Jumping a Fender Bassman

FMmark · Post by **FMmark** » Mon Sep 19, 2005 1:52 am

I have two Blackface Fender Bassman heads. I want to plug in to the normal channel of the first head then jump the bass channel of the first head into the normal channel of the second head. Is this an OK thing to do? I'm trying to send each head to a different cab without adding some rack garbage to split the signal. Seems to me it's somewhat like daisy chaining a couple of Marshall heads, should work no problem right?

Thanks,

Mark

Flames1950 · Post by **Flames1950** » Mon Sep 19, 2005 6:02 am

As long as your blackface Bassmans are the AB165 circuit, you'll be fine, since the AB165 has the same number of gain stages for both the Normal and Bass channels so your signal stays in phase.
Earler blackface Bassman heads (AA864/AA165) do not have the same number of gain stages (the Normal has one less, the standard two-stage Fender preamp found in most other blackfaces, and the Bass gets a third stage) so your signal would have been out of phase if you tried this.
You can't really rely on what the tube chart says the circuit is on old Fenders, they always used up their old stock of charts even after a circuit changed. You'll have to crack it open to really see what you've got. The telltale sign of an AB165 circuit (assuming no mods have been done and it's original) are the 220K local feedback resistors coming off the power tube sockets to a little terminal strip and then to the tagboard.
I'm not sure I follow your jumpering though. If you plug into the Normal #1 input of the first head, you can run a jumper to the Normal #1 of the second using the #2 input of the first head's Normal channel. If you get the Bass channel involved you'd be patching twice, from the Normal to the Bass and from the Bass to the second head's Normal?

FMmark · Post by **FMmark** » Tue Sep 20, 2005 1:22 pm

Yeah I forgot about the other Normal input, that's what I'd use to jump to the other amp.

Thanks for the advice Flames, I'll try it tomorrow night and see if it works. I figure just hooking it up and trying it would be easy. Someone told me you could not do that with Blackfaces, it just wouldn't work. That didn't sound right to me so I thought I'd consult Academy here. Thanks!

Flames1950 · Post by **Flames1950** » Tue Sep 20, 2005 5:05 pm

FMmark wrote:Yeah I forgot about the other Normal input, that's what I'd use to jump to the other amp.

Thanks for the advice Flames, I'll try it tomorrow night and see if it works. I figure just hooking it up and trying it would be easy. Someone told me you could not do that with Blackfaces, it just wouldn't work. That didn't sound right to me so I thought I'd consult Academy here. Thanks!

The problem is the amps with reverb, the channels are out of phase so you may have problems jumpering. And the earlier blonde and very first couple of months of blackfaced Bassmans have out of phase channels.

FMmark · Post by **FMmark** » Fri Sep 23, 2005 10:17 am

It sounded much better than just one Bassman, lots of balls and killer tone. Both Blackface's turned out to be a '64 and a '65. Normal 2 jumped to normal 1, speaker outs of each head going to a different pair of speakers in a stereo switchable cab. Really sounded great! Thanks again Flames.

Mark

Flames1950 · Post by **Flames1950** » Fri Sep 23, 2005 6:11 pm

I love those old Bassmans. They're a neat alternative overdrive sound when you want something different from a Marshall. Mine ghosted like hell though. I had to give 'em an extra 100uF at the screens to shut 'em up.