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Tim Kleinert
Joined: Mar 12, 2004 Posts: 1148 Location: Zürich, Switzerland
Audio files: 7
G2 patch files: 236
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Posted: Fri Jun 11, 2010 8:59 am Post subject:
High end DIY stereo pitch shifter Subject description: offers control over delay size and crossfading |
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As the title says. I've been meaning to build this for a while. Some questions from 3phase in another thread re-sparked the interest. This is based on the "classical" pitch shift design which has been around for a long time. A true granular approach (offering pitch jitter and other goodies) is something I might try next. (Update: Done. http://www.electro-music.com/forum/topic-42431.html )
It offers control over delay size (maximum 500ms) and cross-fading. I also threw feedback in there, as that is an effect I'm very fond of.
The pitching is very accurate due to using LFOs which have excellent exponential tracking. By up-sampling their crude control signals to audio-rate, the best possible sound quality is achieved.
In order to implement controllable delay size, a very precise logarithmic function is necessary. Unfortunately the level scaler module in 6dB roll-off isn't precise enough for this, skewing the tuning quite noticeably when the delay size is changed. I devised a workaround which is rather expensive DSP-wise and also has the drawback that the pitch shifter has to "restabilize" into the new delay length setting after it has been changed. This means that the delay size is manually adjustable, but not modulatable in realtime. However, the tuning is dead on, regardless of delay size or pitch shift amount.
It's a very precise design and sounds as good as it gets. But it's rather expensive, so not really a building block.
cheers
t
Addendum: I've noticed that the feedback loop isn't stable as it is, as DC offsets or nasty HF oscillations can build up. I added stabilizing HP and LP filters.
Important update! There was a omission with the control-rate to audio-rate conversion, causing a minute glitch. I reworked the patch. All old versions have been replaced. Attached below is the new version.
Description: |
offers control over delay size and crossfading. feedback too. |
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Download |
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DIYPitchShift_TK.pch2 |
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3.78 KB |
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2466 Time(s) |
Last edited by Tim Kleinert on Fri Jun 11, 2010 2:56 pm; edited 2 times in total |
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Tim Kleinert
Joined: Mar 12, 2004 Posts: 1148 Location: Zürich, Switzerland
Audio files: 7
G2 patch files: 236
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Posted: Fri Jun 11, 2010 2:49 pm Post subject:
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I thought I'd bump this, as there has been an important improvement. |
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exeterdown
Joined: Oct 13, 2013 Posts: 49 Location: Melbourne, Australia
G2 patch files: 3
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Posted: Sun Jul 12, 2015 2:37 am Post subject:
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Wow, this sounds really freaking good.
I can't figure out what's going on in the patch but it stands up against any other pitch shifter I have at my disposal. Thanks Tim! |
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