Found this when doing a search for John Mayer's equipment on Google. It's a post on one of JM's fan forums from John Himself. Interesting reading.

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Hey (gear) guys and gals -


I thought it might be fun to post a little something regarding gear, specifically that endless hunt for our guitar tone. It’s as much of an obsession for me as it is for some of you, and I want to share a little of what I’ve learned over the past few years. I read through some of the posts in this part of the forum, and I can’t get over how much of a positive spin you’ve put on the guitar community. It’s has a tendency to be jaded, and I love to see that you’re getting happiness and fulfillment out of it and not frustration.

There are some misconceptions that seem to constantly perpetuate, and I want to try and bust one of them up right now. Oh, and it should be noted throughout that this all applies to my take on tone. If you like heavy metal, you’ll probably disagree with everything I have to say.

Distortion pedals – One thing to keep in mind with distortion – I should say overdrive pedals, so as to distinguish them from fuzz pedals, which is more of an effect unto itself - is that they’re really made to simulate overdriving an amp naturally. Vintage tube amps have a threshold where they break up past a certain volume. A distortion pedal is used to make that ‘break up sound’ happen at lower volumes, which is a reasonable expectation. You can’t turn a ‘65 Deluxe Reverb to ‘8’ in your bedroom without making a lot of people miserable. Stevie Ray Vaughan used an Ibanez Tube Screamer (TS-80 , which in the 1980s was regarded as kind of a cheap pedal. Here’s the misconception; he didn’t really use that much distortion at all. He did when he was going for that Jimi sound, but listen to most any early SRV tune and you won’t hear as much break-up as you might think. I hear people all the time (I even remember hearing myself) who just dime the ‘drive knob’ and think the ‘volume’ is a master knob for it. It’s a concept known as “gain staging” - it has to do with the way that the volume of each part of your signal chain interacts with the next. The ‘volume’ knob of an 808 is the most important. That’s by definition, the overdrive part of it. The “overdrive” should be thought of as the “cheat” knob. Remember this – kicking on distortion should make your guitar louder, not quieter. Quiet sounding loud is just strange. Setting gain staging will make sure that when you kick the pedal on, your guitar signal will get appropriately louder. Again – Stevie Ray used so much less distortion than you can possibly imagine. He was loud, and the way it hit the tape (and your ear) made that sound. I use a vintage 808, which has some properties that I like, but it is by no means the holy grail of tone. It has it’s place, though. Everything does. Just remember that turning that “cheat” knob too high also cheats you of the natural tonal characteristics of your guitar. Do work that volume knob, though.
So what if you don’t have the 600 bucks for an 808? Don’t even worry about it. There are so many pedals designed to emulate it, it’s not even funny. Purists want the original 808 because of some fairly esoteric microchip differences. The Voodoo Labs Sparkle Drive is somewhat close, (and dirt cheap!) but it can also have a really harsh high end. (What’s in a name, right?) I think the Fulltone Fulldrive 2 is a FANTASTIC update on the 808. The Keeley-modded TS-808 reissue is very close to an 808. These pedals are what I call “paint chip” close. If you didn’t have an original 808 to A/B with, you wouldn’t know what you were missing. If you’re looking for a good “edgey” tone, check out the Marshall Bluesbreaker pedal from the early ‘90s. Not the BB-2 (bad), but the original. It’s a great beefy sound that colors strat pickups in a really interesting way. The tone knob is like a “B.B.” dial. If you feel like your guitar just won’t cut it in the mix with your band, but you don’t necessarily want more overdrive, check out the Fulltone Fat-Boost, or the Keeley Katana. Kick it on for a solo, and it’s like having your own personal mixing engineer ride your fader. I use a Keeley-modded Boss BD-2 pedal as well. It’s got it’s own thing going on, and I like it. So many pedals are cool, and most every one has a place for something. It’s fun to listen to a pedal and then play to it’s strengths.
Oh, here’s another misconception: True bypass is all-around better than buffered (regular) bypass. Not so. Think of your guitar cable as a hose, and your guitar only pushes a certain amount of water pressure out of it. After a certain length, you’re going to need some more pressure to squeeze the water out. True-bypass takes the “in” and “out” cables of a pedal and connects them as if they were one long hose. After a certain length, you’ll get some pretty hefty tone loss. I learned this when I unplugged my guitar from my pedal switcher and went straight into the amp. Guitar pedals without the TB serve as a buffer for the signal, and naturally keep that water flow going. Yes, sometimes the trade-off can be harsh; some pedals, while buffering your signal, can also adversely color it, even when in bypass mode. That’s a good time to think TB. True bypass is a concept that only really took off as a selling point over the last 5 years or so. It won’t kill you to have it, but it certainly isn’t the only reason to get a pedal over another one without it.

I Hope that helps you out a little bit. There are so many other things I want to share with you, where to put your money, where to save it... Maybe I’ll get to it all over time. I can’t think of anything more exciting than tone hunting, and I hope you can’t either.

PLAY ON

JM