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Post subject: Blues Jr High Pitched Whine
Posted: Sat Apr 30, 2016 7:22 pm
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I just got a brand new tweed Blues Jr about 3 weeks ago. Love this amp. The only annoying thing about it (probably not the amp) is the high pitched whine I get when using my strats. It is not doing it with my Les Paul. Basically at high volume levels I get a very high pitched whine that is not terribly loud but enough to be annoying. It is not feedback because it is there when I am muting the strings. Weird thing is it goes away when I roll the tone knob down or turn my body a certain way. It happens on both my Squire strat and the new mexi I just bought. I've tried unplugging all devices in the room I'm in and turning off all the lights. I even tried 3 different rooms in the house and it does the same thing. Anyone have any ideas?


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Post subject: Re: Blues Jr High Pitched Whine
Posted: Sat Apr 30, 2016 8:34 pm
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Do you live in close proximity to above-ground power transmission lines, a commercial broadcast facility, or a cell-phone tower? Your symptoms sound suspiciously like RFI or EMI.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Blues Jr High Pitched Whine
Posted: Mon May 02, 2016 9:01 am
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MikeSt wrote:
I just got a brand new tweed Blues Jr about 3 weeks ago. Love this amp. The only annoying thing about it (probably not the amp) is the high pitched whine I get when using my strats. It is not doing it with my Les Paul. Basically at high volume levels I get a very high pitched whine that is not terribly loud but enough to be annoying. It is not feedback because it is there when I am muting the strings. Weird thing is it goes away when I roll the tone knob down or turn my body a certain way. It happens on both my Squire strat and the new mexi I just bought. I've tried unplugging all devices in the room I'm in and turning off all the lights. I even tried 3 different rooms in the house and it does the same thing. Anyone have any ideas?


Microphonic squeal and feedback doesn't necessarily go away when muting strings. It's the tube itself that's vibrating.


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Post subject: Re: Blues Jr High Pitched Whine
Posted: Mon May 02, 2016 9:14 am
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Hi Arjay and evets618,

Thanks for the replies. I do not live near overhead power lines a broadcast facility or a cell-phone tower so I don't think it is that.

I've tried different pre-amp tubes but haven't tried the power amp tubes yet. I find it hard to believe it is a tube or an amp problem when my Les Paul does not have the high pitched whine. As soon as I roll my tones knobs to about midway on the mexi the high pitched whine goes away but I guess I would expect that with the high-pass filter created when the cap is engaged on the tone pots.


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Post subject: Re: Blues Jr High Pitched Whine
Posted: Tue May 03, 2016 7:04 am
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When you describe moving you body and affecting the noise, you are describing a directional radio antenna.
Your noise is externally generated.
Walking around the neighborhood with a portable radio tuned to no station may find the source..
The most practicle solution if you can't eliminate the source is to use noise cancelling guitar cables.
You can't buy em. You gotta build em.
Get a mike cable and cut off the XLR connectors.
Connect a couple 1/4" jacks to the grounds and white wire.
Connect the black wire to ground on one end and nothing on the other end. Insulate it.
Mark the grounded end as AMP and the ungrounded end as Guitar. It only works in one direction.
The black wire acts as an antenna and inserts the interference 180 degrees out of phase and cancels the noise.
It is effective with radio stations and computer noises. However, strong signals and electric fences are difficult to supress.
If you use pedals, you will need additional cables.
With unshielded hollow body guitars, I have rewired the entire guitar in this manner to quiet them down.
Other measures can include snap-on ferrite cores on the AC cord and the speaker cable.


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Post subject: Re: Blues Jr High Pitched Whine
Posted: Tue May 03, 2016 7:23 am
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TimsAudio,

Thanks for the post and the cable idea!

As soon as you mentioned electronic fence a light went on. The person that lives behind me has an invisible fence for his dogs and I wonder if that is what I am picking up. Doesn't seem powerful enough but who knows. The guy across the street is going to install one for his dog soon. Maybe they will be out of phase and cancel each other out. :D

One other thing that is odd is that my 5150 combo that is in the basement doesn't have this issue with the mexi.


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Post subject: Re: Blues Jr High Pitched Whine
Posted: Tue May 03, 2016 7:53 am
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MikeSt wrote:
One other thing that is odd is that my 5150 combo that is in the basement doesn't have this issue with the mexi.


The concrete walls of your basement are shielding against the RFI caused by the above-ground electric fence.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Blues Jr High Pitched Whine
Posted: Tue May 03, 2016 8:58 am
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Makes sense. Even with an egress window it is probably enough concrete to block any signal.


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