'Hum' on synth audio lines into Traveler

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Discussion related to installation, configuration and use of MOTU hardware such as MIDI interfaces, audio interfaces, etc. for Mac OSX
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artfarm1
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'Hum' on synth audio lines into Traveler

Post by artfarm1 »

I was gone for a few days, and shut off my studio.

Now, upon re-boot, I have an audible 'hum' coming from my hardware synth line-in's attached to line inputs on my Traveler (Mk I, extremely reliable!)

I have:
- turned power off of synth; 'humm' still there
- tried different electrical outlets; tried same power bar outlets; 'humm' still there'
- tried switching audio line cables; 'humm' still there

When I turn off the Traveler, the 'humm' goes away.

When I disconnect audio cables, the 'humm' goes away.

When I use the 'Neutrix type' audio ins, the 'humm goes away. The hum is still there when I use another pair of regular audio inputs.

In 'CueMix', if I change from '-10db' input on the channel to '+4db', the 'humm' is 99.9% gone.

Any electrical gurus have some ideas to troubleshoot?

(is this some kind of ground loop? should I de-oxidize the inputs? something weird going on in my old Roland synth?)

Thanks all!
DP 11, OS Ventura
MacMini 2023 M2Pro, 16 gig RAM, MOTU M6, SSD drives for everything, various sound/sampled libraries from all major vendors, Logic Pro X, DSP-Quattro
MacBook Pro 2015, OSX Monterey, 2.5ghz, 16 gig RAM (w/duplicate software as in MacMini setup)
Trombones: King 2B SilverSonic, King 2B Liberty, & Conn 88H w/Doug Elliott mouthpieces!
http://www.cammillarmusic.com
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HCMarkus
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Re: 'Hum' on synth audio lines into Traveler

Post by HCMarkus »

Do you have another source that you can use to test the line ins on the Traveler? If so, do it. If the hum is not present, using the cables with which you connect the Roland, you will have shown the Roland is the culprit. Is the hum present on headphones connected to the Roland headphone jack?
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guitardood
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Re: 'Hum' on synth audio lines into Traveler

Post by guitardood »

I had a similar problem going from my Yamaha S-80 and a friend's Motif into one of my 2408mk3 interfaces. As much as the electrical guys will say not to, the only solution that got rid of the hum was a ground lift and polarity reversal at the keyboards plug. This was with all devices plugged into the same power strip.

DISCLAIMER: I can't vouch for the safety of doing as it is typically frowned upon by electrician folks, but: I didn't experience any adverse problems and the hum went away. Try at your own risk or consult an electrician.
________________________________________________________________________
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Guitardood

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"Life is like a box of chocolates. You know, eventually you're going to get the one filled with alien-like nasty tasting goo and have to spit it out and say YUCK".
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HCMarkus
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Re: 'Hum' on synth audio lines into Traveler

Post by HCMarkus »

guitardood wrote:I had a similar problem going from my Yamaha S-80 and a friend's Motif into one of my 2408mk3 interfaces. As much as the electrical guys will say not to, the only solution that got rid of the hum was a ground lift and polarity reversal at the keyboards plug. This was with all devices plugged into the same power strip.

DISCLAIMER: I can't vouch for the safety of doing as it is typically frowned upon by electrician folks, but: I didn't experience any adverse problems and the hum went away. Try at your own risk or consult an electrician.
Another good fix is cut ground wire and shield on USB cable; I've had that issue with my Motif and S90 and the USB mod took care of the problem without reversing hot and cold. The concern when reversing polarity is the on off switch is not disconnecting the hot lead, posing a real safety issue.

This is the reason the MIDI standard requires optical isolators; no potential for ground loops!
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guitardood
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Re: 'Hum' on synth audio lines into Traveler

Post by guitardood »

HCMarkus wrote:
guitardood wrote:I had a similar problem going from my Yamaha S-80 and a friend's Motif into one of my 2408mk3 interfaces. As much as the electrical guys will say not to, the only solution that got rid of the hum was a ground lift and polarity reversal at the keyboards plug. This was with all devices plugged into the same power strip.

DISCLAIMER: I can't vouch for the safety of doing as it is typically frowned upon by electrician folks, but: I didn't experience any adverse problems and the hum went away. Try at your own risk or consult an electrician.
Another good fix is cut ground wire and shield on USB cable; I've had that issue with my Motif and S90 and the USB mod took care of the problem without reversing hot and cold. The concern when reversing polarity is the on off switch is not disconnecting the hot lead, posing a real safety issue.

This is the reason the MIDI standard requires optical isolators; no potential for ground loops!
That's interesting. In my case I wasn't using a USB connection, but had S-80's MIDI IN/OUT connected to the MIDI timepiece, which was then connected via USB to the system and the Motif's MIDI IN/OUT to an M-AUDIO 6-port USB-MIDI box via USB to the system. I wonder if I would have had success cutting the ground and shield on the MIDI cables? Probably not the USB ->MIDI Interface grounds and shields? Never even thought about the MIDI ports being a ground loop potential, son of a gun!

Sorry artfarm1, don't mean to hog your thread, dude.
________________________________________________________________________
Best,
Guitardood

Chuck Fletcher on Reverb Nation
Chuck Fletcher on Facebook


"Life is like a box of chocolates. You know, eventually you're going to get the one filled with alien-like nasty tasting goo and have to spit it out and say YUCK".
artfarm1
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Re: 'Hum' on synth audio lines into Traveler

Post by artfarm1 »

Problem solved!

Turns out it was a strange 'MIDI Loop' problem.

Thanks to all for the various advice. I did even run the Traveler from Firewire bus power just to check that too, and this was a good excuse to tidy up all my power and audio lines.

But, I'd been trying some 'fancy' MIDI merging, etc. with some outboard gear, and somehow created a 'MIDI loop' of some kind.

Glad to know it wasn't any internal Traveler or Roland synth problem. The 'old stuff' just keeps on working!
DP 11, OS Ventura
MacMini 2023 M2Pro, 16 gig RAM, MOTU M6, SSD drives for everything, various sound/sampled libraries from all major vendors, Logic Pro X, DSP-Quattro
MacBook Pro 2015, OSX Monterey, 2.5ghz, 16 gig RAM (w/duplicate software as in MacMini setup)
Trombones: King 2B SilverSonic, King 2B Liberty, & Conn 88H w/Doug Elliott mouthpieces!
http://www.cammillarmusic.com
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