Author Topic: Octave Up  (Read 35292 times)

McGyver

Re: Octave Up
« Reply #20 on: November 24, 2009, 09:24:21 PM »
Hi guys!
I've done this pedal with this schematic http://analogguru.an.ohost.de/001/schematics/Prescription_COB.gif and I build my own Layout. After a lot of time trying to make it work, I had no positive result.
Can anyone post a layout that works fine? I'll post mine so you can see what is wrong and tell me...
The P1.3 is pot number 1 lug 3 and so it goes...

Thanks! ;)

doubleg

Re: Octave Up
« Reply #21 on: November 24, 2009, 10:10:27 PM »
Hi guys!
I've done this pedal with this schematic http://analogguru.an.ohost.de/001/schematics/Prescription_COB.gif and I build my own Layout. After a lot of time trying to make it work, I had no positive result.
Can anyone post a layout that works fine? I'll post mine so you can see what is wrong and tell me...
The P1.3 is pot number 1 lug 3 and so it goes...

Thanks! ;)

I just got done looking through your layout vs the schematic. I could not find anything wrong with your circuit traces.  I myself built the Prescription Clean Octave Blend  based on that very schematic and it works fine for me, although I did have a bit of trouble-shooting to do to get it to work. If i remember it turned out to be a bad solder joint on cap 3. Anyways, maybe another pair of eyes can look at your layout, but as far as I can tell there isnt anything wrong on yours.

McGyver

Re: Octave Up
« Reply #22 on: November 25, 2009, 11:35:40 AM »
Thanks for the answer!
I checked the circuit a thousand times and I realized that the Millenium Bypass was wrong :icon_redface:. So I test only the effect and it works!
Sounds good but not what I was looking for. I'll use it with my bass guitar and I need more clean sound and more "transparent" octaves.
I'll try to put a tone control for the octaves and see if that makes them transparent.
I noticed that the blend control at 14:00 reduce the volume of the wet and the dry signal. Is this normal?
If anyone can give me a solution for more transparent octaves I'll appreciate.
If you need I'll post the Layout and PCB of this pedal.
Thanks!!!

alex frias

Re: Octave Up
« Reply #23 on: November 25, 2009, 01:18:33 PM »
I don't know what you really have in mind, but I think one thing to get very transparent octaves, up and down is something like a EH POG or MicroPOG...
Pagan and happy!

doubleg

Re: Octave Up
« Reply #24 on: November 25, 2009, 01:43:29 PM »
I don't know what you really have in mind, but I think one thing to get very transparent octaves, up and down is something like a EH POG or MicroPOG...

I just went to the EH site, listened to their POG soundsample, I WANTS one of those  :icon_mrgreen:

McGyver

Re: Octave Up
« Reply #25 on: November 26, 2009, 08:17:34 AM »
Yes! that king of sound. "Transparent" octaves like the micro POG :icon_biggrin:. I only want the octave up, the sub octave is not important to me, but is very cool too.
Anyone have the schematic?
Sounds fantastic!
Greets!!

cpm

Re: Octave Up
« Reply #26 on: November 26, 2009, 09:02:47 AM »
there is a "copyrighted" POG schematic around there, but its no more than a bunch of traces going into a DSP chip

alex frias

Re: Octave Up
« Reply #27 on: November 26, 2009, 09:45:18 PM »
Something like that is more expensive to build than buy it, so thonk twice!
Pagan and happy!

gigimarga

Re: Octave Up
« Reply #28 on: November 29, 2009, 04:28:57 PM »
Hi guys!
I've done this pedal with this schematic http://analogguru.an.ohost.de/001/schematics/Prescription_COB.gif and I build my own Layout. After a lot of time trying to make it work, I had no positive result.
Can anyone post a layout that works fine? I'll post mine so you can see what is wrong and tell me...
The P1.3 is pot number 1 lug 3 and so it goes...

Thanks! ;)

Nice work man!
It seems OK to me, too.
Can you post the PCB for it?

McGyver

Re: Octave Up
« Reply #29 on: November 29, 2009, 09:51:28 PM »
Ok here is the PCB. It works fine but it isn't my sound, I'll try some new mods to get a clean octave as possible. If anyone have an idea it will be helpful.
The real size of the PCB is 2.5 x 2.5 inch.
If you have any trouble tell me and I will help you, I'm just trying to make my echo base work >:( !!

Bye!

amptramp

Re: Octave Up
« Reply #30 on: November 29, 2009, 09:57:16 PM »
If you want to check up on the harmonics and their relative strengths derived from full-wave rectification, check this site:

http://www.falstad.com/fourier/e-fullrect.html

It shows the DC value is 0.63662 times the input
2nd (desired) harmonic = 0.42442 = -7.44db
4th harmonic = 0.08489 = -21.42db
6th harmonic = 0.03638 = -28.78db
8th harmonic = 0.02021 = -33.89db

There are no odd harmonics, but the harmonics above 2nd are usually undesirable.  The waveform coming into the device will behave this way if it is a pure sine wave - other waveforms may just become a fuzzy mess.  The site quoted above will show what happens in fullwave rectification of a triangular sawtooth function under the "next" link on that page.  In order to avoid this, it may be best to split the signal into frequency bands and rectify the signals in each band separately before recombining them.

A better way to generate an octave up would be to square it (multiply the signal linearly by itself) using the trig identity that:

cos (F) * cos (F) = 0.5 + 0.5 * cos(2F)

This has the advantage that only the second harmonic is generated.  Once again, it may be best to split the signal into frequency bands and square the signals in each band separately before recombining them.  Linear multiplication can be done in an MC1496 (readily available) or MC1495 (rare - I last used one in the early 1970's).

McGyver

Re: Octave Up
« Reply #31 on: November 29, 2009, 10:32:24 PM »
WOW amptramp! :o this is a complete explanation! but I don't understand very well what mod can I do to this pedal...
Do you think that you can do a cleaner octave up with a MC1496 ?
Sorry if I don't understand very well, but my English is very poor, I'm from Argentina and I think that the MC1496 will be impossible to find here.
Thanks for the answer,
Greetings!

gigimarga

Re: Octave Up
« Reply #32 on: November 30, 2009, 02:53:55 AM »
Ok here is the PCB. It works fine but it isn't my sound, I'll try some new mods to get a clean octave as possible. If anyone have an idea it will be helpful.
The real size of the PCB is 2.5 x 2.5 inch.
If you have any trouble tell me and I will help you, I'm just trying to make my echo base work >:( !!

Bye!

Thx a lot McGyver!

newfish

Re: Octave Up
« Reply #33 on: November 30, 2009, 10:19:30 AM »
FWIW...

I *know* it's not DIY, but the Behringer US600 Pitch Shifter is pretty good for a clean octave-up.

And cheap!

<hides under non-DIY pedal flame-proof shelter>
Happiness is a warm etchant bath.