Hey. I've spent a lot of time this year investigating and experimenting with my Dual Rectifier. There's a lot of misinformation out there, in general and in particular to this amp. Topics covered include the loop mod, getting vintage tones, the EQ, and the voicing circuit. If it helps anyone, it was worth the time.

https://warpedmusician.wordpress.com/category/tube-amps/mesa-boogie-dual-rectifier/

From the main menu, there are articles for other topics, but the Recto seems to be the one that needs the most support from users.

This is a modification for a Dual Rectifier to smooth the distortion. It removes some of the harsh overtones, improves the clean channel, and removes a touch of low frequencies. It changes one resistor. The concept of the mod applies to other amps like: Peavey 5150, 5150 II, 6505, and 6534; Marshal JCM 2000 DSL 100; Soldano SLO 100; and others, though the detail would be slightly different. An analysis of those amps would be needed to show operating conditions, but the change would produce the same sort of result.