Tone Change after shielding?

prokfrog · #1 08-02-2010, 02:48 PM

I finished shielding my bass the other day, and I swear the highs have dulled. Its more noticable in passive mode. Is this common? the pickups are emg hz's with a glockenklang pre
thanks

**line6man** · #2 08-02-2010, 02:50 PM

Did you shield the pickups?

That is common for pickups to lose some high end if shielded.
This is why guitar humbuckers with nickel covers sound a bit smoother than naked humbuckers.

guroove · #3 08-02-2010, 02:53 PM

Really? Even if you are just shielding the cavities? I did this myself, and I thought it was the lack of buzzing that made it seem like there was a loss in highs.

prokfrog · #4 08-02-2010, 03:17 PM

I shielded the pickup cavities too..

stflbn · #5 08-02-2010, 03:24 PM

Are the pickups at the same height they were before shielding?

prokfrog · #6 08-02-2010, 03:30 PM

Quote:

Originally Posted by line6man

Did you shield the pickups?

That is common for pickups to lose some high end if shielded.
This is why guitar humbuckers with nickel covers sound a bit smoother than naked humbuckers.

Actually, I would almost say that in passive mode, they turned "mid-harsh". Definately not smoother. In active mode, I would say it stayed pretty close to original before shielding.

prokfrog · #7 08-02-2010, 03:30 PM

Quote:

Originally Posted by stflbn

Are the pickups at the same height they were before shielding?

Yep

I'm anal that way.

**line6man** · #8 08-02-2010, 03:39 PM

Quote:

Originally Posted by prokfrog

Yep

I'm anal that way.

Uh, that's what she said.

prokfrog · #9 08-03-2010, 08:06 AM

Quote:

Originally Posted by line6man

Uh, that's what she said.

Yeah.. I knew that wouldn't go unanswered. back on topic. Is that the consensus? Shielding around the pickups will cut highs?

cassius987 · #10 08-03-2010, 08:23 AM

Quote:

Originally Posted by prokfrog

Shielding around the pickups will cut highs?

Of course. The shielding makes a capacitor to ground, which acts exactly like a "turned down" tone control, except it can't be modulated. Capacitance will be greater (effect--hinge frequency drops, so you lose increasingly lower frequencies as well as highs) for a tighter "box" made by the shielding. Say, inside a Jazz pickup cover. Shielding a Fender control cavity will not have as much capacitance. A huge control cavity in a Ric or a Gibson (or anything else wired switchable VVTT) would result in almost no extra capacitance. It's all context-dependent.

It's as if before the signal reaches the jack you connected in parallel a capacitor of a small value to ground. The very high frequencies will get zapped pretty quick, and to a lesser extent the ones we care about. This is a much bigger concern for guitarists.

The change in tone should sound similar to your pickups before with the tone knob turned down slightly.

Did you shield to get rid of buzz? Okay then. But if you shielded to get rid of hum, throw the shielding out, unless you like the new sound. Shielding against hum never seems to get anyone anywhere--I've read all sorts of claims to the contrary but have never, ever been given any proof, and I've tried myself on a few occasions.

SGD Lutherie · #11 08-03-2010, 08:23 AM

If you wrap foil around the pickups, and it forms a closed loop, you will lose high end. To prevent this, just make a break in the foil so it does not go all the way around.

I'm not sure if shielding the pickup cavities will have the same effect, but if the pickups don't have foil around the coils, try doing the same thing to the cavities... put a slit somewhere so the foil is not going all the way around the outside of the pickup.

This is due to eddy currents which form in conductors close to magnetic fields. There might also be a slight raise in capacitance.

Jim C · #12 08-03-2010, 08:48 AM

Cassius987

Are you saying that the traditional use of copper tape in the pup body cavity as well as body control cavity will affect tone?
I'm assuming that the pup is left alone and mounted as usual in the now shielded cavity.
Have never heard this before and am curious as to how this would form a capacitor to ground.

SGD Lutherie · #13 08-03-2010, 08:57 AM

It would form a capacitor if an insulated signal wire was close to the foil.

I think eddy currents from closed loops near the pickups would have a greater affect.

I suggest trying to split the foil in the pickup cavities to prevent it from forming a closed loop. If that doesn't work, try removing the foil.

okcrum · #14 08-03-2010, 09:38 AM

A few pf extra capacitance will not matter unless there are impedances in the tens of megohms in the circuit.

The eddy current idea seems more plausible.

prokfrog · #15 08-03-2010, 10:15 AM

Well I'm learning my new thing for today. As Jim C mentioned, yes, its just foil lining the pickup routes, along with the control cavity, and cover plate. Regarding Davids (SGD) comments. I surely have signal wires laying on the foil. That Glock pre is a rats nest of wires. Furthermore, I'm really not sure it made a difference. I still have humming.

SGD Lutherie · #16 08-03-2010, 10:31 AM

Quote:

Originally Posted by prokfrog

Well I'm learning my new thing for today. As Jim C mentioned, yes, its just foil lining the pickup routes, along with the control cavity, and cover plate. Regarding Davids (SGD) comments. I surely have signal wires laying on the foil. That Glock pre is a rats nest of wires. Furthermore, I'm really not sure it made a difference. I still have humming.

Shielding does not remove single coil pickup hum. Hum is caused by magnetic fields. But that higher pitched buzz is caused by electrical fields, and electrostatic shielding will help there.

You must make sure all the shielding is grounded, or it will create more noise because it acts like an antenna.

For single coil pickup hum, you need to find a noise canceling version to your liking.

I don't think the preamp wires by the foil matter, since most electronic devices are in shielded metal enclosures.

**TRichardsbass** · #17 08-03-2010, 10:48 AM

+1 on all the above, but I'm surprised that you can notice that much high end missing.

For example, my vintage Dan Armstrong Modified Danelectro in the original "noiseless" configuration definitely is perfectly quiet and is a little duller. Dan A. added an additional unshielded coil and it definitely has more high end but not significantly overall.

My old Aria Pro II SB-700 had the most noisless pickup ever. It was still super bright and even "hot". It is one of the most super shielded pick ups I've ever seen.

So again, yes, sheilding has a dulling effect, but as others have said it all has to do with how you shield and where you shield.

prokfrog · #18 08-03-2010, 12:04 PM

We are talking soapbar humbuckers, and I guess buzz is the right word. It comes and goes as i move about the room. its most noticable in passive, active mode is pretty much "normal" so I guess that makes sence.

Jim C · #19 08-03-2010, 01:04 PM

Have you tried other basses and cables so as to eliminate these items as variables?
Odd that a decent humbucker would have this problem unless the area is known for high RF fields and / or the amp is espeically sensitive to outside noise.

prokfrog · #20 08-03-2010, 01:26 PM

I have two basses that behave the same. why would the amp or cable be the culprit when the problem only persists depending on where i move around in the room?