Annoying electrical noise from Slim Phatty output-

[Voltor07]

What is your current setup? Do you have a USB mixer? This is very troubling indeed. I'm wondering if a USB mixer would help, because then the audio wouldn't be going straight into the soundcard. Would the whine be lessened if the audio was coming from a mixer? I have no idea.

[ttoxique]

The whole purpose of the new PreSonus sound card was so that I could individually route all three of my instruments to separate channels in Logic. USB Mixers with single outputs would be useless to me, and something like the MultiMix8 by Alesis would be the same technology as my PreSonus, with simply faders and EQs added.

[Voltor07]

Ok, point taken...this has me stumped.

[Mr Shave]

I would try a Ferrite choke on the audio cable...

[ttoxique]

I would try a Ferrite choke on the audio cable...

Will audio cables with a Ferrite choke affect the audio? Please excuse my ignorance on the subject.

Looking into it further, the noise now happens even if the Moog is off- though only when the power adapter for it is in.

[Voltor07]

I would try a Ferrite choke on the audio cable...

Will audio cables with a Ferrite choke affect the audio? Please excuse my ignorance on the subject.

Looking into it further, the noise now happens even if the Moog is off- though only when the power adapter for it is in.

AH HA! Faulty power supply! Try replacing the power adapter, and see if the noise goes away.

[Mr Shave]

I thought the slim had an integral power supply in the unit... Try a different cable, and if that doesnt make it go away, then maybe the power supply inside is defective?

As for ferrite chokes, no, they wont affect the audio, at least not in a way that is audible to you... They act as low pass filter, but with a cutoff freq way higher than what you can hear. In my experience, some devices can take that high freq noise and they will demodulate them into something that is in the audio spectrum... The chokes will SOMETIMES help to relieve that. But not always.

You can also try the choke on the power cable. Currently in my studio i have chokes on the audio cables going to my monitors (for some reason they are demodulating NPR on FM 90.3 station in town), and on the power cable to the voyager... They help, its not perfect, and i still get noise, but they help.

Cheers

[ttoxique]

I thought the slim had an integral power supply in the unit... Try a different cable, and if that doesnt make it go away, then maybe the power supply inside is defective?

Yes, power supply was the wrong word; it's just a power extension cable.

As for ferrite chokes, no, they wont affect the audio, at least not in a way that is audible to you... They act as low pass filter, but with a cutoff freq way higher than what you can hear. In my experience, some devices can take that high freq noise and they will demodulate them into something that is in the audio spectrum... The chokes will SOMETIMES help to relieve that. But not always.

You can also try the choke on the power cable. Currently in my studio i have chokes on the audio cables going to my monitors (for some reason they are demodulating NPR on FM 90.3 station in town), and on the power cable to the voyager... They help, its not perfect, and i still get noise, but they help.

Cheers

Any ideas on where I might purchase choked instrument or power cables? I'll shop around myself as well.

[Voltor07]

If it IS the power supply, it should still be under warranty. It's possible a capacitor or two is bad. Sometimes that happens in electronics, even new ones.

[ttoxique]

Sorry for the lack of updates everyone, and thanks for your help!

I ended up purchasing a clip-on ferrite choke to no avail; I've tried it on the Moog's power chord as well as the instrument cable with no filteration.

I'm now running a more complicated I/O setup- my instruments (including the Moog) go into my PreSonus, which goes via FireWire to my Macbook, which outputs via USB to my Traktor S2, which outputs via instrument cables directly to my Rokit monitors. The digital hash and whine are still there- slightly dampened, but still just as annoying and unusable as before.

I've now narrowed down exactly when the problem occurs:
-The Moog is plugged into any of the PreSonus sound interfaces inputs, wether it's off or on.
-Problem does NOT occur if the Moog is unplugged from a power source.
-Problem does NOT occur if the Moog is connected directly to a Rokit monitor.

Are there any other ideas on how I could fix this- perhaps some cable that'd fix/clean the power going to the Moog- or is it time to call Moog tech support?

Does anyone with a background in electronics have an idea on what is causing the problem? Based on when it occurs, I'm guessing that the Moog's noisy electrical line is somehow reflecting noisy electricity from the sound interface in a loop, but this is a guess with little foundation in how circuitry actually works.

[Voltor07]

Based on when it occurs, I'm guessing that the Moog's noisy electrical line is somehow reflecting noisy electricity from the sound interface in a loop, but this is a guess with little foundation in how circuitry actually works.

This sounds like a reasonable explanation.

[c7sus]

Any chance you have a passive DI and can put it between the Phatty and a mic input on the Presonus? The transformer in a passive DI may help solve a ground loop problem.

Also, do you have lighting dimmers or flourescent lighting in the room?

Lastly, do you have the same problem when using the Macbook plugged in to house power and also when using battery power only?

[ttoxique]

Any chance you have a passive DI and can put it between the Phatty and a mic input on the Presonus? The transformer in a passive DI may help solve a ground loop problem.

Also, do you have lighting dimmers or flourescent lighting in the room?

Lastly, do you have the same problem when using the Macbook plugged in to house power and also when using battery power only?

Unfortunately I don't have a DI box, put perhaps picking up a cheaper one would be a good idea?

There are no dimmers and the lighting is not fluorescent. Also, the problem occurs with house power or with battery power to the MacBook.

[c7sus]

After doing a google search about LP grounding and reading numerous threads from this site on the topic I would suggest a passive DI as a starting point for a fix.

It appears that lifting the ground on the LP power source would only cause more problems.

The Radial JDI is an excellent DI choice, however it is also $200! Maybe try a less expensive Whirlwind and see if that gets you closer to noise-free audio.

[ttoxique]

What is it about the DI that'll solve my problem? Will a cheap passive DI work for this? I see a lot of cheaper DIs roll off at 50 Hz, and considering how I tend to use my Moog solely for bass patches it makes me a bit uneasy.