Can you Jumper the Channels on a BFDR?

TelZilla · July 3rd, 2007, 08:46 AM

What happens (tonewise, I mean)?

PhatTele · July 3rd, 2007, 09:09 AM

No, not really. You can do it (patching from the Normal channel to the Reverb channel), but the extra stages in the reverb section will cause an out of phase situation with the normal channel and will make it sound awful. Try it. It won't hurt anything.

Ironically enough, you can patch one channel of one AB763 amp into one channel of a different AB763 amp and not have that out of phase problem. It sounds pretty good actually (but you have to haul around two amps).

Or, with a couple of adaptors, you can take the recovery signal from the reverb tank (the cable on the left, when looking at the back of the amp) and put that into the input of the Normal channel. I've heard guys use that before. The cabling is sort of awkward, but it works.

sjhusting · July 3rd, 2007, 10:16 AM

I heard one guy jump the two channels in a Fender amp because he liked the weird phasing he could get.

steven

trag-o-caster · July 3rd, 2007, 03:11 PM

I've done it.

It wasn't pretty!

I've also done it on a 62 Tremolux. It was GOD-like!

Any two channel amp without reverb should be fine. I've done it on the old Silvertone heads too, with the same results.

Ben Harmless · July 3rd, 2007, 03:14 PM

You can usually double check by looking at the schematic. Every time the signal goes through a tube (gain stage) it's inverted. So long as the channels have the same number of gain stages, you'll be just fine.

I've heard people swear that their amp became better when they jumpered their two-channel amps with 'verb, but I've never actually seen those people playing like that...

EMan · July 3rd, 2007, 03:18 PM

I agree with the "try it". Phase shift through the amp's various stages isn't exactly 180, and messing with the tone controls will cause additional phase shift.

I did it on a SFDR, and wasn't all that thrilled....and made a single stage trasistor inverter 'box' for that purpose. Still wasn't thrilled...

Wally · July 3rd, 2007, 05:00 PM

Quote:

Originally Posted by PhatTele

Or, with a couple of adaptors, you can take the recovery signal from the reverb tank (the cable on the left, when looking at the back of the amp) and put that into the input of the Normal channel. I've heard guys use that before. The cabling is sort of awkward, but it works.

What this connection does is add a return and tone controls to the the reverb signal. The Reverb pot in the Vibrato channel is the Send, the volume in the Normal channel is the REturn and the Norm channel tone controls funtion for the reverb signal.

jjmantele · July 3rd, 2007, 09:20 PM

Tried jumpering on my SFDR. It merely reduces bass. Poo poo.

justinm · July 3rd, 2007, 10:29 PM

here's a trick.
Use an effect pedal that shifts the phase by 180deg in the jumper loop. That way the signals that are summed before the PI are in phase. I think some clean boost pedals will work. Thay way you can get a linear equalization across the spectrum. IIRC, my Super Hard On is out of phase with the input signal. YMMV.

Justin

tjalla · July 4th, 2007, 12:20 AM

mi audio boost n buff and my dano tuna melt are also 180 out of phase

July 3rd, 2007, 08:46 AM	#1 (permalink)
TelZilla Tele-Afflicted Join Date: Jan 2007 Location: Cleveburg, USA Age: 38 Posts: 1,833 6 Photos	Can you Jumper the Channels on a BFDR? What happens (tonewise, I mean)? __________________ Thanks,Nick Nec Aspera Terrent

July 3rd, 2007, 03:11 PM	#4 (permalink)
trag-o-caster Friend of Leo's Join Date: Mar 2003 Location: Flushing, Michigan Posts: 4,507	I've done it. It wasn't pretty! I've also done it on a 62 Tremolux. It was GOD-like! Any two channel amp without reverb should be fine. I've done it on the old Silvertone heads too, with the same results. __________________ Timothy Jon Lamb

July 3rd, 2007, 03:14 PM	#5 (permalink)
Ben Harmless Friend of Leo's Join Date: Mar 2003 Location: Albany, NY US of A Posts: 3,153 6 Photos	You can usually double check by looking at the schematic. Every time the signal goes through a tube (gain stage) it's inverted. So long as the channels have the same number of gain stages, you'll be just fine. I've heard people swear that their amp became better when they jumpered their two-channel amps with 'verb, but I've never actually seen those people playing like that... __________________ "I think I'll go for the life of sin, followed by the last-minute, presto-change-o, deathbed repentance." - B. Simpson

July 3rd, 2007, 09:20 PM	#8 (permalink)
jjmantele Tele-Holic Join Date: Aug 2003 Location: New Jersey Posts: 846	Tried jumpering on my SFDR. It merely reduces bass. Poo poo. __________________ JJman If it says "Vintage" on it -it isn't.

July 3rd, 2007, 09:09 AM	#2 (permalink)
PhatTele Tele-Holic Join Date: Jun 2003 Location: Richmond, VA Posts: 706	No, not really. You can do it (patching from the Normal channel to the Reverb channel), but the extra stages in the reverb section will cause an out of phase situation with the normal channel and will make it sound awful. Try it. It won't hurt anything. Ironically enough, you can patch one channel of one AB763 amp into one channel of a different AB763 amp and not have that out of phase problem. It sounds pretty good actually (but you have to haul around two amps). Or, with a couple of adaptors, you can take the recovery signal from the reverb tank (the cable on the left, when looking at the back of the amp) and put that into the input of the Normal channel. I've heard guys use that before. The cabling is sort of awkward, but it works.

July 3rd, 2007, 10:16 AM	#3 (permalink)
sjhusting Tele-Holic Join Date: Jul 2003 Location: Germany Posts: 621 14 Photos	I heard one guy jump the two channels in a Fender amp because he liked the weird phasing he could get. steven

July 3rd, 2007, 03:18 PM	#6 (permalink)
EMan Tele-Holic Join Date: Apr 2003 Location: Dallas, Texas Posts: 939	I agree with the "try it". Phase shift through the amp's various stages isn't exactly 180, and messing with the tone controls will cause additional phase shift. I did it on a SFDR, and wasn't all that thrilled....and made a single stage trasistor inverter 'box' for that purpose. Still wasn't thrilled...

July 3rd, 2007, 10:29 PM	#9 (permalink)
justinm TDPRI Member Join Date: Jun 2007 Location: Oakland, Calif. Age: 36 Posts: 11	here's a trick. Use an effect pedal that shifts the phase by 180deg in the jumper loop. That way the signals that are summed before the PI are in phase. I think some clean boost pedals will work. Thay way you can get a linear equalization across the spectrum. IIRC, my Super Hard On is out of phase with the input signal. YMMV. Justin

July 4th, 2007, 12:20 AM	#10 (permalink)
tjalla Tele-Afflicted Join Date: Mar 2003 Location: Perth, Western Australia Posts: 1,825 7 Photos	mi audio boost n buff and my dano tuna melt are also 180 out of phase