Insulating baseplates with tape : why I find it discussible, finally.

[freefrog]

I’m just a tinkering customer but my experience might be useful for pro winders and guitar techs, after all. So, I’ll share it in this topic.

Some times ago, the idea came to me to avoid squeal by insulating the parts of the magnetic circuit with adhesive tape.

I’ve took three pairs of unpotted PAF clones and added a foil of soft plastic on the baseplate…

-under the slugs of the 1st set;
-under the slugs AND magnet of the 2d pair;
-under the magnet alone of the 3d model.


The first tests have shown an unexpected difference: the Q of the resonant peak was a wee bit higher once the tape added.

I’ve not been able to decide if it was due to a change of electrical properties in the magnetic circuits or to a simple relative change of physical location between elements.

Anyway…

Once played, the pickups were good sounding, with a slightly tighter tone and less squeal under high gain… but something was lacking.

This thing has appeared when I’ve excited the PU’s with a 1Khz signal sent by a low impedance coil: there was not much effect with the tape under the slugs only (although the difference of Q was still there). Conversely, the tape added under the magnets appeared to reduce noticeably the harmonics.

I’ve checked it by playing notes @ the 19th fret on the high E (which gives roughly a 1khz signal): according to my frequency analyzer, there was 33% less harmonics above the fundamental when the magnet was separated from the baseplate by a tape. Hence a poorer tone.

So, it wasn’t a so interesting trick, finally.

Hope to be useful...

[Possum]

Gibson used to varnish their magnets in some P13's, ultimately its a waste of time. The screw still contact the baseplate so you're still getting some electrical interaction with the baseplate, but as you found out a cleaner signal doesn't always sound so great. Thats why I use baseplates on my P90's when some dont, the baseplate adds something to the sound, it rounds things out. After awhile the technical measurement tools become boring, you can see the differences but then your ears tell you what works best or not.

[freefrog]

Hi Dave. How are you?

I understand there's some electrical interaction if the screw poles are threaded in the baseplates. That said, my goal was to dampen the squeal possibly due to vibrating magnets or slugs.It worked but with a bad effect on tone...

[big_teee]

I agree with you Possum on the P90 Base plate.
I have been experimenting with a P90 on a Humbucker bassplate.
I guess it is the Eddie Currents, but IMO the brass with 2 A2 magnets sounded best, and my plastic baseplate sounded worse.
The plastic baseplate, was thin and sterile sounding.
T

[David Schwab]

Hi Dave. How are you?

I understand there's some electrical interaction if the screw poles are threaded in the baseplates. That said, my goal was to dampen the squeal possibly due to vibrating magnets or slugs.It worked but with a bad effect on tone...

You want the poles grounded, otherwise they will hum and squeal when you touch them.

I'm not sure how putting plastic under the slugs or magnets dampened anything.

[David Schwab]

I agree with you Possum on the P90 Base plate.
I have been experimenting with a P90 on a Humbucker bassplate.
I guess it is the Eddie Currents, but IMO the brass with 2 A2 magnets sounded best, and my plastic baseplate sounded worse.
The plastic baseplate, was thin and sterile sounding.
T

The brass rolled off some high end. The plastic was brighter, not thinner.

[freefrog]

You want the poles grounded, otherwise they will hum and squeal when you touch them.

I'm not sure how putting plastic under the slugs or magnets dampened anything.

I'm not sure either of what it did but I'm sure of my statements: it caused the Q factor to be slightly higher and it definitively tamed the squeal under high gain. :-)

AFAIK, BK lacquers the mags of their humbuckers for the same reason. https://bareknucklepickups.co.uk/main/howwemakethem.php ("Potting" section).

A winder who is member here has also said once that slugs touching the baseplate could generate noise: Unpotted pups and covers. - MyLesPaul.com (post 9).

FWIW.

Oh, and... thx for the reminder about the reasons to ground the poles.

[rhgwynn]

Although the test is not without it's merits - I think it would have been best if you'd gone about it a different way. The way you wrote it up, seems to neglect the possibility of winding differences resulting in variation. It does not mention if you CNC wound them, hand wound, or bought them. I would have taken individual measurements and recordings of each pickup; then I would have made the changes, so the difference in sound can actually be quantified within each individual pickup.

[John_H]

Although the test is not without it's merits - I think it would have been best if you'd gone about it a different way. The way you wrote it up, seems to neglect the possibility of winding differences resulting in variation. It does not mention if you CNC wound them, hand wound, or bought them. I would have taken individual measurements and recordings of each pickup; then I would have made the changes, so the difference in sound can actually be quantified within each individual pickup.

^^ this is nonsense

[rhgwynn]

^^ this is nonsense

^^ as is this.

Why not say something contributing instead? Since when is eliminating variables that can skew your results a bad thing?

[John_H]

^^ as is this.

Why not say something contributing instead? Since when is eliminating variables that can skew your results a bad thing?

I said "this is nonsense" because it is. I don't want anybody who is just learning to give any credence to your ridiculous statement.

... I would have made the changes, so the difference in sound can actually be quantified within each individual pickup.

What are you measuring?

It makes no sense = nonsense.

[freefrog]

Although the test is not without it's merits - I think it would have been best if you'd gone about it a different way. The way you wrote it up, seems to neglect the possibility of winding differences resulting in variation. It does not mention if you CNC wound them, hand wound, or bought them. I would have taken individual measurements and recordings of each pickup; then I would have made the changes, so the difference in sound can actually be quantified within each individual pickup.

Hello;
The tape has been added then pulled off in pre-existing PU's.
Its effect has been evaluated through a frequency analyzer, along played tracks and with an ultra-low impedance void coil exciting the PU's.
I've not posted these data simply because it's a lot faster for me to type an explanation than to produce readable screenshots - not enough free time for that right now.
Thx for you understanding!


EDIT: I've changed a measurement in readable file before to go to work. Pic below.

The four colored lines show the resonance of the four coils in a set of HB's. Two tests have been done. Eight lines are produced. They stack exactly below the resonant frequency. They don't stack no more upon each others beyond the resonant peak (the green line is not aligned on the green, the blue on the blue and so on). It shows how the added tape has affected the response in one or the three sets that I've tested. Hope to be useful...

[rhgwynn]

I said "this is nonsense" because it is. I don't want anybody who is just learning to give any credence to your ridiculous statement.

What are you measuring?

It makes no sense = nonsense.

Who here isn't learning?? At any given moment? All of us are here to learn and share. It's a discussion - not a lecture. If you think I am wrong - tell me how and tell me why, so that I and others (whom you seem to care for greatly) can all learn together. Otherwise keep your commentary to yourself; because it brings no good, at all. No one is going to take my word for anything without knowing me personally; and if they do, it could possibly end up being a lesson well learned - do your own research. You also speak as if I have doled out facts for OP to chew on - I have not. Merely a suggestion made for a more thorough experiment.

So what are we measuring? You read OP's post John. You know exactly what we're measuring. Q of RP, inductance would also probably be affected as well, levels of harmonics present, ability of the pickup to produce the full range of tones in a pleasing manner. I thought that much was obvious; in addition to my suggestion that there be clear before/after comparisons made. I have no problem with how OP went about his experiment; I just have a lot of love for the scientific process, and thought it could be improved upon.

[John_H]

You can't quantify tone. It is possible to plot a resonant peak on a graph, but there is no measurement for the sound perceived.
Your post #8 wasn't a question. You were speaking from a point of authority, and in it you made a reference that the difference in sound could be quantified. That's Nonsense.

[Rick Turner]

You can't quantify tone? Or is it that you don't want to figure out how to do so?

I'll certainly agree that there's a lot more to the tonal effects that a pickup imposes upon the characteristics of a vibrating string (and the instrument on which it is mounted) than the resonant frequency, Q, and low end roll off of a pickup coil, but those are valid measurements that certainly quantify some of the tone shaping. As for the rest, just because we don't seem to have adequate and agreed upon measuring systems yet doesn't mean that we might not in the future.

I'm working on the design of a universal test fixture that will allow great repeatability testing pickups with vibrating strings. It will be highly controlled, monitored at both string ends by extremely accurate piezo "reference" pickups, and should be able to clear up some of the mysteries around the "tone" of a pickup under real world conditions...with strings, not a signal coil. More to follow.