The delta blues is essentially identical to a Classic 30 with the addition of the Tremelo circuit. If you compare the two schematics, you can see where the trem circuit is added.
I used Steve Aloha's mods, and some of my own, and went to town. I would disagree that you can do his mods without unfolding the circuit boards. Yes, perhaps a few, but a bunch are just too tight to get in there with a soldering/desoldering iron.
One of the resisters in the power circuit had blown (with a nice black mark on the close components and circuit board), but the amp still functioned. I had bought this on Craigslist for $80, and when the guy sold it to me he said he didn't have all the tubes for it. I suspect that while he was playing it, a bunch of smoke came out, and he was afraid to turn it back on and unloaded it as soon as possible.
Oddly enough, not knowing this, I put some tubes in it, and everything seemed to work, but it sounded not so good. I was very disappointed because I had heard the delta blues were pretty good amps, but it didn't seem like it. I figured for the price, I didn't have a lot to lose, so I got the schematics, looked through everything Steve had done, blew the schematics up on a D size plotter and went to town making changes. After I had my plan in place, and a list of components, I ordered everything and got ready to mod.
Imagine my surprise to find the resistor smoked, and fortunately it was a simple 5W power resistor you can get at radio shack. Anyway, I decided to go ahead with my plans regardless.
So........Of Aloha's mods, I did...
Overdrive Channel input
Boost switch relay board (Plus some)
Adjustable Bias Pot
On the relay board. Rather than use Steve's board, I designed my own relay board, and added an additional 1/4" jack in the back for another plug. Then I modified an Ibanez IFS4 quad footswitch, and wired the relay board into the main circuit board. This gives me Channel, Overdrive, Reverb, and Tremelo now on the footswitch for the Delta Blues.
I built a new cabinet using bloodwood with dovetail joinery and replaced the 2X10 stock speakers with a 10" and a 12" Eminence Red Coat Red Fang Alnico speakers. I've got a Telefunken NOS tube in the first 12AX7, the rest are RCA NOS, and Ruby EL84's. (At my work, they replaced the old, old elevators, and the cabinet full of tubes that had been there to repair the systems if they went bad was being thrown out. The rest were not guitar amp tubes, but I got a boatload of 12AX7's from the 50's. And no, you can't have any
I also nibbled out the metal where the power cord went in, and replaced it with a power receptacle from an old server that had it's own power filter circuitry built in. This cleaned up power going in, and allows me to use a regular computer power cord now. I put a 120mm low noise computer fan inside the cabinet to pull air in at the bottom, past the tubes and out the top of the back of the cabinet below the chassis that turns on when you turn the amp on. This resolved the heat issues this amp seems to commonly have. I also put a metal mesh guard in that goes about three inches below the chassis to protect the tubes.
I put an additional 1/4" jack in the bottom of the chassis and wired the speakers into it, and soldered a plug onto the speakers in the cabinet so I could disconnect the speakers when desired. By leaving everything else the same, the two speakers are wired for 16 ohms. If you put a 16 ohm extension cabinet in the external speaker jack, you now are running 8 ohms through both. Or, you can disconnect the internal speakers and plug in an 8 ohm extension cabinet. For playing somewhere big, I have two Rivera thule ported 2X12 cabinets that are 4 ohms and connect in series to plug in the back of this at 8 ohms.
I considered replacing the transformers, but didn't because of the cost. Not counting the tubes, cabinet and speakers which I could use for something else anyway, and the footswitch I already had, total cost for the other mods was about $50 or so.
Now, with everything connected, I can turn the master volume all the way up, all the other knobs to 12, and volume to about 9 before you start getting a slight hiss. (Nigel Tufnel's got nothing on my amp, it goes to *12*)
Everyone who has played this amp since I made the mods has fallen in love. I've gotten a few offers, and more than a few people who wish they could afford to make an offer. I put a box of wipes inside the amp just for them.
I've been exceptionally happy with how everything turned out. If I were ever to revisit this, I would perhaps do Four things:
1: Replace the stock transformers
2: Put an effects loop in between the pre-amp and the amplifier section. I thought about doing this the first time, but decided not to because of the pain in the ass designing and putting an impedance matching circuit in would be.
3: Modify the power section. I'd want to put in a switch that would switch two of the tubes out of the circuit for half power, and also a switch to change between Pentode and Triode for the EL84's. That would give you 15 or 30 watts in Pentode mode, and 7.5 or 15 watts in Triode mode. (the Transformer change is important if I do this because I'd have more impedance options when switching. Pulling two tubes out of the circuit will double the impedance requirements).
4: Boost the output in some fashion when the Tremelo is engaged. It works fine now, but the volume decreases significantly, and the faster the trem, the greater the decrease in volume. Not a huge deal since I don't really use it, but I might if it wasn't such a pain.
That was the long answer. The short answer is Yes, the Delta Blues amp is just as modifiable as the Classic 30.