Let me start by saying that I am not picking on you or on this amp, in particular. I realize full well that you are not touting this as the "drug of choice." I am not criticizing your choice, nor am I discounting that the device may work very well for you and the combination of equipment with which you use it. With all that out of the way, I'd like to ask a question and make a few observations.
I use it for recordings and the occasional live gig where I need more volume
I'm not sure exactly what you mean but if you use this when you need more volume, then it seems you are using it to boost the gain into the next device, be it a head amp or PA, or whatever. Do those devices not have level controls that will get you there?
It doesn't have EQ but it does have: HP/rumble filter (80hz), phase reversal, phantom power (if needed) and a -20db pad.
I read the manual and it is not clear how they implement the rumble filter. It could be a notch filter at 80 Hz or a high-pass filter at 80 Hz. That cutoff is about an octave or so higher than what is optimal to remove infrasonics from the typical ported enclosure. It is certainly less flexible than an adjustable HPF.
The tube aspect is where the coloring may or may not come in. You can really vary the tube and the gain levels to just about anywhere you could want. You can bypass the tube entirely too.
To the extent that the tube has any effect at all, it will be to color the sound or to change the overload and/or the distortion properties. I have no idea what the circuit is that surrounds the 12AX7 tube. In principle, there is no reason that this pre-amp tube would, necessarily, color the sound. It is likely that a circuit has been constructed to intentionally color the sound but that could be done with solid-state components as well.
A case can be made for a tube front-end under conditions where the input is routinely driven into overload as the characteristics of tube overload and distortion are quite different than that of solid-state components. The even-order ("euphonic") harmonic distortion produced by tubes is far more acceptable to the ear than is the distortion of typical solid-state devices. Suffice it to say that, IMO, if one is not overloading the input, there is no practical reason to use a tube.
The hint that the tube is used to color the sound rather than to improve overall performance is that the option is provided to vary the portion of the signal passed through the tube. I trust that you know that this is more gimmickry than anything else.
The pre-amp does have a variety of features (e.g., attenuation pad, phantom power, XLR connections, continuously variable gain) not found on simpler devices such as
fdeck's little pre/HPF but then again it is over 2.5x the price and all of those features can be had without the extra expense of and heat produced by the tube.
I love the VU meter though!
