I apologize for the length of this post, but certain things just have to be said to show the truth of the matter. I have not seen this in any writing aimed at guitar players and musicians of all types, so here goes........... The following facts prove that contrary to many rumors and postings by people who do not know their electronics, different types of capacitors cannot have any effect on tone circuits in guitars and amplifiers. The point is proven using standard electronics theory known to all experienced engineers and techs. It is based upon a simple consideration of the “series equivalent circuit” of a capacitor as shown below. For the benefit of those not familiar with this concept, it means just this: whenever a capacitor is placed in any kind of circuit, the actual circuit looks like this. In addition to the capacitor itself, which is what is actually desired, there also appear additional “components” called parasitic elements. Under some circumstances these unwanted additional elements could have a significant effect, including modifying tonal response functions. But why they don’t for our purposes is totally clear by considering real world capacitors of all types. Here the basic facts about capacitors of ALL types that are used in musical electronics. First: the value of L is negligible at frequencies even remotely close to the audio range. It is typically in the range of a few micro or nanohenries – you do the math! So the inductance factor is non-existent (especially at audio frequencies), leaving only R and C to deal with. Since C is the primary concern in all cases, especially "tone control" circuits, the important question concerns how is R compared to C for a given component. The answer is slightly complicated because it is frequency dependent. The standard way of rating capacitors uses the "dissipation factor", which is kind of an expression of loss, or imperfection, of the cap. It is defined as the ratio of the value of R and Xc (capacitive reactance) and is usually rated in percentage. A cap with a DF of 1% at a given frequency will have an R equal to 1% of Xc. In order for DF to be of any concern in any tone-shaping circuits it must be at least 5-10 % or greater. Even 1% DF will be totally negligible. If you don’t believe this, just analyze any standard tone control using first a perfect cap (DF=0) and then increase the DF to 1% by adding some R – the difference will be insignificant. Now here is the bottom line: all capacitors manufactured and used in any type of standard electronic devices, musical or otherwise, and particularly those with values under 1 mfd., have a DF of less than .1%, and typically in the range of hundredths of 1%. One big reason for this is because in most electronics applications, caps with DF>.1% are generally considered junk by designers and would not even be saleable. The other reason is that the dielectric used in caps <1mfd is typically a low loss material (paper, mylar, mica, ceramic, etc.), which determines the DF. Conclusion: All capacitors used in audio equipment are essentially "pure" C. No R or L, just pure C. The circuit it appears in sees only the C value and doesn't care whether that C comes from a dielectric of mica, paper, ceramic, polyester, or Kryptonite. C is C – end of story. Hence, no possible effects on frequency response (tone) are possible. This implies that anything you have ever heard claiming that different types of capacitors have unique tonal characteristics, is pure fiction - and not even of the "scientific" type. BTW: All of the above is based upon the assumption that any capacitor under consideration is a good capacitor - it is not defective and conforms to the ratings of the mfr. Obvioiusly a defective cap can have huge effects, including complete disfunction or failure of the circuit!