Can I build an AB763 w/ channels in phase?

[Wrongdog]

Can this be done? I used to own a non reverb 64 BF Deluxe and loved bridging the channels but you can not do that to Fender reverb amps. What is the way around that in simple(ton) language?? Thanks if you can help me out on this!

[tbryanh]

Just to define what bridging is:

Non Reverb Channel Bridging Mod
http://www.schematicheaven.com/mods/...ridgingmod.htm

This is an easy mod which requires no soldering. It'll give your Dual Channel Non Reverb amp a Fatter tone. Since reverb equipped amp channels are out of phase, this mod Will Not work on them.

1. Using a short patch cable, patch the #2 Input of the Normal channel into the #1 Input of the Vibrato channel.

2. Plug you guitar into the #1 Input of the Normal Channel.

3. The Volume and Tone knobs on both the Normal and the Vibrato channel will now effect your sound. So turn down the Normal channel and adjust the Vibrato Channel Tone and Volume first. Then bring up & adjust the Normal channel Volume and Tone. (If you experience any feedback while doing this, remember that the Vibrato channel is voiced a little brighter than the Normal channel. Lowering the treble and volume on the Vibrato channel a little will reduce any feedback).

This will give most Dual Channel Non Reverb Fender amps a fatter tone that's kind of equivilent to using a mild overdrive pedal. It only takes a patch cable and 2 minutes to try it & see if you like it. And it's completely harmless to you amp.

[tbryanh]

Here are the schematics for Fender Blackface Deluxes with and without reverb:
http://www.ampwares.com/schematics/deluxe_aa763.pdf
http://www.ampwares.com/schematics/p...a165_schem.pdf

[tbryanh]

The reverb amp has an extra inverting stage in the vibrato input that is not found in the non-reverb amp. This is causing the problem.

A simple solution is to use a pedal of some kind for the reverb amp between the #2 Input of the Normal channel and the #1 Input of the Vibrato channel.

To get the same effect as in the non-reverb amp, the pedal would invert the signal and do nothing else.

Some pedals invert and some pedals do not, and pedals are not usually chosen for their inverting capabilities, so finding out if a pedal inverts or does not invert might be difficult. In other words, the brochure, etc. for the pedal probably will not tell you.

The schematic for the pedal probably needs to be analyzed to find out.

Also, once you find a pedal that inverts, you might be stuck accepting the effect it ads to the signal. This may or may not be desirable.

[JoeM]

Can this be done? I used to own a non reverb 64 BF Deluxe and loved bridging the channels but you can not do that to Fender reverb amps. What is the way around that in simple(ton) language?? Thanks if you can help me out on this!

I'm not quite sure about this, but I think if you do the reverb on both channels mod you can jumper both channels and have them in phase.

Schematic:

http://www.blueguitar.org/new/schem/...s/bothverb.gif

[Wrongdog]

Hey Bryan - thanks for your response. I think you are Misundertaking me! I USED to own that '64 Non reverb and did your first suggestion for years. I want to build a REVERB BFDR but want to know if there is a way to make that Reverb channel in phase w/ the Normal so I can bridge it.. I think if you use the recovery of the reverb return (RCA plug) and plug it in to the normal (1/4 in jack) you can get the 2 channels to drive harder. i want to make one less micky mouse though. I LOVE BFDR for guitar but I also play harp and they are mediocre for Harp but I want EVERYTHING!!

My last build was a Champ voiced for harp. For guitar I built a Bedrock Royale Reverb (killer!!!) but I want a dual 6v6 amp for both. The Class A EL84 is LOUD! I am thinking of making a Bedrock Royale Reverb pre-amp w/ reverb and using a Fender BFDR power section. Or seeing if I can find Bedrocks non reverb Royale deluxe (class A 6v6) and add the Royale Reverb section.

Anyone know where I can find the Royale Reverb schematic??

My "Badrock" EL34 build:

http://www.flickr.com/photos/3237298...ream/?edited=1

The non reverb 6v6 Royale Deluxe:

http://www.flickr.com/photos/7227788...7607268392069/

[Wrongdog]

hmmm - I have to ponder that one. It seems it is putting reverb use for normal and Rev trem channel. I am NOT an amp guru. I build "color by number" amps so I don't get a lot of this stuff.

[JoeM]

hmmm - I have to ponder that one. It seems it is putting reverb use for normal and Rev trem channel. I am NOT an amp guru. I build "color by number" amps so I don't get a lot of this stuff.

The schematic I referred to does exactly that - reverb works on both channels. But I believe in the conversion both channels become in phase, allowing you to jumper them without the phase cancellation problems in typical Fender 'Reverb' amps.

[Wrongdog]

The schematic I referred to does exactly that - reverb works on both channels. But I believe in the conversion both channels become in phase, allowing you to jumper them without the phase cancellation problems in typical Fender 'Reverb' amps.

Wow! I have been looking for that mod (if I understand it correctly) for many years! Thanks Joe! I think I will just build the BFDR with that mod and a grindier normal (the mids mod and no NFB and lower input resistor) channel and live tone happily ever after.

Well, maybe for a week or so...

[tbryanh]

The Reverb On Both Channels Mod (ROBCM) is interesting and would allow the Non Reverb Channel Bridging Mod (NRCBM) to be used, but the resulting sound will probably be different compared to using the NRCBM mod on the non-reverb amp.

The channels are mixed through mixing resistors in the non-reverb amp while the channels are mixed by the plates being connected together in the ROBCM amp.

The mixing resistors in the non-reverb amp allow the channels to operate independantly (one channel does not affect the operation of the other), but the connected plates in the ROBCM do not (one channel affects the operation of the other).

The ROBCM mod was probably not designed with the NRCBM mod in mind, but it would be interesting to hear the results.

[tbryanh]

Can this be done? I used to own a non reverb 64 BF Deluxe and loved bridging the channels but you can not do that to Fender reverb amps. What is the way around that in simple(ton) language?? Thanks if you can help me out on this!

You can go ahead and bridge like you have been doing but use an isolation transformer between the two channels to correct the phase problem. Wire the transformer so that the phase is inverted between the input and the output of the transformer.