You’ve all seen ‘em: bedroom amps, mini- or micro-stacks, practice amps or whatever you may call them, they all share the same promise: Classic tone in a small, affordable package. Well this installment of Tech Talk is here to show you why that’s pure bullshit meant to bedazzle the ever-so-naïve young guitarist. Read the rest of this entry »

Would you like fries for that shake? How about phantom power for your active pickups or onboard preamp/effects?

We usually think of phantom power as related to condenser mics but I’m not talking about the 48V you get from a mixing desk here, although it is pretty much the same principle: carry your power on the same cable as your signal so you don’t have to lug around a battery. On guitars with active electronics this system is particularly useful since:

• Obviously, there’s no onboard battery: no replacing, no recharging, no making room for an aftermarket installation.
• You’re not restricted to batteries, yet you retain the option of using them: you can just as well power your pickups from any standard 9V adapter. Or go 12V or 18V if that’s your cup of tea.
• One cable fits all: the system is compatible with any guitar that has been set up to use it or any other (mono) guitar for that matter:
  • phantom-powered active guitars: all that needs to be done to the guitar is to use a stereo jack and tie tip to signal, ring to where battery (+) would be and sleeve to ground. Anyone with basic knowledge of electronics should be able to figure this out;
  • “standard” active guitars: (i.e. those with onboard batteries) if for some reason you need to use one, just short the ring to sleeve, before disconnecting power, of course. Otherwise you’d be shorting out your battery or adapter. This is necessary because most manufacturers use (or should use anyway) the “insert jack to connect battery” scheme, i.e. the battery is floating unless you short R and S together, which is what inserting a mono jack plug does. This could be accomplished with a switch.
  • passive guitars: if for some reason the original TRS recommendation is abided (which people rarely do) power would again be shorted to ground, which is hazardous if not fatal to the supply. To be safe, you could simply unplug the battery or barrel plug from the adapter or again use a switch, possibly the same one as before: a single pole on-off-on switch can choose what the ring is connected to—supply (phantom power), nothing or ground.

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If we’re to talk tech then it’s vital we all speak the same language, so here are some quick initial issues:

If there’s one word guitarists (and musicians in general) misuse, it’s gain. Gain, as you’ll find in any dictionary, means the ability of a circuit to increase the power or amplitude of a signal. Or as a parameter, we can define it as the (mean) ratio of an amplifier’s output signal to its input signal. So if we feed a 2V signal to an amplifier with a gain of 10 (which equates to 20dB), we would measure an output signal of 20V amplitude (provided there’s enough headroom, which is another topic).
For some strange reason, when guitarists say gain they really mean saturation! As in “A Dual Rectifier has more gain then a JCM800.”, which might be true, certainly is something we can determine but is not what the guy is thinking about when he says it. A Recto might sound more saturated then a classic Marshall but we’re really getting into subjective territory: a fully saturated sound is a square wave, and I’m sure people would agree that doesn’t sound as “gainy” as a cranked stack. So it’s not even the level of signal distortion but the specific harmonic content that results. A shrill sound that emphasizez the pick attack might sound more “gainy” then a dull “bluesy” sound, even if it comes from the same amp, at the same gain setting, being just a matter of EQ (or filtering, to be correct). Read the rest of this entry »