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Output Noise

Output Noise
« on: July 25, 2017, 07:33:53 AM »
Just received my REV2 (yay) and the first thing since plugging it in is a fairly high noise out of all outputs. Not something I've experienced with a Prophet 06. Noise stays static even when the unit is turned off - only disappears when I unplug the unit.

Did find a lot of talk about the headphone noise, but this feels pretty different and recording some sub sounds in it is highly noticeable.

Anyone had a similar problem? 

Re: Output Noise
« Reply #1 on: July 25, 2017, 08:37:16 AM »
Just received my REV2 (yay) and the first thing since plugging it in is a fairly high noise out of all outputs. Not something I've experienced with a Prophet 06. Noise stays static even when the unit is turned off - only disappears when I unplug the unit.

Did find a lot of talk about the headphone noise, but this feels pretty different and recording some sub sounds in it is highly noticeable.

Anyone had a similar problem?

Sounds like a grounding / cable problem, not an electronic one.
Sequential / DSI stuff: Prophet-6 Keyboard with Yorick Tech LFE, Prophet 12 Keyboard, Mono Evolver Keyboard, Split-Eight, Six-Trak, Prophet 2000

Re: Output Noise
« Reply #2 on: July 25, 2017, 11:46:22 AM »
Have you updated the firmware, sounds like a good place to start.
Synth Arsenal - Access Virus TI Polar, Moog Sub37, Nord A1, Nord Wave, DSI Prophet REV2, Roland TR8, Ableton Push 2

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Re: Output Noise
« Reply #3 on: July 25, 2017, 01:51:03 PM »
As stated above, you probably need a Ground Loop Eleminator.

I use the following one on my P12 Desktop and it works flawlessly.

https://www.amazon.com/gp/aw/d/B0002E4YH4/

Expensive, but so worth it!




MILKY WAY STUDIO | Galaxy Class Sound

Re: Output Noise
« Reply #4 on: July 27, 2017, 03:15:58 AM »
Ground loop it is.. surprising is the way it happens - stripped the whole setup into following :

Rev2 ->
UAD Apollo Twin (Thunderbolt) ->
TB to laptop

Whenever one plug is disconnected (Laptop power / Thunderbolt / TS)
the noise disappears so definitely dealing with a ground loop.

Thing is - this has never happened with a P6 or a Voyager, which I assume would have to create a similar loop? Might be my lack of knowledge reg electricity in play too, this appeared for the first time using the Rev2.



kobuz

Re: Output Noise
« Reply #5 on: July 27, 2017, 05:45:01 AM »
If possible, try putting the laptop power into another wall socket than the rest. This has been helpful with  grounding problems at my place.

Re: Output Noise
« Reply #6 on: July 27, 2017, 02:49:56 PM »
Here's the info we give customers regarding ground loops, some of which has already been suggested. Something in here will solve the issue for sure though:

Try changing your plug configurations for the synth and your laptop, i.e. try unplugging your laptop from the wall and see if the problem still exists, and try plugging your DSI synth and the computer into the same outlet. You can also try using a surge protector/power conditioner, try powering your audio interface with a wall plug if it is bus powered normally, try plugging your DSI synth into a different USB port, use a different or shielded USB cable, or try a USB hub if you haven't already.


If none of the above suggestions work, users have had good results using the following method. You must have an extra USB cable you don't mind modifying:

* Using wire strippers and/or wire cutters, Strip away a 10-15mm section of the rubber coating in the middle of the USB cable to expose the braided shielding.
* With the wire cutters, carefully cut the shielding away entirely, exposing the 4 wires surrounded by the shield.
* Make sure the shield is completely disconnected. Verify this by testing for continuity on both metal ends of the cable.
* Cut the black wire, which is connected to pin #4 and represents ground. This creates a "ground-lift".
* Fold the ground wire back and out of the way, then wrap the exposed section of the USB cable with electrical tape. Your ground noise should be gone.


If you'd rather not try a DIY fix, some companies also make USB signal isolators. Here are some examples:

**USA**  USB signal isolator

**EU**  USB signal isolator


You can read more about locating and eliminating ground loops in your system at the following web link (PDF file):

Understanding & Eliminating Ground Loops
SEQUENTIAL