Deluxe Reverb replica build

[martin manning]

Just completed this AB763 Deluxe Reverb in a replica chassis. Top photo is an in-progress shot as this build was done in a test-as-you-go style, where the power supply was built and tested first, then with the board installed the power amp was brought up and adjusted, then the LFO, and finally the reverb and the preamp. It’s in its replica cab now and sounding great.

The ground scheme has been completely redone to separate the preamp and PI grounds from the power section. It has a PI trimmer, and an improved fail-safe bias supply. Bias test points occupy the accessory outlet blank-off plate, with one current sense resistor for each output tube, and a third to ground for balancing the PI. The ground switch serves as a tie point and is still functional. The foot switch has been modified to keep things quiet, with a resistor across the trem switch and the housing is grounded. I’m using a 5U4 to keep plate voltage down around 410. Still missing a padded bag for the reverb tank. Lots of feedback going on there.

[joeboo88]

That’s a nice amp Martin.
Did you make your own boards? What speaker are you using?

I have the same iron as you (well my PT is a 290cx) but should be ok. I just have to buy a chassis and I can try one now that I’m retired.... again great job

Joe.

[martin manning]

The boards were pre-made, and came with the chassis. They are fiber, but they do not seem to be the vintage Fender fish paper type. I added four eyelets, two for the PI trimmer, one for an additional ground point, and one to relocate the 100k LFO resistor from the speed pot to the board. The speaker is an Eminence Allesandro GA-SC64. Still brand new, but it sounds nice.

[Matt J]

Looks awesome, Martin!

Might I ask where you ended up putting your PI and preamp grounds? After being out of amp building for a while during the pandemic, and while I dealt with some kidney stone issues, I've finally started work on a new project. I've been putting together a hybrid AB165/AA864 Bassman build and have thought about applying some of HAD's grounding schemes to it. I just haven't decided on where the best place would be to ground the PI.

- Matt J.

[martin manning]

Thanks, Matt. Here's the reworked ground scheme.

[ViperDoc]

That's a pretty fresh-looking chassis, Martin. Do you paint the inside? Looks great!

[martin manning]

That's a pretty fresh-looking chassis, Martin. Do you paint the inside? Looks great!

Thanks, no it's plated same as the originals. It's nickel, I believe.

[didit]

Hello Martin --

Impressive. Recalling passing comments on your build plan. Cool seeing it all fully finished. I see Dumble influences you'd alluded to. Had anticipated you might have gone with his smaller preamp cathode bypass, and maybe other tweaks in preamp area too. Fine reworked grounding scheme.

Believe your chassis plating would be zinc, probably electo-plate but perhaps dipped.

Look forward to reports once you have a few hundred hours of playtime.

Best .. Ian

[harleytech]

Hi,
Who did you source the kit from ?

[martin manning]

Thanks, Ian. I tried googling around a bit on the plating on the originals, which this one strongly resembles. Some said zinc, some nickel. It doesn't have any of the crystalline appearance of hot dip galvanizing, but I see there are other systems that can produce a smooth finish with zinc.

The plan here was to keep to the original circuit, but fix the ground scheme, improve the bias circuit, and add the PI trimmer. That all seems to have been successful, as it's very quiet, and the PI was easy to balance by injecting signal at the PI input cap and observing the current pulses at the common 1Ω cathode resistor.

There is only a very low hum when the reverb is on, which says that is just stray EMF getting in through the reverb tank's output transducer. I'm also happy that the trem doesn't tick at all, which might be another benefit from the separated grounds.

It's been played with both SC and HB guitars, and it doesn't seem to have any undesirable traits, such as blocking distortion or farty bass. More experience might suggest tweaking here and there.

[martin manning]

Who did you source the kit from ?

The chassis kit, from Sol & FA in Thailand, included faceplates, boards, grommets, and the brass control plate (which I didn't use). It did not include a cap cover, so I used a DRRI pull. All of the electronic components and the knobs came from the usual sources, and the solid pine repro cab came from Guitar Cabinets Direct.

[martin manning]

See updated ground scheme diagram above. I forgot to note that V3 and V4 cathode leads and resistors have been reversed WRT the original Fender layout.

[martin manning]

A couple of glamour shots of the amp all buttoned up. Reverb feedback is now under control thanks to a padded bag from Tuki Covers, which I highly recommend... Don't waste money on reverb bags made from a single layer of Tolex. The final tweak was to increase the trem switch anti-pop resistor to 180k, putting around -4.5V on the LFO grid when the switch is open, enough to stop the oscillator completely with no popping.

[Colossal]

Sweet build, Martin. Looks amazing.

[ChopSauce]

Superb...

It's somewhat shocking how new it shows...