Fattening an amp's tone -- is a booster the answer over EQ?

[bipedal]

A booster-related question, inspired by an SHO thread in the Members Only section but not exclusive to that particular design:

I've read differing perspectives on how a booster paired with a tube amp impacts tone.  My understanding is that sending a hotter clean (or semi-clean) signal into an amp will push the power amp tubes a bit harder to create a slightly thicker tone.  I've always interpreted this as sounding warmer/fuller/bigger, particularly in the mid ranges.

Yet have also seen user comments that a booster like the SHO or Orman's MOSFET, while driving an amp harder, actually seemed to cut a little mid-range while adding top end clarity & presence (due to high input impedance?).

These seem to contrast a bit, IMO -- or are these two not necessarily incompatible?

Am particularly thinking about a booster application in front of an amp that already produces quite a bit of gain/distortion, but even after playing with the amp's tone controls the sound is a bit mid-scooped and could benefit from some more punch/oomph to give it more "life".  A little more crunch would be OK, but not essential.

Given this example, should I be thinking about an EQ rather than a basic pre-amp/booster circuit?

- Jay

[Dragonfly]

Personal opinion....

pushing the preamp tubes harder thins out the tone

pushing the power tubes harder fattens the tone

YMMV

[Papa_lazerous]

Personal opinion....

pushing the preamp tubes harder thins out the tone

pushing the power tubes harder fattens the tone

YMMV

+1

[Mark Hammer]

Following up on Andrew's comments, the thing to keep in mind is what a hotter signal is eliciting from the amp itself.  Although you CAN use a booster to simply bring up an already clean signal to levels that the amp's headroom still permits to remain clean, in service of optimizing S/N ratio, many players will use a booster to push the amp into overdrive and sometimes harder overdrive.  Keeping in mind that the overdrive itself IS additional harmonic content, thin-ness or fatness would depend on:
- how much harmonic content is being elicitted from the amp and where
- how much harmonic content is already in the boosted signal
- how you have the gain and master controls set on the amp (see point 1 above and Andrew's comments)
- how the preamp and/or power amp and/or speakers respond to sudden peaks

Change any of these and the very same booster might result in fatness OR apparent thinness.  So the reason you can't get a straight answer to your question is because there are more participants here than JUST the booster and degree of boosting.

Having said that, there is no reason on earth why you can't consider an EQ pedal as a booster.  When I used to play in bands, some of the best tones I ever got were when I cranked up my MXR 6-band into my little Princeton.  The nice thing about using EQ pedals as boosters is that you can pre-compensate the signal fed to the amp's front end so as to evoke the amount and type of of harmonic content that is appropriate to the amp/speaker/pickup/music.  One of the nifty features of my Crank circuit is that it trims back the treble as the boost amount starts to verge into producing too much sizzle from the amp. You can certainly do that with a booster that has a tone control, or with an EQ pedal, but I thought it would be a nice feature to have it automatically taken care of for you.

[Dragonfly]

Booster in the FX loop gives nice "fattening" results, in my experience. You'll have to mod it slightly to account for the hotter signal that the preamp sends to the booster.

[Processaurus]

Hi, hearing the word "fattening" makes me think of a bassier sound like what you would get with an eq, rather than a more distorted sound like what you would get with a booster overdriving an amp.  Plain, (no filtering afterwards) overdrive shows up as added harmonics i.e. high end rather than low end.

There is a nice looking (though I haven't made it yet) simple eq project at runoffgroove.com called Mr. EQ.  Also there is a neat looking 10 band eq kit at BYOC that has a box with slots already milled for the sliders.  Or Danelectro Fish 'n' Chips EQs are really cheap, and supposedly is the circuit from the Boss EQ, including some mods to reduce the hiss.

[jakenold]

Pushing an amp with a booster will only yield power amp distortion when, as Mr. Hammer writes, the amp runs out of clean headroom. For a 50 watt amp, that is typically at 50+ watts. So for most of us, that is out of the question, unless a loadbox is put into the equation.

I like having a fat lead tone. My rig is basically Fender CS Strat and Fender CS Tele into a SuperReverb. A combo like that is likely to take out any mosquito, shatter glass and make dogs whine. However, with effects such as Doug Hammond's Highway 89 or a classic Fuzz Face, the input impedance is lowered, which shifts the curve frequency of your guitars pickup, and yields a different sound - in my case, a fatter sound.

These kinds of effect-principles are good for single coil guitars. For humbuckers, they can get a bit muddy - my PRS'es sound like they only have a neck pickup when played through any of those two effects.

Kind regards, Jake

[brett]

Pushing an amp with a booster will only yield power amp distortion when, as Mr. Hammer writes, the amp runs out of clean headroom. For a 50 watt amp, that is typically at 50+ watts. So for most of us, that is out of the question, unless a loadbox is put into the equation.

I don't "get" that.  Why is 50+ watts out of the question? 
Whether it's a half watt Ruby or my JTM60, I like plenty of power amp distortion.  So I over-drive both.  The Ruby seems to gain bottom end when driven hard, while the Marshall seems to gain mids and highs.  I also have a "clean" amp - a MusicMan65 that has a completely clean SS pre-amp and 2 x EL34s that don't get "warm" until they (and maybe the speakers?) are pushing a few watts and starting to distort a little.

I *think* that in all these cases you progressively "lose" the base tone (a cacophony of superimposed sine waves), and hopefully gain pleasant harmonics, without adding too much unpleasant non-harmonic content.

[Ronsonic]

This is a giant "it depends."

An EQ will allow you to boost whatever frequencies you think of as fat. It can also add gain to push the front of your amp harder to add more overtones that your amp's tone controls can shape into fat.

What a good booster will do is predistort the signal in a way that enhances the distortion that the amp adds as well as offering some tone shaping from whatever tone controls or fixed filtering is built into the design.

There are about 54,927 dirt box designs on the planet just so everyone can find one that works with his particular gear and tastes.

Ron

[John Lyons]

Yes, It really does depend on the amp and what you put in front of it.
A Rangemaster type circuit works well in front of a marshall type amp which is a little dark sounding traditionally. The ramgemaster is a treble booster which boosts the signal into more clipping. Since the RM is mostly a treble boost the tone stays crisp and doesn't get too sloppy. But this is with a dark amp... WIth a bright amp that is very clean a RM sounds very bad and performs as a trebley volume boost.
The key to the RM is that it clips/compresses the amps slighly distorted input so the level does not increase but the gain does.

A more full range boost like the LPB is going to make the amp seem fatter because it's adding signal at all (most) frequencies.
Depending on the amp this will sound fat or possibly flabby or lose definition. Once again it depends on the amp.

Some people build RM/boost circuits with a switchable input cap so they have a treble or full range boost. The ROG Omega has a simulated input cap type impedance pot which allows a treble or full range boost that is continuously variable. Depending on the amp and sound you want you just twist the knob until it sounds "right" for you. (shameless plug, I love the Omega)

You can also make the input cap variable with a knob as on the Skyripper or a few other Joe Gagan circuits (in the gallery).
Just because something is a treble booster does not mean you get an overly trebley sound. Adding treble boost just insures that you cut through the mud and keep the feel and articulation of your picking.

Playing through an amp with a EQ set to boost is a fun thing and will let you experiment with what frequencies effect your own amp.

John

[96ecss]

Am particularly thinking about a booster application in front of an amp that already produces quite a bit of gain/distortion, but even after playing with the amp's tone controls the sound is a bit mid-scooped and could benefit from some more punch/oomph to give it more "life".  A little more crunch would be OK, but not essential.

Given this example, should I be thinking about an EQ rather than a basic pre-amp/booster circuit?

- Jay

There is some great info in the answers in this thread. I just re-read your original post and if your amp sounds too mid-scooped to you, you might want to try a Tube Screamer type circuit with the drive turned way down. It will then act like a semi clean booster and will definitely add some mids back in. You can get some more crunch too if you like. It will also help you cut through with a band a little better.

I like the sound clips of the Omega and I'll be building one as soon as my order from Small Bear arrives. I have the layout in my gallery if you're interested.

Dave

[DougH]

There are about 54,927 dirt box designs on the planet just so everyone can find one that works with his particular gear and tastes.

Pretty much sums it up. I don't even know what "fattening" means.

[aron]

Try an EQ. Some older EQs actually did give quite a big boost.

[frokost]

For a while I used a Boss GE-7 with everything at max and the treble frequencies at minimum for solos. However, I switched to a Big Muff, I always do, whatever I try to replace it with  .

The reason? Not enough sustain. But what an amazing tone, with the right amp. The amp is always the next most important for your tone, after you.

[bipedal]

Thanks all for the feedback -- a number of good ideas to think about.  Hadn't really considered the preamp vs. power amp issue of "thickening" the mid range.

Am looking at this for one of the guitarists in my band; I think I'll have him "audition" a few of my fun boxes (including a Tube Screamer and the Crank) to see what seems to work.  Probably would help to have him nail down specific purpose (an on-all-the-time tone enhancer or a lead/emphasis boost)... 

Always looking for reasons to justify building another gadget.   

Cheers,

- Jay

[Mark Hammer]

Given this example, should I be thinking about an EQ rather than a basic pre-amp/booster circuit?

I think one has to consider what you want/expect/get when you're NOT boosting.  There are many contexts where what the player desires from the boost is essentially equivalent to walking over to the amp and simply turning up the Gain control.  If you get the sound you want without a boost, and would normally get "more" of it when you turn up the gain, then a simple "clean" bost may be sufficient and appropriate.  In other contexts, particularly where added gain yields frequency content from the amp or speakers that you like plus content you don't like, some sort of tonal shaping at the pedal may be necessary.  In some instances, the tonal shaping is bonehead simple (turn down the treble) and more than sufficient.  In other instances, what the player wants to emphasize and de-emphasize may require something a little less boneheaded, like a mid-boost as well as treble cut.  I don't think that any single approach will be a viable solution for all contexts, and that is precisely why there are 54,927 boxes out there...with maybe 127 of them being necessary and the rest essentially clones.

I know my old 2 x 12 50W Peavey Classic amp that I had in '73 had two distinct personalities: one when the volume was set at 4 and below, and another when the volume was set above 4.  The "personalities" were a function of what I felt were problematic nonlinearities in the speakers.  If you started to push them a little harder, the tone changed dramatically.  There was a case where any boost in signal level hitting the amp would likely have needed somewhat more aggressive re-shaping of the tone at the pedal in order to simply arrive at the same general sound only louder and throatier or more assertive-sounding.

Not all EQ pedals are created equal although there ARE some inescapable uniformities in design sometimes (the same way there is with any 12AX7/5Y3/6V6 amp).  In some instances, diming all the sliders gets you a relatively uniform boost (+/- a couple of db) across the spectrum.  In other instances, the resonant bands may be spaced a little differently or be more selective, and diming them gets you a bunch of peaks and valleys.  In some instances, any "Level" control the EQ has may be able to independently supply some appreciable uniform gain even if the sliders are set to no boost/cut (i.e., midpoint).  In other cases, all it may do is provide some modest offset for when any cut settings reduce the output signal level too much.  Given the fairly basic and unexotic design of most EQ pedals, you could probably mod the output stage for more aggressive boost quite easily.  And since the design of most EQ pedals is quite friendly towards higher supply voltages, you could experiment with that too.