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Passive boost for guitar

unclejed613

Well-Known Member
Most Helpful Member
and combined with the capacitance of the cable creates a filter that kills high frequencies.
there are makers of low capacitance guitar cables for this very reason.

about 30 years ago i had a guitar player ask me to build a clean preamp box for him. it was very simple, a TL072 op amp, one half used as a battery splitter (artificial ground at 1/2 VCC), and the other half as a noninverting gain stage with a gain control. wide open, the gain was 10, and it was a very clean sounding preamp with a very high input impedance.
 
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kubeek

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there are makers of low capacitance guitar cables for this very reason.
How low is that capacitance? Figures I found On the internet were 20pf/ft so 60pf/m. So with 5m of cable and a conservative 1H inductance of the pickup the rolloff point is still around 10khz.
If I am not mistaken, adding a 1:2 transformer will load the pickup with 4x the cable capacitance, therefore the rollof pint would be half of that without transformer.
 

audioguru

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Most audio systems have lots of "headroom" so that when you turn up the volume to make louder sounds, it makes louder sounds without any clipping distortion. The amplifier has plenty of gain so that a low level signal loudness can be turned up to normal loudness and a high level signal level can be turned down to normal loudness.

An electric geetar is very different. Its sound system produces overdrive and fuzz. It has input and/or output clipping distortion all the time. Clipping is trying to get more output level than is possible. Turning it up or "boosting" the signal level does not make the signal any louder, it just makes more clipping distortion.
 

rjenkinsgb

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An electric geetar is very different. Its sound system produces overdrive and fuzz. It has input and/or output clipping distortion all the time.
You have obviously never worked with guitar equipment.

Any decent amp and guitar combination can produce totally "clean" sound! Overdrive is optional and a deliberate choice.
 

audioguru

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Most "clean" guitars are acoustic guitars and if amplified usually do not have the amplifier clipping its head off.
I think that electric guitars used for rock music are played by guys who have been deafened by the loud extreme distortion they produce.
 

Nigel Goodwin

Super Moderator
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Most "clean" guitars are acoustic guitars and if amplified usually do not have the amplifier clipping its head off.
I think that electric guitars used for rock music are played by guys who have been deafened by the loud extreme distortion they produce.

I think you know nothing about music, and distortion doesn't have to be loud - sustain is another reason for clipping though, but desirable distortion is the main one. Distortion is simply a different style of 'instrument', no different than changing from piano to saxophone - and many woodwind instruments (and others) are highly distorted anyway.
 

audioguru

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Most Helpful Member
Electric guitar distortion has many harmonics added. Overdrive and fuzz produced by an electric guitar sounds completely different than a "clean" undistorted guitar.
Sound that is fed back from the speaker to the guitar string creates sustain. Since the feedback is positive then the amplifier output keeps on clipping. I have never heard low distortion sustain done with an AGC loop.

All orchestral instruments sound the same when played live as when played recorded or amplified because no distortion is added.
 

rjenkinsgb

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Most Helpful Member
Overdrive and fuzz produced by an electric guitar
They are NOT produced by the guitars!
They are optional effect, deliberately added in if the performer wants them.

The amount of harmonics in a note can be controlled by where you pluck the string - with both electric and acoustic guitars; the mechanical principles are identical.
Near the bridge give a lot of harmonic content, or near the neck gives minimal harmonics.
 

audioguru

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Most electric guitar payers use a "pedal" that produces most of the overdrive and fuzz distortion then allow the power amplifier output to produce additional clipping distortion.

The waveform from a Jimi Hendricks "Fuzz Face" pedal produces even and odd harmonic distortions.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Electric guitar distortion has many harmonics added. Overdrive and fuzz produced by an electric guitar sounds completely different than a "clean" undistorted guitar.
Sound that is fed back from the speaker to the guitar string creates sustain.

That's acoustic feedback, entirely different to sustain.

The whole point of adding distortion is to alter the sound the guitar makes, it's effectively just another instrument with a different sound.
 

audioguru

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Of course if the amplifier's gain is much too high then clipping occurs when a guitar is strummed. As the guitar signal decays the clipping keeps the output at the same max level causing sustain.

The different sounds caused by the severe distortion on most electric guitar "music" resembles the sounds made by a buzzer.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Of course if the amplifier's gain is much too high then clipping occurs when a guitar is strummed. As the guitar signal decays the clipping keeps the output at the same max level causing sustain.

The different sounds caused by the severe distortion on most electric guitar "music" resembles the sounds made by a buzzer.

Except it's not 'much too high', it's exactly as designed, and is what enables lead guitar to be played as it is - rock music on an acoustic guitar is pretty crappy.
 

audioguru

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Most Helpful Member
Rock music sounds much better with my hearing aids turned off and when my tweeters are disconnected.
But music that has low distortion sounds better with my hearing aids and tweeters turned on.

I wish there is a similar way to convert RAP into real singing.
 

rjenkinsgb

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Most Helpful Member
Rock music sounds much better with my hearing aids turned off and when my tweeters are disconnected.
But music that has low distortion sounds better with my hearing aids and tweeters turned on.
OK, if the difference is that great - a challenge!

Which of the three files linked below is the electric guitar?
(The quality is not that great on any, they are snips of audio from youtube videos..)

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audioguru

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All 3 guitar recordings are electric guitars with effects.
#1 has wah wah sustain. Not much distortion.
#2 has a two bass guitars, one on each stereo channel, ping-ponging back and forth with typical distortion.
#3 has extreme sustain but not much distortion.
 

audioguru

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I have heard people playing an acoustic guitar (with a microphone near it) with the amplifier producing clipping distortion.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I have heard people playing an acoustic guitar (with a microphone near it) with the amplifier producing clipping distortion.
Very probably, and why not - if you want a specific sound, then go for it. It would be a VERY boring life is all instruments played nothing but sine waves, and there wouldn't be any music industry :D
 

rjenkinsgb

Well-Known Member
Most Helpful Member
We could do with this whole topic moving in to a new thread, as it's somewhat taken over the OP's subject!

Anyway, so AG - is this an acoustic guitar??

An Electroacoustic, with a built-in piezo "microphone" and preamp. It can be played on its own or via an amp - and effects, if the user wants to.
(It's one I've been repairing - I got it at a fraction of the full prices as it had been dropped on the way to the retailer and the body underside & back were split apart. It just needs a bit of final refinishing now to match in the colours around the repairs).

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