I hooked it up in my test setup, and for first contact, I did not put it into the dirt pedal position on the test bench, but into the preamp position, using the XLR out and feeding my other pedals into it. Two things became abundantly clear within the first few notes. Firstly, I can't just plop it in, replacing another pedal and expect it to work, especially when the compression, EQ and gain staging of the rest of my pedals all were carefully balanced to cater for the other pedal. The Fifteen has the size, the quality, the reputation and the price tag to demand you create an environment around it, using it as the cornerstone.
Secondly, and this is much harder to put in words, the depth of the thing. I've played a few pedals that hinted towards being B-15 inspired, or B-15 recreations. However, there's a bit more to the iconic little fliptop amp than a tube stage in the preamp and a James (passive Baxandall) EQ. I instantly get the feeling that there are multiple stages my signal passes, and each of them does a little something. This might be true, or it might be clever deception - either by Origin consistently pumping out great pedals for so long that my ear involuntarily finds greatness where there is none, or by tinkering around enough to give the impression of a complex system, albeit just using a simple schematic. I want to go with the true multiple complex stages theory, though.
It feels like your average "Fliptop" inspired pedal is a two dimensional drawing of the real thing, while the Fifteen is a three dimensional object that your ears could actually touch, if they had hands.
Since this is the Dirt Jounal and not the Preamp Jounal, let's focus on the dirt for a second.
Diming the Drive on the pedal instantly yields a sound that is not unlike diming the gain on a mixing desk. You need special ears and a very special taste to like that. In conjunction with the cab sim (or filters, should you go the 1/4" way out), you can tame a lot of the nasty sizzle, but it still feels like poking a badger in the one sore spot on its belly. There's squirming, and sharp artifacts flying around and you want to evacuate yourself from the situation as fast as possible. When you dial back on the Drive knob to get into more credible settings, you reach the regions that are packed with fun stuff. If you set the Drive to be on the edge of breakup, there is considerable push back from the Fifteen, and it feels great under the fingertips. You can make the attack of a note growl just a little, clearing up quickly into a clean, luxurious decay. It's often said that you can't make a James tone stack sound bad. As you can see above, the center frequency for the tone stack is sitting around 400Hz, and the bass knob's range is less than 20dB from fully CCW to fully CW. The EQ is located pre-drive, so when you're going for edge of breakup or a mild drive sound, the EQ shapes the nature of the drive, which works very well.
Between the filters, the cab sim, and the post drive EQ, you get quite a few options to shape your sound even more. I know the filters and the post Drive two band are meant to match your backline rig to the DI sound, but thinking out of the box, you can do more with that stuff.