Noise in DAW when charging Macbook

DarrellV

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Right on, I'm ordering some now. Do these typically clamp down on any size charging cable? My mac charger comes in two parts, one has a thicker 5mm cable, which plugs into the transformer and a 3.5mm cable with a magnet end that attaches to the macbook.
You should only need one for the side that goes into the computer... the 3.5mm side.
 

Freddy G

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Darrell nailed it upstream. It's the switching power supply. Not designed with audio in mind. Use a proper audio interface (built in computer audio stinks)
Nothing cleaner than battery power though if you are not going to use an external interface.
 

northernguitarguy

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Darrell nailed it upstream. It's the switching power supply. Not designed with audio in mind. Use a proper audio interface (built in computer audio stinks)
Nothing cleaner than battery power though if you are not going to use an external interface.
Thanks, @Freddy G . I do have an interface, a Presonus Inspire 1394. It has two 1/4" / XLR inputs and two RCA inputs. Which input should I be using for a send from the Two Notes Torpedo Captor loadbox? It would be easy to just patch into one of the 1/4" inputs, but they are meant for a direct guitar or mic input. Will it work with the line level signal coming from the Captor?

I just sent the same unit to @DarrellV . What do you say?

Here's a pic of the unit, and the virtual mixer I use with it.

 

Freddy G

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the Captor only has balanced outputs? Try going into the XLR mic pres on the Presonus....you'll probably have to cut the gain way down though. If you can go unbalanced then the Presonus does have switchable line/phono inputs. Switch to "line"
 

northernguitarguy

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the Captor only has balanced outputs? Try going into the XLR mic pres on the Presonus....you'll probably have to cut the gain way down though. If you can go unbalanced then the Presonus does have switchable line/phono inputs. Switch to "line"
Yes, the Captor only has a balanced output. I'll try using the 1/4 input so it's an easy direct patch.
 

KP11520

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I'd bet after a search, you'd find Audio Industry Aftermarket P/S manufacturers that sell much cleaner power supply options for Macbooks and laptops. Maybe under noiseless?
 
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northernguitarguy

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You'll be fine using the 1/4" input, Captor can output XLR or 1/4" balanced line level.
Yes, and the XLR/ 1/4” input on the PreSonus is balanced. My concern is the inputs are mic level whereas the Captor sends a line level signal.
 

northernguitarguy

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OK, I know the solution was under my nose the whole time, but I fuckin' love you guys for pointing this out. Using the PreSonus, I was getting a very quiet, normal amp hum when using my Orange. The guitar can hang on me without my hands on it and it's and there's no feedback. On the cleaner 'Natural' channel it's even quieter. B-I-N-G-O!

I'm gonna play with the Gibson LP Special tonight. I haven't played on P90s since using this setup. :dude:
 

spitfire

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Sounds like a possible ground loop. The Mac power supply is grounded when plugged into the wall, this may ground the Mac as well. Your pedal board power supply is grounded as well. Unless your pedal board supply is an isolated type, many are, many are not, then you have two points in your system that are grounded.

The result is noise currents flow around the ground loop. The noise could be from the Mac supply or just about anything in the room. Just plugging in the Mac supply may be creating the loop, this doesn't mean the Mac supply is the noise source.

The problem with guitar rigs is the cable shield is grounded, but this shield is also the signal return. It's every bit in the signal loop as the actual signal on the tip of a 1/4" plug. So any noise currents that flow through a loop that includes the guitar signal and a typical guitar cord (not XLR), will cause the noise current to share the signal path and generate a voltage that adds to your signal.

Again, try an isolated pedal board power supply. Before spending money on one, try running the pedal(s) on batteries with nothing on the pedal board connected to the pedal board supply. And unplug the pedal board supply from AC power, just to be extra sure.

If the noise goes away, then you've proven that a ground loop is the issue. Then you can be confident that spending money on an isolated pedal board supply will solve your problem.

Of course, maybe you have other things in the circuit that also connect to ground. And by connected to ground, I mean AC power ground. I'm just assuming a simple guitar->pedal board-.Mac configuration. You listed other things, like an amp I think. The amp is certainly grounded and this will create another ground loop. If you must have an amp connected and maybe other things, it's not realistic to break all these ground loops. Though you could lift the ground pin on some of them, but this defeats the safety aspect of grounding the equipment.

The next strep is to to break the ground loops using XLR cables or a stereo cable. These will get you +signal, -signal (signal return) and ground/shield. The signal return is NOT using the grounded shield.

For example, if you use an isolated pedal board power supply, then go to your amp, no ground loop yet, but then if you're taking some signal from the amp, or splitting the signal going to the amp and sending it to the Mac, you want to use an XLR type connection AND ONLY connect the shield of this cable at one end. This works because both ends are already grounded. DON'T do this if either end doesn't have it's own ground. That might happen when you are not using the Mac power supply.

Even if you can't break a ground loop, XLR typo connections are still very helpful. You will still have ground loops, but the noise currents run in the shields and the signal does not.

Best thing is to make drawing of your rig's layout and note where all the signals go AND the return signal loops. Every signal is a loop. You want to make sure your signal loop NEVER shares a wire (usually a shield) with a ground loop. Also, keep in mind a ground loop doesn't have to be a loop through the AC wall ground. You can create ground loops in your own signal path if you get complicated.

I know a wall of words like this can be hard to understand, but I hope some of it made sense.
 

northernguitarguy

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Sounds like a possible ground loop. The Mac power supply is grounded when plugged into the wall, this may ground the Mac as well. Your pedal board power supply is grounded as well. Unless your pedal board supply is an isolated type, many are, many are not, then you have two points in your system that are grounded.

The result is noise currents flow around the ground loop. The noise could be from the Mac supply or just about anything in the room. Just plugging in the Mac supply may be creating the loop, this doesn't mean the Mac supply is the noise source.

The problem with guitar rigs is the cable shield is grounded, but this shield is also the signal return. It's every bit in the signal loop as the actual signal on the tip of a 1/4" plug. So any noise currents that flow through a loop that includes the guitar signal and a typical guitar cord (not XLR), will cause the noise current to share the signal path and generate a voltage that adds to your signal.

Again, try an isolated pedal board power supply. Before spending money on one, try running the pedal(s) on batteries with nothing on the pedal board connected to the pedal board supply. And unplug the pedal board supply from AC power, just to be extra sure.

If the noise goes away, then you've proven that a ground loop is the issue. Then you can be confident that spending money on an isolated pedal board supply will solve your problem.

Of course, maybe you have other things in the circuit that also connect to ground. And by connected to ground, I mean AC power ground. I'm just assuming a simple guitar->pedal board-.Mac configuration. You listed other things, like an amp I think. The amp is certainly grounded and this will create another ground loop. If you must have an amp connected and maybe other things, it's not realistic to break all these ground loops. Though you could lift the ground pin on some of them, but this defeats the safety aspect of grounding the equipment.

The next strep is to to break the ground loops using XLR cables or a stereo cable. These will get you +signal, -signal (signal return) and ground/shield. The signal return is NOT using the grounded shield.

For example, if you use an isolated pedal board power supply, then go to your amp, no ground loop yet, but then if you're taking some signal from the amp, or splitting the signal going to the amp and sending it to the Mac, you want to use an XLR type connection AND ONLY connect the shield of this cable at one end. This works because both ends are already grounded. DON'T do this if either end doesn't have it's own ground. That might happen when you are not using the Mac power supply.

Even if you can't break a ground loop, XLR typo connections are still very helpful. You will still have ground loops, but the noise currents run in the shields and the signal does not.

Best thing is to make drawing of your rig's layout and note where all the signals go AND the return signal loops. Every signal is a loop. You want to make sure your signal loop NEVER shares a wire (usually a shield) with a ground loop. Also, keep in mind a ground loop doesn't have to be a loop through the AC wall ground. You can create ground loops in your own signal path if you get complicated.

I know a wall of words like this can be hard to understand, but I hope some of it made sense.
Thank you! Good read, I appreciate all the info. I found my solution by patching in through a PreSonus interface. Plays whisper quiet now, at least on the clean channel. Normal amp-hum on the dirt channel.
 


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