« Uh... »

I have it on loan. It must be at least 20 years old, 2 tubes (I don't know how you can fit a third one in there, there's no room left!), midi and all that...
I tested it out of curiosity, it's the witness of an entire era!
There's a loop that you can program with the sound itself, which is very good, since it spares you from having to buy a second MIDI device.
The headphones output is rated at 600 ohms and more, I don't know what kind of problem they had with their ears back then, but it must have been really bad!
There's and acdc9v output next to the midi connection, which is very practical to power the pedalboard without the need to trouble yourself with anything else. I didn't test it though (I don't see how one single plug can deliver ac and dc at the same time and, unfortunately, I don't have the manual). Edit: this plug is an input. You connect there the output of a 9v adapter, which then supplies power to a pedalboard that supports phantom power with a 7-pin midi connection, shucks! But you can make one yourself that goes out from the ada as a 7-pin, carrying phantom power, and then goes into the pedalboard with 5 pins plus a dc9v plug.

On the other hand, there's no input control, it's pretty bad, especially for that time (my dod and ibanez from the '90s have one).
It worked straight off with my ultra-simple yamaha midi pedalboard (mfc05), a very good point since I don't understand anything about that!

Important edit: This unit was defect. it had 2 badly soldered resistances, so I could rewrite the Sound section.

UTILIZATION

No knobs to turn, except for the master volume. It has lots of buttons hidden under a thick layer of blue plastic...It's awful, but still works without a hitch.
No need for a user manual, the interface is pretty well though-out, it's rather logical, there's no comparison with the infidels at rocktron grr!), so you just press and you know what's going on.

There seem to be to distortion stages (are both tubes?) and an equalizer, plus an analog chorus. Basic, but useful.

The first stage is very biting, almost harsh, while the second one is rounder and more punchy. It generates quite some noise, obviously, so you will need to choose very clean tubes (usually incompatible with a good gain). I think the FX loop is foreseen for a noise gate (considering that a midi multi-effects can handle delays, reverbs and company). But nothing stops you from it...

This device would've been truly awesome with two additional FX loops, there was enough room and they could've easily asked for a stratospheric price.

SOUNDS

I was seduced by something I never expected: The chorus, which is truly splendid.
As for the rest, it's OK, the clean sounds are warm and the clarity of the device is flagrant, good and rich analog sound.

The overdrives aren't bad at all, I think you can achieve almost anything except for a pronounced compression combined with a bit of gain (I'm thinking screamin blues, ts7). But it sounds fine, very subtle and dynamic.

The EQ apparently doesn't allow you to choose the mids frequency, a real pity. Besides, I think it's passive, because it's not too precise nor drastic.

The distortions are fine, with more punch than you'd think, and also quite some background noise.
Heavy rhythm guitars sound awesome. The reaction of the unit to your playing is especially stunning, it's quick and straightforward. For solos, the sustain is sublime, just like the warmth, and the sound remains precise, but you have to try your hardest. Lots of mids, definitely not for numetal (all the better!).

I use a vig eruption with emg hz, that can really delver quite some output level.

OVERALL OPINION

I love the pristine, dynamic, warm sound, the programmable loop, the built-in phantom power for the midi pedalboard, and the device's relative simplicity.

With my favorite compressor on top (only for its class, no boost), it's awesome, just the way I like it.
I can't really say much about residual noise with distortion, since my electroharmonix tubes have a good gain level and grit, but they might be a bit noisy.

Regarding the 3-tube modification, I don't see how that can be possible, given the space inside.
Surely the gain would increase, but with the passive EQ it won't get too far in the Mesa Recto (and company) direction.
Given the price of some good metal pedals, I don't think it's worth it to go for the ada and risk it bursting!

I'm happy I got to try this unit out, which sparked my curiosity, so here's an update two days later:
I went to the adadepot site to get better acquainted with the innards of the machine. The 3-tube mod is simple, you just have to change the miniprint, very well-spotted. But the noise also increases, so you have to do the noise mods, which are more delicate since you have to meddle with the big print and the power supply. I don't think it's worth it.
The only mod that caught my interest is the rectifier/5150 mode, because it's very simple (you only need to change some resistances/capacitors on the miniprint), extremely cheap and it's reversible. The sound becomes more mesa, smoother, and the background noise is gone. Interesting!

...but useless, in my opinion, in light of today's comparison: line6 versus ada. It's a spider4 30w with an eminence legend 121 speaker. I plugged the ada directly into the aux in, so it's just the power amp and speaker. And I plugged the spider directly into the guitar input.
The results are clear, the ada sounds pretty muddled and noisy. It's good for blues, where it sounds as good as the spider.
The cleans, and especially the big distortions are clearly better in terms of edge, precision, speed. And there is simply no noise. It's amazing for some killer rhythm guitars, sorry for the purely analog clan!
Add to that the decent built-in effects, the remote-controlled tap tempo, the ultra-fast preset change and I don't really see a reason to bother yourself with the ada.
I'll do the same with 150W just to see what happens. I'll update my review if there are any changes.