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Old 02-05-2018, 05:02 PM
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SprintBob SprintBob is offline
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Default Hum/Ground Loop Troubleshooting (Tonedexter content)

So yesterday I set up my new Tonedexter (TD) to start learning how to use it and generate the Wavemaps for my collection.

My setup was guitar pickup to input on TD via a 1/4" TS cable, Shure KSM137 mic for getting the mic'd sound from the guitar to the TD via an XLR cable, and a pair of headphones connected to the TD 1/4' monitor headphone jack.

First up was my Jake Robinson 12 fret dread that I had a passive K&K pickup installed. The whole process following the TD instructions went smoothly and I was very happy with the end result of how much the Wavemap sounded like the mic'd guitar.

Next up was my 2017 Taylor K22 12 fret with the ES2 active EQ/pickup. Setup on the guitar was to center all the ES2 knobs as recommended in the TD user guide. When I put the headphones on to monitor the mic'd signal, there was a healthy amount of hum heard and that hum practically stopped if I put my finger on the metal outer frame of the TD. The hum led to a poor sounding Wavemap and I think the hum is interfering with the TD's software algorithms in properly processing the mic signal and creating an accurate Wavemap.

I then tried the same on my 2014 Taylor 812ce 12 fret and the same happened but the hum was not as prominent and the Wavemap was a bit better but not near the result I got with the Robinson/K&K combo. Again, placing my finger on the TD frame pretty much stops the hum.

So it appears the power to the TD is not grounded properly. The power comes out of a wall socket and goes to a grounded power strip that primarily has battery charging duties as well as keeping a trickle charger going for my Ernie Ball string winder. There is a ground light on the power strip and it is it green meaning the ground is functioning. The AC-DC power supply for the TD is a TRIAD WS2U120-0700 with input requirement of 100-240VAC/50-60 hz and output of 12VDC, .7A. This power supply only has a two prong (neutral/hot) plug into my power supply so this leads me to believe the circuit to the TD is not grounded and that is the reason for the hum I hear with the active ES2 system. I wonder if the active ES2 and the TD are "competing" to find a ground in the loop and that is the source of the issue.

Would finding a AC-DC adapter with a ground prong solve the issue?

All feedback appreciated.
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Collings OM1AH (Adi/Mahogany)
Cordoba GK Pro Negra (Spruce/EIR)
Froggy Bottom H-12 (Adi/EIR)
Rainsong P-12 (all carbon fiber)
Robinson 12 Fret SS Dread (Spruce/Mahogany)
Santa Cruz Skye 00 (Adi/Coco)
Taylor 714ce 12 fret (Cedar/Koa)
Taylor K-22ce 12 fret (all Koa)
Taylor 562ce 12 fret (all Mahogany)
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  #2  
Old 02-05-2018, 05:33 PM
James May James May is offline
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Join Date: Dec 2015
Location: Nevada City, CA
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Quote:
Originally Posted by SprintBob View Post
So yesterday I set up my new Tonedexter (TD) to start learning how to use it and generate the Wavemaps for my collection.

My setup was guitar pickup to input on TD via a 1/4" TS cable, Shure KSM137 mic for getting the mic'd sound from the guitar to the TD via an XLR cable, and a pair of headphones connected to the TD 1/4' monitor headphone jack.

First up was my Jake Robinson 12 fret dread that I had a passive K&K pickup installed. The whole process following the TD instructions went smoothly and I was very happy with the end result of how much the Wavemap sounded like the mic'd guitar.

Next up was my 2017 Taylor K22 12 fret with the ES2 active EQ/pickup. Setup on the guitar was to center all the ES2 knobs as recommended in the TD user guide. When I put the headphones on to monitor the mic'd signal, there was a healthy amount of hum heard and that hum practically stopped if I put my finger on the metal outer frame of the TD. The hum led to a poor sounding Wavemap and I think the hum is interfering with the TD's software algorithms in properly processing the mic signal and creating an accurate Wavemap.

I then tried the same on my 2014 Taylor 812ce 12 fret and the same happened but the hum was not as prominent and the Wavemap was a bit better but not near the result I got with the Robinson/K&K combo. Again, placing my finger on the TD frame pretty much stops the hum.

So it appears the power to the TD is not grounded properly. The power comes out of a wall socket and goes to a grounded power strip that primarily has battery charging duties as well as keeping a trickle charger going for my Ernie Ball string winder. There is a ground light on the power strip and it is it green meaning the ground is functioning. The AC-DC power supply for the TD is a TRIAD WS2U120-0700 with input requirement of 100-240VAC/50-60 hz and output of 12VDC, .7A. This power supply only has a two prong (neutral/hot) plug into my power supply so this leads me to believe the circuit to the TD is not grounded and that is the reason for the hum I hear with the active ES2 system. I wonder if the active ES2 and the TD are "competing" to find a ground in the loop and that is the source of the issue.

Would finding a AC-DC adapter with a ground prong solve the issue?

All feedback appreciated.
This is a known "non issue" of sorts. There is a mention of it in the user guide. When using only headphones and no other connection from either of ToneDexter's outputs, under some conditions you may hear hum. You are correct in thinking that it is because the power supply is a 2 prong floating type.

The problem should completely go away if you plug either the 1/4" output or the XLR output into something such as a grounded amplifier or mixer. This will be the normal case for performance. Let us know if that doesn't fix things.
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Audio Sprockets
maker of ToneDexter
James May Engineering
maker of the Ultra Tonic Pickup
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  #3  
Old 02-05-2018, 06:50 PM
SprintBob's Avatar
SprintBob SprintBob is offline
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Join Date: Sep 2013
Location: Covington, LA
Posts: 2,178
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Quote:
Originally Posted by James May View Post
This is a known "non issue" of sorts. There is a mention of it in the user guide. When using only headphones and no other connection from either of ToneDexter's outputs, under some conditions you may hear hum. You are correct in thinking that it is because the power supply is a 2 prong floating type.

The problem should completely go away if you plug either the 1/4" output or the XLR output into something such as a grounded amplifier or mixer. This will be the normal case for performance. Let us know if that doesn't fix things.
That fixed it. Thanks for the quick reply!
__________________
Collings OM1AH (Adi/Mahogany)
Cordoba GK Pro Negra (Spruce/EIR)
Froggy Bottom H-12 (Adi/EIR)
Rainsong P-12 (all carbon fiber)
Robinson 12 Fret SS Dread (Spruce/Mahogany)
Santa Cruz Skye 00 (Adi/Coco)
Taylor 714ce 12 fret (Cedar/Koa)
Taylor K-22ce 12 fret (all Koa)
Taylor 562ce 12 fret (all Mahogany)
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