capacitor orientation / polarity / outside foil direction

[ssstonelover]

I wanted to see what you guys can tell me about capacitor orientation.

Dirk Wacher at Premior Guitar made it a big subject in some articles, but frankly it does not seem to be discussed anywhere else -- in terms of guitar
www.premierguitar.com/articles/Tone_Capacitors_for_Stratocaster_Part_3
www.premierguitar.com/articles/Tone_Capacitors_for_Stratocasters_Part_4

He says, "In a passive guitar circuit, there is no low-impedance side because we use the tone cap as a bypass cap to ground, so the outside foil should be connected to the grounded side in this case. The outside foil will act as a shield against electric field coupling into the capacitor, so you want it to have the lowest impedance return path to ground. With this rule in mind and all the caps connected this way, a tube amp will be much less susceptible to interference from fluorescent lighting and hum, oscillations or frequency-response peaks due to unwanted feedback from nearby signals within the amp."

He further states many non-electrostatic caps (such as the popular Orange Drop) are not marked, so 'correct' connection is problematic (except by ear possibly).

Yes, I could perform such a test, cap-by-cap (with lots of alligator clips poking from the pickguard while awkwardly strumming, etc, or buy an oscilloscope ($$) and follow a procedure outlined below on Youtube but I'd like first to get a handle on the dimension of the issue, or better approaches to a solution, if an issue exists.

Test method:


If you've covered this subject previously let me know and I'll read that thread, as maybe I did a poor search

Thanks in advance!

[JohnH]

Well that's all just fine. Dirk Wacker is one of the most consistent writers on guitar electronics anywhere on the internet. I have the same opinion about all his articles.

[newey]

With all respect to Mr. Wacker, I have my doubts. At one point, he says:

The outside foil will act as a shield against electric field coupling into the capacitor, so you want it to have the lowest impedance return path to ground. With this rule in mind and all the caps connected this way, a tube amp will be much less susceptible to interference from fluorescent lighting and hum, oscillations or frequency-response peaks due to unwanted feedback from nearby signals within the amp.

OK, I'm not sure the analogy to connecting caps in a tube amp has much to do with the tone cap in a Strat, but the example cites to the orientation of the cap as affecting its shielding, to minimize noise. He started the discussion with a story about poor tone, not noise, so I don't get how tone, as opposed to noise, can be adversely affected by the cap orientation. He seems to be talking apples vs. oranges.

And, if:

The outside foil will act as a shield against electric field coupling into the capacitor

Where is this electric field coming from, and how is it affecting tone? And further, how is that effect, whatever it may be, manifested when the tone control is at "10"?

Unless we have a coherent theory as to how the effect he describes could be caused by the cap's positioning, we are left with an anecdotal story of a guitarist complaining about "dull tone", and a technician with a selection bias in favor of believing his customer, since the customer, after all, is "always right" in business. So, the technician hears what the customer hears. And, of course, the alleged poor tone is very vaguely described, as all such subjective things tend to be.

If we accept that there was a problem with the '62 Strat (one that a test to more sets of ears than a customer and his tech would verify as being real), it would seem much more likely to me that his re-soldering of connections had fixed a high-resistance solder joint on one or the other end of the cap, rather than speculation about cap orientation.

But then, call me biased as well, as I'm predisposed to believe that it makes no difference whether a cap is a Sprague Orange Drop or some other type. Wacker clearly buys into the whole "vintage caps are better" debate from the start.

[ssstonelover]

Jul 6, 2016 2:46:37 GMT -5 JohnH said:

Well that's all just fine. Dirk Wacker is one of the most consistent writers on guitar electronics anywhere on the internet. I have the same opinion about all his articles.

Noted. Since this issue never has surfaced before (or since, and only with Mr. Wacher in any case, and apparently only on 'one' or
"a few" guitars he fooled around with) I'll continue soldering my guitar caps in as before, w/o establishing a orientation. Thanks.

[ssstonelover]

Thanks Newey.

Seems some other technician sometime since the 1930's or even the 1950's would have uncovered a similar phenomenon, if there were one. As we know the scientific method means an experiment has to be replicable by different teams at different times to have credibility. Since Mr. Wacker could not get all the caps he tested to react this way....and since no one else has this experience, it could be as you say, due to other factors.

[reTrEaD]

Jul 6, 2016 6:10:51 GMT -5 newey said:

Where is this electric field coming from, and how is it affecting tone? And further, how is that effect, whatever it may be, manifested when the tone control is at "10"?

It's the background electromagnetic field from whatever environment you're in. Shouldn't cause much of an effect at all if your tone pot is at max, since you have the full resistance of the pot in series with it.

And honestly, it shouldn't matter much at all anyway. Unless you have a motor or transformer under the pickguard of your guitar, it won't be any different than having an extra inch of unshielded wire. Do you normally have very short runs of unshielded wire between the lugs of your superswitches? I certainly do. And I don't worry about that one little bit.

I totally understand the concept of grounding the outer foil. It just sensible standard practice. But I really don't think it's all that important in a guitar.

Jul 6, 2016 6:10:51 GMT -5 newey said:

He started the discussion with a story about poor tone, not noise, so I don't get how tone, as opposed to noise, can be adversely affected by the cap orientation. He seems to be talking apples vs. oranges.

I agree.

Jul 6, 2016 6:10:51 GMT -5 newey said:

But then, call me biased as well, as I'm predisposed to believe that it makes no difference whether a cap is a Sprague Orange Drop or some other type. Wacker clearly buys into the whole "vintage caps are better" debate from the start.

There has always been a considerable amount of cork-sniffing in regards to capacitors in guitars. And most of it is laughable. If someone tells me a certain type of cap affects the tone differently when the tone pot is at max, I giggle. It's basically out of the circuit.

That said, there is a difference between different types of capacitor. But you're more likely to hear the difference when they're used to pass the entire signal from stage to stage in an amplifier. Maybe you could detect the difference when the highs are shunted when a guitar's tone control is dialed down. Maybe. But our golden-eared cork-sniffing friends tell us they can hear the silky tone of the guitars with the vintage caps with tone on ten.



Steve Bench published a report on capacitor types many years ago. Good reading, imho.
diyaudioprojects.com/mirror/members.aol.com/sbench102/caps.html

Interestingly, ceramics highly non-linear. "Vintage" Fender tone caps are ceramic.

Paper-in-oil caps are the most linear. "Vintage" Gibson tone caps are paper-in-oil (Sprague Bumblebees)

[newey]

An interesting article, RT. I have never liked ceramic capacitors as the tone is turned down, and I usually use the polypropylene types. This may explain why.

I also applaud his methodology, although the 'scope makes seeing the curvature difficult. Note that he apparently tested each of the caps for uniformity at 0.1µf. When folks talk on the web about capacitors (and I like the "cork-sniffing" metaphor!), they seldom if ever have measured the actual value of the caps they are comparing. Manufacturing tolerances on most of these parts are plus/minus 20%, so when we hear that a paper-and-oil .047 cap "sounds better" than a ceramic one of the same value, I always question whether the values are truly identical. And with vintage caps, which may have degraded over time from their nominal values, all bets are really off.