How to eliminate Bluetooth noise in electric guitar

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luna5
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How to eliminate Bluetooth noise in electric guitar

Unread post by luna5 » Fri Jan 20, 2017 8:55 am

After learning more about this problem, I have continued this question here.

I am trying to remove noise from an electric-guitar circuit that I have created called the ArduGuitar. My circuit comprises 2 opto-isolated parts: the audio circuit between the guitar pickups and the output jack, and the control circuit consisting of an Arduino Micro and a Roving Networks RN42 bluetooth module powered by a 9V battery.

A full description is available on the ArduGuitar webpage but in brief, I wrote an Android App that sends controls over bluetooth to the Arduino via the RN42 bluetooth module. The Arduino interprets the commands and adjusts PWM signals on its output pins to control Vactrol (LED-LDR) LEDs which change the resistances attached to the pickup outputs. Thus, I simulate potentiometers and switches, just as per an "normal" electric guitar circuit, while keeping the analog audio fully opto-isolated from the digital control circuit.

Globally, this works very well and I am happy with the result which I would say scores 90% of perfect.

However, despite the use of all shielded cables and a fully shielded RN42 bluetooth module, significant noise still gets into the audio and comes out the amp. This noise is of 2 kinds:

whistling: this is present as soon as the bluetooth is switched on. I have done extensive testing of the use of capacitors across VCC/GND to try to filter this but it all fails. This noise is not very strong, but significant;
clicking: at each data transmission, a click comes out over the audio. It is not very loud, but significant nevertheless.
I use all shielded cables and wiring internally on the audio circuit.

The noise level changes depending on where I position the Bluetooth module, and strangely, the best result seems to be when the module is inside the guitar electronics bay (which is unshielded). The worst result is when the bluetooth module is close to the guitar output cable that connects to the amp.

I have been working on the problem for several months and am now at a loss as to how to proceed...

I wonder how this problem is handled in wireless guitar systems?

Would anyone have any ideas as to how to reduce or eliminate this noise?

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Buzzard
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Re: How to eliminate Bluetooth noise in electric guitar

Unread post by Buzzard » Fri Jan 20, 2017 10:31 am

Welcome to the Yamaha Forums. :D

That's an interesting project 8) do you have any pictures of the circuits mounted in a guitar ?
Does it require routing and drilling to get space for circuit boards, battery and switches ?
If all the devices are built close together in the guitar body, you're likely to get noise/interference.

Being a keen, but not very skilled guitarist, I really don't bother with wireless gear that doesn't work 100%

Instead of trying to reinvent a wireless system, I buy one that has proven reliability, and worth it's price.

:idea: Have a look at the gear I have used: viewtopic.php?t=8892 :idea:

I can highly recommend the Line6 Relay G10, but there's lots of good gear costing less.

I avoid using Bluetooth, it tends to cut out and/or loose connection,
generally disturbed by other Bluetooth devices.

Best Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: viewtopic.php?f=24&t=7004 :idea:

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Saul
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Re: How to eliminate Bluetooth noise in electric guitar

Unread post by Saul » Fri Jan 20, 2017 10:51 am

Not being an electronics engineer I can't help although we do have some people on the forum who no doubt would be able to contribute.

I think the thing luna5 is trying to do is use 'Bluetooth' which is different from more traditional wireless systems. I only have limited experience of bluetooth in guitars and that was with the Fishman Triple Play, which worked fine in terms of no latency or noise but was difficult to control in terms of sound.

Personally I am with Peter on this one. There are already some great wireless systems out there and the Line 6 Relay G10 would get my vote...and my money :)
Saul
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Re: How to eliminate Bluetooth noise in electric guitar

Unread post by jeff-carolina » Fri Jan 20, 2017 12:54 pm

Here is a video where the originator of the project explains how he solved these problems. Hope it helps


https://www.youtube.com/watch?v=vYXJW2Wdejc
Last edited by Buzzard on Fri Jan 20, 2017 1:11 pm, edited 1 time in total.
Reason: embedding youtubeclip directly into topic

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Re: How to eliminate Bluetooth noise in electric guitar

Unread post by Buzzard » Fri Jan 20, 2017 2:20 pm

Aha ....... now I get it ....... VERY innovative and cool tech, however .......

First of all, Bluetooth is NOT the most reliable way of transmitting audio signals,
it tends to cut out, disturbed by other Bluetooth devices, and the range is often rather short.
Bluetooth technology will probably improve, but as of now, not reliable enough.

The sound tech in the guitar is impressive ..... but ......
Remote controlling from a phone or a pad is ridiculous.
The standard switches on electric guitars are easily reached, so why should you have to reach for a phone to tweak the sound ?

Of cause, since the knobs have been removed, you can stick your phone to the guitar with velcro, .....
but keeping a phone near pickups will give a lot of unwanted bleebs and noises.

Still, I love the tech, but find the usage somewhat more challenging than using an ordinary twanger.
The built in effects/sounds are fine, and if the guitar is controlled by a footswitch, it would be more user friendly.

:idea: This is not meant to flame the product, but only my personal opinion and possible lack of understanding. :idea:

Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: viewtopic.php?f=24&t=7004 :idea:

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parametric
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Re: How to eliminate Bluetooth noise in electric guitar

Unread post by parametric » Fri Jan 20, 2017 4:58 pm

Buzzard wrote:Of cause, since the knobs have been removed, you can stick your phone to the guitar with velcro, .....
This is precisely what I was referring to in another thread.

Bluetooth being arrogantly fielded as a (flawed - IMO) replacement of something that DOES work - rather than - an ALTERNATIVE (that CAN be

selected, IF desired) . . . :roll:

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Re: How to eliminate Bluetooth noise in electric guitar

Unread post by Buzzard » Fri Jan 20, 2017 11:35 pm

The topic is also discussed here: http://electronics.stackexchange.com/qu ... ric-guitar

Now, these guys know their parts and diagrams, but I've given the issue some more thought.
My simple solution may be TOTALLY wrong, but here goes.

When you install a transmitter AND its antenna close to the audio circuit board and ESPECIALLY the pickups, this could well be the recipe to failure and noise issues.

On other wireless gear for guitars, the transmitter (AND its antenna) is at least installed outside the guitar body.

In conventional gear like the Sennheiser Freeport, the transmitter is usually mounted at the back of the strap, more than a foot (30cm.) away from the guitar.

In the case of the Line6 Relay G-10 , the antenna is closer, but still more than a couple of inches away from the guitar.

Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: viewtopic.php?f=24&t=7004 :idea:

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