Varitone: Pull DOWN resistors=misnomer?

[rjb]

If my "magic formula" is right and (as I suspect) all that matters is the input impdedance (and, to a lesser extent, DCR), I've found a substitute for the -019 that's physically smaller and a few pennies cheaper, plus a shielded version that must be good because it costs almost twice as much. But I'm not going to list them here, because I'm afaid if I did they'd be sold out at Mouser by the time I got around to placing an order.

[Chuck H]

Holy crap... Just figured it out. I thought it was just my formula illiteracy keeping me from understanding 2PI (2*power*current) Which didn't make any sense to me because it doesn't make sense. Current is a denote of power... Hmmm??? You meant to write 2Pi, right? Got it now. Other formulas for inductance I've seen are out of reach because they include greek lettering and $h!t. I can use this one.

Thanks

Chuck

P.S. On a "bad news" note I'm gonna hunt down those other inductors (possibly transformers) you found in the Mouser catalog and buy them all so they go on back order JK

[David Schwab]

That's another thing- I don't understand what constitutes an "appropriate" inductor. I look at the specs for that thing and see input impedance of 4Kohm +/-10% at 1KHz. Do the math thing... Z = 2PI x f x L, solve for L... looks like 0.64 Henry. Isn't that kinda low for this application? I must be doing something wrong, but the designs I see floating around the web don't seem to "work on paper" - I get bandwidths over 2KHz. I don't have any real test equipment, and don't wanna mess with it (at least not right now, and not for an old PBass).

Because people tried them, and either they worked or didn't. You are free to reinvent the wheel of course, and try a bunch of transformers to find something that works. Maybe one will work better.

Obviously none of them are the same rating as the original Gibson inductors, so the notch wont be as deep. I have also used an audio coupling transformer sold at RadioShack. But they do work. I first built one of these back in 1975 when Anderton's book came out and installed it in my Rick. I've had them in several other basses and guitars too. For bass you need to increase the cap values. Anderton uses different caps than Gibson, and he suggests to double the values.

Just try it and see what you get. Don't get all hung up trying to do it on paper.

You can also wind your own using a bolt, a nut, and a few washers, and of course some magnet wire. This is the inductor used in the Gibson L6-S and L9-S Ripper.




The Gibson frequencies (with the Gibson inductor) are supposed to be:

• Position 1--> bypass
• Position 2--> -5db at 1950hz
• Position 3--> -12db at 1100hz
• Position 4--> -16db at 620hz
• Position 5--> -18.5db at 360hz
• Position 6--> -21db at 120hz

[David Schwab]

Un-unh. The bypass switch position shorts the 100K.

Duh... yes, of course. What was I thinking...

[EDIT]Now I see... the Anderton circuit has a 47K resistor in the signal path all the time.

Anderton also doesn't use the bleed resistors.

However... if you leave out the 100K resistor, the depth of the notch theoretically is reduced by about a factor of ten, BUT, using the "Anderton" transformer (10K input @ 1KHz) and estimates of 6H and 12Kohm for the DiMarzio PBass pups,....... scribble, scribble, scratch,... that looks like a bandwidth of about 250Hz. Damn.

Thanks a lot, David. Now I *have* to buy an audio transformer and a DPDT pot!

Try out some caps to see what you like. I had figured out some good values for bass years ago using the Anderton circuit, but I lost that list.

I'm actually getting ready to make some Varitones, so I need to figure them out again.

[52 Bill]

The idea behind the 10M resistors is that they are across the switched terminals. The noise caused by the charge or discharge of the cap is lessened because the two sides of the switch are held at the same potential by the resistor.

It's the difference of potentials on each side of the switch that are suddenly changed by the switch wiper that cause the noise to be generated.

And it's my personal belief that the 1.5 Henry value is wrong for the vintage Gibson circuit. I think that it actually was 15 Henries. I've measured two different original vintage chokes now and both were closer to the 15 henry value.

[rjb]

You meant to write 2Pi, right? Got it now. Other formulas for inductance I've seen are out of reach because they include greek lettering and $h!t. I can use this one.

Golly, you wouldn't be pulling my leg, wouldja?
Yea, I meant 2Pi, as in
Paw: Whad ya learn in school today, Sonny?
Sonny: I learnt Pi R squared.
Paw: Why that ain't right! Pie are round.

[rjb]

The idea behind the 10M resistors is that they are across the switched terminals....

THANK YOU, BILL!
Que sound of scales falling from eyes.
That makes sense. I just needed the right explanation. And it didn't involve any math! Thing is, I'm pretty sure I used to know this. I *know* I used to know this. Damn.

And it's my personal belief that the 1.5 Henry value is wrong for the vintage Gibson circuit. I think that it actually was 15 Henries. I've measured two different original vintage chokes now and both were closer to the 15 henry value.

I'd have to crank the speculator into overdrive to comment on that....

Not to mention the "M" word, but if you take the notch frequencies David listed, correlate them to the caps on the schematics, then follow this link resonant frequency - Wolfram|Alpha and plug in the numbers, you get L's in the range 6.5-8.0 Henry. If L is actually the series inductance of the pickup and the choke, 1.5H would be in the ballpark. I dunno what else to say, except THANKS AGAIN!

[rjb]

You are free to reinvent the wheel of course

I wouldn't ordinarily consider substituting a component as "reinventing the wheel". Knowing which parameters are important would be nice. Then, when all the "Torres" and "Anderton" transformers are sold out, I could say "No problem, this part will work just as well".

and try a bunch of transformers to find something that works. Maybe one will work better.

If I needed to build a wheel, I might start with the fact that most wheels I've seen are round and use an axle- rather than try a bunch of objects to find something that might work better.

Just try it and see what you get. Don't get all hung up trying to do it on paper.

GOOD advice! Thank you.

You can also wind your own using a bolt, a nut, and a few washers, and of course some magnet wire.

Maybe I will. Keep an eye out for my e-business, when I start selling them for $100 per henry.

[nekodensha]

Hi everyone.

David and/or 52 Bill, could you please post whatever further specs or info you may have on the Gibson nut-washer-and-bolt inductor?

I'm keen to reproduce it pretty much as exactly as possible. That way I can copy the rest of the Gibson varitone circuit and get some fairly pronounced notch filter effects.

Love the forum BTW. It's done wonders for my education.

[Chuck H]

Golly, you wouldn't be pulling my leg, wouldja?

Easy now... I thought YOU were trying to multiply power times current and I didn't call you on it

Cheers

[Rick Turner]

But does this shit sound any good?

I'm not a major fan of passive "tone control" madness. Most of it sounds crappy, and the perceived volume differences from one setting to the next are intolerable. Just because you CAN make a passive electric guitar or bass sound different doesn't mean that it's musically useful.

If you can't make pickups that sound good on an instrument that sounds good, no amount of capacitors and inductors and resistors will make it any better.

This is like attempting to build a great recording studio with nothing but SM-58 mics and a pile of equalizers rather than getting a good selection of mics first.

[Chuck H]

Dude... What???

Race car drivers don't all want to be truckers either just because both things involve driving. A lot of guys use passive tone controls on guitars and basses to good effect. No one said you had to. I don't use ANY tone controls on my guitar. But I sure wouldn't want to miss out on all the great recordings done by guys who do use their passive tone controls because they liked how it sounded. What else matters besides that and why should anyone feel just like you do about such a subjective matter???

[rjb]

EaI thought YOU were trying to multiply power times current and I didn't call you on it

My bad, then. I thought you knew I meant Pi and were horsing around. Just one of those cases of what I think programmers call an "overloaded variable"- where the same symbol, initial, or acronym can have different meanings depending on content. Like Industrial Programmable Controllers (IPCs) used to be just PCs until personal computers came along. Or take Large Scale Devices (LSD) for instance...

Later,
-rb

[rjb]

I'm actually getting ready to make some Varitones, so I need to figure them out again.

Roy Bookbinder used to tell a story about painstakenly learning a song from an old 78 RPM, and recording his own version on an LP. Over the years, he no longer played the song and totally forgot it. Then he started getting requests for *that* song. So he went back and painstakingly learned his own version from the old LP.

Does this happen to sound familiar?

Anderton says to try and double the values. I used his values and it worked great for bass. I replaced the Baritone push button in my EB-2 with a Varitone using the existing choke..

Later,
-rb

[rjb]

Race car drivers don't all want to be truckers either just because both things involve driving.

I'm more of a wheelbarrow guy myself.

I've got a problem with mine right now. The wheel is flat, but only on the bottom. And I can't replace it, because the one all the guys on the Wheelbarrow Forum recommend is backordered.

-rb