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|11/21/2002 1:50 PM|
|Stephen Giles||Digitech Hyperphase|
I saw an advert for this, apparently it has a number of different sweep type settings including a continual rising or falling ramp. Could this be the Barberpole Phasing effect for which nobody has been able to obtain the circuit? Has anyone got one of these, have I understood the advert correctly??
|11/21/2002 4:47 PM|
I suspect it is. The BOSS PH-3 also has a barber-pole effect setting. You can hear samples of it at Larry Spence's modezero.com site. That's the place for learning about modulation pedals of any kind.
I posted an old article from Polyphony on Shepard function generation at my site which can serve as a base for producing one's own barberpole effects.
|11/21/2002 9:24 PM|
Thanks Mark, that'll save a trip in to our attic! By the way, I had a quick look at the Stormtide flanger circuit just now, and what do I see buffering the clock.....you guessed it, a 4049!
|11/27/2002 8:14 PM|
I can't help thinking that we could cobble up the Barberpole phasing effect using say 3 four stage all pass sections and a bunch of 4007s. Maybe I'm oversimplifying here, but if each separate all pass group is modulated by a triangle say 90 degrees apart from the others, and a VCA after each mutes the down sweep could there be an illusion of continual rising sweeps or if required, continual falling sweeps? Or am I talking absolute bollocks?
|11/27/2002 8:15 PM|
........one has to speculate, 'cause nobody has the sodding circuit!
|1/2/2003 9:40 PM|
|Sean Costello||Barberpole Phasing( was Re: Digitech Hyperphase)|
I had put this in another post, but here's a quick summary:
I am pretty sure that the "Barberpole" phasing effects out there are based around a frequency shifter, with the shift frequency between -6 Hz and 6 Hz. The Barberpole phaser, as an effect, was patented by Harald Bode in 1983 or so. His system was based around a frequency shifter, with some additional (fixed) allpass stages following the output of the frequency shifter, and the straight signal mixed in with the output of the allpass stages. For a more resonant sound, there is a feedback path around the frequency shifter/allpass system.
You can find a detailed explanation of this by going to http://patft.uspto.gov/netahtml/srchnum.htm, and typing in 4,399,326.
An analog implementation of this is certainly possible, but might be difficult to construct. The phase differencing network that is used requires 12 op amp stages (for 2 parallel chains of 6 allpass filters), and precision components to ensure accuracy, or trimpots + an oscilloscope to tune the network. For a dedicated barberpole phaser, you could use a simpler quadrature oscillator than most frequency shifters, and an LM13600 or LM13700 for the two ring modulators.
I have created various implementations of this effect, starting with a Csound version in early 1999, as well as plugins for various DSP systems. I am considering porting my work to a VST plugin.
By the way, a barberpole flanger can be constructed, by having a delay line in series with a frequency shifter, and feedback around the whole system. However, the range for this effect is somewhat limited, compared to crossfading between two (or more delay) lines that are being swept by sawtooth waveforms.
|1/3/2003 11:30 AM|
Thanks for your information. I remember seeing this patent on my local library internet terminal just before my time was up, and never had a chance to download it. I'll certainly get it now I have the patent number (written on a scrap of paper that got away!). I think I mentioned on a previous post that the Boss PH3 uses microchip technology to achieve the effect. When I next get access to a scanner I'll do a scan of the service notes, if only to demonstrate the impossibility of cloning a PH3.
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