the tone cap myth...

[Possum]

,,,

WOOD??? Sure, you could cast a les paul body in concrete and it wouldn't make any difference.....ok I'm lying :-)
Actually its true and poly finishes too, I hate poly finished sprayed on an inch thick. I had a cheap Chinese Squire strat I traded a guy, it was so ugly and new looking I took a heat gun to it and burned off and sanded off most of the finish and left it ugly. The tone of the guitar changed amazingly for the better. Its sad to see some nice looking guitar with a ton of plastic smothering the wood.

Then there's STRINGS. Has anyone tried the Snake Oil brands pure nickel strings? Alot of classic rock like Jimmy Page etc. was done on really light guage strings too....

[pdf64]

Steve A, re tone stack caps
'I thought that it explained how the Vox AC-30 tone stack with a 50pF treble cap is not, say, 5 times brighter than a Marshall tone stack with a 250pF treble cap. Intuition tells me that a 50pF treble cap would be too harsh and bright for at least my own tastes. In practise it isn't that much brighter and I thought it had to do with the comparative ESR values of the 250pF vs 50pF caps: the 50pF cap passes through a lot less audio signal than a 250pF cap'
The difference is that a fender 250pF cap is feeding a 250k pot (giving a turnover freq of 2k5Hz), whereas the vox 50pF is feeding a 1M pot (giving a turnover freq of 3k2Hz). So once the pot difference is taken into account, the affected frequency ranges aren't that different really. Peter.

[rocket]

Im a big fan of the CTS 500k pots from RS Guitar Works. Roy has CTS make a pot for him which is different than the standard CTS 500k. This one is more durable and built to higher tolerances. The have a brass shaft with locking ring so its harder to ruin the pot. They are within 5% tolerance (rare for a pot) and generally measure between 540-560.

b.

A 500K pot with 560K is hardly within 5% tolerance!

[Joe Gwinn]

Thanks for arousing my curiosity.

They're interesting and you can find a few early patents on them. The obvious benefits are that they are inexpensive. Most tables list paper dielectric constant around 2.0, wax paper is similar but moisture resistant. These caps would be larger than similar film capacitors (excepting teflon, of course).

Paper ruled until modern plastics arrived. The standard big multipair telephone cable was lead-jacketed (with soldered joints) and used dry paper to insulate the wires. The cable was pressurized to prevent the ingress of water, and monitoring of internal pressure allowed early detection and localization of leaks in the lead jacket.

A company still provides mil spec paper/foil caps:
http://www.dearbornelectronics.com/pdf/HSecscr.pdf

Dearborn, Michigan. One assumes that their main business is (or was) the automobile business, from the days when cars had breaker points and capacitors (the Kettering ignition system design). Actually, ignition systems may still have capacitors, only as resistor-capacitor "snubbers" used to protect the semiconductor switches that replaced the breaker points.

Their selection guide suggests that the paper-polyester hybrid dielectrics are better.

Seems likely. The strength of polyester would allow thinner films to be wound, and fills in the pinholes. High-voltage capacitors were always wound with multiple thin layers of paper, rather than one thicker film, so the pinholes in the layers wouldn't line up and allow an arc to punch through, destroying the capacitor. Filling pinholes and defects was also one reason for oil immersion.

The extreme example of this was a capacitor design invented by Sandia Labs for energy-storage applications (like the Z-pinch machine http://zpinch.sandia.gov/). The capacitors were wound of metallized polyester and housed in a pressure vessel filled with sulfur hexafluoride liquid (which is a gas at atmospheric pressure). The trick was that the liquid is a better insulator than the polyester film, and also is very good at quenching arcs, so the capacitor was self healing after a breakdown. This allowed the operating voltage to be much closer to disaster, allowing much more energy to be stuffed into the capacitor. It doesn't take much added voltage to be worthwhile, as energy stored in a capacitor is proportional to the square of voltage.

Polyester, being very smooth, also makes for a better surface to metallize. Although one can metallize paper, pinholes are a problem.

[SteveJ]

I have been trying out tone caps for quite a while now. I agree that there is a noticeable difference. If you guy's can find them, any of the old paper and oil caps that have the sealed glass ends are great. Vitamin Q, Good-all, Gudeman, Pyramid etc. They seem to add a vocal quality in my LP's that I can't get out of other caps. I haven't seen where voltage makes any difference when we are dealing with millivolts. I have the 400V Vitamin Q's in my main guitar and I have tried 100/200v in others and they sound the same. Try them and see what you think. Some guy's keep talking about the Russian PIO's and I have tried them but they seem to have a bit too much high end. They get tiring after a while. No scientific tests but a friend and myself have been experimenting with 4 different LP's. The Vitamin Q type smooth out the top end and a vocal quality. Try some and report back guy's. I'm curious to see if you get the same results. Here are some examples.
http://cgi.ebay.com/2-NOS-022-200v-S...QQcmdZViewItem
http://cgi.ebay.com/Capacitor-0-022m...713.m153.l1262

[Possum]

...

Thanks for the link, I bought the set of 2, will be curious to see how these compare to the real thing and the singlecoil.com caps with my pickups...thanks.

[SteveJ]

Cool! I'm looking forward to a tone report.

[David Schwab]

I used to have a bunch of those mil spec caps from when I worked at ITT. A lot of the early effects I built had some expensive parts in them!

[Mark Hammer]

Question: Do ceramic or other caps get "weird" because of how we solder them?

I know from my tinkering with stompswitches, that a large segment of the "switch failures" reported by hobbyists actually result from the liquification and reflowing of the small dab of stabilizing grease inside the switch when too much heat is applied for too long. The reflowed grease inside ends up coating the little rocker contacts inside the switch which then fail to make contact the way they are supposed to. Take the switch apart, clean the grease off and the switches are as good as new.

I mention this because rumours abound about "lousy switches" and which brand is better than which, when really what we are dealing with is component behaviour arising from the mistreatment of a component by an ill-informed and/or underskilled user. What I have to keep reminding the zealous of is that it costs a bloody fortune to set up facilities to make footswitches, and that no footswitch manufacturer would take that leap, or could last very long in business, if the failure rate were as high as reported. The failures happen, but not because of what the switches are like when they leave the factory.

So, to close the circle here, I have noticed that sometimes when I get a little "overenthusiastic" about soldering a ceramic disc cap, that it "sweats". That is, the heat causes what I gather is wax to reflow. I'm assuming that ceramic caps are spec'd for behaviour exhibited when the consistency of the materials inside has NOT been altered. Of course, because of the aluminum can and plastic surrounding them, I have little idea about what my soldering fervour does to electrolytics or any other type of cap whose construction does not make the consequences as easily visible as they are with ceramic disc types.

So, my question is really "How much of the bad rapping that ceramic (and perhaps some other cap types) caps take is really a result of some of us misusing them and causing them to be off-spec?". You will note that one of the quirks of the famed bumblebee caps is that those are some BIG mothers, and likely to sink any excess heat away more effectively than thin ceramics.

There may very well be some clear theoretically defensible reasons why one might expect the passing of audio-frequency content can be affected by cap type, but I really want to factor out the "mistreatment" aspect first before knowing how much causation to attribute directly to cap type, over and above anything else. And this "ceramics are microphonic" thing; is that in spite of installation conditions or because of them?

[jcollins]

My buddie and performed the following experiment over the weekend.

Took my epiphone dot with a Gibson Burstbucker in the treble position. Replaced the stock 0.022 capacitor with a couple of clip leads. The tone
pot was 250K.

Playing through the burstbucker we tried caps with different values connected by the clip leads. Trying as much as possible to play the same lick the same way and picked close to the bridge to get high frequencies to dominate. Niether of us could hear any difference between the two different .022 caps I had. I thought I might have heard a difference between one 0.022 cap and two in parallel (didn't have any 0.047), but, it was very subtle.

LIstening to the difference between a 0.01 cap and simply shorting the
clip leads together it was very difficult to discern any difference.

All tests were performed with the tone pot on 10.

The amp was a Fender Blues Junior set clean and at low volume.

I frankly only heard very subtle differences if any between different value caps.

A few months ago we performed a blind study on different types of guitar patch cables. We could easily and consistently tell the difference between our highest and lowest quality sample.

[TD_Madden]

wonder why they aren't using a 500K pot for tone in those guitars...?

[Mike Sulzer]

I frankly only heard very subtle differences if any between different value caps.

A few months ago we performed a blind study on different types of guitar patch cables. We could easily and consistently tell the difference between our highest and lowest quality sample.

That all makes sense to me. With the cables you heard the different resonant frequencies resulting from different values of cable capacitance. Quality is a relative term here. The ideal resonant frequency is very much a function of the player, type of playing, maybe, the pedals or amp, too. But many of us would think that one of those cheap coiled cables with really high capacitance is not good.

[Steve A.]

Steve A, re tone stack caps
'I thought that it explained how the Vox AC-30 tone stack with a 50pF treble cap is not, say, 5 times brighter than a Marshall tone stack with a 250pF treble cap. Intuition tells me that a 50pF treble cap would be too harsh and bright for at least my own tastes. In practise it isn't that much brighter and I thought it had to do with the comparative ESR values of the 250pF vs 50pF caps: the 50pF cap passes through a lot less audio signal than a 250pF cap'
The difference is that a fender 250pF cap is feeding a 250k pot (giving a turnover freq of 2k5Hz), whereas the vox 50pF is feeding a 1M pot (giving a turnover freq of 3k2Hz). So once the pot difference is taken into account, the affected frequency ranges aren't that different really. Peter.

I was referring to the darker tone stack in a Marshall, and specifically to swapping the tone cap back and forth between 50pF and 250pF, so there was no change in the 1M treble pot I was using.

Actually besides the ESR value of the cap, another explanation would be the RC filter value, since a wider frequency range will have a stronger signal level... I hadn't thought of that before.

Steve

[Steve A.]

... All tests were performed with the tone pot on 10.

The amp was a Fender Blues Junior set clean and at low volume.

I frankly only heard very subtle differences if any between different value caps...

With the tone control set to 10 you may not hear as many differences as you would when evaluating the range of tones you hear as you turn the control up and down. Both in terms of the value and the composition of the capacitor.

Also you might hear more differences if you turned the amp up a bit. Some of the subtleties are more noticeable when you have a little grit in your sound.

Finally even using different caps there is the possibility that they were all of the same basic type- can you post the markings and colors of the caps so we can check to see if they are polyester or polypropylene (or whatever).

Thanks for going to the trouble to conduct this experiment!

Steve Ahola

[Possum]

....

250K pot for humbuckers is wrong, Epiphone is probably trying to compensate for crappy shrill pickups. If you're doing tests between cap types a Blues Junior is not an ideal test amp. Ideally where you're going to hear the most differences is through a large stage amp with some power and clarity. The Blues Junior is cathode biased and an amp I totally avoid in testing pickups, I have one. That amp tends to make everything sound way better than it really is, I used to test pickups on it in the beginning, then when I got my '73 deluxe reverb some of my pickups sounded like crap through that, that amp really shows whats going on way better than a BJ......