Noise issue with 8Khz - on Boss me 25

[splashsky]

Need some help on this.. on how to cut the noise please

The Output from My Boss Me-25 guitar processor seems to send a high pitch sound around 8 Khz.. tried the following

1. Changed the power supply to different adaptor
2. Used only battery
3. Bypassed to the tuner mode (no effects etc.,)
4. Changed cables
5. used wireless guitar system

Since the issue prevails..

- I tried the low pass filter circuit with TL071 but did not work.. ( not sure if I created correctly).
used tripod for resistor.

see below for scans

 

[betwixt]

I downloaded the service manual, it uses a DSP and doesn't seem to have anything oscillating at 8Khz so fault finding would be very difficult unless you have good test equipment.

Brian.

 

[dick_freebird]

I suggest replacing the guitar with a basic dynamic microphone
and see if the noise changes. I only ever took apart one
electric guitar but what I saw for the wires, caps, pots and
pickups inside makes me think about stray coupling and
oscillation.

 

[splashsky]

I suggest replacing the guitar with a basic dynamic microphone
and see if the noise changes. I only ever took apart one
electric guitar but what I saw for the wires, caps, pots and
pickups inside makes me think about stray coupling and
oscillation.

Tried multiple guitar as well..!

 

[splashsky]

I downloaded the service manual, it uses a DSP and doesn't seem to have anything oscillating at 8Khz so fault finding would be very difficult unless you have good test equipment.

Brian.

I dont mind using a external filter if that'd help.. but not very sure on what to use.. may be a eq

 

[barry]

I dont mind using a external filter if that'd help.. but not very sure on what to use.. may be a eq

That’s a band-aid, not a solution.
Since it also has that 8KHz signal even in tuner mode, I would suspect a problem in your output stage. ( I’m presuming that, like most inline guitar tuners, the input signal does not propogate to the output when enabled). Maybe a bad compensation cap somewhere, but 8 KHz sounds kind of low to be an oscillation, but you never know.

 

[splashsky]

That’s a band-aid, not a solution.
Since it also has that 8KHz signal even in tuner mode, I would suspect a problem in your output stage. ( I’m presuming that, like most inline guitar tuners, the input signal does not propogate to the output when enabled). Maybe a bad compensation cap somewhere, but 8 KHz sounds kind of low to be an oscillation, but you never know.

I agree Barry - its a pain in the "dash" - I wanted to try out other pedals but cost wise everything is a nightmare.. - unsure how to proceed otherwise.. its like finding needle in the hay stack...

service manual is nice.. to test.. but even if I do.. unsure how to fix - or where to look..

 

[FvM]

It's not clear how the 8 kHz tone is related to input signal and connected source. I'd expect that it's also present without signal?

 

[splashsky]

It's not clear how the 8 kHz tone is related to input signal and connected source. I'd expect that it's also present without signal?

I need to recheck.. but last time it was present without connecting a guitar..
The guitar processor turns on after the input 6.5 pin is inserted..

 

[betwixt]

Just a guess- 8KHz sounds like it could be a sampling rate or divided clock frequency. Is the manufacturer still around?

Brian.

 

[splashsky]

Just a guess- 8KHz sounds like it could be a sampling rate or divided clock frequency. Is the manufacturer still around?

Brian.

Its Boss me 25

 

[D.A.(Tony)Stewart]

I wonder if headphones, or a fresh battery, or anything else makes any difference to the pitch or amplitude.

 

[splashsky]

I wonder if headphones, or a fresh battery, or anything else makes any difference to the pitch or amplitude.

I guess it does - very mindly lower in Phones out and (tried batteries)

 

[FvM]

The guitar processor turns on after the input 6.5 pin is inserted..

I know, you can insert a bare plug without cable for test.

 

[KlausST]

I know, you can insert a bare plug without cable for test.

.. and do a test on
* open signal input
* short circuited signal input

Klaus

 

[splashsky]

Ok will update..!

--- Updated Aug 1, 2024 ---

No luck.. - i'll see if Service testing as per the service manual would help.. but dont have osiloscope