Why Would I Want a 'Transparent' Sounding Amp?
A lot of amps - including most of the ones we sell at Gollihur Music - tout "transparency" as a key feature. What does that mean, exactly?
When applied to amplification, "transparency" describes a lack of "coloration" -- meaning, there is nothing added, nor taken away, from the sound plugged into the input jack, to alter its tone or timbre. Equalizers (Low/Mid/High, or Bass/Mid/Treble, etc.) are often used by players to alter their tone once the signal reaches the amp -- but if those controls are "flat" -- aka set to "0" -- theoretically, the amplifer should not add any coloration.
You can draw the comparison to a watercolor artist painting a new painting. If his canvas is blank white, he can paint using whatever color scheme he wishes to use. However, if the canvas has been pre-tinted with a rose color, there will be certain choices he may not be able to make in what and how he paints. Similarly, some amplifiers have a built-in "tonal character" - and there are specific timbres that they can create, as well as some that they cannot.
It's important to recognize, though, that this isn't a bad thing. You might be wondering why any amplifier company would choose to give an amp "a sound" that might make it hard, if not impossible, to achieve a full spectrum of different tonal options. But there are good reasons, and they are likely driven by the amps' developmental intent. I see it like this, from a philosophical perspective: expectations for what upright -- and electric -- bass amplification "should" sound like are a result of amplifier history, going back to the days of tube amps, far less capable speakers, and noisy components.
"Imperfect" amps from the early years of bass amplification have molded the expectations for what an electric bass should sound like, since it has always been purely an amplified instrument. Round, direct, in-your-face "tube-y" sound has become sort of the "standard," because of the shortcomings and limitations of technology of the day. But those negatives became positives as we decided, over time, that those imperfections are exactly what make electric bass sound "good" and "right" to us. Hence, we have modern amps that attempt to recreate those idiosyncrasies with preamp tubes, and contour controls, etc., and we have amp lines that intentionally have a recognizable "character." For instance, if I announce that I play an "Ampeg" or "SWR" or "Hartke" or "Aguilar" in a room full of e-bassists, they immediately can begin to presume the styles I might play, and what my essential bass tone sounds like. And it's why SansAmp pedals, Line6 amps, and computer amp sims exist.
Now, on the other hand, upright bass amplification hasn't developed that way, since it's always been primarily an acoustic instrument. Amplification has always been, and continues to be, an attempt at achieving MBOL (My Bass, Only Louder) -- at least for most players. Earlier amps were not so great at this, but we persevered, and waited for better, more transparent, less colored options to come along. Since the acoustic reference sound (the bass played acoustically) hasn't changed, neither has our perception of what the amplified sound should be. And now we have amps that get much closer to that Holy Grail of total transparency.
The amp designers from Acoustic Image, Genzler Amplification, and Euphonic Audio are generally adherents to the MBOL philosophy, but from slightly different angles - the Acoustic Image amps have always focused on acoustic instruments (hell, acoustic is in the name!) while EA and Genzler have primarily been more concerned with the needs and opinions of electric bass players. So while all of them are generally pretty transparent and uncolored when run "flat" (all EQ settings at "+/- 0"), when you invariably make some EQ adjustments, the AI gear is "tuned" to maintain that acoustic vibe, while the EA and Genzler gear is better for making an electric bass sound girthier/ballsier/(fill in the blank). And some of the amps have specific "coloration" functions - for example, you can often find "contour" or "filter" controls which "scoop mids" or "sculpt your tone" or "expand the low end." These are intentional colorations to achieve a specific tone.
All of that is not to say that you can't make an electric bass sound good through an Acoustic Image head (I certainly have), or that the EA Doubler and Genzler Magellan can't have a natural sound for upright (they do). What it means is that it's easier for most players to dial in the sound in their brains more quickly and intuitively on one amp vs. the other, relative to the kind of bass they play and the amp's design intent.
So which amp is "best?" That's the question. It depends what you need it for. That's why you have us -- if you're trying to figure out which amp will work best for you, you can call us, and ask someone who actually has used all the gear, and is familiar with all its pros and cons for specific types of basses/venues/music styles/ensembles/etc. It's what we do here!
I hope that offers some perspective - though I'm sure others have differing opinions and philosophies (which is why there are so many amp companies!)