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Re: tone capacitors?!?


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11/27/1999 4:20 AM
JC
Re: tone capacitors?!?
Mark.  
 
Thank you very much.  
That was perfectly clear. You don't underestimate my electronichs knowledge at all; it's as reduced as it appears to be.  
My "problem" is that I don't know very much about electronics, but I know which kind of sound I like, so I can't explain why I like one guitar or amp, or even a setting, more than another.  
 
For example, I love the sound of my Orange and strat with '50 custom shop pu's at any setting, but I don't "know" why.  
 
I've been in a shop today, and tried a few amps that even turning and re-turning the tone controls I dind't like as much. They where "too bright" to my likings: a beautiful small Ampeg combo and a Crate vintageClub 50. And a few days ago, I listened to an Engl Screamer 50w combo, that could be very clear and bright too, but it also had some of "that" that I like most...  
I don't know if it is midrange, or the capacity of reproducing certain amounts of both bass and highs, or what... I only know that some amps are capable to reproduce some frequencies??? that make me vibrate and "feel" the notes coming out of that amp (I'm sorry about that I don't really know what I'm talking about, technicaly speaking. That makes me feel horrible sometimes)  
 
Or maybe it is just an auditive problem/idiosyncrasy of my ears.  
 
Thank you again. Your answer helps me a lot.  
 
jc
 
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11/27/1999 8:19 PM
Ed Rembold
for Mark- some clarity
Mark,  
Your post made me laugh, Thanks.  
I think what I was trying to bring out in my own post,  
is that the "tolerance" of the ceramic cap is Most Important, not the value. the tolerance of most ceramic caps  
is an almost unbelieveable +80 to -20 percent- at this rate  
the value chosen is almost a moot point- (see what I mean?)  
The tolerance of the better ceramics is + or - 20 percent,  
so then the "value" chosen would at least be close.  
On a Strat (with no other tricks) I prefer a .022 on the  
neck PU and a .01 or a .022 (which measures on the low side-like .015 or so.)on the bridge PU , with no cap on the middle PU. since its use is mainly for quack in position #2 and #4. I also like to lower the middle PU , which helps fight "stratitis" , gives great quack ,and promotes sustain by reduced magnet attraction- Try it. Also something to think about- The way you mentioned doing the caps and most  
other methods that are used, end up putting the caps in parallel on one or more of the pickup selections- This is not smart, we all know that caps in parallel Add their value.  
Ed R.  
 
 
11/29/1999 9:06 PM
Mark Hammer

Happy to bring a grin to your day.  
 
Not that you need my approval, but your own personal Strat tone solution is very Hammer-approved.  
 
As you allude to, it is important to realize that WHERE the tone control is in the circuit is important. Ideally, tone controls should PRECEDE the volume control. Where there are separate tone and volume controls, either the tone controls or both tone and volume controls should precede the pickup selector switch, in order to keep them from interacting or having summing effects. E.g. two tone controls w/.02uf caps turned all the way down, would be equivalent to sticking a .04uf cap on the output, if the tone controls followed the volume control.  
 
As an aside, this always struck me as a VERY big downside of guitars that had their switching system at the complete opposite end of the instrument relative to the controls, like Les Pauls. How does one run cables from the pickups to the controls, then across to the switch and back to the output jack? Even if you did, how do you do so without incurring noise and tone sucking from cable capacitance?  
 
As for the tolerance vs value debate, my own experience with ceramic discs is that they are generally pretty close to what they say they are, unless heat or something equally extreme comes into play. The +80/-20 spec refers to off the shelf value, not an operating fluctuation, and is largely like a contractual loophole ("Yeah I know it SAYS .047uf, but .059uf is still within the terms of our agreement so get off my case"). If anything, even with an 80/20 tolerance spec, modern fabrication techniques should probably achieve more accurate values on a fairly consistent basis. I'm constantly amazed at how easy it is to match caps withing 5% for filters and such with my meter. Rather than look for types of caps, just measure them and use the value that is appropriate for your tonal goals. If it *says* .01uf, and *measures* .013, and it works for you, fine.
 
11/30/1999 2:20 AM
Ed Rembold

Mark,  
Those are more great points that you mention.  
And you know what, That's exactly how LP's are wired -  
as you said- un-believable huh?  
By the way Mark, I know you're busy, but don't forget  
about that "Delay/chorus Tone Control Fact" that you were  
going to put together and send to R.G. to post on his site-  
I'm waiting for that one, (Hint,Hint)  
Thanks Ed R.
 
11/30/1999 5:12 PM
Mark Hammer

I've been working on it, and it's up to about 8 pages now. I figured I'd put together a "Technology of BBD-based effects" paper. I have a large family function to coordinate this week but I'll try and finish it up before the holidays set in. Trouble is, when you try and make something fairly sprawling, it's easy to lose track of what has and hasn't been said already. I also have to work on the graphics. You'll like it when it's done, though.
 
11/30/1999 6:52 PM
Doc

Mark, have you tried using any linear tapers for tone control pots? Might there be any advantage in useful control range over the usual audio or log taper pots?  
 
Thanks,  
Doc
 
11/30/1999 10:24 PM
Mark Hammer
Nailing down your ideal tone pot
"...have you tried using any linear tapers for tone control pots? Might there be any advantage in useful control range over the usual audio or log taper pots?"  
 
I honestly couldn't tell you what I have and haven't tried. Hell, I'm not even sure if the volume pots in my guitar are even audio taper. I just go through the box of pots until I find something of the desired value that tests good and use that.  
 
Having said that, I can see arguments offered for all kinds of tapers, from the anti-log through linear through log or combination tapers. It really depends what you are trying to do and what you are trying to do it to.  
 
For example, the late Danny Gatton (listen and be humbled) had a tone control on his Tele that could be used like a low Q wah. The effect was contingent on having a modest amount of pinky action produce a robust effect. Somewhere in there is a combination of specific taper and cap value, such that the "voice" of the guitar would be introduced easily, otherwise it would hamper picking style. For all I know, the remaining 180 degrees of rotation might have produced negligible change.  
 
Other players might view their tone pot as a "mood changer", such that the ideal pot would be one that easily identifies and distinguishes a few different tonal moods (strident, confident, sombre) but doesn't have to do a heckuva lot otherwise. Still others want the tone pot to help achieve sonic balance, perhaps by compensating for the room, the speakers, or FX that add harmonics.  
 
So much for the "mission" of the tone pot. The context in which one tries to accomplish that mission is another thing. Different pickups and guitars may have different resonances, and the point in the pot's rotation where that resonance is affected (resulting in the perception of a change in the tonal "character") may vary. This is, of course, the source of my unswerving crusade about different cap values for different pickups. If the player routinely uses a distortion device, then different points in the rotation may be "magic" with respect to changing the balance of harmonics.  
 
Personally, I would vote for the following general protocol in nailing down what you consider to be the "ideal" tone pot.  
 
1) Start with a larger value pot, say 500k-1meg. Doesn't really matter what taper, for the time being, although linear might be better for doing your calculations. High values are good for being able to fake NO tone pot (i.e., conserve all possible high end in the signal). Some folks like 250k volume pots for single coil pickups to take away the brittle-sounding high end, but even with that compensation, a 500k tone pot will let you keep ALL of the tone you like.  
 
2) Select a cap value in the ballpark; .02-.047 for front pickup, .0082-.015 for rear or single coil. If you aren't sure, just stick an assortment of caps across the two outside lugs of the volume control and think long and hard about whether the voicing provided with the cap is something you would like to play *with* or something that you would rather get around.  
 
3) Wire up the tone pot as per usual, with the preferred cap, and turn the tone up full. With the amp's treble up full or just a bit past where you would usually position it, rotate the tone pot bit by bit until you start to hear what you think of as a taming of treble. Measure the pot value and write it down. Turn the pot a bit more and note the point where the vocal aspects of the pickup start to be affected (i.e., upper bass, lower midrange starts to be affected).  
 
4) Now you can plan out the taper that works for you.  
- what is the difference in resistance between max and the first change?  
- where would you like that changeover to be situated on the control; between 9 and 10? between 7 and 10?  
- what is the difference between max and the second change? between the first change and the second? where would you like that one to be?  
 
So, suppose that your ideal first changeover comes at around the 300k mark, and you'd like it to be situated at around the "7" mark on your tone control. So, we intend to have 30% of rotation (number-indexed knobs usually can be treated as referring to percent of rotation) accounting for 40% of the resistance change. Perhaps your next changeover point comes at around 50k, and you'd like it to happen at around the 4 mark on the knob. What happens after that is just more muting.  
 
Okay, so now we have the following requirements:  
- turn down about 30% to get 40% resistance change  
- turn down about 30% more to get an additional 50% resistance change  
 
Plot this out, then go to RG Keen's site and look at the document on pots Then figure out which taper comes closest to what you want, and - using the tips listed - mod the pot from there.  
 
http://www.geofex.com/Article_Folders/potsecrets/potscret.htm  
 
Just bear in mind, that the document at GEOFEX is largely pitched at using pots in voltage-divider mode. You will want to use the pots as variable resistors, which will mean bridging one of the outside lugs and wiper, in addition to use of a parallel resistor.
 

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