AB763 channels out of phase?

[Randall]

I had a customer ask me a question today that I didn't know the answer to. He said he uses a AB763 Super Reverb with a AB763 Deluxe Reverb. When he uses both reverb channels they sound fantastic together, and that he tried switching one to the Normal channel and the volume dropped. He asked me if they were out of phase in that configuration. Does the extra gain stage in the Reverb channel put it out of phase with the Normal channel?

[potatofarmer]

Yes, it does. If he wants to always run this pair of amps, one on reverb channel, one on normal, the easiest way to correct for this is just to switch the speaker lugs on the deluxe reverb.

People who want to jumper both channels on an AB763 amp typically modify the amps to have "reverb on both channels" and there are a couple well-documented ways to accomplish this.

[robrob]

This is how Fender didthe "reverb on both channels" mod in the 68 Custom Deluxe Reverb which puts the two channels in phase for jumpering the channels together: https://robrobinette.com/AB763_Modif...nel_Reverb_Mod

[Leo_Gnardo]

This is how Fender didthe "reverb on both channels" mod in the 68 Custom Deluxe Reverb which puts the two channels in phase for jumpering the channels together

Thanks for the headsup on this robrob. It's not the way I've done it but so what. Just had a RI SF Vibrolux reverb in here that had norm chan fed to reverb & vibrato. Can't be sure but if Fender did it this way, it sounded OK, no complaints.

[robrob]

This is the other way to do it, the "Fritz Mod."

[Leo_Gnardo]

This is the other way to do it, the "Fritz Mod."

That's closer to what I do. Instead of ramming the signals together Y-cable style, I mix 'em with a pair of 220K resistors. No gargle-tone that makes the amp sound like it's on the Fritz.

[Chuck H]

This is how Fender didthe "reverb on both channels" mod in the 68 Custom Deluxe Reverb which puts the two channels in phase for jumpering the channels together

When did Fender start using turret boards