will draw plenty of grid current well before the diode conducts (I need to update the webpage, ahem).
-
Merlin, thank you for providing your input. I have read your website pages many times! I need to order a copy of your book.
I really appreciate your writing.