Jumping Channels In A Blackface Deluxe

[ojaverde]

Is it possible to jump the normal channel into the Vibrato channel on an AA763 Deluxe? I think I remember reading somewhere that the channels are out of phase on this amp. Does that mean that this can't be done?

 

[jrfrond]

It is true. The BF amps have their channels out-of-phase due to an extra gain stage in one of the channels that flips the phase. I suppose you could experiment with it, as it wouldn't hurt anything. How usable the sound is would be up to you.

 

[ojaverde]

My impression is that jumping the channel will get earlier breakup. is this correct? If not what effect do you get by jumping? I'm not looking for more volume.

 

[DickensCPA]

I just went thru this today. Got a suggestion from another forum. Buy a Radial Bigshot ABY pedal with a 180* inverter. Allows you to play thru normal channel with reverb and not get the nasally tone with your OD pedal.

I was at my wit's end and listed my DRRI for sale. Keeping it now. All my pedals go thru the normal channel and I leave the Vib channel strictly for cleans.

 

[Rumble]

My impression is that jumping the channel will get earlier breakup. is this correct? If not what effect do you get by jumping? I'm not looking for more volume.

I've got an old 4-input Marshall and it definitely adds more gain when it's jumpered, which is the only way I play it. It doesn't go from clean to metal, but it adds a good bit more grit to a slightly dirty tone. It also adds more volume, but I have a PPIMV so the volume is not a problem.

Jumpering is not exactly like adding a gain stage because it's not linear- an extra stage does not cascade directly into another like water going through a hose. It's more like parallel (or double) signals are going into the same gain stage as if two rivers are converging and flowing towards one dam. This inevitably adds more gain and volume, but maybe not as much as cascading through another gain stage and re-amplifying all the original gain. I hope that makes sense.

However, on a Fender you have to figure out how to deal with the out-of-phase channels, as others have suggested.

 

[varakeef]

I have tried jumpering in SF Pro Reverb and in Quad Reverb. I don't think it works well. The controls interact very strange and I don't see any benefits in sound either. Different matter is that using either normal or vibratoi channel and have a A/B pedal works well. But simultaniously it IMO sucks.

On the other hand in my 64'ish Vox AC30 all three channels are permanently tied together and it's just great.

 

[sjhusting]

Yeah, you get phase cancellation. The reverb channel has an extra triode in the signal path (the reverb driver). Every triode (except a cathode follower) inverts the signal, so they are out of phase. You could try what was suggested above, and invert the phase on the jumper cable.

steven

 

[Bluesbob]

No phase problems...

If you had a Deluxe Reverb you wouldn't see any real advantages, but since you're talking about a Deluxe non-Reverb, jumpering the channels can give you more gain and as a result a meatier, slightly dirtier tone, especially when cranked. Let us know how you like it.

 

[sjhusting]

oh yeah, if it's non-reverb, it shouldn't be a problem. just do it.

steven

 

[vjf1968]

No reverb no problem. If it has reverb than you need one of these:
http://www.barberelectronics.com/LaunchPad.htm
It will correct the phase issue and allow you to mix between the two inputs apart from other things it can do.

 

[Wally]

And...this doesn't add gain at all. IT merely adds another channel....which can add tonality complexity especially in an amp such as the 4-holer Marshall that Rumble has. Those two channels are very different tonally, and the lows in the second channel add girth a complexity to the sonics. Another amp that works well with this is a Fender BAssman from the AB165's on..all 2 6L6 BAssman amps from the 165 on. Just like Rumble's Marshall, these Bassman have two very distinct channels adn mixing them adds complexity...especially for 'thin sounding' single coils like Hendrix used.
There are other Fender amps besides the REverb models that don' do this channel linking thing well....the '64 Bassman for example.
One thing that can be interesting with the REverb modelse is to use this channel linking when using the vibrato function. This can add another dimension to the effect...you might like it or not.

 

[bradpdx]

And...this doesn't add gain at all. IT merely adds another channel....which can add tonality complexity... Those two channels are very different tonally, and the lows in the second channel add girth a complexity to the sonics.

IF the two channels are in phase (they are not in all traditional Fender reverb amps) then paralleling the 2 channels will indeed add some gain - +6dB to be exact. If you are trying to drive the amp extremely hard, this might help - but it is far less gain than you can easily achieve with an external clean boost, as just one example.

As to the channels being different tonally - sorta kinda but not by design. The Fender amps used identical tone stacks for each channel, but due to the reverb mixer the Normal and Vibrato channels do sound a bit different. On the non-reverbs, there is no difference at all because there is no mixer stage.

On amps like the tweed Bassman and older Marshalls, both channels share a common tone stack, and so the only channel difference is due to the "bright" caps on the respective volume controls.

 

[Wally]

IF the two channels are in phase (they are not in all traditional Fender reverb amps) then paralleling the 2 channels will indeed add some gain - +6dB to be exact. If you are trying to drive the amp extremely hard, this might help - but it is far less gain than you can easily achieve with an external clean boost, as just one example.

As to the channels being different tonally - sorta kinda but not by design. The Fender amps used identical tone stacks for each channel, but due to the reverb mixer the Normal and Vibrato channels do sound a bit different. On the non-reverbs, there is no difference at all because there is no mixer stage.

On amps like the tweed Bassman and older Marshalls, both channels share a common tone stack, and so the only channel difference is due to the "bright" caps on the respective volume controls.

STill learning...

How does this 'jumping' add gain? Does using a 'Y' cord add gain?

IN the Model 1959 ane 1987, the cathodes are separated in V1 and have very different resistance and capacitor values. This does indeed yield very different tonalities that, when combined, yield very complex tonality.
IT is true that the first Marshalls resemble the 5F6A more closely in that those cathodes are tied together. IN the early Marshalls, the shared cathodes arrangement did yield similar tonality in the two channels with the only difference being the bright cap. There was enough of a difference that players would 'jump' the channels in these amps also to get that extra meat form the 'dark' channel.
The Models 1959 and 1987 were introduced in 1966. Did HEndrix use the Md. 1959 Super Lead or were his amps the older JTM 45 100 watters?

 

[bradpdx]

STill learning...

How does this 'jumping' add gain? Does using a 'Y' cord add gain?

"Jumping" (connecting input 2 from one channel to input 1 of another) or using a Y-cable are almost the same. Both result in the simultaneous use of both channels.

You are correct about the variations in later Marshalls. I was thinking of the very early versions (JTM45) that were essentially Bassman clones. I never use Marshalls and so tend to forget the model numbers. My playing is closer to James Burton than Jimi Hendrix, I suppose

 

[Wally]

And just to get it straight in my head, how does 'jumpering' or using a 'Y' increase gain?
AS I see it, one would merely be adding an input to the second channel. In order to increase gain, we would be talking about adding a gain stage/s to one or both channels...and that is not what is accomplished, is it?
IT seems to me in order to add gain, we would have to do what Randall Smith did with the early Boogies....take one channel's signal and insert it into the other channel's structure.

 

[Ben Harmless]

I believe there is actually some extra gain when the channels are jumpered, if only because there is some extra signal hitting the PI. Otherwise, you've just got two channels running in parallel, which can sound really cool anyway - usually thicker and more robust.

I love it on a Bassman.

 

[Wally]

"I love it on a Bassman."
IT works for the AB165 and later 2X6L6 Bassman amps. IT doesn't work for the aa864 which has 3 stages in the Bass but only 2 stages in the Normal channel.
The 6G6 amps have 4 stages versus 2. Therefore those channel are in-phase....unequal but in-phase,right?

 

[Tim Swartz]

No, 6G6 amps have 3 stages on the bass channel and 2 on the normal channel. The bass channel on first glance looks like 4, but one triode is a cathode follower which neither increases gain nor inverts the signal.

 

[Wally]

Thanks for the clarification/correction, Tim.

 

[peterjasper]

Yeah, you get phase cancellation. The reverb channel has an extra triode in the signal path (the reverb driver). Every triode (except a cathode follower) inverts the signal, so they are out of phase. You could try what was suggested above, and invert the phase on the jumper cable.

steven

Sorry for resurrecting this old threat , but is it possible to rewire a standard patch cable to invert the phase?

Thanks!