The discussion in this thread prompted me to post about a subject that seems to come up again and again and about which I've sent many a PM. Many of us play amplified these days with our own rigs (as opposed to using the PA). The acoustics of the rooms we play in can differ dramatically so that it is a useful skill to be able to "listen to a room" and quickly discern how to adjust our tone controls to get close to the sound we want. This requires a working knowledge of exactly what our tone controls do, how to use them, and how they can be used to tame room responses. I am a fan of the parametric tone-shaping circuits on amps like the EA iamps. Many find these to be somewhat overwhelming and just too many knobs and sliders. I've argued that they're well worth learning to use but how does one do that? How does one go about being able to walk into a room and say "Hmm.. I need a cut around the region of 250 Hz and a boost at 2 kHz."? Below, I describe a procedure to do just that. It will work for any type of tone control circuit even ones that are not specifically labeled with numerical frequency parameters. The procedure is easiest to describe for the typical "graphical equalizer" type of circuit, so I'll do that (although it can be applied to any type of tone shaping circuit). The first thing you need is a source of wideband noise (commonly referred to as white noise). A good source of this noise is the inter-station (between stations on the dial) noise you get on an FM receiver if you can turn off the muting circuits that hide this noise from you. Another way is to generate white noise via any number of computer programs and burn it to a CD. Now, play the white noise through your rig with your eq. set flat. One by one, take the frequency sliders and listen to how the character of the noise changes as you boost each frequency region. Pay particular attention to the 125-, 250-, 500- 1000-, 2000-, and 4000-Hz regions. You'll hear that just a small boost around 1000 Hz is VERY noticeable. It imparts a "nasal," "forward" quality to the sound. Remember that one. Now try the same thing for slight cuts at each frequency region. Again, you'll hear how noticeable is a change around 1 kHz. If you spend just a modest amount of time doing this, I think you'll be surprised how quickly you will learn the characteristics of each of the frequency regions. With some practice, you'll be able to listen to a room at a gig and know which dial(s) or slider(s) to reach for. IMO, it really is worth the time. It will also allow you to assist the sound guys. I hope this helps!