Boosting Mystery: How and Why They Work!

As most LegendaryTones readers know, we’re an information site dedicated to writing features, tips, and artist profiles, all in the name of great guitar tone. But what some of you may not know is that we introduced our first product, the Time Machine Boost, a little over two years ago. And other than a banner ad on the front home page in the bottom left corner, we’ve made sure that we would never use the site for overdoing the promotion of the Time Machine Boost, and we still will not.

However, with that said, there are quite a few misconceptions about how boosts work and what they are used for versus an overdrive stompbox for example. I’ve received many e-mails asking questions about boosting applications and have replied to all of them. When the last question came in that asked why they couldn’t just usual a volume pedal instead of a boost, that’s when I decided to finally take this subject and put it all into the context of an article.





And no doubt, I AM going to “plug” our own Time Machine Boost so you’ve been warned! But if I didn’t think it was the best booster in the world, it wouldn’t be out on the market today so you have to excuse the fact that I am very proud of the TMB. With that shameless plug aside, let’s talk about boosters and decide if they’re for you, how they work, how they affect your signal chain and amp.

In the Beginning…

The idea behind boosting has been around since the beginnings of rock and roll, it’s just that different devices have been used to achieve different effects. Some of the earliest applications for boosting were discovered accidentally and in fact it was through boosting that distortion itself was invented! As the story goes, a recording engineer in a studio had a faulty preamp stage in his board that then learned that it became easily overloaded with any signal that hit it. Well, a studio musician that played guitar through the board actually liked the resulting “distortion” effect and it made it to tape. That was in the late ’50s and I should just informally reference the book, “The Stompbox” by Art Thompson because that’s where the story originated. And it’s a great book to boot so pick up a copy on Amazon.

In the early 1960’s, most players didn’t have access to very large amplifiers, so they were looking to increase their volume and treble response to get heard over the drums. Tube amplifiers thicken up nicely when run at loud volumes because of the tube compression, so treble boosters were deployed to compensate for this and add much-needed highs to the mix.

Treble-boosting was so popular that amps themselves such as the Vox AC-30 featured a built-in treble boost circuit (also known as the “Top Boost”) and many amplifiers such as those by Fender or Marshall, often included a treble-emphasized in addition to a normal channel.

However, none of those amp circuits could do what standalone devices such as the famous Dallas Rangemaster box could do. It not only featured increased top end to help amps cut through the mix, but the circuit itself used germanium transistors that also added a bit of unique overdrive to the mix that resulted in something very musical and dynamic and blended perfectly with tube amps. And cranking up a Rangemaster to a full or near full setting, not only produced the high-end cut, but also helped overdrive the tubes themselves in an amplifier, creating a range of distortion previously unheard of.

Rangemaster and rangemaster-based modified units can be heard in rock recordings of Brian May in Queen running his custom guitar through a Vox AC-30, as well as heavy metal pioneers Black Sabbath, where guitarist Tony Iommi would slam the front end of his Laney amps to get that thick and heavy guitar tone.

In the late ’60s, ElectroHarmonix introduced its LPB-1 Line Booster which was a very simple solid-state transistor based preamp design that could be used to overload the input stage of tube amplifiers in a similar fashion to the Rangemaster. The difference was that the LPB-1 didn’t have a germanium based circuit and was also designed to be a fairly neutral clean boost. The only negative impact caused by the LPB-1 circuit is that it couldn’t carry a very strong signal relative to what designers can do today so the result is that if you wanted to really hit the front end of an amp hard to overdrive it, the LPB-1 could do so, but with some compromises. Basically a cranked LPB-1 is a device that “runs out of gas” as far as its ability to amplify a signal. And it’s silicon transistor circuit just didn’t have the musical qualities of a maxed out germanium boost like the Dallas Rangemaster. So a cranked up LPB-1 is a bit “mushy” and the guitar feels really loose and loses the punch that it would otherwise have.

Still with that said, a testimony to this day of the LPB-1 is the fact that many of today’s boutique pedals are based off of – or are pure clones, of the LPB-1 and they’re obviously selling so people are obviously enjoying them!

Other designs in the ’70s emerged that were similar to the LPB-1, most notably the MXR MicroAmp.

Enter the ’80s, competition, and the idea behind a Booster versus an Overdrive

Those of you who have read the Marshall tips and tricks article for the Super Lead may recall the technique of using an overdrive box as a quasi-clean boost. The idea was that if you take an overdrive box and put its volume level on full and the drive control at a minimum or low setting, you’ll be able to send a hot signal to the front of your amp that will enable the amp to create more distortion than what is otherwise possible.

And because you’re pushing your amp with a quasi-clean tone, you don’t get the effect of running distortion “on top of” distortion, which results in LOTS of noise, and over compression and loss of feel.

In anycase, the ’80s really brought about two camps of players that “boosted” in rock and blues – those who used overdrives as boosts similar to how the players in the ’60s and ’70s used Rangemasters and LPB-1s and MXR Microamps, to those who modified their amps for greater gain. Also at this time, high-gain amps most notably from Mesa Boogie, also emerged.

The “hot-rodded” Marshall sound was big in the ’80s and is in fact beginning to enjoy a bit of a renaissance again as the Marshall vintage market has exploded in the past couple of years. The problem with the modded hot-rodded Marshall is that these were single channel amps, so any modding would result in amps that really became “one trick” ponies. They also had so much gain that cleaning up the signal by rolling the volume control from the guitar was pointless.

Countless Marshalls were hacked up for the purpose of getting greater distortion from the head “naturally” rather than using a floor box. What musicians didn’t realize is that the added gain stage on a Marshall was often a 12AX7 added within the circuit and set CLEAN to “push” the first gain stage. They were simply clean boosts that were made with a tube!

Other players found that the quasi-clean boost technique using a floor box worked really well for them. Countless ’80s rock and metal guitarists in particular used this approach and sometimes mixed this with modded amps or hot rodded preamp stages within their guitars. The 1980’s, more than any decade before or since, would definitely be the decade where more the majority of experimentation seemed to occur with regard to getting more drive out of rigs.

And if you liked the Boogie sound, then great; but if not, then tone experimentation began, from modded amps to new rack-gear. The Boogie sound involved heavy work on the preamp stage, but even Boogie lovers will note that their amps still didn’t get the greatest tones possible until they were driven a bit at volume to allow the power tube compression to occur.

Understanding the Distortion Curve: What a Boost can and cannot do

So a boost sounds like a great solution, but it’s interesting to see and note how people can get confused about how to really get the most out of it. Then there’s confusion about why a boost won’t act a certain way, etc. Most of the “confusion” can be explained when you take a look at the distortion curve of a tube amp and understand how it works. There is also a roundabout lesson and explanation of why many tube amps sound so good!

Let’s take the simplest approach first and imagine an amp with no added preamp gain. It has a simple volume control and you know that when you turn it up, at some stage, the amp will begin to distort. You may also note that the type of guitar you use will also determine how much distortion that amp will create when pushed (a Strat will have less than a Les Paul for example).

So what’s REALLY happening when your tube amp is distorting? It’s quite simple actually. The power tubes in your amplifier (the big tubes) are responsible for providing power. They in essence ARE the amplification circuit. The preamp tubes are also amplification circuits for that matter and are designed to take your next-to-nothing signal from your pickups and amplify them to the point where the power tubes can take over and provide a great deal more final signal output to the speakers.

Ever notice that when you first turn up the volume on your amplifier, it seems to get really loud, really quickly as you go from about 0 to 2 on the dial? Then as you begin to turn up the volume control on your amplifier, you may begin to hear it start to clip/distort at about volume 4 or 5. But you’ll notice that as you went from 2 to 4, it was still getting louder, but maybe not with the same dramatic intensity as going from 0 to 2 was. That’s because as you’ve begun to clip the tubes and hear distortion, that distortion is your tubes way of saying, “wait a minute, I don’t have much more power (i.e. volume) to give!” Then if you go from volume 5 to 7, the amount of volume is now decreased in proportion to the distortion. Then note on some amps as you go from 7 to 10, there is little or NO volume increase and it’s ALL distortion.

You’ve gone to the point where the amp has given all the power it could. And that sound and tone are what make tube amps sound great. We as players love the fullness and the rich harmonics that come out.

So now that we understand the distortion curve in an amplifier, let’s put this in perspective to what a booster can do. If you’ve played a Vox AC-30, you’ll notice that when playing it on 10, it can get some nice moderate distortion. But there’s no way that it could sing like Brian May of Queen’s AC-30 can. The secret is in the booster and pushing the tubes into continued distortion past what could otherwise not be achieved.

It’s the same thing when you listen Tony Iommi on a Laney. Or George Lynch or Yngwie Malmsteen on an old Marshall. Or Stevie Ray Vaughan through his Marshalls or Fender amps for that matter.

Now days we have master volume amplifiers as well as multi-channel high-gain amps. It would seem to make boosting obsolete, except for ONE thing. The high-gain multi-channel amps can’t replicate the dynamics and warmth of the vintage amps. And not to knock these amps (many are VERY good and I like them for certain tones), but many of these high-gained amps are tuned for their preamp gain stage distortion with little thought or consequence to the results when turned up.

Another factor in this is that there is some truth to the adage, “they don’t make them like they used to.” Simply put, a cranked up modern production amplifier may not be able to deliver the goods as sonically well as the vintage amps because their transformers (notably their output transformers) just aren’t up to the task. They are built for low-cost, not tone in many cases. That in itself is another story so let’s steer back to our boost discussion.

There was an interesting period in the ’70s and ’80s when amps emerged with master volumes to achieve higher gain at lower volumes, but many players still wanted more. Taking our distortion curve discussion in effect, boosting the front end of these master volume amps works in the same way. In fact, amps such as the famous Marshall 2203 (both in JMP and JCM 800 form) are still incredibly popular as they have moderate preamp gain on their own, but when driven with a boost, they’re able to literally create meltdown rich heavy metal that takes these amps into territories of the high-gain amps of today. But on top of that, the master volume Marshalls also sound GREAT when cranked so they truly are a “best of both worlds” amp of choice – and especially for hard rock and metal players. From Zakk Wylde of Ozzy Osbourne, to Slayer, to early Metallica, the foundation of many of these heavy metal tones was from pushing master volume Marshalls. The cool thing about boosting a master volume Marshall is if you have the preamp gain control up to a good degree, when you hit the front end of the amp with a boost, there is not going to be a dramatic volume increase, if any at all. Just more gain and rich sustain – but now controllable and adjustable at ANY volume. Works just like the high-gain amps of today.

All in all, the resurgence in vintage amps and semi-vintage amps (of which I categorize the Marshall 2203/2204 master volume series) has everything to do with tone. And with that, there’s a demand and need to drive these amps tube stages to more singing distortion just as they did in the past.

How I use the Time Machine Boost and where it came from.

Here’s where I do the pitch for the Time Machine Boost itself – Let me start a bit in the beginning. When I was personally looking to boost my signal on my vintage amps in particular, I was looking for a way to do so and retain ALL the tone of the Marshall, Fender and Vox gain stages, but just get MORE overdrive. I found that using an overdrive box in quasi-clean boost mode was o.k., but it still colored the sound either by adding too many mids or lopping off my low end. Other clean boost designs for me made my signal too “flubby” and loose.

Enter the search for something new where I could dial in the perfect tone, once and for all with no compromises. In my research, I met up with Robert Keeley (he actually came to me in an ad I put together looking for an engineer – back before he was selling thousands of compressors and pedal mods!) and together with both of our ears and thoughts, and with his design engineering background, we were able to create what is in my mind the ultimate boosting device: the Time Machine Boost. It took us well over a year in total development time and research to get it just right.

Initially, I just wanted one for myself. But when I thought about it further, I came to the conclusion that I thought many people would enjoy the benefits of the TMB and they have and nothing makes us prouder (the team consists of myself, Robert Keeley as Chief Designer, and Tom Lindenstruth, our builder who builds TMB’s one at a time, completely by hand with meticulous detail).

The premise of the TMB was simple. Create a channel of boost that didn’t effect the tone OR feel of the great amps and guitars I was using. The Modern channel is just that and it’s based on a proprietary circuit that I guarantee is not copied from anything in the past.

On top of that, I really enjoy the magic of germanium-based boost circuits – especially for lead work. So I thought, “what if we could do our research on some of the great stock and modified ‘old school’ germanium boosts and add an additional circuit for additional flexibility?” I wanted something to use personally for unique lead tones. The vintage side is what was developed with that research. Inspired largely by the Dallas Rangemaster with added unique tweaks to make it even more versatile for Strat or Les Paul players, and for virtually any amp or application where players like to run their their amplifiers at least “on the verge” of breakup and then let the Time Machine Boost do the rest.

So my personal favorite application of the TMB is to play my amps with some breakup for a great straight-ahead rock tone. I can then clean up the signal using a volume pedal or simply by using my volume control on the guitar as well as adjusting my playing dynamics to one that’s lighter.

Then when it’s time for a hotter rhythm tone, I almost always switch on the Modern channel. It’s everything I’ve got, but more of it with the lowest noise and highest-fidelity clean seen in any boost pedal. Then when I want that germanium magic, I almost always go to the vintage channel if I don’t keep it on Modern.

While people may think of me as biased, the TMB is quite simply the most musically useful device I’ve been able to insert between my guitar and amp. And I’m really a purist at heart so I think of the TMB as a device that can (and has) won over the “no pedals” crowd. It’s certainly not cheap, but we wanted the TMB to more like a hand-wired and skillfully crafted musical instrument (like how many of the great vintage amps were wired), for a lifetime of musical enjoyment, rather than just building something as cheaply as possibly. It’s also two independent circuits working together as one and fully switchable between three operating modes and two channels. Many hours of passion and pride go into every unit.

Update: Check out www.robertkeeley.com to see the most revised variation of the TMB now available and on sale in 2014.