Inductors, Varitones, etc...

[ZiggyZipgun]

I've doing some renovations on my Hagstrom Swede, which has a really odd tone switch with different caps on each side and bypass in the middle. The caps that come installed are pretty awful, so I already swapped one out for a .001μF, very subtle and mellow - like the first position on a Varitone. Now for the other side....I'm thinking about using the other setting as one of the more drastic Varitone settings, which would require an inductor. Any ideas where I could find one for this purpose, preferably on a site with music-related terminology?

[wolf]

I don't know about a site with music-related inductor information, but I'd say you might want to try a wah pedal inductor. These are usually about 500 millihenries, but be cautious about spending too much for one. Some places charge $20. Why? Because it is an absolute reproduction of the Fasel inductor that was used in the original wah pedal (or some other over-hyped nonsense).
Anyway, high-value inductors (500 millihenries and more) are difficult to find in this day and age. I believe the largest value inductor that Mouser Electronics sells is 150 millihenries. (a rather low value when you want to do any serious tone modifications). You could wire three of these in series for a 450 millihenry inductor but I've found these inductors have too much resistance to be sonically useful. It seems that generally, inductors used in audio circuits have low resistances.

So, maybe at a guitar shop (especially a guitar repair shop) you could buy a wah inductor that's just hanging around in their repair shop. (Wah pedals need fixing fairly often).
Still, you might want to take an even larger step and use a modem transformer. I used one from an old dial-up modem and if my meter was working correctly, it measured 1.4 Henries of rock and roll inductance (and it had low resistance). I used it in a tone circuit and it worked very well.

[ZiggyZipgun]

More inquiries in two parts

Part 1
I used it in a tone circuit and it worked very well.

After looking at some current Varitone offerings that are out there, I'm still not sure what role the inductor plays in the circuit - my father just put one in his guitar, and it seems like the transformer is placed in line with the ground, and everything just grounds through it. Are all positions on the Varitone then affected by it? As I mentioned before, I already tried the same .001μF cap as on the Varitone's #1 position, and it sounded very much the same (didn't do an A/B comparison, so I can say it sounds like I expected it would). What gives?

Part 2
The Kent Armstrong ToneChoke

Since I've only seen this on a small handful of online shops in England and nowhere else, I've had no luck finding any reviews or specifications on it. Has anyone tried it? Would this be wired into a tone switch/pot instead of a capacitor, or with it? The same question applies to wah pedal inductors and basic transformers.

[ChrisK]

The inductor in the Varitone circuit along with the cap in series with it forms a series resonant tone circuit. Since both a cap (lower impedance with higher frequency) and an inductor (lower impedance with lower frequency) are in seres to ground, a maximum of pass current (limited by the resistance of the inductor - it's actually very important) occurs at the resonant frequency.

Therefore, (scroll down to series resonant) it forms a band pass filter to ground and hence, a band attenuation or notch filter.


Modem transformers aka coupling transformers are ideal for this. they have both high inductance and high resistance.

From one of my post yarns ago on the FDP

"Bill Armstrong sells a 1 Henry inductor ($20) for this purpose. I do know that one similar (if not the same part) to the Torres is commercially available, it's made by HI-Q and sold by mouser.com for $1.37/1.

It really is an audio coupling transformer (that's why you cut leads off, see www.geocities.com/guitarwiring/index.htm for instructions).

Based on a 4K Ohm primary impedance and a stated inductance of 1.5 Henry, it would indicate that the reactance is measured at 400 Hertz. Based on this, one can "generally" interpolate the inductance of the other offerings accordingly.

They do have a minimum order, I've never checked what it is. Since I buy from them corporately, I'll get a selection someday.

A clever fellow would buy enough of the following to meet the minimum:

42TL022 1.5K Ohms .56 Henry
42TL021 4K Ohms 1.5 Henry
42TL018 7K Ohms 2.6 Henry
42TL019 10K Ohms 3.75 Henry
42TL025 17K Ohms 6.4 Henry
42TL017 20K Ohms 7.5 Henry

If you put two in series, the values add.
If you put two in parallel, the value is
A*B/(A+B). Same things happen when you connect one to a PU(s).

I use a 1 to 3 Henry value since I have several inductors left over from the 60's (when they actually were common). I have a 20 to 200 Henry miniature variable one, but that's a different tale.

Hope this helps, have fun."


I once tried a 1 H 1,000 Ohm unit that I have with bad results. Remembering the above statement about resonance, the 1,000 Ohm DC resistance to ground acted just like a, uh, 1,000 Ohm path to ground.

[ZiggyZipgun]

So, while we're talking about inductors, what kind of resistance do the more talked-about inductors such as Fasels have, and could they be used in this context with half-decent results?

[ZiggyZipgun]

Anyone? Anyone?

[ChrisK]

Don't know. Don't know.

(I've never seen a Fasel inductor).


I would suggest that you look at my post, and log onto the mouser.com web site.

You will then know what the typical resistance is for the transformers with a particular inductance.

(All transformer's are an inductor, but an inductor is not a transformer.)

[sumgai]

chrisk said:

(All transformer's are an inductor, but an inductor is not a transformer.)

Just to dot the i's and cross the t's...... That should read "All transformers are made up of one or more inductors, but a single inductor by itself is not necessarily a transformer."


HTH



sumgai

[ChristoMephisto]

Here's some links that could help you
www.guitar-mod.com/rg_passive.html

www.geocities.jp/dgb_studio/index_e.htm
look for the LC calculator

I too have a vintage Swede, and the tone filter at the top is for sharp, mellow,deep. one goes in series with the .0047us, bypass, then add the .015uf cap to ground.

Unforunately, I don't think mine is soldered/wired right. Like you said its an odd switch, slightly different than a 3 way pup selector.
Would you have any pics of your switch, even if you did swap out the one cap for a .001. I can only get bypass and the deep sounds.
This is really stumping me.

Thanks
ChristoMephisto

[ZiggyZipgun]

Actually, mine is a recent re-issue Swede, and the two 3-way switches are the same as any Switchcraft toggle (the shorter straight ones). The cavities in mine are all well shielded with conductive paint, and after a little experimenting I noticed that had to keep the leads on the caps short if I didn't want them to short out on the inner walls. One of the leads probably popped off the .0047 in yours. However, the original switches used in the Swedes were the angled type that you'll often find in a Gibson SG or PRS, since the control cavities are shaped differently. A straight one will probably give you a little more room and easier access if you do plan on swapping out the caps for different values. Both of the caps in mine (same values as you mentioned) were far too muddy for me, but while I have a big order of various Mojo caps on the way, I put a the Mallory .001μF (that I had laying around for a treble bleed) in there, and left the .0047μF in there as well. The .0153μF I believe is based on Eric Clapton's over-hyped "Woman Tone" or at least that's the same value that Rothstein, Griblin, HAS, and all of these other custom tone switch makers use for that sound.
What actually got me thinking about all of this is that my dad actually just bought a custom Varitone from one of the above for his Hagstrom Deluxe F, as his old ES-345 had one, and I started reading up on the originals. I'll probably just end up wiring my Swede's switch with my two favorite caps and a resistor for each to cut down that popping sound (like Gibson used), but I still want to do some experimenting with inductance values.

Wolf never did say what that mystery modem tone circuit did exactly...

[ChristoMephisto]

The switch adds the .015uf cap to ground to the tones path with the .022/tone pot. If you want the woman tone, you need to switch the caps at the volume and tone pots.
Thanks for trying, yeah I do have the right angle toggle. Its only difference is one of the blades has the contact bump on the opposite side versus the pup selector.

cheers

[ZiggyZipgun]

What difference does would it make whether it was the cap on the tone control or a cap on a switch? He rolled it all the way down anyway, or so I thought - not that that's the sound I'm going for, I was just curious. The caps on my re-issue are .047μF, it goes from mud to mud if I use any of the stock caps on the switch. I still don't really understand what effect the inductor has on the Varitone, but I'll find out soon enough when my Kent Armstrong ToneChoke arrives (can you say impulsive shopper?).

[ChristoMephisto]

Didn't know they changed the switching system on the Swede that much. If you look at the original schems, you'll know what I'm talking about.
Rumor had it Clapton used a .015 cap with the tone rolled back, yes,
until you had told me the switch cap values were much different, I assumed it was the old values and was confused.

From what I've read about inductors is it boosts/cuts frequencies depending on the set up. Most are calculated to acheive a certain response. Did you check out the LC calculator link i posted?

[sumgai]

Ziggy,

............ I still don't really understand what effect the inductor has on the Varitone

In short, a capacitor wants to prevent frequencies below a certain range from passing through - frequencies above that point pass through just fine. A coil (an inductor) works just the opposite...... lows pass, highs are prevented from passing. The important part here is, it's all or nothing - above or below a certain point (determined by the component's value), all frequecies are treated the same.

When you combine the two components, you can manipulate those 'certain points' such that all frequencies outside of a small range are allowed to pass, but within that small range, they are cut down. (Often called a 'notch' filter.) If you add some amplification, you can reverse that action. (Sorry, you can't get something for nothing. ) This is called a 'bandpass' filter, for obvious reasons.

So it is with a Varitone circuit. Instead of a simple treble cut, the circuit cuts a small slice out of the frequency range, and the differences are noticible. But note here, there's another electrical property at play. When two inductors are connected in series, such as a pickup's coil and the Varitone's inductor, the total inductance is the two values added together. That seemingly adds to the mid-range frequencies, as this larger-than-normal inductance value acts to suppress the lower frequency range.

A frequency chart showing these results is rather dry, and doesn't convey much at all about the tonality of what's happening. In brief, the tones are quite different (compared to no Varitone at all), and usually desirable.

HTH



sumgai

[ZiggyZipgun]

Oh, another odd thing I've noticed on the new Hagstroms, at least on mine and my dad's - all Volume pots are linear, and all Tone pots are audio taper. I've seen two different wiring diagrams for the original Swedes, and the cap values for the tone knobs were different, but I don't know where the other diagram came from.

[ChristoMephisto]

The first one is from '77, with the .022uf caps, and the second I guess would be the reissues being from '05.

Thanks for your help
ChristoMephisto