Guitar Distortion/Overdrive Pedal

[audioguru]

The circuit has the 40k resistor to prevent a high input signal from destroying the opamp. The input bias current of the opamp that flows in the 40k resistor is so low that the voltage across it is nearly nothing.

What is this circuit driving? A speaker?
It is supposed to drive a power amplifier. The power amplifier drives a speaker.

 

[TrevorP]

This circuit is supposed to just do distortion on the guitar cable signal and then it can be put through the actual amp later.

This would be similar to what a BOSS Distortion Pedal does or something along those lines.

Am I going to have to do any drastic changes because I literally need to present this to my class tomorrow...

 

[audioguru]

Post the opamp's pins numbers on the schematic for us to check.

 

[TrevorP]

https://www.electro-tech-online.com/custompdfs/2006/12/lm107.pdf

Like that?

 

[audioguru]

Post your schematic with the IC's pins numbers marked.

 

[HiTech]

You like distortion? Are you deaf or something? Most deaf people like fuzz sounds because they can't hear how bad it really is. Guess how they blew up their hearing?

Sorry, I thought this was the thread about the Auto-Wah filter circuit.

Huh? A fuzz box of any sort isn't going to destroy one's hearing! Very high sound pressure levels (regardless of % distortion) will affect hearing though. You do realize that distortion is an optionally added "effect" just as many other circuits are created for some electric instruments like phase shifters, wah-wahs, tone benders, vibratos, etc. A majority of the time I enjoy some clipping when playing rock riffs. Between distortion and sustain, that's the key behind many a rock n' roll tune. If you want to listen to a clean guitar, play a bluegrass song on a 6-string acoustic or a banjo! The other choice is a good electric guitar, a big tube amp and speaker cabinet, and a 9v battery driven circuit that produces THIS!


BTW here's a simple fuzz circuit:
**broken link removed**

 

[audioguru]

Hello HiTech,
Your extremely distorted riff doesn't have any dynamic range and doesn't have any highs. Its clipping causes it to be compressed and it cuts frequencies above about only 500Hz. If it was wideband then it would blow your ears off.

Undistorted music has a wide dynamic range. Its amplifier reaches max power only occasionally. The high frequencies are at a low level and can be seen by the fragile nature of tweeters, and the fact that amplifier clipping destroys them.

Your "fuzz" is many added high level high frequency harmonics. Sure they will destroy tweeters and your hearing.

 

[Nigel Goodwin]

Hello HiTech,
Your extremely distorted riff doesn't have any dynamic range and doesn't have any highs. Its clipping causes it to be compressed and it cuts frequencies above about only 500Hz. If it was wideband then it would blow your ears off.

Undistorted music has a wide dynamic range. Its amplifier reaches max power only occasionally. The high frequencies are at a low level and can be seen by the fragile nature of tweeters, and the fact that amplifier clipping destroys them.

Your "fuzz" is many added high level high frequency harmonics. Sure they will destroy tweeters and your hearing.

Do you only listen to Mozart and such?.

Guitar fuzz boxes have been popular for 40+ years, some people (heavy metal for example) using incredible levels of distortion.

Yes it adds high harmonics, but that doesn't destroy your hearing, nor properly rated tweeters - bear in mind you're NOT clipping the output stages, merely amplifying an existing sound.

Dynamic range isn't a concern, part of the fuzz effect is no dynamic range at all, so the guitar sustains for a considerable period - sometimes infinately, because the gain is so high you get feedback from the speaker to the strings - a common heavy metal technique!.

 

[Dr.EM]

Yes, its a fairly common effect. You'd find it hard to not hear it if you listened to popular radio stations even. About as soon as guitar amps and electric guitars were used someone had overdriven them

 

[audioguru]

"High Fidelity" is a flat frequency response from 20Hz to 20kHz with very low distortion. Guitar speakers do not have a flat response, the bandwidth is only from about 100Hz to only about 5kHz. The extremely high distortion doesn't burn out their tweeters because they don't have tweeters. Tweeters aren't needed because the deaf listeners can't hear high frequencies anymore.

 

[HiTech]

You're mixing apples and oranges there AG. Most electric guitars aren't intending to produce flat response let alone harmonics well into near ultrasonic freqs. Fuzz or other types of distortion are merely "effects" designed to complement the sound (if you wanna call it that)... more like alter it. Nigel explained it pretty clearly. I can bet you for sure that there must be a Canadian group or two that you enjoy listening to that has incorporated a fuzz box or similar clipping device. Even the old has-beens, The Guess Who, used one in their hit No Time Left for You.

And as for destroying tweeters, instrument amplifiers use horns before they'd use tweeters. But it's rare for guitar amps to even employ those. Band performers aren't going to go deaf provided the speakers are placed out infront of them and they rely on stage monitors instead. And for that matter when more speaker cabs. are also placed midway into the audience, volume levels can be reduced further. Not everyone cranks their amps full tilt. If you ever sat in on a philharmonic performance, the dynamics and SPLs can get pretty high as well.

 

[TrevorP]

I have never seen a guitar amp with tweeters. For some reason the sound quality curve on most guitar amp its shaped unlike any other instrument amplifier.

Its probably to mimic what the early day Valves did.

 

[audioguru]

I like wideband flat frequency response without distortion. Acoustic guitars sound nice and natural without all the effects of an electric guitar that messes up the sound.
The frequency response of an electric guitar speaker is shaped to sound worse than an old AM radio. Like the riff that is played here.

 

[TrevorP]

Thats because people like the old sound...and thats what they are going for.

 

[audioguru]

Deaf old people think an old AM radio sounds the same as a new FM radio because they can't hear high freqencies. They remember hearing high frequencies when they were young and weren't deaf yet but didn't like it because it was nothing but distortion.

 

[ArcaneDreams]

what program are you using to simulate these designs?

I have multisim, but it obviously doesn't let me "hear" the waveshape..I can only see it.

 

[Sceadwian]

LTspice (AKA SwitcherCad 3) allows .wav files to be both input and output of a spice simulation. In other words, if you have a sound card you CAN hear what your simulated circuit will produce from a given input. Just not in real time.

 

[ArcaneDreams]

Thanks man

 

[Sceadwian]

Did I mention it's free? =) Not to plug the company, but Linear's okay in my book for offering this software up to the public. I've lost more than one night's sleep playing around with it.

 

[ArcaneDreams]

hmm this thing is a totally different monster compared to multisim.

Not sure if I like the whole component placement thing...

And I'm having a hard time just finding out how to apply a ac current source to a circuit... hmmm