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PH3 Clone

1/2/2003 4:48 AM
Sean Costello PH3 Clone
PH3 Clone:  
First of all, have a nice DSP, A/D, D/A convertors, and all of the parts to run it.  
Second, create several phase shifting algorithms. The building block is the 1st order allpass filter equation:  
output = coef * (input + lastOutput) - lastInput;  
lastOutput = output;  
lastInput = input;  
Have several of these filter sections in series, depending on the order of the phaser. The allpass coefficient (called "coef" above) is controlled by a time-varying waveform, in the range  
-1.0 < coef < 1.0  
Since the 90 degree phase shift frequency of the allpass filters will have a nonlinear relationship with the value of coef, you will need to do some fancy warping of coef in order to get it in the proper range. Also, you may wish the minimum and maximum range of coef to be wider for slower sweep frequencies, and narrower for higher sweep frequencies.  
The phasing sound is produced by adding the output of the allpass filter sections to the straight signal, just as in an analog phaser. Feedback around the allpass stages produces a similar sound to what is heard in the analog signal.  
Now, the Up/Down phase shifting algorithms of the PH-3 will use a different algorithm. My guess is that they are using a frequency shifter, with low shift rates, where the straight signal is summed with the shifted signal, and there is feedback around the frequency shifter. I produced a similar effect in Csound in 1999, and added the required Hilbert network to the Csound source code. The Boss PH-3 came out in late 2000, which makes me a bit suspicious, but I know that someone from Creative Labs had described a similar use of a frequency shifter in 1998.  
All of these effects can be produced in analog. However, the frequency shifter technique of phase shifting requires a lot of precision components (specific resistor values, analog multipliers, quadrature oscillator, etc.). It is far cheaper to produce the effect digitally.  
Would a VST plugin that produces the Up/Down phase shifting sounds earn me a bronze medal? ;)  
Sean Costello
11/19/2002 6:05 AM
Tim Shortnacy
Re: ZVex schematics?
I remember the day I dared to snoop around for some Fuzz Factory schematics... now that I think about it, a friend put me up to it because he wanted to make a poor man's Fuzz Factory, and at the time I thought he could do it...  
It was hilarious... absolutely NO one responded to my question on, and I definately got this crazy vibe that I had asked the "unspoken" and "forsaken" question to ask... *smiles*  
But, now being older and wiser, and trying to develop my own effects for mass consumption, I can completely understand why it's just kind of a respectful thing _NOT_ to ask....  
Wait a decade or two... then they'll be vintage and the schematics will be everywhere... *smiles*  
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11/21/2002 11:56 AM

Why don't you guys just do what the big man did himself, lock yourselves away for a while with a soldering iron & some parts, and come up with your own 'fuzz factory.'  
That's what i did, and i'm pretty pleased with the results, tho i wouldn't say it's as good as Z's.  
I think the trannies he uses has a lot to do with the sound of the circuit.  
(I can do the 'Plug In Baby' thing though!)  
11/26/2002 3:18 PM
Chris Winsemius ( CMW amps )

"Why don't you guys just do what the big man did himself, lock yourselves away for a while with a soldering iron & some parts, and come up with your own 'fuzz factory.'"  
Too busy with amps :) , as soon as I can charge Dumble-prices for a couple of years I'll start designing fuzzy things .  
11/27/2002 9:26 PM
Stephen Giles

.........or Barberpole phasers........
11/29/2002 7:23 AM
I too once looked for vex schematics years ago. And as a matter of fact I did have one mailed to me by a prominent online guitar effects guru. However, I much more enjoy my real fuzz factory than I do the schematic. Totally worth the money.  
To me zvex is not a small business considering has posted his monthly finances here in the past. But what do I know? I guess the one thing I do know is vex is not a total asshole to the curious persons (as some makers are) and he is not making straight clones of schematics from the net... So I have a huge amount of respect for his designs and turn away potential clients on a daily basis requesting clones of his pedals. It is a person choice to make your schematics known to the public. I would do it because much of my knowledge I consider common knowledge. Boutique guys work hard to not expose their work when making mere clones due to the loss of potential credibility? Vex units are different and currently worth the money that the market demands.  
12/24/2002 6:00 PM
David Barber

I had hoped this was true, that the DIY forums out of respect for the small businesses don't post our schematics. Many in this small community of hand made effect builders were hit very hard by 9/11 and have only started to be able to see any profit again (this is a hard business at times, but I really love it!). I had felt safe from the worries of having a design of mine pirated. I had read this post about ZVex and felt better seeing how this community felt about posting his designs. Sadly, I saw last night Robert Strand's schematic of my Direct Drive posted on the internet; I wondered what would make someone post this? why be so petty when this is a $99 hand built pedal (not like he would have to fork out $300+ to have one) the parts alone to build just one cost close to the retail price! And after the time Robert Strand has invested in being able to copy my design (for who knows what purpose) could have had him a Direct drive. I had designed and marketed this unit for the player, for the guy or gal that could not afford the "high end" we make very little profit on these units.  
For better or for worse Robert Strand's schematic of the Direct Drive is erroneous and will not sound like a Direct Drive nor will it operate like one, it is a very poor schematic (not everyone is as talented and in possession of good judgment as the good folks here). This among many other reasons is where posting these schematics can only be done to hurt the business of the boutique designer. Some will build from this schematic and declare the Direct Drive dismal sounding, in reality they will have never heard anything resembling the Direct Drive (because of Robert Strand's immense flaws in his schematic). In other cases new pro designers and old alike will benefit from my work without having to go through the process of having to call a dealer or get a unit from a friend to rip apart, no doubt Robert’s flawed schematic makes this less useful to the curious hand builder, but enough is correct to start grabbing some of my details (and after all, the details are what make these designs). When I read his schematic notes he acknowledges that the schematic is a guess thrown together from pictures and from looking at my free tweaks page (he even reprints the ideas for my mods even though they are thoroughly detailed at my site, quite curious behavior!), Robert then goes on to encourage others to contact him with proper values and connections (many of his connections are wrong too) so that he and others can make an exact copy of my Direct Drive, then again the Direct Drive complete with dual sided PCB will cost less new than trying to cobble together a pirated version of my work with the same features, I really don’t understand what separated me from the idea of not posting Zvex schematics…it seems the ethics of the many here are not shared by all…or at least the ethics are not shared by Robert Strand…Happy Holidays to all.  
David Barber  
PS. I have tried to contact Robert Strand at a few of his email addresses to politely explain my position and how his posted schematic could hurt my business and compromise the security (finance) of my co-workers and their families, I also explained to Robert that 9/11 hurt us and that all my co-workers lost their jobs after 9/11, the Direct Drive is the first sign of hope and the first stability we have had. Robert has not responded to my emails.
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