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At 4:19 AM -0600 3/14/98, John Pollock wrote: >Sean T Barrett wrote the stuff with >, and Kim's quotes get > >: >> >> kim: >> >I guess you're not a guitar player, right? An electric guitar >> >by itself is only half the instrument. >> [snip] >> >That is also why a guitar through a flat PA system will sound >> >very bad, and to the player, it will feel lifeless. > >That _can_ be the case, but isn't necessarily always true. It depends >on the guitar's pickups, the impedance loading them, the strings, and >the musical context. > >Most electric guitars have passive magnetic pickups. If they're loaded >too heavily (i.e., the input impedance of the amplifier is too low), the >high frequencies will be rolled off severely. The hi-Z inputs of most >PA systems, typically 50K, will of course strangle the signal from most >passive magnetic pickups. (The typical guitar amp's 220K is actually a >bit low as well, but in this case it's a _feature_, slightly rolling off >the upper harmonics so they don't clash quite so badly with the >harmonics the amp has been carefully designed to generate.) probably the last I have to say about this, since it's getting off topic.... Another effect of the guitar/tube amp thing, and what I meant by the "amp is half the instrument" comment, is that the input impedance of a tube amplifier is not a constant thing. It changes as the current in the tube changes. This means that the impedance will change a bit depending on the signal. Guitar pickups are high output impedance devices, so the impedance of the input stage of an amplifier will have a strong affect on the pickup's frequency response. So this means, as you pick a note, the tube amp input will actually change the frequency response of your pickup over the course of the note. I think most of this effect will occur during the attack since you would have a large current change then, and that's where most people hear it. For any other amplifier application, this is a serious flaw. But for guitars it's a bit different. In that case, this strange affect becomes something you use as a means of controlling timbre in your sound, therefore making it part of the "instrument". I don't think most people are real conscious of what is going on, they just know that a big variation in sound happens depending on how they pick. It becomes an intuitive part of how you play. (Tube amp player's often refer to this as "bounce".) If you then play into a solid state input (by putting some pedals between guitar and amp, using active pickups, or using a solid state amp), you notice that the sound is less responsive. It seems lifeless. This is because the input impedance is very stable, and that frequency respnse jiggle in the pickups is gone. (similar things happen between the output of a tube amp and the speakers.) This doesn't have much to do with the character of the sound itself. It's really about how the guitar/amp combination feels to the player. And that of course, can inspire the player in creative ways. It also leads to people obsessing about amplifiers and they're signal chain. And as far as the response of "I've done it this way for years, and it sounds fine to me", well, I been there! I had pedals and solid state guitar amps for the first 18 years of playing I did. And then I took that tube amp drug, and before long I was totally hooked. Once that bounce has gotten worked into your playing, and you learn to control that aspect of the sound, you'll be heading down to the corner tube pusher on a regular basis, mainlining EL-84's, doing 12AX7/6L6 speedballs.... kim ______________________________________________________________________ Kim Flint | Looper's Delight kflint@annihilist.com | http://www.annihilist.com/loop/loop.html http://www.annihilist.com/ | Loopers-Delight-request@annihilist.com