Boston Section

Last night the Boston Section of the AES (Audio Engineering Society) held it's April 2008 meeting, focusing on guitar amplifiers. The overarching question of the evening was: "why do these things sound so different from one another?" It was pointed out at the start that the Marshall head present and the 1961 Fender brown super 2x10 contain the same 12AX7 pre-amp tubes and 5881 output tubes. Yet the couldn't sound more different! To address this question, BAES imported guitar guru Jim Mouradian, of Mouradian Guitar Repair in Porter Square Cambridge. Mike Burke was also asked to attend to play guitar through the series of amps present at the meeting so that we could all derive a common "aural vocabulary" to talk about the amps. He brought the aforementioned Fender Super. BAES member Steve Martin brought his homemade Matamp 120 copy. A Vox AC30HH, Marshall JMP-1/9100 head, and an Orange Tiny Terror were provided by Digital Bear Entertainment.

To address the question, Mr. Mouradian began with some history of amp design. His point was that each amp manufacturer had specific design goals that influenced their circuits and thus their "sound". Early Fender designs were intended to achieve clean volume culminating in the revered Bassman 4x10. It was after people began to abuse these circuits by deliberately overdriving them that Fender realized that the customer wanted those tones and so added that overdrive as a feature to existing designs. Marshall, on the other hand, began with a copy of the Fender Bassman circuit, but substituted British components and realizing the need to fill stadiums, moved quickly to larger wattage, stackable cabinets, and closed back cabinets. Vox, renowned for their "chimey" or "piercing" voicings, were rolling off the low end to allow high volumes at the same power in order to "throw" to the back of the hall. Ultimately, it became clear that the choices made by each manufacturer were far more instrumental in their sound than the controls provided to the user.

Steve Martin, who is presently running a DIY amp building "collective" had some insight into the actual circuit designs and how they are constructed. Interestingly, both he and Mouradian attested that Marshall amps were designed to allow the nominal signal through at full marks on all the controls, and parameters were all cuts from that. In other words, "diming" a Marshall is exactly what it is designed to do. Mesa-Boogie, on the other hand, is designed to be run closer to "5" on each dial, and can sound odd when pushed beyond its "happy place". As we all know from our experience in audio engineering, most gear has such a "happy place" in which it is neither inefficient nor overly stressed. Gain staging is critical with guitar amps just as with mic pre-amps!

As usual, the meeting ran late into the evening with Q&A and further guitar playing. It was most interesting to understand how the design goals of the manufacturers ultimately were more relevant to their chosen sound than the components they used.