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DIY Stompboxes => Building your own stompbox => Topic started by: JamMan on April 21, 2004, 09:01:03 AM

Title: Self -oscillation with PT80 using MN3207?
Post by: JamMan on April 21, 2004, 09:01:03 AM
Hi,

I'm almost certain I'll make the PT80 digital delay by Scott Swartz. It only lacks one thing I love in analog delays: the self -oscillation thingy where you can adjust the pitch with the delay time -knob.

So my question is: can I make a special cirquit that is footswitchable and would add a BBD, say MN3207 (actually that is the only option for me), that would do the trick?
Title: Self -oscillation with PT80 using MN3207?
Post by: bobbletrox on April 21, 2004, 09:20:14 AM
I wonder if it's possible to get that effect without having to build a whole delay circuit -because I love it too!
Title: Self -oscillation with PT80 using MN3207?
Post by: claydavis on April 21, 2004, 09:29:04 AM
the PT-80 will self-oscillate with no modification (or at least mine will). you could always play around with the repeats pot value and any associated resistors to get more feedback, if that's what you want.
Title: Self -oscillation with PT80 using MN3207?
Post by: JamMan on April 21, 2004, 09:55:31 AM
Quote from: claydavisthe PT-80 will self-oscillate with no modification (or at least mine will). you could always play around with the repeats pot value and any associated resistors to get more feedback, if that's what you want.

Oh...I thought you could do that only with analog delays...

By the way, I don't know if the term "self -oscillation" is appropriate. What I really want is that "change pitch with delay time" -thing, I don't know if self -oscillation has anything to do with it...
Title: Self -oscillation with PT80 using MN3207?
Post by: claydavis on April 21, 2004, 10:07:25 AM
it'll do either. i added an expression pedal to control the delay time on mine, and it does the time-stretching/pitch-shifting thing just fine. self-oscillation happens when you crank the repeats pot up, and the pedal goes into runaway feedback, becoming a tone-generator of sorts.
Title: Self -oscillation with PT80 using MN3207?
Post by: JamMan on April 21, 2004, 10:25:33 AM
OK

So the PT80 does those two things, thats great!

But I'm still sceptic about the pitch thing... Every digital delay I've tried just makes these popping noises when the delay time is changed.

One other thing: is it possible to have 2 pots for repeats, and a footswitch to switch between them, that way I could have kind of like two "presets" for two different repeat times?
Title: Self -oscillation with PT80 using MN3207?
Post by: Scott Swartz on April 21, 2004, 10:57:58 AM
Since the delay time is set by a resistor to ground you have a lot of flexibility.

The switching will work fine.

The expression pedal discussed also above works great, no glitching, the pitch change is very smooth.
Title: Self -oscillation with PT80 using MN3207?
Post by: Brian Marshall on April 21, 2004, 11:39:06 AM
Anyone selling a PCB for the pt80.  i have all the parts.

Brian
Title: Self -oscillation with PT80 using MN3207?
Post by: Fret Wire on April 21, 2004, 12:02:32 PM
GGC has them.

http://www.generalguitargadgets.com/v2/index.php?%20option=displaypage&Itemid=154&op=page&SubMenu=
Title: Self -oscillation with PT80 using MN3207?
Post by: Brian Marshall on April 21, 2004, 12:04:05 PM
Quote from: Fret WireGGC has them.

http://www.generalguitargadgets.com/v2/index.php?%20option=displaypage&Itemid=154&op=page&SubMenu=

I'M SO THERE.
Title: Self -oscillation with PT80 using MN3207?
Post by: Fret Wire on April 21, 2004, 12:16:55 PM
GGC has a PCB board..fits in a 1590BB...Scott and JD have info files, and lay-out to the 9th degree.....gez, sounds like another project.  :D
Title: Self -oscillation with PT80 using MN3207?
Post by: Brian Marshall on April 21, 2004, 12:22:36 PM
i just ordered the pcb, and pcb's for the DOD440, and the green ringer.

:D:D:D:D:D:D
Title: Self -oscillation with PT80 using MN3207?
Post by: JamMan on April 21, 2004, 02:10:15 PM
Thank you for the information.

I'll make the PT80, too. I try to make it with two pots for repeat, so I can switch between a normal delay and an atmospheric, "background noise" delay with repeats maxed. That is something I need, and it can't be found, at least not easily, in delay pedals on the market.