Amp starts to sound like tuning a radio when i turn up tone knob

[mixmastermike]

I have an MIM Jazz Bass 2002. I just bought a hartke half stack HA500 head with an HX115 hydrive cab and when i turn the tone knob past 2 the speaker starts to whine. I can't imagine that it is a problem with the amp and driver, but i don't have the problem with the combo i play at church (40 watts i think). Don't know much about guitar electronics but i am an electrician, hopefully not too ignorant
thanks

[wshines1892]

are both pickups maxed? Most Jazz pickup sets are hum canceling when both are maxed. Also, things like facing the amp, proximity to things like tv screens, computer monitors, and fluorescent lighting can contribute to a noisy signal. The tone knob rolls off the higher frequencies where the whine is, so when you turn it up they will become more present again.

It could have something to do with grounding too, does it go away when you touch the strings or bridge? It could be insufficient shielding around the pickups too that would block out a lot of interference. I've had unshielded guitars pick up radio stations before.

[bassbenj]

Originally Posted by mixmastermike

I have an MIM Jazz Bass 2002. I just bought a hartke half stack HA500 head with an HX115 hydrive cab and when i turn the tone knob past 2 the speaker starts to whine. I can't imagine that it is a problem with the amp and driver, but i don't have the problem with the combo i play at church (40 watts i think). Don't know much about guitar electronics but i am an electrician, hopefully not too ignorant
thanks

Depends what you mean by "whine" and like "tuning a radio". I presume you mean has a high frequency whistle as opposed to a low AC hum.

And by "2" on the tone knob I presume you mean from full rolled off toward "brighter".

If all that is true, then your bass is picking up some noise where you have it. The tone control is simply rolling off the highs (shunt them to ground) so you don't hear them. They are still there being picked up though. This can especially be true if shielding is poor or with a Jazz you have singled one of the pickups.

Answer it to eliminate the noise source (will be something high frequency like a switching power supply or computer) or better shield the bass. You also can try to move away from the source. (The power supply in my combo puts out a lot of noise)

Some times the problem is more subtle than that. Do you use pedals? I have a reverb pedal (which I don't use with bass) that puts a nice whine on the 9v pedal supply line. It sometimes takes a lot of trial and error to track down what is causing the noise. Just try to substitute (even if you have to borrow gear to do it) things one by one to try to find which thing is making the noise.

On the other hand if you mean your amp is picking up actual radio stations, THAT is a totally different problem.

[mixmastermike]

It is definately the high pitched whistle. Yes i towards brighter. The sound doesn't go away or even diminish when I touch the strings or the bridge, nor does it go away when i have both pick ups cranked. As far as the interference from other sources goes I can't think of anything that would affect it where it is at but i will move it around and see what happens.
It is an MIM jazz could it be lower grade electronics? Maybe a bad cap? Bad pot?

[Bobster]

I would say this sounds like a shielding issue.

You can also try placing split chokes on the bass's leads and see if they make any difference.

I've used these http://www.radioshack.com/product/in...ductId=2996360 before and they are good for knocking out RF interference.

Good luck,

Bob

[wshines1892]

It could be a cracked solder joint I suppose? Or something along those lines. You could try plugging it in somewhere else, or even try switching basses to see if it's the bass or the amp making the sound. It sounds like it may be the power source you're plugged in to if it's not a bass grounding issue and it's not just pickup hum. Have you messed with the wiring any or is it stock?

[mixmastermike]

I haven't messed with anything yet i bought the bass used and the guy didn't mention anything about the electronics just the neck. i'm gonna tear into it more tonight and check and see if the ground is good and continuity is okay.

[mixmastermike]

Just pulled the cover off and low a behold there is no wire from the input jack to the bridge (ground) so i'll be fixing that little problem tomorrow. I'll check back and you know tomorrow.

[wshines1892]

That'd probably do it.

[mixmastermike]

okay so I checked the connections the ground seemed pretty good through the cover plate, but i hooked up a wire from the jack to the tone pot gnd anyways. Didn't really seem to help. So i looked through my manuals (the amp and cab are brand new) and it said not to use shielded cables so i checked the cables that the vendor (not hartke) gave me and sure enough they were shilded cables so i grabbed some cheap cables laying around and used them, and sure enough the sound is all but gone. live and learn. Why would shielded cables cause the whine??

[mixmastermike]

correction not to use shielded cables from head to cab (which i was not) but i was using the same type of none shieled cable from my bass to the head chincy cheap cable i'm using right now is shielded and pretty much no noise. oh well live and learn we all start out ignorant

[bassbenj]

Originally Posted by mixmastermike

correction not to use shielded cables from head to cab (which i was not) but i was using the same type of none shieled cable from my bass to the head chincy cheap cable i'm using right now is shielded and pretty much no noise. oh well live and learn we all start out ignorant

Ah yes. The noise pickup was from the non-shielded cable from the instrument to the amp.

The rule to learn is you ALWAYS use shielded cable from the bass to the head and you NEVER use shielded cable from the head to the speaker cab!

Live and learn.