# Clean boost: Why?



## devnulljp (Mar 18, 2008)

Just a question: what do you use a clean boost for? How's it different from just turning up a notch? I have an AC boost, which I use for dirt, and a treble booster, but I guess I'm missing something with a clean boost. I don't get it.
What am I missing?


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## Guest (Apr 25, 2008)

At unity gain, to preserve my signal over a long cable run. Shows my guitar a high impedance load and the pedals after it a low impedance load.

Above unit gain, to hit the front end of my amplifier a little harder. See: Dave Barber's How-To: Cook a Tube Amp.


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## devnulljp (Mar 18, 2008)

iaresee said:


> At unity gain, to preserve my signal over a long cable run. Shows my guitar a high impedance load and the pedals after it a low impedance load.


 Interesting - So where do you put it in the chain? At the end as suggested in the Dave Barber link? It's more of a signal preserver then rather than a "boost" in volume? I have a jfet buffer in my wah, so I can use the fuzz after the wah. Isn't that doing pretty much the same thing (albeit without an on/off switch)? 


iaresee said:


> Above unit gain, to hit the front end of my amplifier a little harder.


 That's kinda what I'm using the AC for - but it's real dirty; get a little sweet dirt out of the amp, then use a fuzz or tube driver to push it further into distortion when needed.
Thanks

So, can anyone recommend a good one? That Barber looks fairly versatile. RC boost? Catalinbread Serrano Picoso looks pretty simple? Super Chile Picoso? Keeley Katana? Mr Clean?


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## mhammer (Nov 30, 2007)

Clean boost serves a number of purposes.

First, it is a basic principle of signal processing that one strives for the hottest source signal possible without clipping so as to optimize signal to noise ratio. One acquires hiss over the signal chain, so starting out with a strong signal permits it to still compete very favourably with that accumulated hiss. In the case of feeding your signal to a guitar amp, that doesn't mean you can use a *lot* of gain, but you'll find that even a gain of 2-3 helps to get a little more oomph from the amp with less hiss overall.

Second, one generally does not see any sort of clean booster that does not perform a hi-to-lo-z impedance conversion. If the booster in question is right at the top of your signal chain, and you have it set for modest gain, you can plunk all the true-bypass pedals you want after it, without having to worry too much about all the cable capacitance after it on the way to the amp. Some folks actually like the effect of cable capacitance as a means of "warming up" single coil pickups by losing highs to the cable. I'm not one of them. That's why there is a tone pot on the guitar.

Third, the way any pedal reacts is a function of the amplitude of the input signal. Compressors compress more, distortions clip more, envelope filters sweep more easily, and so on. So, some folks use the clean booster to essentially make other pedals behave as if they were more sensitive. In some cases, such as distortion, you can extract sicker sounds from the distortion by means of a hotter input. I have an original Shin-Ei FY-2 fuzz and a clone I made, and boy oh boy do those puppies get perverted when the input level goes up.

Fourth, there are plenty of pedals where people like the tone but the output level is nothing spectacular. For instance, a person may like subtle grind on a Tube Screamer or a Distortion+, but at less than max gain, there is much less output than they would like (those pedals in particular are infamous for this shortcoming). The solution there is to tack a clean booster on the output of such pedals that simply produces more of what the player already likes without changing the tone. The caveat for those instances is that sometimes it is the specific impedance-related interaction between the pedal and the amp that actually produces the signature tone, and sticking in a clean booster between wrecks that. The perfect case in point would be a Dallas Rangemaster or any of its cousins. Those sorts of pedals assume a direct path to the amp input.

Fifth, sometimes people have a signature tone that involves having one or more pedals on, and they simply want a level boost for solos that does not change the tone, only the level. True, you *can* simply have a volume pedal and raise the level, but sometimes people want juuuuuuuuust a little more grind from the amp for a solo, so a clean booster helps them do that. If I liked to have a phaser on for rhythm *and* solos, sticking boost ahead of it might send the FETs in the phaser into clipping (and such clipping is usually not particularly musical). In such an instance, it is wiser to place the booster after the phaser for purposes of a same-tone level hike.

There's likely more than that, but that's a reasonable list of uses to start with.


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## Guest (Apr 25, 2008)

devnulljp said:


> Interesting - So where do you put it in the chain?


It really depends on what I'm doing. I move the pedals on my board around. Alot. More than is healthy I'm sure. I'm actually thinking of going the bike chain link route so I stop futzing about with pedal position so much.



> At the end as suggested in the Dave Barber link? It's more of a signal preserver then rather than a "boost" in volume?


Correct: it keeps your signal hot and hitting the amp nice and hard. I'll do this if I'm packing a light load: guitar, tuner, OD, boost (sometimes I'll use my HBE ComPressor Retro here, just for a little more variety). If I'm bring the big board, more toys, I'll put the CPR after my wah near the front of the gain and my home made FatBoostered at the end. 



> I have a jfet buffer in my wah, so I can use the fuzz after the wah. Isn't that doing pretty much the same thing (albeit without an on/off switch)?


Yup. I'm actually fixing to build a set of AMZ Super Buffers, one for each end of my big board.



> So, can anyone recommend a good one? That Barber looks fairly versatile. RC boost? Catalinbread Serrano Picoso looks pretty simple? Super Chile Picoso? Keeley Katana? Mr Clean?


Mr. Clean. Great pedal built by a really nice guy. The Barber is great if you want to run into both channels on a dual channel Fender and once because it's got a phase inverter.


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## mhammer (Nov 30, 2007)

Go see/contact JC Maillet on Gabriola Island. He's brilliant and a sweet guy. You can see his handiwork here: http://www.lynx.bc.ca/~jc/ he sent me a copy of his "Inside fender and Marshall Tube Amps" book, and its excellent, if sometimes over my head math-wise.

I'm confident he can solve whatever interfacing problem you have or can conceive of.


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## PaulS (Feb 27, 2006)

mhammer said:


> Clean boost serves a number of purposes.
> 
> Fifth, sometimes people have a signature tone that involves having one or more pedals on, and they simply want a level bopost for solos that does not change the tone, only the level. True, you *can* simply have a volume pedal and raise the level, but sometimes people want juuuuuuuuust a little more grind from the amp for a solo, so a clean booster helps them do that.
> 
> There's likely more than that, but that's a reasonable list of uses to start with.




That's the way I use mine. As you put it .. just a little more grind


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## devnulljp (Mar 18, 2008)

So, here's another question -- if you want the boost at the end of your chain, how would you use it with a stereo setup? I use a DC-2 as a stereo splitter into two amps. I imagine putting a boost in front of the DC2 might introduce some distortion, but after would only be able to go on one channel -- use two boosts? 

mhammer: Thanks for the info about JC Maillet...I've actually been trying to get around to having him look at my amp, just haven't got around to it yet...got snowed in the last time I tried.


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## mhammer (Nov 30, 2007)

DC-2? Are you talking about the Boss Dimension C chorus, or something else?

If so, where most simple chorus pedals do not include any companding for noise control purposes, the DC-2 does. That provides some protection for the BBDs against clipping. Consequently you may be able to provide modest boost (e.g., x2, x3) in front of the DC-2 so as to retain stereo outs but increased level without incurring a distorted sound. Of course, since it also uses FET switching, you may need to exercise caution so as to avoid pushing the FETs too hard.

Alternatively, in the case of JFET or MosFET booster pedals, the degree of boost/gain is generaly set by a resistance to ground. It would not be unreasonable at all to have two boosters where the resistors that go to ground reach ground via a common switch. Step on the switch and both parallel units go into boost. Cancel and they both go back to near unity-gain mode. Piece of cake to make.

If you see JC, tell him I sent you :wave: and that he can have my home-made salsa any time he wants.....if he's willing to come out for it.


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## devnulljp (Mar 18, 2008)

mhammer said:


> DC-2? Are you talking about the Boss Dimension C chorus, or something else?


Yes, an old MIJ DC-2. I've also got a new stereo clone in the mail from one of the guys at TGP...we'll see how that turns out.


mhammer said:


> If so, where most simple chorus pedals do not include any companding for noise control purposes, the DC-2 does. That provides some protection for the BBDs against clipping. Consequently you may be able to provide modest boost (e.g., x2, x3) in front of the DC-2 so as to retain stereo outs but increased level without incurring a distorted sound.


Great. 


mhammer said:


> Alternatively, in the case of JFET or MosFET booster pedals, the degree of boost/gain is generaly set by a resistance to ground. It would not be unreasonable at all to have two boosters where the resistors that go to ground reach ground via a common switch. Step on the switch and both parallel units go into boost. Cancel and they both go back to near unity-gain mode. Piece of cake to make.


Ya lost me. You mean using a loop?


mhammer said:


> If you see JC, tell him I sent you :wave: and that he can have my home-made salsa any time he wants.....if he's willing to come out for it.


Hey, send it to me, and if any survives the weekend I'll pass it on


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## mhammer (Nov 30, 2007)

Here's an illustration of what I meant. Look at the second diagram shown here: http://www.muzique.com/schem/mosfet.htm The diagram shows (and the text explains) that when R6 is connected to ground, the gain of that circuit can be increased above unity. Sever the connection to ground and it reverts to being a unity-gain circuit.

I had originally suggested that if you had a pair of such single-transistor boosters, you could plug each output of the chorus into one of them, and use a single stompswitch to boost the two outputs simultaneously. While this is true, in hindsight the suggestion to have one single connection be used to tie the two different R6's to ground was foolish. It occurred to me that if the two gain-setting pots from each booster were connected to each other, but not to ground, then there would be bleedthrough from one channel to the other. Bad, that.

Consequently, if one were to use a circuit like this, one independent set of contacts should be used to independently (but simultaneously) tie each R6 to ground and effect a gain increase in both outputs. A standard 3PDT stompswitch like you can buy so many places for $4-6 will do that, and still leave you a set of contacts for implementing a status LED.


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## devnulljp (Mar 18, 2008)

Cool, a project. Thanks for the tips. 
(Where do you get 3PDT switches for $4-6 though. I bought one from guitarpartscanada and aside from the 2-3 month wait while they nipped over to China to have one made specially for me, it cost ~$15). 
I'm not very good at reading circuit diagrams so if you hear a loud bang accompanied by a cloud of smoke and a spark, that'll be me.

This has been a great thread so far.


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## mhammer (Nov 30, 2007)

Show my post to JC and he could whip you up that in an afternoon. Undoubtedly he already has the switch.


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