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Discussion Starter · #1 ·
This is brand new, hasn't happened before, the pedal is in front of the amp, but but not playable as is. Nothing has changed on my rig, settings all the same as last time I picked up the guitar. MXR Micro Flanger is creating a high hiss that oscillates with the settings and is bleeding through even though it is disengaged.

I tried unplugging the power supply from all pedals and giving it a minute, thought it maybe the BB chip or something thats loaded up as the same thing would happen with my Electric Mistress if plugged in for a long time. Its not helping this time.

Any tips to cure this? I'll have to ditch the pedal in the mean time.
 

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Are you using a switching power supply to power it?
If so, the PS has a clock, and so does the Micro Flanger. It will want either a battery or a plain old vanilla analog wallwart to power it.

The problem arises when unfiltered spikes on the power line (which are so high up that we can't hear them) interact with the clock spikes created within the flanger (or chorus, or delay, or anything that has its own HF clock). The clock internal to the pedal interacts with the clock spikes on the power line in a manner similar to ring modulators, creating sums and differences. Many of those are inaudible (especially the sums!), but many are quite audible, such that the pedal sounds excessively noisy.

It's a fairly common phenomenon, particularly with the glut of digital pedals out there these days.
 

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I had a similar issue with an MXR chorus, it was causing a high pitched hum, even when the pedal was bypassed. In the end I had to send it back to MXR, they told me it was inadequate shielding on the BBD chip that was allowing noise to bleed into the wiring. They fixed it for nothing.
 

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I had a similar issue with an MXR chorus, it was causing a high pitched hum, even when the pedal was bypassed. In the end I had to send it back to MXR, they told me it was inadequate shielding on the BBD chip that was allowing noise to bleed into the wiring. They fixed it for nothing.
That explanation they gave you makes no sense. BBD chips are never shielded. Besides, it's not the BBD that produces HF noise - it's the clock chip.
Having said that, proper filtering is required to keep delay-generated noise out of the final audio path. If one or more caps providing that filtering do not make appropriate contact with ground, then the effect is a bit like cranking the treble on the delay path, such that residual hiss would be more audible.

But all of this assumes that any bypass switching arrangement would somehow permit noise from the delay path to enter the audio output. And from what I can see in the schematic I have, that simply could not happen with the Micro-Flanger. I own an older one, and also a Stereo Flanger from the Commande series (which is near identical to the Micro-Flanger). I can check when I'm at home, but my sense is that once that puppy is bypassed, hiss from the delay path can't physically leak into the output. That's why I suggested the power supply issue.

Just out of curiosity, does changing the Regeneration control setting change the hiss level?
 

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That explanation they gave you makes no sense. BBD chips are never shielded. Besides, it's not the BBD that produces HF noise - it's the clock chip.
Having said that, proper filtering is required to keep delay-generated noise out of the final audio path. If one or more caps providing that filtering do not make appropriate contact with ground, then the effect is a bit like cranking the treble on the delay path, such that residual hiss would be more audible.

But all of this assumes that any bypass switching arrangement would somehow permit noise from the delay path to enter the audio output. And from what I can see in the schematic I have, that simply could not happen with the Micro-Flanger. I own an older one, and also a Stereo Flanger from the Commande series (which is near identical to the Micro-Flanger). I can check when I'm at home, but my sense is that once that puppy is bypassed, hiss from the delay path can't physically leak into the output. That's why I suggested the power supply issue.

Just out of curiosity, does changing the Regeneration control setting change the hiss level?
Fair enough, but whatever they did it fixed the problem. I used the same power supply and signal chain and the noise was completely gone. Its possible they just sent me a new pedal, I didn't write down the serial number or anything before I sent it. Its the only time I have ever had a pedal that caused noise when bypassed, so it was an odd issue for me as well.
 

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Discussion Starter · #11 ·
Just out of curiosity, does changing the Regeneration control setting change the hiss level?

Yes, speed and regen alters the bypass hiss. They suggested sending a video, but it was easier to just record a quick sample of the problem for them. I emailed a minute ago. Although I did forget to change the settings while bypassed to show this. The noise is VERY apparent as it can be heard while playing still dirty licks, but with the guitar volume down.
 

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Fair enough, but whatever they did it fixed the problem. I used the same power supply and signal chain and the noise was completely gone. Its possible they just sent me a new pedal, I didn't write down the serial number or anything before I sent it. Its the only time I have ever had a pedal that caused noise when bypassed, so it was an odd issue for me as well.
Oh I won't take anything away from the customer service, merely the "quasi-technical" explanation.

If it was a different sort of build, where there were wires to pots or jacks passing over areas where clock noise was in abundance, I could see this sort of thing happening. But the nature of buikls these days is such that there are no wires to pots switches or jacks; everything is mounted to the board directly.

And since it was not addressed in any of the other posts, how is the Micro-Flanger being powered?
 

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Discussion Starter · #15 ·
And since it was not addressed in any of the other posts, how is the Micro-Flanger being powered?
Powered by a one spot daisy chained for three of the pedals, the Empress has its own wallwart.

My rig was completely silent at stage volume with the guitar volume down a couple days ago.

Guitar>MXR 10 band>MicroFlange>Input 5150 III 50 watt>FX send>Empress Superdelay>TU2>FX Return. Pretty simple really.
 

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The One-Spot is a switching power supply, which puts it at risk for the heterodyning noise I described earlier. Your Superdelay and TU2 are also digital, increasing the risk, particular when daisy-chained. Thankfully, your Superdelay is effectively isolated from everything else via the separate PSU.

However, just for the hell of it, take the pedals out of the FX loop and try powering the Micro-Flanger with a more traditional linear wallwart, rather than the One-Spot. Let me know if that makes a difference. My friend RG Keen, who designs for Truetone/Visual Sound, designed the One-Spot and is always on the lookout for incompatibilities between PSUs and pedals. They used to have a document on their website listing known compatibilities and incompatibilities. Don't know if its still there.

But certainly try a non-switching PSU first and see if that helps.
 

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Even if it made a difference why would it go from silent to barage of noise?
A ring modulator will produce the sum and difference of a carrier and modulator frequency. So, take a 1khz tone, and modulate it with 50hz and you get 950hz and 1050hz added to the 1khz and 50hz. These are referred to as sideband products.

The spikes on power lines can interact the same way. The spikes from each device/source may be way above human hearing range, so the pedal sounds quiet, even though it is still generating lots of spikes on the power line. But let's say one of the many clock pulses in the power supply is at 90khz, and the flanger is also generating clock pulses at a similar range (e.g., 70-100khz). You won't hear their sum, but goshdarnit, you will likely hear their difference. All of a sudden noise well outside the hearing range gets tossed well into hearing range,and stuff that used to be dead quiet suddenly becomes noisy. Trust me, it has been a regular source of complaint, especially among those who brught home a 2nd digital pedal, hooked it up to a shared power source and suddenly started experiencing ungodly noise from pedals that were formerly dead quiet. Actually,they weren't quiet. Theywere just noisy where you couldn't hear.
 
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