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 Forum index » DIY Hardware and Software
Phase Shifters
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synthmonger



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PostPosted: Tue Jun 16, 2009 3:23 am    Post subject: Phase Shifters
Subject description: Some questions
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I haven't seen any designs for modular phasers out there so I've decided to take it upon myself to build one from scratch using only the textbook phase cells.

Instead of transistors or vactrols I've decided to use something way out of the ordinary -my VCOVR's. The results have been very pleasing and interesting. A lot of questions came to mind when I was getting similar results between feedback control and adjusting the bias.

Is self oscillation possible with all filters?

Is there a difference between 'feedback' and 'resonance'?

Is center frequency the same as cut off frequency?

I've read anything above 12 stages isn't really worth it. Yet I've heard Scott Stites 32 phase Multi-phase samples and totally loved the sound. What do you guys think?

I have no experience with the Doepfer Vactrol phaser nor have I seen any demos. Is it really worth adding all the feedback inputs?

I'll try posting some audio clips of what I have so far in the next couple of days. Super busy this week! Crying or Very sad Crying or Very sad Crying or Very sad

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RF



Joined: Mar 23, 2007
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PostPosted: Tue Jun 16, 2009 4:50 am    Post subject: Reply with quote  Mark this post and the followings unread

MFOS has an 8-stage phase shifter...

http://www.musicfromouterspace.com/analogsynth/PHASESHIFTER2007/PHASESHIFTER2007.php

I'll be interested in hearing and seeing what you come up with!

bruce

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synthmonger



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PostPosted: Tue Jun 16, 2009 5:13 am    Post subject: Reply with quote  Mark this post and the followings unread

RF wrote:
MFOS has an 8-stage phase shifter...

http://www.musicfromouterspace.com/analogsynth/PHASESHIFTER2007/PHASESHIFTER2007.php

I'll be interested in hearing and seeing what you come up with!

bruce


Oh forgot about that one. I did check that one out. Any others? ;d

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fonik



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PostPosted: Tue Jun 16, 2009 5:37 am    Post subject: Reply with quote  Mark this post and the followings unread

thomas henry's phase shifter from the 21th century synthesizer, LM13700 based.

maybe we could get magic smoke to be this project their next PCB!?

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synthmonger



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PostPosted: Tue Jun 16, 2009 6:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's a quick audio clip of mine.

Direct to soundcard and no digital effects other than fade ins and shortening it.

The audio input is a pulse wave whose width is controlled manually but only a little. There is a triangle LFO controlling the phase frequency moving at a slow speed in the begining then I tune it to the same frequency as the input frequency. Listen for some very smooth sounding bass at :29 and later at 1:40ish.

I also adjust the LFO modulation knob from all to nothing a couple times as well as the resonance and drive knob.

This is all done with a 4 stage module. I think the final module will have 8 stages and include VC drive, VC modulation frequency, VC frequency, VC modulation resonance, VC resonance, individual stage outputs and I'm contemplating weather or not of having individual stage inputs. I wouldn't want to copy Doepfers design but it seems almost too silly to pass it up with individual outputs. Whatcha guys think?


early_phase_shift_demo.mp3
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 Filename:  early_phase_shift_demo.mp3
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Sebo



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PostPosted: Tue Jun 16, 2009 7:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here is another one:
http://hem.bredband.net/bersyn/vcp.htm

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toppobrillo



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PostPosted: Tue Jun 16, 2009 7:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

jurgen is releasing an interesting project: http://electro-music.com/forum/topic-32897.html

and of course there was a Tau PCB as well, but these are quite a bit more advanced ideas...

FWIW, personally I think that all the individual stage outputs would be overkill and wouldn't serve much purpose in application.
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synthmonger



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PostPosted: Tue Jun 16, 2009 7:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

topp wrote:


FWIW, personally I think that all the individual stage outputs would be overkill and wouldn't serve much purpose in application.


I can see inputs being overkill but individual phase outputs seem useful to me for CV applications in self-oscillating mode.

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synthmonger



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PostPosted: Wed Jun 17, 2009 3:59 am    Post subject: Reply with quote  Mark this post and the followings unread

synthmonger wrote:
topp wrote:


FWIW, personally I think that all the individual stage outputs would be overkill and wouldn't serve much purpose in application.


I can see inputs being overkill but individual phase outputs seem useful to me for CV applications in self-oscillating mode.



NM self oscillate mode doesn't mean each output will be oscillating at the same level.

EDIT: had one thing wired wrong causing the levels to be whacky. Now I might make individual ouputs! ;d


That about covers it. PCB this weekend maybe!

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