Deluxe AB763 build advice please -minus reverb and vib

[rogb]

Hi
I have decided to pull the trigger on a Deluxe AB763 BF build into a 17" chassis and fit into a combo cab with my G1265. I would like to use the 2 channels, Normal and Vibrato, but I never ever use vib. Also I have a good Dlator and TC rack fx, so I really don't need the reverb.

I plan to mod the Normal channel so it has a more D style flavor, maybe using those mods 1, 2 or 3 that are around, but leave the Vibrato as is for those lovely BF cleans. I plan to channel switch with an ABY footswitch.

I plan to use Mercury Mag iron, maybe even the Fat Stack so I can use 6L6 for more headroom and the Super feel.

Question is, how much of the original circuit can I lose before I lose the unique Deluxe sound and if anyone has ever done this, what is the best way to go about it.
I don't mind building the vibrato in, to start with, if that is the best way forward. But the reverb I want to leave out

All advice/tips would be appreciated!
Thanks
Rog

[crbowman]

Hi Rog,
Short answer is that, of course, any diversion from the original circuit is going to have some sonic consequence and really, only you can determine if you've strayed too far from the classic DR sound.
That said, I have a silver face DR that I've AB763'd so I have some experience with this amp.
I've never tried to bypass the reverb so I can't really speak to that, however, for a while I had the tremolo on a switch so that it could be more or less taken out of the circuit. This results in a little more gain and a little more brightness. The tricky part about this amp is that it tends to be really bright to begin with and that it's really easy to go too far in that direction if you aren't careful. If you plan on doing some of the Dumble tricks, that brightness is liable to be problematic and result in some less than desirable high end fizz. The 25mfd bypass caps will also probably be an issue as you are liable to get the dreaded 'farty' Fender low end distortion if you plan on implementing a D style overdrive circuit.
As you remove tubes from the circuit, which you will be doing if you leave out the reverb and tremolo, the voltages go up and again, the inherent brightness increases. You would need to, at the very least, adjust the dropping string to get the voltages back in line.
The 6L6's will give you more headroom and overall girth, but you will lose some of the sweetness that the 6V6's and the DR are famous for.
I will say that after all the different mods I've done to this amp, I eventually removed them all, returned it to the stock AB763 circuit, and overall, am much happier with it.
So, what you are looking to do is very do-able, and may sound very good. Just be aware of the brightness issue, and don't expect it sound like a classic Deluxe Reverb cos it probably won't.

[rogb]

Hi Rog,
Short answer is that, of course, any diversion from the original circuit is going to have some sonic consequence and really, only you can determine if you've strayed too far from the classic DR sound.
That said, I have a silver face DR that I've AB763'd so I have some experience with this amp.
I've never tried to bypass the reverb so I can't really speak to that, however, for a while I had the tremolo on a switch so that it could be more or less taken out of the circuit. This results in a little more gain and a little more brightness. The tricky part about this amp is that it tends to be really bright to begin with and that it's really easy to go too far in that direction if you aren't careful. If you plan on doing some of the Dumble tricks, that brightness is liable to be problematic and result in some less than desirable high end fizz. The 25mfd bypass caps will also probably be an issue as you are liable to get the dreaded 'farty' Fender low end distortion if you plan on implementing a D style overdrive circuit.
As you remove tubes from the circuit, which you will be doing if you leave out the reverb and tremolo, the voltages go up and again, the inherent brightness increases. You would need to, at the very least, adjust the dropping string to get the voltages back in line.
The 6L6's will give you more headroom and overall girth, but you will lose some of the sweetness that the 6V6's and the DR are famous for.
I will say that after all the different mods I've done to this amp, I eventually removed them all, returned it to the stock AB763 circuit, and overall, am much happier with it.
So, what you are looking to do is very do-able, and may sound very good. Just be aware of the brightness issue, and don't expect it sound like a classic Deluxe Reverb cos it probably won't.

Thanks for the excellent response, this is really helpful!

I think I will build it pretty stock, to start, make sure all is OK.
If you look at the Deluxe AB763, the first iteration was without reverb, so I have that circuit to work from, just need to lose the trem. I will tube it up as per this schem maybe, just disable the trem like yourself?

My speaker is well mellowed and certainly tames brightness in an amp.

I may well not bother with the 6L6 thing, just use JJ6V6, I really want the Vib channel to be zingy BF clean so may look at ways of reducing gain there, like with a 12AY7, there are so many possibilities here.

[crbowman]

Cool Rog.
I think you're on the right track, particularly with that schem and layout.
Let us know how it turns out!
FWIW, I've tried for years to replace my DR but I've never found anything that i consistently like better.
PM me if you need the benefit of my (lack of) expertise.

[rogb]

Cool Rog.
I think you're on the right track, particularly with that schem and layout.
Let us know how it turns out!
FWIW, I've tried for years to replace my DR but I've never found anything that i consistently like better.
PM me if you need the benefit of my (lack of) expertise.

Thanks man, I'm getting a good feeling about this build

[Gibsonman63]

Two channels, with no reverb, no tremelo and running 6L6s sounds like a Bassman to me. You might compare it to your modified schematic to see how close it is.

[rogb]

Two channels, with no reverb, no tremelo and running 6L6s sounds like a Bassman to me. You might compare it to your modified schematic to see how close it is.

You know, I just looked and you are right! It is pretty close, but I have my heart set on the AB763 + 6V6's now, and like others on here , I may well end up reverting to stock after tweaking.

I remember Aspen Pittman saying something like a '65 DR was his desert island amp

I have always wanted one so now is the time to fulfil the dream

[tubeswell]

So a DR without the reverb is a BF Deluxe AB763 http://ampedia.redbeartrading.com/data/ ... _schem.gif right?

[rogb]

So a DR without the reverb is a BF Deluxe AB763 http://ampedia.redbeartrading.com/data/ ... _schem.gif right?

Looks like it, but see what is said here, without the 1/2 the Vibrato tube, the Deluxe stays cleaner after volume 4-5. If what is said is correct, then the Vibrato 12AX7 needs to wired as per the DR to get them to sound the same

http://fenderguru.com/amps/deluxe

EDIT: I just took a look and the Vib tube seems to be wired the same, perhaps he means the extra reverb tubes adding gain?

[tubeswell]

So a DR without the reverb is a BF Deluxe AB763 http://ampedia.redbeartrading.com/data/ ... _schem.gif right?

Looks like it, but see what is said here, without the 1/2 the Vibrato tube, the Deluxe stays cleaner after volume 4-5. If what is said is correct, then the Vibrato 12AX7 needs to wired as per the DR to get them to sound the same

http://fenderguru.com/amps/deluxe

EDIT: I just took a look and the Vib tube seems to be wired the same, perhaps he means the extra reverb tubes adding gain?

The reverb circuit in BF amps doesn't add extra gain. In fact the reverb wet signal insertion point is via a 470k resistor that is part of a 3M3/470k voltage divider which cuts the gain in the dry ('vibrato channel') signal to a level whereby the wet signal can compete. (Note that in the BFDR there is also 220k in parallel with the 470k when the reverb level pot is set to 0.)

The normal channel in both amps is the same. You could build a BF Deluxe and emulate the BFDR '3M3/470k' voltage divider in the vibrato channel side if you want. Its only a few resistors and a (10pF) cap.

[Firestorm]

Without the reverb mix stage, your build would sound like the Deluxe Amp rather than the Deluxe Reverb. As tubeswell says, the 3M3/470K/220K divider knocks the dry signal back to a level where the wet signal doesn't get lost. Attenuation is on the order of 95%. But the mix stage is set up for gain of about 60 so the net gain for the dry signal is around 2.5, which definitely makes a difference.

[rogb]

Thanks guys, excellent advice. So I guess the Fenderguru isn't really

The attenuation network is definitely worth trying, as you say it's only a few resistors. I see on the Weber he uses 3M3 but the Fender AB763 uses 4M7. Maybe switched too ( I like switches, lots of them )It would be great to get the Vib channel as BF Fender as possible while the Norm can tweaked for some more gain and harmonics, Hotel Hog/UP style.

It has been said that the modded Deluxes don't have cascaded gain so I will look at the published mods 1,2 and 3 for a start.

[Firestorm]

There's a useful mod that Dave Funk used to do: you take V1 and wire the second triode as a direct coupled cathode follower (like on a blonde Bassman) and feed the tone stack and volume from there. For tone recovery, you swipe half of V3 (which won't bother you since you don't want the verb; and you can use half a 12AX7 instead of half a 12AT7). This gives you the stock two gain stages the Normal channel already had, but the source impedance of the CF cause the tone stack to have much less insertion loss so the net gain of the channel is higher.

Since the channels are still out of phase, you could join them in front of the 3M3 instead of after V4b, which puts the channels in phase so you can bridge the inputs for yet another sound.

And then, although there isn't much need for a master volume in a DR, when you build the 3M3/470K/220K divider network, if you replace the 220K with a 250K rheostat wired pot, it becomes a pre-PI MV that doesn't change the loading characteristics of the circuit (when it's turned up).

[rogb]

Oh yes, some great ideas coming out here, try one and if you don't like it give another mod a shot. I wonder if I can tweak my way to the "sound in my head"?

I played a TR Studio Pro and that was a 35w 6L6, very clean and toothy,I wouldn't mind the Vib channel having that feel at a lower volume, while the Norm can be modded with switches so it can be back to stock with a click or two.

I am going to build the cab this weekend, as I have no spare money, but I have a chassis and some free time. Something to look at at least then!

Thanks for everything and keep those thoughts coming. If you decide on a modded Deluxe, be sure to let us know what you're up to.

[macula56]

[quote="Firestorm"]There's a useful mod that Dave Funk used to do: you take V1 and wire the second triode as a direct coupled cathode follower (like on a blonde Bassman) and feed the tone stack and volume from there. For tone recovery, you swipe half of V3 (which won't bother you since you don't want the verb; and you can use half a 12AX7 instead of half a 12AT7). This gives you the stock two gain stages the Normal channel already had, but the source impedance of the CF cause the tone stack to have much less insertion loss so the net gain of the channel is higher.

So wouldn't that be like building the bass channel of a 6G6B Bassman for the most part?