Parentheses noise floor

[r.nandez54]

Am I the only one getting a ton amount of hiss from the full size Parentheses when the octave is activated? Is there a way to fix this?

 

[TGP39]

I just built two of the Parentheses. Rat side=dead quiet. Rat+boost = dead quiet. Click on the octave switch and I’m in a wind tunnel! This is on both my builds. I’m using Fv matched 1N34a and matched D9E diodes for my germanium section.

 

[zipfool]

Same. A ton of noise when octave is engaged. I figured it might just be the nature of this snarling beast of metal.

 

[TGP39]

Does the original have this noise issue when octave is engaged? Can anyone else who has built a parentheses chime in on their experience with the octave switch/noise level? Much appreciated.....

 

[jesuscrisp]

Will check the Mini I built, but from all my experiences no matter if its vero or PCB, the Tentacle/Green Ringer that the octave in the Life pedal is based on is just noisy.

 

[Betty Wont]

I've never used this pedal, but I'm curious what they did to the Rat portion to make it quiet, even with a boost. The Rat is one of the few circuits that I find absolutely unusable due to its noise floor (also looking at you HM-2)

 

[TGP39]

I've never used this pedal, but I'm curious what they did to the Rat portion to make it quiet, even with a boost. The Rat is one of the few circuits that I find absolutely unusable due to its noise floor (also looking at you HM-2)

I’m really pleased with the distortion + boost. Low noise floor and powerful sound. When I switch on the octave though, the noise is significant.

 

[jeffwhitfield]

I'll need to test this myself but, based on how the octave feature works, wouldn't surprise me at all that it adds a significant level of noise to the mix. I use a good noise gate anyways so that does help a lot in cutting out the noise.

 

[soggybag]

I’m getting a lot of noise from the octave circuit. As the original post describes it sounds like a wind tunnel.

anyone got any tips for quieting it down?

 

[Big Monk]

I was under the impression noise comes with the price of admission for octave pedals.

 

[Chuck D. Bones]

Germanium diode = leaky diode = noisy diode. Use Silicon or Schottky and point them the right direction (cathodes connect together). The Rat section comes after the Octave section and the Rat will amplify signal and noise.

My Aion Vulcan (Foxx Fuzz Tone) & PedalPCB OctaMayer (Roger Mayer Octavia II) are not noisy. The Vulcan uses BAT46s in the octave section and the OctaMayer uses 1N4148s. Neither one has much gain after the octave circuit.

 

[soggybag]

I’ve been playing with this recently here are a few observations.

- With the gain all the way up and the volume all the way up I get significant noise on the Rat without the octave. Which seems to expected because the op-amp stage has a gain of x100.
- when the octave is on get the huge wind tunnel sound. This is like a whistling oscillation. This is more than the noise you get from the Rat alone.
- using the oscilloscope I can see noise at pin 6 with the octave off gain 100%.
- with the octave on and the gain 100% the noise doubles.
- I can’t see any of this noise at the input pin 3 of the op-amp or at the emitter of Q4.
- if I use the bench power supply it reduces the noise.

Seems like the noise comes from the op-amp. I’m using a 741 Without the 30p C15

Picture 1 - gain 100% octave off 1spot
Picture 2 - gain 100% octave on 1spot
Picture 3 - gain 100% octave on bench power

 

[Chuck D. Bones]

Sounds like power supply noise. Most, if not all, of the wall-wart power supplies are switching regulators. The switching freq should be above 20KHz, but it might not be. Some of the switching power supplies have stability issues and will oscillate at audio frequencies with certain loads.

The Rat part of the circuit has good power supply rejection, which is a fancy way of saying it's not susceptible to power supply noise. The Octave part of the circuit has lousy power supply rejection and will pick up and propagate power supply noise. If a bench supply or battery solves the noise problem, then blame the pedal power supply.

How sensitive is your 'scope? Noise is like germs; just 'cause you can't see it, doesn't mean it isn't there.

Why did you choose a 741? It's like the Budweiser of opamps.

 

[soggybag]

Good questions.

- I have an analog scope. Not sure how sensitive it is. Like I said above I'm not seeing any noise anywhere except at pin 6. It gets worst when the octave is engaged but there's not noise at the input pin 3 or at the output the of the octave circuit. It does feel like there is something going on with the power supply.
- I chose 741 because I had these on hand and didn't want to pay $5 or more for LM 308 which are hard to get.

I just tested a few other single op-amps. The noise seems to be worst with other op-amps. I tried 071, 081, 3140.

For the record I have the gain and volume at 100% which is extreme.

 

[soggybag]

Increasing C14 can eliminate the noise entirely. I experimented with some different caps. As value goes up the overall sound is darker. Seems like you can tailor this cap to your preference.

I experimented with these results:

- 33n and larger the noise gone even with the Gain and volume at 100%
- 15n with the gain and volume at 100% the noise/oscillation can be heard in the background but it's pretty quiet. I settled on this for myself. I liked the overall change in tone. But it is less bright than the original 100p value.

 

[Chuck D. Bones]

Band-aid.

 

[soggybag]

I’m curious if people using LM308 are having this noise issue? And if this happens on original EQD Life pedals?

The issue could just be part of the circuit or it be parts or it could PedalPCB version has the issue?

 

[Dan M]

I finally checked mine. Probably not helpful, but it’s a data point.

It’s quiet for all combinations of foot switches.
If I crank up the octave and step on the switch, I don’t hear a jump in the noise floor.

I used an OP07 and matched D9K diodes in the octave.