Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Porpoise Head on December 26, 2023, 10:56:01 am
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Hi all,
I had some great help here for my dual rectifier/lightning dual channel preamp build. That project came out great so thanks. I now wanted to take a break building some 'regular' stompboxes but then offcourse a friend gave me some ec91/6aq4's and 6ak6 tubes as a fun project.
So I thought I'd make a deluxe mated with a jcm800 sort of low wattage Amp. Thing is, these ec91 tubes are really different from the good old 12ax7's. Most notably, a very low internal plate resistance of 12k and hence a lot of current. I drew some loadlines but wanted your opinion for a nice center biased stage.
For 250V HT:
Option A. 24k plate, 330 ohm cathode.
Option B. 47k plate, 510 ohm cathode (for lower current at expense of more noise). Any thoughts?