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Thursday, 16 April 2020 11:25

The active pickups are hotter than passive pickups myth explored

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Active vs passive output voltage comparison Active vs passive output voltage comparison

Active pickups are notorious for their hot outputs, and if there was ever a culprit for unwanted distortion, it's active pickups. Er, right...?

On forums throughout the web, and on pickup manufacturers' websites, you'll find meaningless terms such as "8 kilo-ohm!" and "hot!". This doesn't really tell us mere-mortals how powerful our pickups truly are, though, in a way that's useful to us. So forget kilo-ohms - let's talk volts*.

"Volts? Shut up, you nerd!", I hear you shout. Bear with me, it's actually pretty simple. Most guitar and bass pedals run on 9-volt batteries or power supplies, so it follows that you want your guitar signal to be less than 9 volts. Much like how you wouldn't drive a double-decker bus into your garage.

Let's take three pickups, scientifically-selected by a process of "I have them laying around". First, let's see how powerful they are on their own, then plug them into a pedal and see what happens. We'll be using something called an "oscilloscope", also known as a "sillyscope", and I'll strum as hard as I can.

These pickups are: a Seymour Duncan Little '59 in a Telecaster, a SH8b Invader in an Ibanez RG370, and an EMG SSD in a Spector Legend bass. The first two are passive, while the last one is an active pickup, custom-designed by EMG for Spector. All are in the bridge position.

So what do the pickups' outputs look like when you strum a chord straight into the sillyscope?

Little 59 Pickup

invader pickup

emg pickup

So the EMG is the weakest of the three. Wuuuut?! Crazy stuff. While all these pickups seem quite powerful, they're all below 9 volts.

Now let's play them into a buffer, which is probably the most simple type of pedal, and doesn't add any gain or amplify the guitar signal in any way. You'll find a buffer as the very first circuit your guitar meets in most pedals.

pickup buffer clipping

Oh, dear. Turns out, most 9-volt pedals actually have 6V or less of headroom, so some of these pickups are screwed from the get-go. Strum lightly, and you may get away with things. Strum hard, and you'll distort a pedal which isn't hasn't even added any gain.

What happens when you DO add gain? Let's say a mere 10dB (which should make the signal about 3.2 times stronger). Let's use a clean boost pedal.

Invader Pickup gain curve

This poor waveform didn't stand a chance. These pickups will make "clean" pedals distort, and will make dirt pedals distort at a much lower setting on their Gain knobs.

What can be done? Well, you could either use a volume pedal before any other pedals, use an 18-volt supply on pedals which allow it (always read the manual!), or you could avoid these pickups. Why don't amps have this problem? Well, because solid-state amps usually clip at about 30 volts, whereas tube amps can accept hundreds. A wee bit more than your 9-volt battery.

-Grant Stab

*It's really "Volts peak-to-peak", or Vp-p, that we're measuring, but you would have stopped reading if I tried to spring that jargon on you.

Read 995 times Last modified on Thursday, 16 April 2020 11:37

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