Gibson Guitar Amps


[ Louden Up! ] [ Music/Guitars/Amps ]

Introduction

These pages will cover areas of interest related to Gibson guitar amps, especially the older ones, that don't seem to be covered elsewhere. Over time they will likely grow in scope. For things not covered here, the most complete Gibson tube amp site I'm aware of is maintained by Bjorn Anger at http://hem.passagen.se/ekabjan/GibsonAmps.htm. This site is still being revamped; in the interim if what you're looking for isn't covered there, you can see a copy of the original site (no photos, but more complete coverage).

Observations on Golden Age Gibsons

During the golden age of tube guitar amps, Gibson produced at least as many models as Fender. While Fender tended to cover a wider spread of power ratings (especially at the upper end), Gibson had many more distinct circuits available to the public, using a wider variety of tubes. (I suspect that Fender was more marketing driven.) A few examples:
  1. Power tubes: Fender pretty much stuck to the 6V6, 6L6 and 5881, with one very brief foray into 6BQ5 territory. Gibson used these, but they used a lot of 6BQ5s, as well as 6AQ5s, 6BM8s, and 7591s (at least).
  2. Preamp tubes: After the very earliest amps, which did use pentode preamps, Fender stuck pretty much to the more common dual triodes, and moved early to the miniature 9 pin 12A?7 series. Gibson continued to use pentodes here and there, and used a wider variety of triodes. They also continued to use octal dual triodes long after Fender had converted exclusively to miniature glass dual triodes.
  3. Frequent model changes: While Fender apparently followed a process that didn't make changes frequently, favored micro-evolution, and reused circuits as much as possible, Gibson not only overhauled models apparently on a whim, but they were constantly trying new things, and had far more variety in their amp circuits-- including what I call transition models.
  4. Innovation: Gibson tried applying almost every trick in the book at some point or another. In addition to the three main inverter types Fender used, Gibson also used transformer inverters, and produced models with triode amplifiers between the inverter and power tubes. Fender (and most other companies) stuck with either a basic tone control, or the classic bass/mid/treble (perhaps with fixed mid) stack. Gibson used these, but also played around with James/Baxandall circuits, and a wide variety of bass and treble boost and cut circuits, as well as a tee filter for mid cuts that was essentially a fixed version of a Cutler duo-control bass/treble boost.
  5. Transition models: While Gibson might publish two different schematics for the same amplifier over time, they often produced amps that were somewhere in-between these schematics, incorporating the preamp of one and power section of another, or changing only one or two tubes at a time instead of converting completely to the new tube set.
  6. Along with this, it's easy to find examples of many Gibson amps with other, minor variations from the schematics. These variations might be in component values, or they might be circuit topology changes. It's unclear whether this was sloppy quality control, simply using whatever was on hand, the use of far more engineers in designing the amp electronics, or a case of everyone on the assembly line getting to try their hand at design. In any event, there seems to be no guarantee that any given Gibson will exactly match any published schematic-- even if that schematic was stapled to the amp at the factory! Some of us refer to this as "the Gibson amp circuit du jour". ("Du minuet" is perhaps more appropriate.)
  7. Layout variation: While Fender again tended to come up with something that worked, and then stuck with that, Gibson component layout and lead dress could be nearly as random as their circuits. This was more readily possible with Gibsons since they stuck with true point to point, flying lead builds well after Fender had gone exclusively to using boards to hold their components.
What does all this mean to someone thinking of getting an old Gibson amp?

Probably the biggest thing to remember is that there is much more sonic variation in old Gibsons than in most major brands. At the same time, I've yet to meet, or even hear of, an old Gibson that couldn't be made to sound great. Fortunately (from a player's perspective) Gibsons are not as "collectible" as Fenders, so (a) prices are lower and (b) there's far less resistance to changing them (there are a few exceptions to this).

[ Louden Up! ] [ Music/Guitars/Amps ]
Last updated: 01 September 2005

Copyright Y2K Miles O'Neal, Austin, TX. All rights reserved.

Miles O'Neal <roadkills.r.us@XYZZY.gmail.com> [remove the "XYZZY." to make things work!] c/o RNN / 1705 Oak Forest Dr / Round Rock, TX / 78681-1514