Please let me clarify some incorrect and misleading information that is being presented in this discussion. First of all, I am the engineer of record for the Shuttle and GBE products, so I am absolutely qualified to comment on the specifications and design intent of our products.
1. IMPO, the original testing methodology used for the "BGM" tests was so flawed as to produce worse than meaningless results. Line voltage must be held at 120 volts to produce the rated output, this is true (in general) of most amp products by most manufacturers. The problem with the tests is that the voltage drop is due to the current being drawn and the big (linear) amps that have no VI limiting will always draw more current and the output power will fall off by the SQUARE of the input power voltage drop. So, the bigger the amp, the greater the deviation (by exactly the square) between their measured power and the rated power at 120 volts. It was unfortunate that their technician did not appreciate the importance of the squared factor flaw in his test. Since the GBE-1200 was the largest amp tested, it showed the greatest deviation. I performed the testing on the same amp here at my R&D lab with proper equipment and found that it passed the power spec with no problems at all, and that IIRC the line voltage would have had to fall to roughly 109 volts to replicate their invalid data. There were also significant measurement errors that we discovered after the magazine was released that ANY engineer worth his salt would have seen as an impossible value, but the technician did not understand why the number didn't make sense. (extra credit... identify the flawed measurements). Also, you can not use purely distortion numbers for powet testing thresholds on musical instrument amplifiers because many of the functions inherent in tube amp stages and emulation processes generate harmonics. I wonder how an all tube amp would have faired in this test... probably not well because the base line distortion would quickly exceed the measurement cutoff threshold.
2. The power versus frequency test was so inaccurate and meaningless as to make me question what the tech was trying to quantify. The only thing this produced was a frequency response profile which matches the preamp's inherent voicing. The power amp delivers full rated power from 20Hz on up, and any (intentional) rolloff or boosts in the preamp would of course be reflected in the corresponding output levels of the power amp. This is how amps work, not rocket science. Additionally, the tech did not do this measurement with the LF extend filter engaged, which extends and alters the low frequency rolloff point down. This function (switch out) is useful for players who must tame challenging rooms or will be playing with compact cabinets and want to avoid overexcursion.
3. The limiting function was not engaged, and the tech did not understand one of the fundamental design features of the amp. ALL of my output limiters are multi-function in that they emulate how a tube power amp overloads from the gradual rolling into soft clipping and then a dB or two later (after about 3-6dB of input level) another transition as the power amp begins to actually clip. This is well described in the owner's manual but clearly not comprehended. This feature is something I have used in various forms for well over 20 years now. This function increases the area under the power curve (hence an increase in power) while controlling the addition of higher ordered harmonics. It requires a true RMS meter that looks at the real power, not based on an extrapolated sine wave conversion.
4. Regarding the way the Shuttle gain and volume controls work... the execution is exactly as we intended it to work and how most of our customers use it. The Shuttle 6.0 is not designed to do the heavy overdrive thing, the tube circuit gain is adequate to getthe tube flavor and mild grind from most pickups, and with higher output pickups it is certainly possible to get significant overdrive. If the heavy overdrive thing is what you want, use a booster (preamp) pedal with ~12dB of additional gain. The ShuttleMax has this additional gain built into the high gain switch function, so it's more appropriate (without a pedal) for getting the heavy overdrive thing going. The tapers for the controls is to allow a good feel and operating range with a wide variety of today's pickup levels.
5. The CLIP/LIMIT LED has 2 function, the first is to indicate that the player has crossed the threshold of the output tube emulation limiter and that there is roughly 6dB of compliance left before output stage clipping is approached. It is an INFORMATIONAL indicator so that you as a player know where you are operating the power amp before you run out of steam. IMO, it is an important and useful bit of information that if understood makes perfect and logical sense.
From my discussions with Tom and his new engineer, I understand that they too have determined that testing amps in a meaningful way is much more difficult than it seems on the surface and that they are in the process of reformulating thesting procedures and propocols. I have spent almost 30 years learning everything I possibly could about REAL WORLD amplifier performance and how each variable impacts the player and the tone. I also split my design projects between musical instrument amps and full-on pro audio products, so I have a pretty wide angle view of how things work. I ask that you all consider that sometimes reviews are not accurate for whatever reason, and testing errors and methodology affects every manufacturer differently depending on their particular design philosophy. By the way, it hurts me to see a competitor's product bashed in a review when it's basd on invalid or inaccurate testing methodology too. It's just not good for anybody, including you the consumer. Play as many products as you can and buy what works for YOU, even if it's not our product. That's ok, really
