hissing sound on new bass

hanx · #1 05-22-2010, 02:24 AM

I just got a new fretless Cort 4 string, it was rather old stock on a cheap sale, but seemed fine in the shop other than a few superficial scratches.

But i noticed when i got it home that there's a bit of a hissing sound

When i'm not playing anything - particularly when i've got the volume up - there's a hiss. It changes a little when i fiddle with the knobs, but not much, just things like it gets louder when i turn volume up. I didn't notice it in the shop, it seemed to appear when i switched the pick up switch to passive, but didn't go away when i switched it back.

I checked it with two different leads and that made almost no difference, i also tried my other electric bass in the same amp and it sounded fine, so it must be the bass itself.

It's under warranty (they claimed 3 years, so well within that) and not real bulky to get back to the shop, but if it's something real simple maybe i should just fix it myself. Could it be dust or something? How do i clean that out? It was old stock (i first saw it a year ago) so may have acquired a fair bit of dust in the shop?

hanx · #2 05-23-2010, 07:53 AM

seemed to be fixed by getting the settings just right, must have just been i didn't try both treble and volume cranked to the max at the same time in the shop.

curious to know exactly what it is though, my other bass doesn't seem to do it, at least not until i turn everything insanely high, this does it over about 755 of full volume/treble.

Kipaste · #3 05-23-2010, 06:54 PM

What kind of a cort are we talking about here, ie. what kind of pickups does it have? If the pickups are single coils, there is no way of getting around some hum when other pickup is favored over the other. That kind of thing wouldn't happen with your other bass (according to your profile a double humbucker bass) due to the differend nature of the pickups.

If the hum only comes around when cranking treble, the preamp is one thing that can cause it. Many pres will do that, especially the affordable ones. If you set the treble control flat, is it still very noisy?

Also, are you playing near a CRT monitor, non flat tv or fluorescent tubes? All of these can give you some noise..

M0ses · #4 05-23-2010, 07:00 PM

If it goes away when you crank the treble, then yeah, that's single coil hum. Live with it, or use humbuckers.

hanx · #5 05-23-2010, 08:47 PM

pick up is a fully-enclosed so i can't see if there's one or two rows of magnets, "bartolini mk1"

closest old fashioned TV is in the next room, and i think it was off

yeah totally fixed by turning treble down, there's a knob (which i assume is supposed to be treble) the function of which seems to be just "make bass hiss" but meh, if i wanted treble i'd play guitar. I think having volume and trebble both high was what did it, i'd only tried them at max separately when i was testing it in the shop.

the one with the two humbuckers does it when i put both treble and volume at the absolute max, this one does it with the volume in the middle and the treble any more than about 30% of full boost.

it reduced to the price of a very simple entry-level model, so heck, who needs treble boost anyway... wonder if i can boost the treble on my amp instead to avoid it...

hanx · #6 05-23-2010, 08:50 PM

... nup... treble on the amp amplifies the hiss as well.. which seems a bit odd given the hiss doesn't really seem that high-pitched, how does that work?

Kipaste · #7 05-24-2010, 07:58 AM

Quote:

Originally Posted by hanx

... nup... treble on the amp amplifies the hiss as well.. which seems a bit odd given the hiss doesn't really seem that high-pitched, how does that work?

Mk1 most likely means bartolini oem's. Those are basic soapbars, so no single coil hum. Is your bass a series? If the treble knob cures it, I'd point my finger at the preamp. Many affordable pres produces hiss when treble is cranked. You could try shielding to see if it helps a bit as some of that hiss may come from electrical interference (or insert a better suited term here, I don't have the words), but I don't think it will completely cure the problem.

hanx · #8 05-24-2010, 08:22 AM

soapbars?

not sure what you mean by series? it's a curbow fretless if that's what you're asking.

do you mean the preamp in the pick-up itself or somewhere after that (i never actually fathomed the difference between active pickups and passive pickups with active EQ).

who do you mean shield it?

to be honest it doesn't bother me too much, if i wanna see a silver lining it's a good warning i've got the volume cranked too high for the neighbours, but if there's a fix that would be good.

Kipaste · #9 05-24-2010, 04:59 PM

Soapbars is a common name for pickups that are a bit wider and don't have exposed polepieces since they kind resemble soapbars. They're humbucking, so no single coil noise.

By series, I meant if the bass was cort A or artisan series, just out of interest as I noticed they have bartolini soapbars.

Shielding is done to minimize the electrical interference messing with tone. This is usually done with copperfoil/tape. Basically you just cover the cavities with copper and ground it. It might not get rid of all the noise, but could make a decent difference and costs next to nothing.