Ocelot Octave subtle distorted sound

waarp

New member
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-TL072Q1-2n3904Q2-2SK30AQ3-2SK30A
1- 01- 01- 4.93v1- 4.93v1- 4.93v1- 5.03v1- 4.69e- 4.21s- 4.88s- 4.93
2- 02- 9.07v2- 4.93v2- 4.93v2- 4.93v2- 4.94v2- 4.96b- 4.84g- 0g- 0
3- 9.06v3- 9.08v3- 4.48v3- 4.93v3- 4.61v3- 4.91v3- 4.93c- 9.06d- 4.93d- 4.93
4- 04- 04- 04- 04- 04- 0v4- 0
5- 05- 9.07v5- 4.93v5- 4.61v5- 4.62v5- 4.91v5- 4.93v
6- 06- 9.08v6- 4.93v6- 4.93v6- 4.94v6- 4.94v6- 4.93v
7- 07- 07- 4.93v7- 4.93v7- 4.94v7- 4.84v7- 1.52v
8- 5.0v8- 08- 9.06v8- 9.07v8- 9.08v8- 9.08v8- 9.06v
9- 09- 0
10- 1.52v10- 0
11- 011- 0
12- 012- 0
13- 9.06v13- 0
14- 9.06v14- 9.06v
15- 0v
16- 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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Last edited:
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.
 
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 :)

1659433119402.png
 
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!
 
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.
 
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-TL072Q1-2n3904Q2-2SK30AQ3-2SK30A
1- 01- 01- 4.93v1- 4.93v1- 4.93v1- 5.03v1- 4.69e- 4.21s- 4.88s- 4.93
2- 02- 9.07v2- 4.93v2- 4.93v2- 4.93v2- 4.94v2- 4.96b- 4.84g- 0g- 0
3- 9.06v3- 9.08v3- 4.48v3- 4.93v3- 4.61v3- 4.91v3- 4.93c- 9.06d- 4.93d- 4.93
4- 04- 04- 04- 04- 04- 0v4- 0
5- 05- 9.07v5- 4.93v5- 4.61v5- 4.62v5- 4.91v5- 4.93v
6- 06- 9.08v6- 4.93v6- 4.93v6- 4.94v6- 4.94v6- 4.93v
7- 07- 07- 4.93v7- 4.93v7- 4.94v7- 4.84v7- 1.52v
8- 5.0v8- 08- 9.06v8- 9.07v8- 9.08v8- 9.08v8- 9.06v
9- 09- 0
10- 1.52v10- 0
11- 011- 0
12- 012- 0
13- 9.06v13- 0
14- 9.06v14- 9.06v
15- 0v
16- 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!
Can you confirm R26 - 10K - BROWN, BLACK, BLACK, RED, BROWN ????
 
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...:rolleyes:
 
Last edited:
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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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)
 
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
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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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-TL072Q1-2n3904Q2-2SK30AQ3-2SK30A
1- 01- 01- 4.93v1- 4.93v1- 4.93v1- 5.03v1- 4.69e- 4.21s- 4.88s- 4.93
2- 02- 9.07v2- 4.93v2- 4.93v2- 4.93v2- 4.94v2- 4.96b- 4.84g- 0g- 0
3- 9.06v3- 9.08v3- 4.48v3- 4.93v3- 4.61v3- 4.91v3- 4.93c- 9.06d- 4.93d- 4.93
4- 04- 04- 04- 04- 04- 0v4- 0
5- 05- 9.07v5- 4.93v5- 4.61v5- 4.62v5- 4.91v5- 4.93v
6- 06- 9.08v6- 4.93v6- 4.93v6- 4.94v6- 4.94v6- 4.93v
7- 07- 07- 4.93v7- 4.93v7- 4.94v7- 4.84v7- 1.52v
8- 5.0v8- 08- 9.06v8- 9.07v8- 9.08v8- 9.08v8- 9.06v
9- 09- 0
10- 1.52v10- 0
11- 011- 0
12- 012- 0
13- 9.06v13- 0
14- 9.06v14- 9.06v
15- 0v
16- 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!
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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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

Can you confirm R26 - 10K - BROWN, BLACK, BLACK, RED, BROWN ????
yep confirmed on both builds.

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


yep confirmed on both builds.


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.
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.
 
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.
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.
Q2Q3
S- 4.92vS- 4.92v
G- 0vG- 4.31v
D- 4.92vD- 4.92v
 
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