Designing multistage signal phasing.

Discussion in 'The Projects Forum' started by E.E., Apr 3, 2008.

1. E.E. Thread Starter New Member

Apr 2, 2008
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Hey guys! Just a little backround, I am a student of E.E. working on some projects for my own learning experience. So I am building a circuit called a phasor for a guitarist buddy of mine. The idea is I have a buffer OP Amp(OP07 for low noise) that has its neg. feedback loop connected to 4 Dual OP Amps(8 stages in total). So my question is what kind of timing I should use. I need the signal to be 90 degrees out of phase. With the original signal passing through the buffer, would it be better to use a 555 timer to delay the signal or a 12 bit counter with an alternating reset voltage. Or any other ideas?

2. Wendy Moderator

Mar 24, 2008
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There is something called a bucket brigade that will delay a signal, but I don't remember much more than that. Both the alternatives you mention are digital, I don't see how they can work. Do you need 90 degrees across the specturm, or just for one frequency?

3. E.E. Thread Starter New Member

Apr 2, 2008
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Crap, thats right it is digital. Yes the full spectrum 90 degree shift. Thanks for your input man!

4. Wendy Moderator

Mar 24, 2008
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I'm probably inserting foot at this point, but a 90 degree phase shift would be a different delay for each frequency. I'm not sure how you would accomplish that.

An RC circuit would do it, but it is also a filter, which sounds pretty undesirable from here. There might be a way to equalize the signal after the shift though.

The bucket brigade shifts (delays) an audio signal by a fixed number of milliseconds, which isn't quite it either.

There is probably a way to do it, but I'm not the one to know how.

5. SgtWookie Expert

Jul 17, 2007
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http://www.geofex.com/
There's a phaser schematic, 2nd link down.

(Dang, 2nd time today I've referenced that link)

6. E.E. Thread Starter New Member

Apr 2, 2008
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Hm, well I was thinking about this. I'm wondering if I can use a digital counter as a trigger instead of running the audio signal through it. So I would have a trigger voltage for each OP Amp, if you understand what I am saying.

The shift does not have to be 90 degrees at all times, just no more than that. I guess I should of clarified.

Hm, the RC would work, but I do agree with the filter.

7. Ron H AAC Fanatic!

Apr 14, 2005
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I think you need a Hilbert Transformer (Google). Unless you happen to stumble across someone with experience, I think you will have a tough time. I believe digital implementations (but not the ones you suggested) are simpler than analog.

8. E.E. Thread Starter New Member

Apr 2, 2008
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I've actually referenced that circuit, but I cannot see how it works actually. The thing is, I want to trigger each of the OP Amps(like at the bottom of the schematic) with a slight(nano sec) delay so the signal is out of phase if you understand what I am saying. Thanks though.

9. E.E. Thread Starter New Member

Apr 2, 2008
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Digital is not an issue for me actually. I just want to avoid D/A and A/D conversions for such a small circuit.

10. SgtWookie Expert

Jul 17, 2007
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Actually, you could do the whole thing in an MPU; there are scads of them around with multichannel ADCs and DACs built right in.

Your problem then would be reduced to what to do with all the leftover machine cycles.

11. E.E. Thread Starter New Member

Apr 2, 2008
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I'm sorry, like I said I am a student so what is an MPU?