I want to build a varitone in a box got pics? or layouts?

[gregd]

Hi,Id really like some pictures and layouts for a 12 posistion vari tone in a box projects. no hand drawings ,cant see em. Very little exact info is available on line. Do I need a 10 meg r for each cap to eliminate pops? Do I need a make before break switch ? or vice a versa? do I also need to buffer it? If I use a larger box does it matter the size of the caps?      thanks 

[pinkjimiphoton]

Hi,Id really like some pictures and layouts for a 12 posistion vari tone in a box projects. no hand drawings ,cant see em. Very little exact info is available on line. Do I need a 10 meg r for each cap to eliminate pops?

probably. at least one for each of the switch poles. never saw a 12 position varitone, but doesn't seem too hard. just go up in values from a start point in decades. but pretty sure  12 steps would be overkill. going from say, a .22 cap to a 2.2 cap is a huge difference; going from a .047u to .1u is a huge difference even.

Do I need a make before break switch ?

if you want it to seemlessly switch from one position to the next, probably. not that familiar with the circuit, but sure someone else will chime in more knowledgably.

or vice a versa?

the other would give you an audible dead spot while switching most likely...probably why it has such huge pull down resistors.

do I also need to buffer it?

you don't need a buffer to use it most likely, tho i'd imagine it would work better as an active cct than a passive one.

If I use a larger box does it matter the size of the caps?      thanks 

you want to make sure your caps are rated about double the voltages you expect to pass thru them. if it's passive, and just a guitar or line signal, 9-15v caps should be fine. bigger caps will cause other issues with parasitic inductances, equivalent series resistance, etc..

but in general, use whatever ya have for caps. you may wanna breadboard a simpler version to start. some of the values may not be all that useful.

that said, tho, if you put in high enough rated caps, you could get double duty as a cap decade box.

[gregd]

This box is for the shop only .Not going to use it to play live.With the correct caps I could test to guitar or bass. I have loads of PIO caps and thought If it dont cause a problem Id like to use them .Large box is fine. I am winding some pickups and want to test different pickups to different caps.Do I really need 1 resistor per caps . doable yea?

[pinkjimiphoton]

if you're just gonna use it for testing, hell yah, use whatever ya have around the junkbox and shop.

if all you're gonna be using it with is to test pickups, pretty much any voltage value is fine, tho some high voltage caps may not have close to the rated capacitance
at really low voltage levels.

but for what you're doing, oh, hell yah, you should be fine i would think. be interesting to see what ya come up with, so please post again, greg!

[gregd]

thanks for the ok    Oh--What henry inductor 7k or??   thanks

[pinkjimiphoton]

pink don't be knowin' nothin' bout no inductors. bra'h.....

but it seems to me that would be pretty gig, i believe most of 'em are around 1500mh, but i am probably wrong.

i'm  a simple fuzzbox guy.

[chptunes]

Have a look at Craig Anderton's classic circuit.. I've built a few of these.  It was my first attempt at building from a schematic a few years ago.. my first couple of units were dreadfully ugly and of minimal affect.  But, when built properly.. this Varitone variant is a great tool.

The Inductor here is the 42TM019.. Small Bear has it.  The Primary side measures around 11.6 Henry (full coil) and 3.5 Henry (half coil).  Use this online calculator to factor your Resonant Frequencies:  http://www.1728.org/resfreq.htm

A 0.047 µf Cap at 11.6 Henry calculates to 215Hz, and 392Hz at 3.5 Henry.

This 12-Position Rotary Switch has shorting actuation, so no Pull-Down Resistors are needed:  Lorlin CK1589

Schematic from Anderton's Electronic Projects for Musicians book:


photo uploader

-Corey

[Mark Hammer]

If one wants a very flexible unit, build the Anderton circuit, but use a 3-position toggle to shunt either the caps OR the choke OR neither.

With simply a series resistor, and an inductor and variable resistance to ground, it becomes a variable bass cut.  With the inductor shunted instead, it becomes a multi-position treble cut.  And with neither shunted, the LCR circuit function as a notch filter.

There is a reasonable amount of both loading and passive signal loss resulting from the circuit, so what I do is stick a simple JFET buffer/booster in the front.  In my case, I used a Stratoblaster circuit, but anything with a high input impedance is fine.

[chptunes]

If one wants a very flexible unit, build the Anderton circuit, but use a 3-position toggle to shunt either the caps OR the choke OR neither.

With simply a series resistor, and an inductor and variable resistance to ground, it becomes a variable bass cut.  With the inductor shunted instead, it becomes a multi-position treble cut.  And with neither shunted, the LCR circuit function as a notch filter.

Mr. Hammer.. I am interested in the added toggle switch.  How would you wire it up.. can you lend a practical explanation or rough sketch?  How many poles would this toggle switch need?

-Corey

[Mark Hammer]

Fairly simple, actually, and only requires a SPDT toggle of the on-off-on variety (3-position).

The circuit will have a 47k resistor in series between the input and output, plus a capacitor, an inductor, and a pot (variable resistance) going to ground, right?  In your case, the cap value is one of twelve selected via a rotary SP12T switch, instead of the 6-position switch shown i the posted schematics (I can't seem to post a link here, but if you image search for "EPFM passive tone control", you'll see a bunch of places with essentially the same diagram shown).

We'll pretend, for the moment that there is ONE cap, ONE inductor, and the pot going to ground.

Okay, run a wire from the junction of the cap and inductor to the middle lug of the toggle.  Run a 2nd wire from one of the outside lugs to the junction between the inductor and the pot "input".  Run a 3rd wire from the remaining outside lug to the "far side" of the cap/s, where it/they are tied to the output of the circuit.

When the toggle is in the middle position, both the cap and inductor will be in circuit and your rotary switch will select one of 12 different notches, with the pot adjusting the depth of the notch.

When the toggle is turned to one of the outside positions, it will shunt the inductor such that it is as if there is no inductor there, and all you have is a cap and pot to ground.  This will give you twelve different rolloff frequencies where you can adjust treble cut.

Flick the toggle in the complete opposite direction, and the cap/s will be shunted so that the circuit behaves as if there is only the inductor and a pot to ground.  This will give you a variable bass cut.

[chptunes]

Super!  Thanks for taking the time to give us that explanation.

[gregd]

That schematic has a lot going for it I dig the switch on the inductor. I could still use a 12 posistion switch right? I dont know why Im stuck on that switch, I guess I want a very full range. Is there a pc board and layout available ? Oh Some one mentioned a decade unit ,what is that and what is it used for? are there layouts and pc boards available?

[Mark Hammer]

At a certain point, if one wants more, more, and more flexibility, it starts to become more sensible to build an active filter of some type, such as a state-variable, or a parametric EQ section, where you can adjust depth, width, and frequency.

I understand the charm of a simple LCR varitone-type circuit, but once you start adding a switch here and there, and all the wiring, you may just end up with something that makes you think "Maybe I should have just made one of those."

Just a thought.

[gregd]

any chance of a simple version schematic with inductor in here? A layout is even better cause Im schematic challanged   thanks

[Mark Hammer]

There, how's this?

[jimbeaux]

This is the Passive Tone Control from the first edition of EPFM - simple and easy.

The inductor listed is a Radio Shack # 273-1378 which they don't carry anymore - a 42TM019 (Mouser) should still work?
(10K Primary / connections "F" & "J" as shown in fig. 5-23)

[smallbearelec]

If you want a "clean" filter of this kind, the Anderton circuit is fine. If you want something that can do way more "honk" and dirt (like the "Paperback Writer lick), try a Wild Mouse:

http://www.smallbearelec.com/servlet/Detail?no=3

The present kit is fairly beginner-friendly since it includes a PC board and an almost-finished case.

Regards
SD