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Tone cap: technical specs?

Discussion in 'Tele-Technical' started by SSL9000J, Jul 28, 2019.

  1. SSL9000J

    SSL9000J Tele-Meister

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    Disclaimer: this is not an attempt to debate the merits of any particular components' brand, age, value, manufacturing methods, etc.

    Greetings!

    What I have are a selection of capacitors salvaged from various sources which appear to be in good condition. (Bumblebees, orange drops, etc.) When tested via ESR meter, the capacitance values are within spec, at least according to how the caps themselves are labeled. (Full disclosure: it is a cheap ESR meter, far from pro workbench quality, but good enough nonetheless.)

    What I don't understand is how to make sense of the effective series resistance or voltage loss readings. Is less better? What is an acceptable range? Does it even matter, as long as it doesn't indicate an open or short circuit?

    I haven't found much if any technical info pertaining to actual tests, with the exception of electrolytics. And it seems like a good idea to validate the electromechanical what-have-you before getting into trying out & auditioning these "vintage" (ok, OLD) caps.

    Thanks!
     
  2. awasson

    awasson Poster Extraordinaire Silver Supporter

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    I assume you’re just talking about standard tone cap usage and in that case the voltage ratings really mean nothing. Those old .1uf disc ceramics fender used on old Strats were 1kv but the signal they are affecting is measured in millivolts. A lot of orange drop caps are 400 volt rated but it just means they will tolerate that high a voltage. The important reading is the value in microfarrads.

    I think when you go down the tone cap rabbit hole, you can make a lot of valuable changes without spending a ton of money. Sure it takes time but you can fairly quickly determine what range of a cap you personally prefer.

    I’ve got a go-to formula for my preferences for single coils and it’s probably not a standard recipe but here goes:
    • Volume Control - Linear (type B) 250k potentiometer.
    • Tone Control - Log/audio (type A) 250k potentiometer.
    • Tone Capacitor - 0.015uf -to- 0.022uf.
    • Aside from that I like the 50’s Gibson tone mod where the tone control connects to the output side of the volume control as opposed to the input side of the volume control.
    The results are a very smooth and consistent set of controls.
     
    Last edited: Jul 28, 2019
    SSL9000J likes this.
  3. SSL9000J

    SSL9000J Tele-Meister

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    I understand. But aside from the rated voltage, which is well and above what's actually required, how does measured voltage loss relate to how a particular cap functions as a high pass filter? (If at all.)

    Edit: What had me pondering this in the first place was trying to find data from when some of these caps were new, and comparing it to how they measure up now.
     
  4. kbold

    kbold Tele-Afflicted

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    The capacitor in a guitar is, with the tone pot, creating an RC circuit. The nature of capacitors is to block DC signals and pass AC signals, so their effect (reactance) is determined by the signal frequency.
     
  5. Ricky D.

    Ricky D. Doctor of Teleocity

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    I thought I understood this stuff, but maybe not. D.C. Voltage drop across a capacitor should be 100 %, right? Anything else indicates a problem.
     
  6. jvin248

    jvin248 Poster Extraordinaire

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    .

    I've heard that caps can pass ESR and still not work right.

    I measure the capacitance as that is important, and I'll choose higher voltage rating, but the actual measured value is most important.

    Many capacitor testers read the label that says "0.047uF" and compare different manufacturers with the same marking and then after comparison testing on a guitar proclaim one brand is better than all the others -- when the reality is that cap was at one end of the very wide tolerance band while the others were all at the other end of the wide spec. Typical capacitor can 'acceptably' vary by a 10% range, but the extremes of that spec might be a problem for your guitar tone.

     
  7. Dacious

    Dacious Poster Extraordinaire

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    I reckon I can hear the slightest difference in volume on cap 4 in the second and third run throughs - but, as the dude said, maybe he was just picking softer. Tone - sounded absolutely identical.

    It's like the 'CBS brown caps are little turds' thing. There are so many other things that account for why CBS-era and particularly late CBS sound different other than brand of coupling caps post Blackfaces.

    I always think of the tone cap as like a high jump with a second high beam above it, between the pickups and output. Very low frequencies can't get over it, as you start winding the tone down from 10, the beam starts dropping towards the bar, and very high frequencies start hitting it, meaning the range between highs that are cut and lows that are cut narrows.

    The value of the cap and pot makes a difference to your starting points to the beam and bar but presuming they're both in spec - not the type.

    It doesn't even seem to matter with caps what voltage you use - so why use bigger/more expensive than you have to?
     
  8. Corvus

    Corvus Tele-Meister

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    Over the years I've tried all makes and all sorts of types and I'm just not convinced by the old "everything made then was better" argument or that buying an expensive "original" will give to the "original" tone. Certainty as regards caps many were poorly made in the past and way out of spec and with guitar signals there is no need for them to be large or high voltage -or to be over expensive. Capacitance is actually an effect - capacitors in themselves do not have a tone - that's marketing hype; tone modification comes from dumping some of the high frequencies to ground through a variable resistor - a pot. What I would say is that if you go for a decent make of cap or pot you are more likely to get something close to the marked value. However I think you have to consider if one can really hear small differences due to the type/make of cap (not the value which does make a difference) because there are many other factors affecting your guitars perceived tone. Decent pots can make a huge difference; we've all come across those which are "sudden" and don't work across much of the range and then there's the frequencies coming out of the pickup - a Fender type single coil has a lot less middle than a humbucker and so seems to go darker quicker. You could try different pot values or log v lin but 250k and 0.047 was chosen to tame the shrill treble of a telecaster.
     
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