Tube Amp

If you're testing guitar pickups or effects, then you must have a good reference amp when you go to plug in and listen to what you've got.

If you aren't into building custom stuff yet, then I would suggest picking a classic Fender tube amp as your default, reference amp.

My Fender reference amp isn't a vintage one, but I find that it does the trick. I use a Pro Jr. model when I need to really check something out.

There are several "tricks" that a good tube amp will provide, but the primary one that most classic tube amps will do well is provide the "standard" high input impedance of around 1MΩ. Without this, pickups all sound the same, special pickup switching doesn't impress, and turning down the volume and/or tone knobs can sound bad or much worse than they should.

I have found guitar techs in distress trying to figure out why the volume control on a customer's guitar didn't have the "right sound," or turned the volume up and down abruptly... they may have already installed the "correct" CTS audio pot that matches the pickup impedance, but it still sounds bad... what's wrong?? At that point, try an old tube, preferably a Fender. I can't believe how many solid state amps have "tone sucking" input impedances.

The next trick the tube amp provides is that "natural" tube overdrive that they are famous for. Even without really driving the amp, there is a sonic difference that shouldn't be ignored with most tube amps. Many overdrive/fuzz/distortion boxes are specifically designed with a tube amp in mind, and may or may not sound better or different when put into a tube amp. Sometimes a customer gets picky on tone, and it's best to use something close to what their using when evaluating the sounds. In general, I'd say the pickier the guitarist, the more likely it is that they use a tube amp. So it makes sense to do final evaluations with a tube amp.

I don't normally listen to my repairs on a tube amp. I use an op amp preamp system I built for myself that feeds a mixer circuit and then a stereo power amp IC that drives 2 medium-small hi-fi speakers. That works great for analysis. A pedal might be producing several volts of output, which would be slamming any tube amp "guitar" input, but it can be totally clean on my solid state system. Once I've heard all I need to on the solid state system, I will plug into the tube amp to hear how it "really sounds." It can be very different!