Author Topic: Help with High Pitched Directional Whine - Activators (Read 433 times)

ojo · « **on:** February 15, 2012, 08:29:18 AM »

Hey all,

I finally got around to installing Activators into my '96 Hamer Cruisebass, and a high pitch, directional whine comes through the amp. The behavior is similar to a 60cycle hum with single coils, but it's a totally different sound. The whine is additional to the normal tone and operation of the pickups and electronics. Meaning, the bass sounds like it should, but also has this irritating noise. I'm assuming it has to do with grounding, or something like exposed wiring.

Details and things I've noticed:
- Controls are Vol/Pan/Filter (though I have them arranged as Vol/Filter/Pan because of short wires).

- The cavity of the bass is factory shielded, and it has an aluminum cover plate.

- The output jack is body mounted, and I wired up a switchcraft stereo jack (152B) to make the connection - as well as a 9v battery connector.

- The noise exists if the pickups are disconnected from the pot, and gets worse with the pickups attached.

- The noise goes away if I rotate away from the amp.

- The noise lessens if I wave my hand over the pickup, jedi-style.

- The pickups were cut from the quick connects, and I had to solder the wires back together. I admit, not my best soldering job.

- There is no ferrite bead for the pickup wires.

So, does anyone have any experience with this, or thoughts on how to fix it?

Thanks,

Joe

stout71 · « **Reply #1 on:** February 15, 2012, 09:11:52 AM »

Sounds like RF interference to me. There are possible other causes of course, but if the sound diminishes when your hands are over the pickups or you turn in another direction, that is the hallmark of RFI. You might try insulating the pickup cavities with copper or silver foil, and you might try doing the same with the electronics cavity. I know you said it was already factory-shielded, but it couldn't hurt to try.

terryc · « **Reply #2 on:** February 16, 2012, 02:04:52 AM »

PU's could have failed ie microphonic, are they second hand?

ojo · « **Reply #3 on:** February 16, 2012, 10:07:10 AM »

Terryc: They are second hand, but I'm not sure that's the issue. I was running the pickups passive (with an outboard boost) before installing the Alembic electronics, and never had this issue. Actually, now that I think of it, I had them installed passively in TWO different basses before adding the electronics.

Stout71: Thanks, I was wondering if it was an RF issue. I had read all sorts of postings here about RF interference, but wasn't sure that was the issue.

Anyone else have an opinion?

mica · « **Reply #4 on:** February 16, 2012, 10:24:32 AM »

The pickups are internally shielded with a complete copper Faraday cage. The wire from the pickup is shielded, so shielding the pickup cavity and route to the electronics will probably have little effect.

Check to see that the soldering you did is correct. There is a polarity to the pickup connections.

There is no charge to test pickups and electronics, so if you can't isolate the problem, you can always send in here and we can see what the deal is.

mica · « **Reply #5 on:** February 16, 2012, 04:21:31 PM »

Also - is the sound the same in both pickups - meaning at both ends of the pan control? Why shape pickups do you have?

ojo · « **Reply #6 on:** March 14, 2012, 11:52:22 AM »

Dang, can't believe it's taken me a month to finally get around to posting a response. Sheesh!

Anyhow, I think this is an RF issue because I can replicate it with both my Epic AND my other Alembic-outfitted parts bass.

The most offending bass is the one I originally posted about (Jazz Bass clone), and the pickup shapes are the classic Jazz Bass style (traditional single coil-esque housing). I've checked the soldering, and while sloppy, it's correct.

My other Alembicized bass has the same high end noise, but way less pronounced (East-Meets-West setup with an AXY and a Fatboy).

My Epic also has it, but only when I get close to the amp.

My two Alembicized basses do NOT have the ferrite bead, and my Epic does.

So, any new thoughts?

Thanks!

Joe

mica · « **Reply #7 on:** March 14, 2012, 08:27:50 PM »

Close to the amp is normal, I mean like 3 feet away or less, so if that's the case, let's ignore it for now.

What I need to know to try and trouble shoot is if the sound is the same in both pickups (at each end of the pan control).

Is there any chance the shield is not making a connection under the sloppy soldering?

I doubt the ferrite bead will not have much impact unless you are using wireless (are you?). You can always pop it out of the Epic and try in on the other basses. Of course, that's not super easy since you have soldering to do, and you should take care on the Epic pickups and remove the housing on one of the pickups before unthreading the bead.

Plan B is to send them in for testing. Helpful if you can send me a picture of them mounted in the electronics cavity as well.

ojo · « **Reply #8 on:** March 15, 2012, 11:42:46 AM »

Mica, thanks for the replies!

The Epic only gets noisy CLOSE to the amp, w/i three feet or so.

The E-M-W frankenbass has it further away, but barely noticable.

The bass in question has noise anywhere in the room. I noticed the noise with BOTH pickups unattached, then with both attached. Panning doesn't really make much of a difference, though it IS more pronounced when I start panning the bridge pickup. I figure that's due to the pronounced treble response, opposed to issue with pickups. The noise lessens as I engage the filter, or dial back the treble on the amp.

To clear up some confusion. When I received the pickups, the wires were cut about an inch from the quick connects. Fortunately, I also got the one inch of wire with the quick connects attached, so I stripped both ends of the original wire, soldered the middle and ground together, and have then hooked up normal style - that is, connected via the quick connects to the appropriate pot. I don't have the bare wires soldered directly to the pegs on the pot. So, I'm able to plug and play.

I'm also using a standard 1/4 cable, no wireless here, I'm not that fancy!

I'll snap some pics this weekend.

Thanks again!

Joe

dfung60 · « **Reply #9 on:** March 15, 2012, 11:01:10 PM »

You've got some symptoms that make it sound like the EQ board is bad -

#1 - the pickups worked passively
#2 - the noise is the same regardless of the pan
#3 - you've never heard this eq board working properly

The most effective way to test this is to swap a known good EQ board in (as if one is available!). The next best is to try it with a different or non-Alembic EQ board and see if the problem is still there or not.

If there's a socketed IC, then carefully remove and replace it being careful to note the polarity of the device.

I think you're right about it being a grounding problem, but the previous owner may have flexed the board and messed up an internal shield.

One other interesting thing to try would be to remove the EQ board entirely from the cavity of your bass. Leave the wiring intact, but remove the nuts from the knobs and whatever else it takes so the circuit is lying out on the back and see if it still hums. If the noise goes away, you're shorting something out when the board is installed.

Good luck,

David Fung