Not to be confused with the vintage non-tube EHX Hot Tubes, this version is an all tube distortion. According to a review on analogman's website, there's no sand on the signal path, so all you get is oozy 12VAC 1000mA powered valve distortion. The stock tubes are 12AX7WB (supposedly, there might be some variation). I think this one came out before the English Muff'n. So it's all nice, then we get into the EQ, and things get strange. You have BASS and TREBLE controls, and from my experiments, they work like this: With both off, you get a straight up overdrive with nothing changed on EQs. This usually sounds a bit harsh and trebly. When you start rolling the BASS up, you a frequency peak that begins appearing between 2khz and 3khz, and as you keep rolling up, it rolls down all the way to 150hz, and increases in gain. The TREBLE control does the same, but instead of moving down it goes up to 7.5khz. Apart from that there are GAIN and DRIVE controls, and I'm not sure in what each of them differentiates from the other, but they're different. Maybe gain is the input gain and the EQ is applied after the tube gain and the DRIVE is applied after that… who knows? If you roll the GAIN and both EQs down, and roll the DRIVE all the way up you get a slight breakup sound. As EHX states, the controls are very interactive amongst themselves. I find myself using it mostly with the EQ off or with both set almost all the way up. Apart from that there's a master volume control, which does exactly what it's supposed.