Randall RM20C

Tube config

Power valves: 2 x EL84s (Sovtek)

Preamp valves: 3 x electro-harmonix 12AX7EH - www.amplifiedparts.com/products/T-12AX7EH

Ultra module: 2 x 12AX7s (JJ) - www.amplifiedparts.com/products/T-12AX7-S-JJ

Speaker

Celestion G12M greenback

Modifications

Here are some possibilities:

• first gain stage: all modules must use the first gain stage that is built inside the Randall; Changing the cathode bypass (C1) from 22uF to a smaller value will raise the cut-off frequency.

Module tube choices

Warning! The tube in the V2 position is used by the module as a cathode follower.  This tube is subjected to high voltages that not all 12AX7 tubes can handle.  It is not recommended to use anything manufactured by New Sensor (ie: Tungsol and Mullard reissue, EH, Sovtek) in this position.