# Ocelot Octave subtle distorted sound



## waarp (Jul 29, 2022)

Hello,

Having an issue after building two Ocelot pedals, The octaves are working 100% however there is a subtle fuzz/distorted signal coming through that is driving me mad.
This distorted signal only comes through while the pedal is on and when I play notes. It happens with both just clean signal and just octave -1, -2 or any combined, basically any setting.

Has anyone encountered this before? I did find this unresolved post from finebyfine as well with the same issues.
Thank you in advance!

here are some of my voltage settings with all pots set to off.


IC6-CD4013BEIC7-CD4027BEIC1-TL072IC2-TL072IC3-TL072IC4-TL072IC5-TL072Q1-2n3904Q2-2SK30AQ3-2SK30A1- 01- 01- 4.93v1- 4.93v1- 4.93v1- 5.03v1- 4.69e- 4.21s- 4.88s- 4.932- 02- 9.07v2- 4.93v2- 4.93v2- 4.93v2- 4.94v2- 4.96b- 4.84g- 0g- 03- 9.06v3- 9.08v3- 4.48v3- 4.93v3- 4.61v3- 4.91v3- 4.93c- 9.06d- 4.93d- 4.934- 04- 04- 04- 04- 04- 0v4- 05- 05- 9.07v5- 4.93v5- 4.61v5- 4.62v5- 4.91v5- 4.93v6- 06- 9.08v6- 4.93v6- 4.93v6- 4.94v6- 4.94v6- 4.93v7- 07- 07- 4.93v7- 4.93v7- 4.94v7- 4.84v7- 1.52v8- 5.0v8- 08- 9.06v8- 9.07v8- 9.08v8- 9.08v8- 9.06v9- 09- 010- 1.52v10- 011- 011- 012- 012- 013- 9.06v13- 014- 9.06v14- 9.06v15- 0v16- 9.07v



Troubleshooting done:
1- replace all IC and transistors, no difference.
2- replace 1u electro in audio path with 1u film, no change
3- attempted audio probe to find where the fuzz starts but the probe is too noisy and everything has a bit of a white noise sound to it.

Thanks!


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## finebyfine (Jul 29, 2022)

If I still have my Ocelot build that I had this issue with (never resolved it, although another Ocelot build did not have the issue) boxed up I'll try to record the faint distortion as well. It's like there's a parallel sidechain that's a Rat distortion with the volume turned down real low. Present with all sorts of different instruments, amps, cables, power supplies, etc. Drove me stark raving mad trying to fix it.


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## Dan0h (Jul 29, 2022)

I too would like to know how to remedy this. My build sounds perfect clean. But any boost or drive and the fizzy artifact shows up exactly like @finebyfine described it a parallel side chain of a turned down rat.


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## waarp (Jul 29, 2022)

yep! that description is absolutely spot on!


finebyfine said:


> It's like there's a parallel sidechain that's a Rat distortion with the volume turned down real low. Present with all sorts of different instruments, amps, cables, power supplies, etc.



I couldn't figure out how to add a quick demo of the pedal so I added an .mp3 here of the sound received from this pedal.  (https://drive.google.com/file/d/1hJ8QfA3Rr9S4eC65q3JfH2dTJP1JD9Et/view?usp=sharing)


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## PJS (Aug 2, 2022)

I am not sure if this matters or not, but the only difference I can see that is in the audio path that is common to all the octaves is that there is a capacitor and resistor missing in the output of the pedal pcb schematic.  This is the output section.  C8 goes to the line that carries the mix od direct, oct 1 and oct2 - the audio out pathway essentially.  R20 goes to Vref.  I don't know enough to know the significance of these being missing.  C8 looks liek some kind of DC blocking, and R20 looks as if it might be to bias the output transistor.  Hope they aren't that important because I've just bought this board


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## Dan0h (Aug 2, 2022)

Bump.


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## waarp (Aug 2, 2022)

PJS said:


> I am not sure if this matters or not, but the only difference I can see that is in the audio path that is common to all the octaves is that there is a capacitor and resistor missing in the output of the pedal pcb schematic.  This is the output section.  C8 goes to the line that carries the mix od direct, oct 1 and oct2 - the audio out pathway essentially.  R20 goes to Vref.  I don't know enough to know the significance of these being missing.  C8 looks liek some kind of DC blocking, and R20 looks as if it might be to bias the output transistor.  Hope they aren't that important because I've just bought this board
> 
> View attachment 30197


Looks like the c8 might just be a high pass and r20 could be for bias, most likely it was removed since we are using a different transistor in the pedalpcb schematic.

I did a little more digging around with an audio probe and found ic1 very noising coming out of pin 1 changed a few tl072s out and all the same, realized I was going down a rabbit hole though since the distorted tone drops when the octave decay ends and the sustained note sounds fine.

one interesting thing I did find is vcc is playing the distorted sound, coming into the collector of the 2N3904, at pin 8 of every single TL072 and anywhere there is vcc coming in.

Vref does not have the noise though.

I did order all new ICs and transistors from a different source this time in case I got a bad batch, still getting the same sound with the new ones installed.

One thing that did help to drop the distorted tone a bit was I swapped the input capacitor C2 for a 10k resistor and 100n film cap in series. It is still there but less prominent than before... or maybe my ears are just playing tricks on me.

Hopefully this thread will build some traction soon!


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## Robert (Aug 2, 2022)

PJS said:


> I don't know enough to know the significance of these being missing.  C8 looks liek some kind of DC blocking, and R20 looks as if it might be to bias the output transistor.  Hope they aren't that important because I've just bought this board



The Ocelot is based on this schematic.


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## finebyfine (Aug 3, 2022)

Here's a recording of my ocelot that has this issue. Around 35s is when it's really apparent at that point I have all knobs but Oct 1 zeroed out. The rest is doing knob sweeps, with an initial clean tone to get an idea of the noise floor on my recording setup. I've had this issue present in isolated power supplies but I am not using one here - this is basically my bedroom playing setup and not my pedal testing setup. I'm also playing higher on the neck than I usually consider like, the "safe tracking zone" of the OC-2 just because it's more apparent at higher frequencies but is present throughout. 

__
		https://soundcloud.com/finebyfine%2Focelot-distortion-troubleshooting%2Fs-HQy6um0Hpyg


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## music6000 (Aug 3, 2022)

waarp said:


> Hello,
> 
> Having an issue after building two Ocelot pedals, The octaves are working 100% however there is a subtle fuzz/distorted signal coming through that is driving me mad.
> This distorted signal only comes through while the pedal is on and when I play notes. It happens with both just clean signal and just octave -1, -2 or any combined, basically any setting.
> ...


Can you confirm R26 - 10K - BROWN, BLACK, BLACK, RED, BROWN ????


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## fig (Aug 3, 2022)

Maybe add a coupling cap between R25 and Q1?

I know...._it's not that simple Fig_. No need to hit me with a math book. Be gentle, I'm fragile...


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## Robert (Aug 3, 2022)

If you add a coupling cap you'd also have to add a pull-up resistor to the base of Q1.

I've built two of these.  I still have one, it doesn't have any fuzziness in the clean tone.   The other one is hacked to bits (Super Ocelot prototype) so I can't test it, but I don't recall anything like that.


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## Robert (Aug 3, 2022)

I have to wonder if some noise is bleeding back through VREF since the low side of all three pots connect at that point.

Maybe a low ESR cap or an additional parallel low value cap might help?  (Or just swapping the 220uF)


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## zgrav (Aug 3, 2022)

Not to derail a good substantive discussion, but the demo sounds like the opening notes to Scott Joplin's The Sting.


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## finebyfine (Aug 3, 2022)

zgrav said:


> Not to derail a good substantive discussion, but the demo sounds like the opening notes to Scott Joplin's The Sting.


it is indeed the intro to the entertainer which is used in the Sting 

Also for what it's worth I've built another Ocelot that didn't have this issue - which makes me imagine that 





Robert said:


> Or just swapping the 220uF


 or similar is the culprit and I may just have been more selective with components in the build that did not have this problem.


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## music6000 (Aug 3, 2022)

waarp said:


> Hello,
> 
> Having an issue after building two Ocelot pedals, The octaves are working 100% however there is a subtle fuzz/distorted signal coming through that is driving me mad.
> This distorted signal only comes through while the pedal is on and when I play notes. It happens with both just clean signal and just octave -1, -2 or any combined, basically any setting.
> ...


Just got confirmation from a working build from Member *aefpv*!
Both Q2 & Q3 transistors were similar in voltages.
S- 4.7
G- 2.07
D- 4.7
If you do not engage the pedal, the gate will be 0.


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## music6000 (Aug 4, 2022)

Did you measure or test D1 & D2 Germanium Diodes prior to fitting?


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## waarp (Aug 4, 2022)

music6000 said:


> Did you measure or test D1 & D2 Germanium Diodes prior to fitting?


I measured them using this cheapo transistor tester but forgot to write them down



music6000 said:


> Can you confirm R26 - 10K - BROWN, BLACK, BLACK, RED, BROWN ????


yep confirmed on both builds.



Robert said:


> I have to wonder if some noise is bleeding back through VREF since the low side of all three pots connect at that point.
> 
> Maybe a low ESR cap or an additional parallel low value cap might help?  (Or just swapping the 220uF)


I ordered some higher quality audio caps from mouser. I am thinking these tayda ones are more often than not giving me issues.
I didnt hear any noise in vref with the audio probe but definitely heard the faint distortion signal in vcc. once i get the new caps in I will try one build with just a replacement and the second one with a 100nf cap in parallel and see if that helps.


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## music6000 (Aug 4, 2022)

waarp said:


> I measured them using this cheapo transistor tester but forgot to write them down
> 
> 
> yep confirmed on both builds.
> ...


I thought you had left us!
So you have built 2 Ocelot Octaves & they both do the same thing????
What reading do you get with Q2 & Q3 ?
This is from a working Ocelot build on both transistors with pedal switched on!
S- 4.7
G- 2.07
D- 4.7
If you do not engage the pedal, the gate will be 0.


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## waarp (Aug 4, 2022)

music6000 said:


> I thought you had left us!
> So you have built 2 Ocelot Octaves & they both do the same thing????
> What reading do you get with Q2 & Q3 ?
> This is from a working Ocelot build on both transistors with pedal switched on!
> ...


haha sorry been a super busy week, one pedal was posted up top but my other pedal looks like its getting a different reading on G of Q3

These are with nothing plugged in or out and all knobs set to full off.

Q2Q3S- 4.92vS- 4.92vG- 0vG- 4.31vD- 4.92vD- 4.92v


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## waarp (Jul 29, 2022)

Hello,

Having an issue after building two Ocelot pedals, The octaves are working 100% however there is a subtle fuzz/distorted signal coming through that is driving me mad.
This distorted signal only comes through while the pedal is on and when I play notes. It happens with both just clean signal and just octave -1, -2 or any combined, basically any setting.

Has anyone encountered this before? I did find this unresolved post from finebyfine as well with the same issues.
Thank you in advance!

here are some of my voltage settings with all pots set to off.


IC6-CD4013BEIC7-CD4027BEIC1-TL072IC2-TL072IC3-TL072IC4-TL072IC5-TL072Q1-2n3904Q2-2SK30AQ3-2SK30A1- 01- 01- 4.93v1- 4.93v1- 4.93v1- 5.03v1- 4.69e- 4.21s- 4.88s- 4.932- 02- 9.07v2- 4.93v2- 4.93v2- 4.93v2- 4.94v2- 4.96b- 4.84g- 0g- 03- 9.06v3- 9.08v3- 4.48v3- 4.93v3- 4.61v3- 4.91v3- 4.93c- 9.06d- 4.93d- 4.934- 04- 04- 04- 04- 04- 0v4- 05- 05- 9.07v5- 4.93v5- 4.61v5- 4.62v5- 4.91v5- 4.93v6- 06- 9.08v6- 4.93v6- 4.93v6- 4.94v6- 4.94v6- 4.93v7- 07- 07- 4.93v7- 4.93v7- 4.94v7- 4.84v7- 1.52v8- 5.0v8- 08- 9.06v8- 9.07v8- 9.08v8- 9.08v8- 9.06v9- 09- 010- 1.52v10- 011- 011- 012- 012- 013- 9.06v13- 014- 9.06v14- 9.06v15- 0v16- 9.07v



Troubleshooting done:
1- replace all IC and transistors, no difference.
2- replace 1u electro in audio path with 1u film, no change
3- attempted audio probe to find where the fuzz starts but the probe is too noisy and everything has a bit of a white noise sound to it.

Thanks!


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## music6000 (Aug 4, 2022)

waarp said:


> haha sorry been a super busy week, one pedal was posted up top but my other pedal looks like its getting a different reading on G of Q3
> 
> These are with nothing plugged in or out and all knobs set to full off.
> 
> Q2Q3S- 4.92vS- 4.92vG- 0vG- 4.31vD- 4.92vD- 4.92v


Did you purchase the 2Sk30's from Tayda?


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## waarp (Aug 4, 2022)

music6000 said:


> Did you purchase the 2Sk30's from Tayda?


I did, however I swapped them with 2N5457's and had the same result. Fun fact though it did boost the octave levels a bit having the 2N5457 in


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## music6000 (Aug 4, 2022)

You realize the pinout is different, D S G VS 2SK30 D G S !!!


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## waarp (Aug 4, 2022)

music6000 said:


> You realize the pinout is different, D S G VS 2SK30 D G S !!!


yeah haha dont worry I checked and put them in the right way. I went back to the 2SK30 though since the distortion issue was still present. Saving those 5457s for another build.


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## harmaes (Aug 14, 2022)

I just finished an Ocelot build and experienced noise/static like behavior only in the dry signal.
I had the PCB populated yesterday and quickly connected it to my breadboard to see if I build the circuit correctly.
Everything worked correctly but I noticed a little bit of noise/static on the dry signal with my P-Bass. 
I boxed the pedal today and now it had noise/static constantly on the dry signal. 
I experimented with the input and output wires and moved them away from the PCB and the static went away. When using the breadboard there were no wires going across the PCB. 

So I replaced the single wires with shielded wire and the problem went away. Connected the mass to ground of the jacks and to the ground of the switch. Hope that this could solve your issues as well?


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## Dan0h (Aug 14, 2022)

harmaes said:


> I just finished an Ocelot build and experienced noise/static like behavior only in the dry signal.
> I had the PCB populated yesterday and quickly connected it to my breadboard to see if I build the circuit correctly.
> Everything worked correctly but I noticed a little bit of noise/static on the dry signal with my P-Bass.
> I boxed the pedal today and now it had noise/static constantly on the dry signal.
> ...


I will wrap my wires and see if it resolves the issue. Thanks for the idea.


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## Nic (Dec 15, 2022)

Sorry to bring back this thread to life ... did anyone find the problem ? My build is now almost perfect, I had one bad IC from Tayda on the -2 side. 
Now, the pedal sounds really good, except that I have the described static/buzzing sound.
1 - Only when engaged
2 - Only when strings are vibrating.
3 - Only when -1 is turned on.

So with the -1 knob turned all the way down, no buzzing. 
Thanks all


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## PJS (Dec 16, 2022)

If you are looking at parts of the circuit that are unique to -1, then on the schematic you are basically looking at R11 through Q2, IC 1.2 and through to IC2.2 I think.  I am a bit hazy on it, but I think the purpose of that network is basically to buffer and filter what starts out as a square wave.  I would check that part of the circuit for bad connections and wrong value components.  An audio probe may be able to tell you more precisely where the buzz is coming from


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## Nic (Dec 16, 2022)

Yes, I took voltages everywhere yesterday and will post the values when I have a chance... I've got 3 drastically different from values in the OP. I also thought that part of the circuit would be where the problem sould be, time to take out the probe... I wish santa would send me an auditorium pcb.


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## Nic (Dec 16, 2022)

I marked in red the values that are really far from the original post values ... but those could be ok, just not sure. To me IC7 pin 3 at 0 correspond to the path linked to IC6 pins 2 and 5, so that should be normal. 
Where do IC6, pin 1 go ? 
IC5 pin 1 has a lot of current, is that normal ? 

I also think probing and inspecting R11 to IC2.2 will be the key. 

I will let you know my findings as soon as I hate time to probe it, might be during the week-end. 


IC1-TL072IC2-TL072IC3-TL072IC4-TL072IC5-TL072IC6-CD4013BEIC7-CD4027BEQ1-2N3904Q2-2SK30AQ3-2SK30A14.594.604.574.59*7.7**8.36*0E: 3.83S: 4.54S: 4.5324.574.604.584.574.5408.33B: 4.43G: 0G: 034.154.594.304.534.558.34*0*C: 8.33D: 4.54D: 4.514000000054.594.304.274.534.5408.3364.604.594.574.564.5608.3374.604.594.574.581.540088.438.428.398.378.367.690900101.54011001200138.330148.338.33150168.33


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## Nic (Dec 16, 2022)

Oh yeah, I get all my voltages values are relative to running this on an 9v battery that right now would output around 8.3 to 8.4 volts


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## Nic (Dec 17, 2022)

Ok, after some probing and troubleshooting, the problem occurs around IC4. But there is a lot going on in this circuit. 
I found out that when oct 1 AND 2 are full on or off, there is no buzzing, but any other setting will buzz.

Without IC4, no buzzing at all. 
I swapped the IC around and troed new one from PPCB, the IC is not the problem. Could it be the diodes ?


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## Nic (Dec 19, 2022)

Quick follow-up, I had a bad pot on OCT2. I had soldered/de-soldered/modified them quite a lot to fit. I hade only one spare, a lug type which was perfect. I still have a little buzz, but nothing that compares, I'll end up replacing the OCT1 as well when I reorder from Tayda... Maybe even the third one for good measure.


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## waarp (Dec 20, 2022)

I was never able to completely remove the buzzing but a few things ended up making it hardly noticeable, one was to replace all internal wires with shielded wires, swap all the electrolytics in the signal path with tantalums , and the last was replace r9 and r18 with trim pots. I am not sure which of these helped the best but it became usable for me and I eventually gave it to a friend of mine.


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## Nic (Dec 20, 2022)

With your last comment, I suppose it could be marked as solved ?


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## waarp (Dec 24, 2022)

Nic said:


> With your last comment, I suppose it could be marked as solved ?


if youd like! the buzzing never fully went away though i did abandon fixing it and just treat it as a feature.


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