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Topic: How to take the hum out of a pre-War Rickenbacher B6? |
Mike Bonnice
From:
Arizona, USA
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Posted 27 Dec 2008 8:27 am |
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Does anybody know of a non-destructive way to take the hum out of a pre-war bakelite B6? When I touch the magnet, the hum goes away. But, the strings are not grounded, so I can't lift my hand off the magnet when I play. The tailpiece of the post-war B6 must have solved that problem.
I'm thinking of making my own solution: a plate of steel that is located under the body through which the strings would pass. It would be retained by the strings. Then, a wire from that metal piece to the jack (probably I'd solder the wire to a washer that would be placed under the jack retaining nut).
Can you see any problem with this idea? Are there others? I'm open to any crazy, reversible concept!
Mike |
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James Williamson
From:
California & Hawaii
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Posted 27 Dec 2008 12:45 pm Ground noise
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Mike,
I have a very similar coversation with Rick Aiello and he thought it would defeat the sustain characteristics of having the through hole strings in contact with the bakelite.
His suggestion if its too bad is to use a grounding strap like they use when working with electronics equipment.
After I cleaned up my electronics per his website, I really don't find the little bit of ground noise occationally to be objectionable...you might try to locate other sources of the noise as well .
jaes |
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Rick Aiello
From:
Berryville, VA USA
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Posted 27 Dec 2008 7:49 pm
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If it's bad enough to bother you ...
And you don't want to wear a "static bracelet/anklet" clipped to your 1/4" sleeve ...
Try weaving a very, very thin gauge copper wire through the strings ... like one of the "stands" from a 22 gauge stranded wire ... wrapped around each string ...
Between where the strings leave the body and hit the bridge ...
Then run it to the "half moon" mounting tab ...
That way you don't loose the "nothing but - bakelite to string connection" ... that alot of folks attribute that prewar "moan" to ...
I only seem to notice the problem ... during the winter up here ... when the humidity is very low.
I'm sure some folks have never experienced this "issue" ... but it can be annoying ... especially when trying to record ...
Hope that helps ...  |
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Mike Bonnice
From:
Arizona, USA
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Posted 28 Dec 2008 8:42 am More about hum in my instruments
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I think I'm going to weave the wire through the loops at the end of the strings, where they anchor to the body. Then I'll connect it to a washer at the jack. It will be under the body, invisible. It won't impact the interface between string and body. I'll report back on whether it works.
I've already experimented with hum with my Supro, and I've determined I have inadequate grounding at my electrical outlet (it's an old house). Plus, I have experimented with cables, and I have found a low-noise cable made by Proel that reduces the noise.
Where I live (Phoenix), the humidity is low year-round, so I have no experience with high humidity.
My pre-war model 59 has no hum or noise with any cable, and I don't need to touch the strings or body. Same with any modern guitars. I consider this to be the standard of performance.
What I dislike is switching instruments, plugging in my B6, and being reminded, "oh yeah, it has a hum and I can't take my hand off the magnet". It limits playing style.
I wonder if I need a new amplifier...  |
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Joshua Grange
From:
Los Angeles, California
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Posted 28 Dec 2008 5:19 pm
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Hey Mike,
I had a similar problem with my B6.
I bought it about an hour before a show, and when I tried it out before in the shop it had a nasty buzz that went away when I touched the magnet.
My tech recommended using alligator clips. Good for short term, bad for an ideal solution.
I simply took off each metal body plate, the pots too, and lightly moved and wiggled the wires around. I saw a fair bit of oxidization in some components and lightly traced over them with a flathead screwdriver. There were a couple exposed sections of cloth wiring that I made sure weren't touching anything else.
When I played the guitar that night- NO BUZZ, and it's been ground hum free since then.
Give it a shot, can't hurt! |
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Mike Bonnice
From:
Arizona, USA
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Posted 30 Dec 2008 8:57 am How I removed the hum in my pre-war Rickenbacher B6
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The trick to getting rid of the hum was to ground the metal covers over the pots.
The source of the noise is probably flourescent lighting.
Here are the first things I did:
- rewire according to Rick Aiello's diagram (a standard way of wiring electric guitars; the original way had the volume as a variable resistor, the standard voltage divider works better)
- used a new 100K audio pot for volume, new 250K audio pot for tone, and 0.1 MFD capacitor (the original capacitor)
- make the pot on the audience side be the tone control, it's more accessible while to change while I'm playing. The volume is on the player's side, I usually don't change the volume
- ground the cases of the pots, and this grounds the metal covers
I got the good result by grounding the covers before I changed to the new pots, so I'm confident that helps. The original pots have plastic cases, so they can't be grounded; I grounded the covers experimentally by wrapping a wire around the pot mounting stem and running it under a pickup mounting bracket.
Interesting result: on my desk, the hum went to zero when I grounded the covers. However, on my lap I still got hum. I must radiate (or conduct) electromagnetic radiation into the sides or bottom of the guitar, while the covers ground the radiation from above. So as a further step:
- shield the pot cavities by lining them with aluminum foil and ensuring the foil contacts the covers
This takes the hum to very low levels, but doesn't eliminate it, so as a final measure:
- ground the strings so the noise goes away when I touch them. I looped a strand of copper wire through through the ends of each of the strings, fed the strand up through a string hole, and placed the strand under a pickup mounting bracket (half-moon support).
Now I'm quite happy with the sound, plus with the new pots I have better control over volume and tone. I might forego the grounding of the strings in the future since now the hum is not so bad.
Remaining questions: Has anyone tried re-wiring the guitar with shielded cable? Would this replace the need for aluminum foil (as long as the pot cases are grounded)? I didn't put foil in the pickup cavity so I don't know if I could eliminate the last of the lap hum; maybe there is radiation into the lead wires under the pickup. What role does the pickup coil play in the hum? Do the magnets act as a shield so the coil sees very little radiation? |
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