A True Classic
I've had this amplifier for 6 months and have used it in a lot of different settings, with numerous guitars and at many different volume levels. I've also installed an attenuator and experimented with a replacement speaker.
The Superdrive 18 is an amp that I had had my eye on for quite a few years before finally purchasing one, and it's an amp that essentially began the "low watt" trend in amp design. At this stage it's become a classic in its own right and represents one of the all-time great guitar amplifier circuits.
First, the build quality throughout is absolutely first-rate. I've owned many amps over the years, and so far my benchmark for build quality is Rivera. The Budda ranks up there with the Rivera's for beefiness of the build, but also for the internal component quality. Nothing is spared and it is nice to see you are really getting what you pay for with these amps.
Plugging in, you get two voices: Rhythm and Drive.
Starting with what made these amps legendary, the Drive setting (I won't call these channels as the topology of the amp is really closer to a single-channel amp and there is a shared EQ) gives you a huge amount of gain, and a unique voice that is all its own. This amp doesn't sound like anything but a Budda (which is part of the draw - there are enough Marshall clones out there already). It's got a singing, sustaining quality to it, not grainy in the way many high-gain amps are. It's very detailed and extremely responsive both to picking dynamics and to the guitars volume and tone knobs. It's one of the best amps I have ever played for dialing in both dirty and clean using just the volume knob on the guitar. Plugged straight into the amp you could do a classic/hard rock gig with nothing more than this amp and your guitar. There is also a pull "modern" voicing on the mid knob that changes the EQ curve and adds gain. Using it gives a lot of versatility for those rock sounds.
The Rhythm setting cleans things up nicely but gives you huge amounts of greasy EL-84 grind. This is nowhere near a high headroom amplifier, so using this setting gives you a fairly dark but very expressive voice then tends toward edge-of-breakup. There is a pull "bright" on the rhythm volume control for some added glass, but where the rhythm setting shines is as a pedal platform. The Budda take pedals extraordinarily well, and in from of the rhythm setting you can sculpt pretty much any tone you are looking for. It is so versatile that this is what I primarily use, with my pedals out front providing texture and tonal flavor (except for the delay, which is in the effects loop along with my looper pedal). Between the basic, somewhat Vox-ish tone of the amp on the Rhythm setting and some carefully chosen pedals I have the sound I have been looking for. There is of course no onboard reverb, but the effects loop is really well implemented and balanced nicely, so a reverb or delay pedal fits in seamlessly and gives a lot more versatility than a dedicated built-in 'verb would.
As mentioned, I have fitted mine with an attenuator so that I can get the power section working at lots of different volume levels. The Buddas are exceptionally LOUD amps for their given power ratings. This amp is rated at 18-watts but easily outguns 50 watt amps that I have owned, so I feel the attenuator is a necessary accessory for these amps unless you are using it strictly for gigging.
I should mention the speaker: The Buddas come stock with their "Phat12" driver that is manufactured for them by Eminence. The story goes that this speaker was painstakingly designed by Budda founder Jeff Bober to enhance the performance of the amps. I will say that they seem to have an unusually long break-in period, so long that at one point I felt the speaker did not sound very good so I replaced it with a WGS ET-65 (which sounded great in the amp BTW) and hooked the Phat12 up to a stereo to break it in - I played guitar recordings through it at moderate volume for several days until it felt like the spider and surround had loosened up, then put it back in the Budda. All I can say is, WOW!! What a difference once it is broken in fully. It completely changes the character of the amp and I believe is an integral ingredient in the Budda sound. I would not dream of changing it now, as every aspect of the amp got better, so I say please make sure you factor in plenty of break-in time when you get yours and you will be very happy.
All in all, this is probably the best amplifier purchase I have ever made in 37 years of playing guitar. It really is that good.