catalinbread heliotrope problem

[joer0952]

Before I begin I want to apologize if my description of the problem isn't totally clear, I am new to this and am still learning how all this stuff works.  I just made a catalinbread heliotrope using the schematic I made below from a layout I found at http://img203.imageshack.us/img203/5048/verifiedcatalinbreadhel.jpg (schematic below).


when I plug it in the guitar plays with alittle distortion but I don't get the effect im supposed to get with this pedal.  the volume and gain pots work with the guitar, but the resolution and sample rate do not, although there is a ringing in the background that is effected by these two pots.  So, I guess the 741 and those two pots are working properly together, but for some reason they aren't effecting the guitar signal.  I know I have to go through the whole debugging process.  I will do that tomorrow after work, I was just wondering if anyone notices any problem with my schematic or has any tips or ideas as to what the problem might be. 

[El Heisenberg]

Aw man where is the parts list?? Had no idea this pedal would be up here.

[rousejeremy]

That ringing you hear in the background is the carrier wave. It's normal. It's also what makes this pedal almost unusable live.

[earthtonesaudio]

That schematic is pretty wrong.

[El Heisenberg]

Is there a correct one out there?

[earthtonesaudio]

FSB

[El Heisenberg]

I dunno what FSB means

[the3secondrule]

I dunno what FSB means

the "other" forum.

free stompboxes(dot)org

[earthtonesaudio]

I dunno what FSB means

the "other" forum.

free stompboxes(dot)org

Yep, that's what I meant.

I just looked a little more closely at the schematic and I have to take back what I said earlier.  The schematic is correct, it's just really hard to read (for me anyway).  Sorry for that.

[El Heisenberg]

r1 = 3.3k      c1 = 10uf (e)      ic1 = lm741
r2 = 12k      c2 = 0.022uf      ic2 = tl072
r3 = 47k      c3 = 100uf (e)
r4 = 10k      c4 = 100uf (e)   q1 = 2n5457
r5 = 100k    c5 = 0.005uf 
r6 = 4.7k     c6 = 47uf (e)      d1, d2, d4, d5 = 1n4148
r7 = 10k      c7 = 10uf (e)     d3 = 1n4001
r8 = 1k        c8 =  0.05uf
r9 = 1k        c9 = 4.7 (e)      vr1 = 1mb
r10 = 1m      c10 = 0.05uf    vr2 = 100kb
r11 = 10k                         vr3 = 100kb
r12 = 10k                         vr4 = 100ka
r13 = 47r
r14 = 47r
r15 = 1k
r16 = 2k

[Gabriel]

Dear all,

I  build de design of the Heliotrope. Works very nice to be a Noisy-ish pedal.

The situation to resolve is: when bypassed, it still makes a sounding whine-noise on the circuit (from the sample rate). I don´t know how can this be possible...I also tried also the "grounding input" technique, with no positive result.

I heard other reports of this circuit with the same problem of getting this whine on the signal path..

So i had to configure the 3pdt to power on/off. I really need to have a clean bypassed signal.

The question is: how to do a power on/off switching? closing the positive or the ground? any suggestion?

The best to all.

[earthtonesaudio]

All you should need to do is stop the oscillator during bypass.  If you have a free switch section you could wire it to ground the + input of the oscillator opamp.  If you use a 3pdt currently, you could rewire the LED pole such that it grounds the LED cathode in the On position, and grounds the opamp input in the Off position.

[tommycataus]

Sorry to bump this thread, but I've built this pedal and I am having a similar whining problem. However, this effect is golden when bypassed -  there's no problem there. The problem is that when I engage the effect there seems to be a lot of oscillation when I mess with the resolution and sample rate controls.

I've watched a few demos and nobody seems to be having this problem with the original. I've got a filter on my power supply but I have also tried a 9v battery, high value electrolytics to filter out high frequencies, nothing...

The noise seems to be a drone in the background that changes pitch with the Lo / Hi switch and becomes very high pitched when the sample rate knob is turned full counter clockwise. It would mean that, like Jeremy says, this pedal would be unusable live. I would just throw in the towel but the original sounds fine...

It also seems that I am not the only one having problems with this on the net, so I hope you guys can help!

Thanks in advance

[earthtonesaudio]

The logical approach says, if the original doesn't have this problem, and the schematic is valid, then the layout is to blame.
Keep your high-impedance wires (like input lines) short (to avoid inductive noise pickup) and far from noise sources (to avoid capacitive noise pickup).

The approach I take is to always use short shielded wires for weak signals, and route them far away from oscillators and power supplies (well, as far as possible given the constraints of the enclosure).

Once the layout is optimal, if you still have the issue, you could try:
* more power supply decoupling between oscillator and audio sections
* reduce oscillator current (use a lower-power opamp perhaps)
* put the oscillator in a sub-enclosure
* use an optical switch instead of the JFET (requries redesign)