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 Forum index » DIY Hardware and Software » ChucK programming language
Guitar Feedback Enhancement
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Stream Operator


Joined: Oct 13, 2007
Posts: 5978
Location: San Antonio, Tx, USA
Audio files: 258

PostPosted: Wed Aug 06, 2008 4:08 pm    Post subject: Guitar Feedback Enhancement
Subject description: Jimmi Hendrix meets ChucK
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I just played around with feedback using my guitar + amp, and I want to do ChucK-enhanced feedback. I ordered the adapter jacks that I need to establish the hardware loop through ChucK, so I have a few days to code up an effect. It seemed like a good topic for discussion here, so I thought I'd post for your comments as well.

What I found with the feedback was that if I put my amp on heavy distortion and cranked up the volume, feedback would occur. I could take the guitar from 10 feet away with no feedback, push it into the speaker's proximity to get a feedback squeal, then back off and sustain that feedback in a controlled way. I want to enhance this phenomenon.

One enhancement is anti-squeal. It would be great if the output signal were somehow attenuated particularly at the squealing frequencies when it got too large.

Another enhancement is harmonic amplification, using either distortion or some other effect to increase the harmonics.

A final enhancement would be range control, limiting the distance that the feedback was maintained so that the performer could do this without backing a full 10 feet away.

I figure a good algorithm for this will be FFT/IFFT with little routines that detect the RMS and adjust various spectrum amplitudes upper or lower as required. But I have just some general ideas and a lot of time to do this, so I thought I would post for comments before jumping into the coding. Besides, I thought it would be fun to think about. Comments?

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kijjaz



Joined: Sep 20, 2004
Posts: 765
Location: bangkok, thailand
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PostPosted: Thu Aug 07, 2008 3:48 am    Post subject: Reply with quote  Mark this post and the followings unread

Hmm.. for limiting feedback on some frequencies,
one easy way I might try to implement first is Multi-band Compressing..
but it's gonna be quite basic, so i guess fft would help create much more sophisticated system for use with guitar & amp feedback.
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Inventor
Stream Operator


Joined: Oct 13, 2007
Posts: 5978
Location: San Antonio, Tx, USA
Audio files: 258

PostPosted: Thu Aug 07, 2008 5:16 am    Post subject: Reply with quote  Mark this post and the followings unread

kijjaz wrote:
Hmm.. for limiting feedback on some frequencies,
one easy way I might try to implement first is Multi-band Compressing..
but it's gonna be quite basic, so i guess fft would help create much more sophisticated system for use with guitar & amp feedback.


Well, I figure the squeal has got to happen when one of the fundamentals or harmonics gets larger than a certain amount, so If the algorithm simply checks the magnitude of each harmonic and shrinks each one to some specified limit, then squeal can be eliminated.

In that case, the squeal event would produce a strong hum result as each of the harmonics filled to the maximum. So you press your guitar into the speaker and you get HUMMMMM, then you withdraw it and the hum persists but decays with distance.

Could be cool, eh?

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Stream Operator


Joined: Oct 13, 2007
Posts: 5978
Location: San Antonio, Tx, USA
Audio files: 258

PostPosted: Thu Aug 07, 2008 3:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

the attached mp3 file records a guitar feedback session on my setup. This is normal, non-ChucK enhanced. Notice the squeals mixed in with the pleasant sounds. Basically I want to remove the squeals and enhance the good stuff.


feedback1.mp3
 Description:
Regular Guitar Feedback

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 Filename:  feedback1.mp3
 Filesize:  787.35 KB
 Downloaded:  394 Time(s)


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