Updated: Mar 31, 2020
Now that my "Psuedo-Eagle" is in a good place (without an onboard buffer at the moment) I decided to pivot and convert my Fender Deluxe Reverb Reissue to a handwired variation to chase 2018 & 2019 Dead & Company tones. After building a few Dumble-style amplifiers and learning a bunch about amplifier design, I decided to see how far I can modernize a Fender Deluxe Reverb AB763 circuit. This time, I wanted to incorporate some modifications that I think would be super cool.
I picked this amplifier up from GuitarCenter for $650 and it sounded good with a Warehouse Guitar Speaker Retro30 speaker, but I wanted to try to achieve John's Dead & Co tones where he used a JBL D120. The next question about the D120 is if it had a paper surround or a cloth surround E120 recone. Through some networking, I learned that the speaker was a D120 with a paper surround like an original D120. Cool! It turns out that those D120 speakers (or even D131 like my SSS #004 cabinet) are pretty darn expensive! So I decided to try the Weber California AlNiCo 12" with aluminum dome. The members on RUKind share positive opinions about this speaker so I thought I'd give it a try. Long story short, these speaker have BITE and I have not found the neutral and warm tone that my JBL D131's have... yet.. I'm going to continue breaking them in to see how long it will take for them to loosen up a bit.
Moving on from speakers, the amplifier clearly was tinkered with. The normal tone stack seemed to be modified and it would never bias correctly. Worst of all, it would red plate one of the power tubes randomly. I discovered this was due to the octal tube socket was worn out and was losing connectivity between the pins once the amplifier warmed up. I could have just replaced the sockets but I was unsure what else the amp was suffering from. I know that online, folks say their vintage Deluxe Reverbs are "clean" until 5 or 6 on the volume knob and this is exactly where John Mayer sets his volume. It seemed like my amp would start to distort and break up around 2.5. Especially on the bottom end. I tried various tricks such as pulling tubes, 6L6 tubes, solid state rectifiers, etc but nothing seemed to get that wonderful tone folks talk about when they think of a Deluxe Reverb. After studying the component selection and such of the DRRI, I could see a few areas of opportunity. I tried a few mods first before gutting the whole thing such as making Normal input a Bassman tone stack like the custom '68, and adding that channel to have reverb. I learned a lot from RobRobinette.com so I recommend checking that out for sure.
Modifying the legend
List of tasteful modifications that I'm implementing that allows me to maintain an honest '65 vibrato channel circuit, but with additional tricks. I learned a lot of these tricks from comments on my YouTube channel as well as from Rob Robinette's website.
* NOR channel tone stack will be a Fender Custom Shop Dual Professional stack
* Polyester Orange Drop capacitors - (Original '65 used polyester, the DRRI uses polypropylene blahh)
* Metal film resistors anywhere that's going to ground as well as RN70 plate load resistors
* Mogami coax internal wiring for sensitive signal areas
* Silver Mica caps replace all ceramic caps
* Move the power supply from the dog house to inside the amplifier
* NOR channel added reverb
* Wirewound power supply resistors for the lowest thermal noise floor
* VIB/NOR channel with push/pull volume pots for bright cap
* Mid pots added in place of Input 2 on both channels
* Alembic style preamp out so I can run the preamp into another power amp (like my SSS) 😎 Jerry Garcia style mod
* Vibrato disconnect switch like SRV's Vibroverb 50KRA with switch https://www.tedweber.com/wp503ras
I really like my Fender Custom Shop Dual Professional tone stack and how it does that Jerry thing so I'm hoping that some of that is maintained with just implementing the tone stack. I do know that the tone stack is just a piece of the entire tone so I don't expect a total clone of a Dual Professional to now be in the Deluxe but I can certainly try! I met some folks who are really big into Jerry Garcia's amplifiers and such and the Dual Professional tone stack is pretty close to Jerry's. I tried the Bassman tone stack like the '68 Custom Deluxe and it was ok, but not different enough so I'm going with the Dual Professional tone stack. I'll be adding a push/pull volume pots on both channels so I can engage and disengage the bright cap as needed without going into the amplifier.
The silver mica caps will smooth out some of the high end. This was a thing that the Alembic team does with their Twin Reverbs before handing over to Jerry Garcia. Other folks have tried this swap as well and enjoyed the results, especially with pedals. Polyester capacitors might be the biggest tonal difference between the '65 DRRI and the Fender '64 handwired. The polyester caps being closest to the original '65 circuit and used in all my Dumble-style builds.
The cathode bypass caps are F&T dual 25uF/25v like the original Mallory caps. F&T has extremely low ESR and I use them extensively because of this. Remember, higher ESR = higher noise! For example, I have a Sprague 25uF/25v and the ESR is 1 Ohm. The F&T cap is .3 Ohm. Incredible! I ordered these caps from AmplifiedParts.com For plate load resistors, I'm using RN70 Dale precision resistors. These are known for low noise (hiss) and should stabilize the amplifier. Jerry Garcia's amplifiers had their 100k plate load resistors swapped out with RN70s for their reliability and low noise. I'm also using Mogami coax from the input to the grids on V1/V2 as well as back up to the volume pots. This should reduce crosstalk from running under the preamp board.
Cesar Diaz (Stevie Ray Vaughan's amp tech) had a few tricks up his sleeve too that I'm incorporating. One of the tricks was the pull V1 to increase gain of the preamp since V1 and V2 share the same power source. Removing V1 tube will lighten the load on the power transformer which will increase voltage (gain). Another trick is removing the vibrato intensity pot. This pot drags the signal down considerably because of the 50k pot to ground. Removing this load will increase the gain yet again. I purchased a 50RA with switch from Weber's site so I can completely disable that pot and signal load in the off position and I can bring it back into the circuit by clicking the connection to "on". https://www.tedweber.com/wp503ras
A neat trick that Jerry Garcia used to get more levels out of his Twin Reverb is to tap into the preamp and run the Twin's preamp out to a McIntosh solid state power amplifier. I think this is a really cool idea so I found Waldo's forum where he documented Jerry's rig and the Alembic mods to Jerry's amplifiers. http://wald-electronics.freeforums.net/ The extensive documentation of Jerry's amp tweaks is not included on his site but you get a good idea of the modifications. I plan on trying to run the preamp out of this amplifier and running it into the 100 watt power section of my Steel String Singer for tone tests turning this 22w computer into a 100w clean monster :-) .
Here is a few comparisons from an all-original '64 compared to a new photo from my build this morning. Unfortunately, my blog website (Wix) received an update and I'm unable to allow a high resolution pop out picture, but hopefully the pictures do some justice. I'm going for a "restomod" with this amplifier. Meaning, that it will look a lot like the original amp upon first glance, but then you'll notice more and more improvements as you look. For starters, I'll be using 600v cloth wire for a majority of the amplifier.
I'll be updating this post with the progress and hopefully I'm getting close to finishing up the amplifier! For the time being, enjoy my progress update video series. Be sure to download my latest layout for my design on my GitHub.
And you can cruise my high resolution photo album here: https://photos.app.goo.gl/qdeyZiWzQgZVJ32V7