How important are high-quality filter caps?

[bluemonk]

Hello. I understand that very high quality filter caps are far better for reliability and long lasting.
I wonder how much important they are for tone.

Regards.

[Enzo]

Like any other component, it is not about the part, it is about the circuit. You may well hear differences in any given amp when comparing two brands of cap at a particular point in the amp. But when taken out of that context, it is darn hard to make a meaningful response.

How much current is being drawn from the supply? How many stages of filtration are there? What value caps are they and how does that compare to design convention values? High gain amp? Little low gain Fender clone? Single ended or push pull? Etc.

[MWJB]

"I understand that very high quality filter caps are far better for reliability and long lasting." There's very little difference in typical part life from cheap, basic, Asian electrolytics compared to more expensive US & German made caps. RIFA do some long life E-caps (rated for 27500 hours/>30yrs), but not always in useful values for typical 6L6/EL34/6550/KT88 amps with substantial filtering (e.g. 450v caps don't seem to be available at more than 47uf, so if mounted in series for a 500v supply, you get a max uf of 23.5uf, unless you want to use 4 or more expensive caps).

Despite the short-ish rated part life of regular e-caps (5000hrs?) they are typically robust enough to last 10-20yrs at reasonable operating voltages. If you were pedantic, you could change them every 7-8yrs.

For long life, non-electrolytic caps may be preferred, like Solens Fast Caps BUT these are HUGE compared to electrolytic caps and hard to find over 10uf in value, so again finding space for enough caps to give say 100uf at the main B+ stage becomes a problem.

For tone, some are of the opinion, that physically bigger is better...how much space do you have? Mid priced, mid sized Asian caps like HL have proven to be fine. Very small, cheap caps can have thin leads which don't inspire confidence when amps are thrown in the back of pick ups, dropped off stands etc.

[Steve Conner]

I use the Asian caps all the time, apart from main filter caps in solid-state amps, where I prefer the Rifa screw terminal type. (What used to be called "computer grade" back when computers still had linear power supplies.) If the leads are thin, I'll secure the body of the cap to something with a zip tie.

And once I bought some F&Ts because I needed a 500V part in a certain size to fit a mounting hole in an existing amp.

The life figure for an electrolytic capacitor applies when the capacitor is at its rated operating temperature, and it's a strong function of temperature. In layman's terms, the caps are full of goop ("electrolyte"), and when that goop dries out, the cap stops working. If you can keep them cooler, then the goop stays slimy and the life can be dramatically longer. 105'C rated caps can last longer, because they're operating further under their rated temperature than the regular 85'C ones.

F&T claim that their caps should last longer, because they put more goop in to start with.

As well as drying up, electrolytics have a different failure mode where they can go leaky or short out completely. This can be caused by not using them for a long time, but it can also be caused by excessive heat. If you have a piece of kit that's used regularly, and the electrolytics are kept cool, they can go on forever.

Again I'm of the opinion that capacitors have no effect on tone, over and above the effect you'd expect from changes in capacitance. There's some debate over whether ESR can couple signals between stages that should be decoupled, though.

[jrfrond]

High-quality filter caps?

ALL components are high-quality..... until they fail prematurely. Then they suck!

Seriously though, I do stick to a few name brands that I have had good luck with. I won't purchase second-rate components either for my own builds and repairs, nor here in the shop. For caps, I stick to Panasonic, Xicon, Illinois Capacitor, Cornell-Dubilier, Vishay and BC Components. For can caps, we are somewhat restricted nowadays, but JJ, F & T and CE Manufacturing have worked out well so far. I am NOT saying that these won't give up the ghost either, but sticking with known brands, like anything else, does minimize your chances to a degree. FWIW- the level of component quality in most production amps nowadays is piss-poor.

[kldguitar]

couple Cap is important

the couple cap is important in guitar amp also, you need use good quality poly cap. IF do you need use expensive cap? it is wholly depend on what you want?If you are professional guitarist, maybe. if you are only hobby, I think Asian cap is o.k, in fact many asian cap are used by marhsall ,Vox .Tube Guitar amplifier,effect pedal and studio gear manufactory kldguitar