(Image credit: Michael Ochs Archives/Getty Images)

Nobody knows the ins and outs of Jimi Hendrix's guitar sound like Roger Mayer.

Mayer had already worked with Jimmy Page and Jeff Beck and produced a number of different fuzz boxes by the time he met Hendrix at a gig at the Bag Of Nails pub in London. The two hit it off and Mayer showed Hendrix his Octavia, a unit that added an octave overtone to the original note. Hendrix loved the sound and used it on the solo to "Purple Haze."

"After that we became close friends and started hanging out; and as they say, the rest is history," Mayer says.

He went on to look after Hendrix's gear both live and in the studio, gaining a unique understanding of his requirements, playing style and working methods. Today Mayer produces a range of pedals that take his original designs into the 21st century.

Mayer says an important part of Hendrix's sound was due to his use of carefully selected string gauges, which evened out the guitar's response from string to string.

"First of all, we weren't using a flat-radius fretboard," Mayer says. "We were using the normal one, not the very high radius but definitely curvy. The actual strings we used were not what people would expect. The string gauges would run .010, .013, .015, .026, .032 and .038.

The big difference there is that you're using the .015 for the third, because if you use the .017 for the third, the actual sound of the guitar is very G-heavy. The electrical output of the strings is dependent on the square of the diameter; if you square all the diameters and look at them, you can get much more of an idea about the balance of the guitar.

"You should always remember that, because many, many times people use a set of strings that are completely imbalanced and they just don't sound that good. Most people would say a .010 to .013 is the correct jump. And the .015 is much better for the G than a .017. An .015 squares out at .225 and .017 is 289. So you're going to get 28 percent more output just with a two-pound different in string size."

Although Hendrix used a custom string gauge, Mayer certainly didn't mess with the stock pickups in his Strats. He didn't feel the need.

"When I was working for the government, we had access to certain kinds of equipment. We were encouraged to have a hobby, so I went through all the different number of turns you could have on a pickup very quickly, right from square one. I wound up a whole range of pickups.

"Basically, what became very apparent with pickups is exactly what I thought before we started: They really don't make much difference! I would say they're one of the most vastly overrated parts of the guitar itself. If you understand electronics, you understand that as the inductance of the pickup increases—that is, as the number of turns on the pickup increases—all that happens is you get a larger output, and you effectively get less high-frequency response due to the fact that the inductance of the pickups rises. It's a trade-off.

"And after making several experiments, which probably covered all the number of pickup turns that are available now, I came to the conclusion that Leo probably had it about right! There wasn't much to be gained by deviating from the 7,000 turns or so on a regular pickup."

Naturally, because Hendrix was a left-handed guitarist playing a right-handed guitar strung for a lefty, the guitar responded slightly differently to if it was a left-handed guitar.

"When you flip the guitar, the actual cavities in the guitar now appear on the bass strings, right? Because the volume control and all that is facing toward your head. So the actual resonances of the cavity do change. What happens then, of course, is that now you're faced with the fact that the actual string length on the bass string is now the other way around and conversely, on the treble strings.

"So yeah, that will make the guitar feel slightly different because the actual string length affects the kind of strength needed to bend the strings. That's one of the reasons we used to tune the guitar down a little bit."

Mayer says Hendrix's approach to sound in the studio was particularly abstract, but that a shared love of science fiction gave the pair a common language to discuss and achieve what Hendrix was looking for.

"The actual vocabulary of audio is visual. People say 'a bright sound,' 'a dark sound' and so on. So we thought in colors and about the actual way the sounds were moving around, and that's how we worked, really. Jimi was very free-form and he liked to improvise an awful lot, so the actual structure of the songs was very free-form. But once we knew what the song was about and the vision for the song, that would dictate the kind of sounds we might use, or the various effects we would use, from studio effects to panning to various echoes."

In chasing those sounds, Mayer would often alter circuits in between takes in the studio.

"There's a big difference between the actual sound produced in the recording studio and the control room, so I guess I was running backwards and forwards between the control room and the actual studio to treat the sound and adjust the amplifiers and so forth."

Mayer also looked after Hendrix's gear at many gigs, and in the days before electronic tuners he often had to rely on placing the guitar's headstock against his ear to hear whether Jimi's axes were in tune.

"You had to do that because you have to remember that in those days electronic tuners didn't exist. The only thing you possibly had was a tuning fork. If you go on stage and a red spotlight might hit you, that's going to put the guitar out of tune. The blue one, not so much, but if they hit you with a powerful red, that's going to pull the guitar out!"

Peter Hodgson is a journalist, an award-winning shredder, an instructional columnist, a guitar teacher, a guitar repair guy, a dad and an extremely amateur barista. He runs an awesome blog, I Heart Guitar, which allows him to publicly geek out over his obsessions. Peter is from Melbourne, Australia, where he writes for various magazines (including Guitar World) and for Gibson.com.