"Clean" boost a hoax?

[earthtonesaudio]

I just feel the need to get this off my chest...
There are tons of different "clean boost" pedals out there, and people rave about them.

But the human hearing system has a frequency response that is all crazy and varies with loudness, phase, duration, and all sorts of perceptual things... Basically, even if you have a totally clean soundsystem with infinite headroom, any change in loudness results in a change in EQ once the sound reaches your brain.  So due to the fact that we are all human, there can not be a booster that does not color the sound.

...Not to mention that most people use boosters with guitar amps and speakers whose frequency response is anything but flat.


[/rant]


That said, I like boosters!

[drk]

well, i think when it is refer some booster as clean, it means it doesnt change so much the sound, obviously it cant be 100%

[sean k]

Exactly, it's like cleaning your hands with bleach and two seconds later they'll be dirty again. Not that I'd clean my hands with bleach but it's all about a perception of finite in an infinite universe. More white than black!

[railhead]

Clean boost = the circuit provides minimal clipping to the signal. This is desirable when you only want the boost to charge-up your amp tubes, etc., so that the tone change comes mainly from the amp -- not the pedal.

[Mark Hammer]

D'ja ever notice that there is not one single "clean booster" on the market, not even amongst the best and priciest, that has a clipping indicator LED?  While in theory, any sort of ostensibly flat-response preamp could be used to bring the signal level up to some optimal level that might maximize S\N ratio, in practice nobody uses them that way.

[John Lyons]

Three things going on (at least)

The guitar or input devices level will affect the "clean Booster"
Possibley clipping the input etc.
Lots of different guitars/pickup output levels out there.

The Booster's circuit characteristics whether "clean" or "cleanish".
Some are clean and some are dirty in a pleasingly soft way.

The way the amp/pedals down the line react to your "Clean Boost"
A super clean amp and a clean boost will stay clean.
A clean amp near soft clipping will get into overdrive with the " clean" boost.
A slighly dirty amp while relatively clean sounding by itself will overdrive and compress
that clean boosts level and not jump up in volume. Basically making the clean boost into an
overdrive though the amps input threshold.

There are more details but you gotta figure the whole picture here.

Try a clean boost (assuming a relatively mild input source like a strat single coil) into a mixer channel (set to line level) and your'll hear how clean the boost really is.

john

[Dragonfly]

clean = warm = fat = liquid = transparent = a whole bunch of other "generic" terms we use to describe the sound of something.

[ayayay!]

What is a distortion?  What is an overdrive?  What is a fuzz?  Why aren't they all called clippers instead?

Is it truly a compressor, or is it merely a limiter labeled as a compressor because that sounds more cool?

Why isn't a clean booster just called a line amplifier?

...Pandora is quickly opening her box in this thread...

[earthtonesaudio]

I guess it's just the fact that hearing and describing what you hear is subjective.  Ah well.  Thanks for chiming in, guys. 

[railhead]

Like I said, though, it's no so much about what you hear as it is the design of the circuit. Some boost circuits add clipping to the signal by their very design, while other add hardly any at all. This is mechanical, not aural. Those that add clipping are not "clean" because they add clipping to the signal.

[R.G.]

We've been through all of the "clean boost" and "transparent gain" stuff several times. Search should turn them up.

[JDoyle]

Like I said, though, it's no so much about what you hear as it is the design of the circuit. Some boost circuits add clipping to the signal by their very design, while other add hardly any at all. This is mechanical, not aural. Those that add clipping are not "clean" because they add clipping to the signal.

Ah, but without a control to adjust the drive isn't the clipping dependent on signal level? And therefore couldn't the same circuit be 'clean' to an old Ric, but monsterously clipping to a couple of DiMarzio 'Super Metalbuckers' or whatever they are called?

Basically - until someone invents a 'straight wire with gain' there is no such thing as 'clean'.

Jay Doyle

[Paul Perry (Frostwave)]

My definition of clean boost:
If you run a sine wave in, you get a bigger sine wave out, no distortion. And the gain is flat over the audio band.
Like any amplifier, there will be an input level that overloads it - and causes distortion and/or clipping.
Simple as that.

[Mark Hammer]

I don't know why we are rehashing this.  It is child's play to arrange for an op-amp or FET or bipolar transistor to provide several or several dozen db of gain with a flat frequency response and less than .1% THD.  Where it stops being "clean" is a result of the fact that it is being used to make an input signal a higher amplitude than the overall system or signal chain is designed to reproduce without artifact.

If I take two phono preamps that "The Absolute Sound" has raved about, and audiophiles are willing to sell their children into sex slavery in order to purchase, each of those preamps may be cleaner than God's own hands, but cascade those 60db-gain suckers and the result will NOT be audiophile.

DO NOT confuse the properties of a simple 12db flat-response gain stage with the audible outcome of hitting a subsequent stage with 10db more than its headroom can readily accommodate.

[Ben N]

D'ja ever notice that there is not one single "clean booster" on the market, not even amongst the best and priciest, that has a clipping indicator LED?  While in theory, any sort of ostensibly flat-response preamp could be used to bring the signal level up to some optimal level that might maximize S\N ratio, in practice nobody uses them that way.

I've been called nobody before, and worse.

At one time, inspired by Anderton, I had a Microamp at the front of my chain, turned as loud as I could go without noticeably overdriving my non-distortion pedals, for the purpose of having as high a signal level, and therefore as high a S/N ratio, as possible. I also wanted to have as hot a signal as possible going into my amp, even clean, per Barber's posts about driving the input stage to near saturation.

Eventually I took it out because (a) the benefit, such as it was, wasn't worth the pedalboard real estate, (b) the noise contributed by the Microamp canceled out the benefit of the stronger signal (probably could have benefited from a better opamp and metal film resistors, but I wasn't up to it, esp. with the thru-plated MXR board), (c) some of my overdrives didn't sound great, and (d) I didn't like running the distortions at unity.

It's probably still a good idea, but in a well-integrated, tightly designed system, like a Cornish, where the input and output stages of each effect are optimized to be used together, in a particular sequence, and EVERYTHING is modded for lowest noise.  As a tack-on, simplicity is probably still the higher value.

[DougH]

clean = warm = fat = liquid = transparent = a whole bunch of other "generic" terms we use to describe the sound of something.

Exactly. It's just a term. It doesn't actually mean "clean" in the sense of "zero distortion". When people mention amps that sound "clean" or "cleaning up the sound" etc they are usually referring to a sound that has more treble and less distortion. It's more of an EQ thing.

A 100% distortion-free signal with a flat frequency response (100% "transparent" - another one of those terms) sounds pretty dull. Most people don't want that sound.

[Mark Hammer]

I shall call you a gentleman, rather than a nobody.   I should have originally said "practically nobody", because, in fact some people such as yourself and myself HAVE used them that way.  Indeed, I think if one were to invest/waste some time in digging up any of my previous posts regarding the usefulness of onboard preamps, I have regularly implored people to set them for only very modest gain, expressly for the purposes of optimizing S/N ratio without introducing unwanted clipping.  So, not everyone uses them for clipping the bejeezus out of things.

Having said that, you will note the arrival over the past 2 years, of a bunch of overdrive+gain pedals that permit the user to introduce a certain baseline degree of clipping, and then hit the "other" stompswitch to overdrive the amp with that basic clipped signal for soloing.  The resulting signal at the speakers is a combination of several cascaded clipping stages, one of which is in the pedal, and rest of which are in the amp and other parts of the signal path.  The added gain stage is not before the overdrive part of the pedal, but rather after it.

Clean boosters are wonderful for a bunch of other duties, too.  To whit, every pedal with a sidechain / envelope-follower, like a compressor, limiter, noise-gate, or autowah, builds in a certain range of "sensitivity" or "threshold" adjustment based on assumptions about the typical input signal.  Plenty of folks out there can easily find that their autowah really only sweeps in a pleasing way when the sensitivity is up full and the guitar is maxed.  Sticking a booster ahead of the filter pedal gives the envelope follower more to work with, and is tantamount to increasing the range of sensitivity adjustment.  With compressors, you can get a better signal to noise ratio and more squish if a bit of boost is applied pre-compressor.  With noise gates, a hotter signal pre-gate lets you set the gate threshold low enough that you don't miss the tail of the decay.

What links all of these things is the consideration of the boost as one element in an entire signal path, and thinking strategically about what role it can play in that location and sequence of events.

[puretube]

I don't know why we are rehashing this.  It is child's play to arrange for an op-amp or FET or bipolar transistor to provide several or several dozen db of gain with a flat frequency response and less than .1% THD.  Where it stops being "clean" is a result of the fact that it is being used to make an input signal a higher amplitude than the overall system or signal chain is designed to reproduce without artifact.

If I take two phono preamps that "The Absolute Sound" has raved about, and audiophiles are willing to sell their children into sex slavery in order to purchase, each of those preamps may be cleaner than God's own hands, but cascade those 60db-gain suckers and the result will NOT be audiophile.

DO NOT confuse the properties of a simple 12db flat-response gain stage with the audible outcome of hitting a subsequent stage with 10db more than its headroom can readily accommodate.

Those two phono preamps still remain "clean boosters" in the words meaning.
Here`s wondering if the OP meant to say: "clean boost", or rather: "clean booster" ?

[JDoyle]

As far as S/N ratio - I think anyone would be hard pressed to find another 'source' that starts off with a WORSE s/n ratio than a guitar pickup...

[puretube]

As far as S/N ratio - I think anyone would be hard pressed to find another 'source' that starts off with a WORSE s/n ratio than a guitar pickup...

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