inductance readings

[Gus]

Found some old notes

I measured a bunch of pickups years ago.   I recorded a range of 2H tele neck to 3.5H overwound strat, a few  2.9H strat pickups.  Measured on a sencore 102

So a 2H to 3H humbucking wound inductor with a resistor etc(to sim the guitar) should be something what will sound good after a buffer and into a FF.  Jack has a page with the sim circuits

Anyone measure the transformer Jack has at that page for resistance and inductance?

[aron]

WOW, I missed this article. Hmmmmmmm....... Interesting.

http://www.muzique.com/lab/pickups.htm

[aron]

I don't see anything on my list that would be that high:

http://www.diystompboxes.com/smfforum/index.php?topic=51510.0

[R.G.]

Stephan Moeller, our friend who sold his design for the AC-30 simulator to TC electronics as the basis for their TC-30 simulator, did a comprehensive run down of pickup simulation on his web site before he removed the site. I neglected to make a copy of his stuff before it was taken down. I think it predated the simulator at Jack's place by a couple of years. Jack may be reinventing Stephan's work accidentally.

Most pickups measure 1H - 4H, with a self-resonance between 1kHz and 5kHz. Cable capacitance and controls loading cause a lot more effect than the self capacitance, I read.

I'd quess that having any largish inductance there is better than nothing.

Using two transformers side by side can be arranged to be signal and inductance aiding, hum suppressing by careful connection of the wire phase.

I have some other info, in more detail, about pickup simulation somewhere in the archives.

[aron]

>Most pickups measure 1H - 4H, with a self-resonance between 1kHz and 5kHz.

R.G. is that what my Sencore tester defines as "ringing" (I'm trying to remember). So each inductor has a self-resonance?

Hmmm maybe not.

RINGING TEST:
- A dynamic test of inductor quality determined by applying an exciting pulse to the inductor and counting the number of cycles the inductor rings before reaching a preset damping point.
Inductor Range: 10 uH and larger, non-iron core
Accuracy: ±1 count on readings between 8 and 13 Rings
Resolution: ±1 count
Exciting Pulse: 5 volts peak

[R.G.]

All inductances have parasitic self capacitances. In that sense, they all have a self resonant frequency. However, all inductors also have parasitic resistances from the wire they're wound from. So the Q, or sharpness of resonance, may not be there for a real "ringing". There also may be several resonances as the self capacitance is not a simple capacitance, and may act like several capacitances and give different rings.

Every inductor definitely has a frequency where the parasitics keep its impedance from continuing to rise with increasing frequency. Above that frequency it quits looking like an inductor.

[Dai H.]

would two or more 500mH wah inductors in a steel box work? And what happens in a performance situation when you just want the fuzz without the wah in front of it. Switch it(the inductor in the front) out? Maybe some enterprising pickup maker, etc. can make a product out of this.

[aron]

>would two or more 500mH wah inductors in a steel box work?

I think it would work.

Aron

[Dai H.]

that's what came to mind as far as easily obtainable (more or less) parts (large value inductors). (Maybe a lot of people have some lying around that they removed for Dunlop Fasels.) The steel I mention for magnetic (hum) shielding. I should just try it but I don't feel like doing much in this heat and humidity.  I am seriously longing for cooler weather...

[aron]

The problem is that most wah inductors are overpriced compared to the cheap ones I mentioned (mouser). One thing that my friend mentioned (not sure if it's true) is that for the Torres midrange kit, I think he used to use a wah inductor - and apparently it sounded a lot better than now.

[Dai H.]

the cheapest ones I know of here with such high values are some "TR use" (transistor radio use??) inductors with the highest value avail. at 500mH for about the equiv. of 3 dollars (I have no idea if they would work though). Apparently these MIJ inductors have gone out of production and will be subbed with China made ones as stocks run out. As far as the Torres kit, I remember reading somewhere about how real inductors used for EQ cct.s can sound better than opamps. IIRC there were some old studio EQs which used actual inductors (Pultec?). I think there was a place (UK) selling inductors (as well as transformers) to people trying to repro those old EQs but as I recall the prices for the inductors were not cheap.

[Dai H.]

(DOH!) I guess I completely missed the gist and the link to Jack's article above...  Anyhow, scrounged some inductors (a GCB-95 wah inductor, some dinky one apparently for transistor radios wired so DCR shows series R, and another dinky one cannibalized from some old Sony cassette player found in the garbage (using the side showing higher DCR)) and hooked them in series (I have no idea what the exact inductance is since I don't have an LCR meter) to try the experiment. Didn't work well by itself between the wah output and fuzz (Roger Mayer version FFace with better working transistors) so tried a bypassed Pearl flanger (not true bypass) and it worked but gave too much high end. Then, I remembered I had a FET buffer project PCB from a DIY book, so I tried that but changed to higher output coupling cap (10uF from 1uF) and in conjunction with a series trim pot at the input of the wah'ed fuzz worked much better. It hums somewhat noticeably when the wah rocker is in the bass position (*I think* I have an inkling of what the noise cancelling series inductor wiring but not completely sure--I'll have to try it after I get a couple cheap transistor radio transformers). FWIW, Sansui makes a line meant most for transistor radios here (apparently have been for decades)  :


Sansui/Hashimoto Denki Xfrmers:

http://www.jarl.or.jp/Japanese/7_Technical/lib1/sansui.htm

and a bit of googling turned up inductance measurements for a couple of them:

             Pri.     Sec.    Pri.      Sec.      Pri.        Sec.   P+S in series   ratio

ST-48     600Ω    4、8Ω    38Ω   0.59Ω   916mH  14.5mH   1.2H           8.46:1

ST-54　 400Ω　  45Ω 　  21Ω　 2.9Ω 　  854mH　101mH    1.32H　        2.9 :1

ST-55   750Ω   120Ω   37Ω     8.7Ω     1.51H   320mH     3.5H          2.42 :1

ST-14　 500kΩ　1kΩ    6.2k     32Ω      128H     0.23H       n/a            22.4:1

autotransformer/choke
ST-30    12.5kΩ  50kΩ   (sec.supposedly usable as wah inductor)

Price is around USD$6-10 for most of them IIRC. Look similar to the Mouser ones (but don't seem to be exactly the same, so diff. manf.?).

-----------------------------------------------------------------------------------

a page with some pickup inductance measurements:

http://www.buildyourguitar.com/resources/lemme/table.htm

[brett]

Hi
The primary and secondaries in those little 1k:1k and 3K:3K transformers at Radio Shack and everywhere else have high inductance (400 to 2000 mH).  In fact, you can use them for wah inductors.  If I recall correctly, the 1k:1k transformers are close to 500 mH, and have about 150 ohms of DC resistance, but I can't recall their self-capacitance.
cheers

[Dai H.]

thx. Right, R.G.'s wah article (which came out some while ago) has mentioned that. Good to know but these days it doesn't seem to be too much trouble to find purpose-built wah inductors. Some seem quite inexpensive like the "Eleca". Maybe they can be used in other ways though like the pickup simulation above, tone controls, or whereever an inductor would be handy or interesting.

[brett]

For those wishing to DIY, there are "wind your own inductor/transformer" kits for a couple of $.  They are simple - a plastic spool that fits inside a hollow two-piece ferrite donut. 

The FX2240 is the one I use.  900 gives 2000 mH (ie AL = 0.0025mH).
In each case, fine enameled wire is required (about 0.15 mm for 900 turns).  DC resistance will only be 40 ohms, so the Q can be very high, if desired. 

450 turns gives 500mH and 20 ohms with 0.15mm wire.
cheers   

[MR COFFEE]

Hi all,

Here is a pic of some miniature inductors that really pack the inductance in -

6 Henries 850 ohms series resistance



Two in series or parallel placed top to top makes them humbucking, too.

I have a few spares. PM me if you want some. They also make regular humbuckers get more of that bluesy soap bar sound without the hum (put in series with the pickup hot lead). Good for slide.

[Gus]

Don't forget about the pickup(s) resistance.

[Dai H.]

I have an LCR meter now, so was able to take some readings of the inductors used for the experiment.

(transformer winding from salvaged Sony cassette recorder transformer) 1819.1mH
(unknown transistor radio type small Xfrmer with P and S windings connected in series) 236.2mH
(wah inductor removed from GCB-95) 606.3mH

total 2661.6mH, or about 2.66H (so within the 2 to 3H range Gus states as probably good for the PU simulation--except this wasn't a humbucking coil)

I'll have to try this again without the inductor(ance) since I forgot to try it with just the buffer.