Comment

Comment by carverman on December 6, 2010 at 3:04am

Interesting story about shouting at a unpotted guitar pickup and actually hearing your voice
come out.
Well a dynamic microphone is like a speaker in reverse, sound waves from your voice, move (modulate) the movement of the diaphram inside a magnetic coil. It doesn't take a lot of effort
to move this very sensitive diaphram..the guitar pickup OTOH is not what you would call a good
microphone. The case reduces the sound waves a lot and what movement there is inside
on the coil isn't going to be a lot...microphonic p_ups in my experience, just cause squeal.
Even on a potted P_up, you can tap it with a non metallic object..(like a small dowel), and get a audible response. Any vibrations can cause that..it doesn't have to be from the strings.

Comment by colin mcgrath on December 4, 2010 at 12:42pm

whoa Eric that is cool! how do i get a microphone pup!! 8) maybe with a force full voice one could get some cool sounds from yelling at the strings. 8), nice info, still, in this thread.

Comment by eric gittins on December 4, 2010 at 11:57am

On microphonics, I just remembered a story of Jeff Lang playing a Gyatone(?) lap steel live. Fully cranking, big susstain style, but his pickup was so microphonic he could pick the instrument up and yell a verse in the pickup as a microphone. Nice parlour trick!

Comment by eric gittins on December 4, 2010 at 11:53am

Well done folks, a bunch of helpful information for those looking.
I second what Juju said about the windings being insulated from the magnets. Wound directly against the magnets is the most desirable for a compact pickup, and there may well be tonal advantages too, but a decent insulation layer between magnet and wire seems sensible to stop the mentioned problems.
As to the 'grittier' sound from an un-potted pickup Caverman, I can't say for sure, but there seems enough anecdotal evidence to suggest it likely there are tonal advantages to some coil microphonics. Also, a well wound coil is a pretty firm structure in itself in my experience, it's realy only the last couple of turns after you remove the pup from the winder that may be noticably loose, and these are locked in by tape or other wraping around the coil. I guess if a whole coil was 'flabby', microphonics could be through the roof?

Comment by carverman on December 4, 2010 at 6:10am

If they are potted, there may be telltale traces of wax on the underside or on the magnet.
I just opened the bottom of these single coils I got from CB Gitty, and they seem to be wax
potted. Potting seems to the standard method now..but many years ago, that wasn't
necessarily the case, and guitar players survived. Wax does stop microphonics..which may or
may not be a bad thing.

Certainly if your ears are full of wax, you may have trouble hearing those unique tones..LOL!

Comment by JUJU on December 4, 2010 at 5:44am

Hi Eric yes mate i have noticed the resistance reading goes up after the the coil has been left for a while - also i pot my pickups with acrylic varnish as i'm winding i dont do the wax method - i just like to do it this way because i make most of my bobbin tops from wood so i'm not sure how the wood will react to hot wax so i just stick to this method it seems to work good for me

well the size of your bobbin would explain why i thought the bobbin had more winds than 8,500
i tried the reed switch method with my winder but run my Mechanical 1-1 counter at the same time but the reed switch one had far less turns than the mechanical one - i guess it may have worked better if i had a bigger flywheel on my winder - would have liked the digital counter to have worked because it was silent whereas the mechanical counter makes noise not too much but enough to stop me winding all night long lol!
Re Colin -you can usually tell if a pickup is wax potted by inspecting the Bobbin flatwork a wax potted bobbin will show signs of wax - also it's not undesireable to wind the wire on the magnet as long as you have good insulation between them - theres a video of the seymour duncan pickup works that shows them dipping the completed bobbin in clear laqure - this is what they use on the old strat type pickups the clear laqure insulates the magnets from the winding wire

Carverman yep there are lots of pickup makers that dont wax pot the coils and i agree they have a gritty sound but i'm not sure what the lifespan on such a pickup would be - this is what i like about making pickups its a good learning curve

Comment by colin mcgrath on December 4, 2010 at 4:41am

Cool, lots of info there I must say some of it I might have to reread for full comprehension. From looking at pups and reading about making them I never got the impression that it would be undesirable for the wires to touch the mag. Is that type of info misleading?
I am in the process of installing a Golden Age 'caster sing in a standard 6er; it doesn't appear to be potted. I must admit, I have several different kinds of pups around, I cannot tell if any are potted or not? What is a tell tale sign?

Comment by carverman on December 4, 2010 at 2:36am

The dc resistance will also change with the slight die size change as the copper wire is drawn through. Even a thousands of an inch in diameter makes a big difference in the dc resistance
per 1000 feet. Here's the copper wire table again.
http://www.mwswire.com/barecu6.htm

Incidently, the earlier Gibson pickups (like the p-90s and the early hbuckers were not wax
potted. S_M is offering a 'Golden Age" P-90 sc "parsons st"..(after the Gibby Kalamazoo address),
that is offered unpotted for a more "grittier sound"...
any comments?

Comment by eric gittins on December 3, 2010 at 1:08pm

Cheers Juju, the pic may be deceptive, but the coil in sensible metric terms, is about 9mm ID x 19mm OD x 8.5mm tall. That extra 4mm height you have would make a big difference, and a little also for that narrower ID on yours too.
My counter is one of the standard modular kit digital counter, with a seperate adjustible de-bounce circuit, and a reed switch and magnet trigger. It will cheerfully count up to about 1000tpm in current trim.
So yes, only 8K5 turns.
On an aside, have you noticed how much the DC resistance readings for a coil change with temperature? Even the heat generated by winding the coil can make a difference. I rarely get the same readings just off the winder as I will later on when the coil has settled.

Comment by JUJU on December 3, 2010 at 12:57pm

yep thats right its a bar magnet but in rod form with north one end and south the other - the magnets dont need to touch the windings but the further away the magnet is from the windings the less magnetic feild you have within the coil also the coil ends up bigger in size - i think the problem with a lot of the earlier Strat pickups is they never wax potted them - potting the coils in wax displaces air gaps in the coil which in turn stops the windings/coil being microphonic - microphonic means the coils move under use as the magnetic and electrical feilds react against each other thuss over time the enamel coating on the windings rub against each other or the magnet and cause a short circuit = dead pickup also if the coils ore microphonic it can cause Feedback
hope that helps

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