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spiritwalker

Aqua Marine

Posts: 3,612 Member Since: 14/02/2011

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A young musician has come to me for help upgrading his Mexican Jazz bass that he's had for 12 years. You know, emotional attachment.

So this stock bass makes a lot of noise unless he turns the treble down, and buzzes when you take you hands off the strings.
Not a bit of shielding in the cavities.
The pots probably could be replaced and the tiny cap in there at the same time.
The bridge is causing problems as it's rusted and the allen screws are stripped.

So what would you suggest for pickups and a bridge?
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weedywet

Ruby Baby

Posts: 5,774 Member Since:20/01/2011

#1 [url]

BadAss 2 bridge. 
And I'd put either Duncan Antiquity II (if you want 'faithful') or Status Graphite (if you want better) pickups. 

...if it were me. 

 

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soapfoot

Ruby Baby

Posts: 7,044 Member Since:04/02/2011

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Make sure the strings are grounded. There's a ground wire that goes from the electronics cavity to the bridge. It often breaks, and this can cause some of what you're talking about re: "noise when you take your hands off the strings."

I would replace all electronics-- some good pickups (the Antiquities WW mentioned are fine; there are other very good pickups out there, too). Replace pots with CTS or another good brand; often the higher quality pots are designed to fit imperial-mesaurement hole sizes, so if your J should happen to be metric, the holes might have to be enlarged slightly. A nice new jack, finally-- Switchcraft brand, preferably.

brad allen williams

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gregdixon

Gold Finger

Posts: 468 Member Since:30/01/2011

#7 [url]

Be careful with the Mexican Jazz pickups. For a long time they used two that were the same size. I can't remember when they changed it. Early '00s I think, but am not sure.

Jazz basses always need a lot of shielding, but it's definitely worth the effort. A lot of the Mex instruments are quite good, once you upgrade the pickups and hardware too.

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soapfoot

Ruby Baby

Posts: 7,044 Member Since:04/02/2011

#8 [url]

Someone with more electronics knowledge than me can school me, perhaps--

It's interesting to me to read that people find that shielding control cavities helps with hum in single coil pickup systems. For high frequency interference, this makes sense to me.

But I've never personally found it to help with radiated 60 Hz hum, and can't understand the mechanism behind how a foil shield (as opposed to a high-permeability shield like Mu-metal) could have a significant benefit at hum frequencies, particularly when the pickup coils themselves are mostly not going to be shielded. What am I missing?

Thanks in advance!

brad allen williams

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zmix

Aqua Marine

Posts: 3,889 Member Since:20/01/2011

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soapfoot wrote:
Someone with more electronics knowledge than me can school me, perhaps--

It's interesting to me to read that people find that shielding control cavities helps with hum in single coil pickup systems. For high frequency interference, this makes sense to me.

But I've never personally found it to help with radiated 60 Hz hum, and can't understand the mechanism behind how a foil shield (as opposed to a high-permeability shield like Mu-metal) could have a significant benefit at hum frequencies, particularly when the pickup coils themselves are mostly not going to be shielded. What am I missing?

Thanks in advance!

You are correct, shielding the control cavity isn't going to stop the primary source of hum, which is the enormous coils of wire specifically designed to be sensitive to electromagnetic interference  aka "the pickups".

RF noise can be reduced by shielding,  and in Fender guitars where the wires themselves are not shielded this *may* help...

The Jazzmaster I owned had a soldered, solid brass shield in the entire rout, it was no less hummy than any other Fender, certainly..

Guitars are fairly high impedance environments, so they are susceptible to interference.  I noticed that in cold, dry weather, brushing my hand on the pickguard of my Telecaster produced a lot of static, it sounds like a Geiger counter..!  If I were to coat the bottom surface of the pickguard with a conductive material this would dissipate the static charge and reduce that noise.
Lower resistance pots would help too.. (this one has the 1966 1MΩ tone and volume pots).

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soapfoot

Ruby Baby

Posts: 7,044 Member Since:04/02/2011

#10 [url]

Yeah, the jazzmaster is a great example. All of the originals had not only the big brass shielding tubs all throughout the cavity, but a shielding plate below the pickguard as well, to complete a total faraday cage around all electronics...

save, of course, for those massive wide, flat coils.

Which were like antennae for magnetically radiated hum, making the jazzmaster one of the most notoriously noisy guitars ever in mass production.

You make a great point, too, that I had overlooked-- all Gibsons have braid-shielded wire throughout, from the pickup leads all the way to the output jack. From the factory, the coils themselves are also shielded with metal covers... though nobody seems to complain about (and I've never noticed) any noise penalty from removing those covers, as is common practice (obviously the common mode rejection of the humbucking coil would help with a lot, anyhow).

brad allen williams

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maarvold

Aqua Marine

Posts: 2,933 Member Since:23/01/2011

#11 [url]

soapfoot wrote:
...nobody seems to complain about (and I've never noticed) any noise penalty from removing those covers, as is common practice (obviously the common mode rejection of the humbucking coil would help with a lot, anyhow).

 
When I took the covers off my humbuckers, I think I remember a slightly higher noise floor: enough that I bought some commercially-available nickel-plated covers I found with the tops cut out, but not enough to inspire me to get them 'reliced' and install them, although I will probably do it eventually.  

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seth

Ruby Baby

Posts: 5,476 Member Since:26/01/2011

#13 [url]

Admittedly I'm prejudiced, but to me the sound of a good jazz bass is both pickups all the way up and the tone either all the way up or down. A passive Fender, a good one anyway, gives you a lot of options for sounds using just your hands. It takes a lot of work to learn how to get the sounds out of it, but if you put the work in it can be very rewarding. Any sort of active electronics or humbucking pickups take away some of those options from under your hands which is why I don't have any basses with active electronics or humbucking pickups. If the passive sound is not what you want, a Fender is probably not the best option.

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gustav

Silverado

Posts: 97 Member Since:12/02/2011

#14 [url]

I have worked on two older MIM Jazz Basses. They had the same size pickups and were not reverse polarity and reverse magnets to each other for humbucking when both were at equal volume.
One I installed CS60s(needed to open up the pickguard and body route to fit the pickups) the other I reversed the magnets and wiring of one of the pickups and wax potted the pickups in 20% beeswax 80% paraffin. I am not 100% sure what the wax potting does but it does seem to take some of the edge from ceramic magnet steel pole piece pickups. The wax has different dielectric constant than air(so it changes the pickui capacitance) and also damps microphonics. The stock controls and tone cap were fine. I also twist the signal wires and shorten wires if possable and sometimes adjust the grounding wires.

Gustav

Last Edited By: gustav . Edited 1 time.

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