Capacitors for audio purposes. One cm is about 0.4″

Capacitors play a very important role in audio. The choice of the type of Capacitor are very crucial in powersupplies, in decoupling stages and in filters like RIAA correction, active crossovers and tone controls. Also they make a lot of difference in crossover filters for speakers. Please note that the powersupply of your amp is also in the signalpath, so good capacitors are really recommended.

Capacitors differ a lot in sound. It is very important to use the right capacitor in the right place. Using the right capacitors will give a lot of improvement in the sound of the system. Try not to use the same capacitor all the time, the sound of that one type can get very pronounced. Try to see it like seasoning your sound. Adding only pepper will make it very hot, adding a good mixture of spices will make the sound very tasty!

For film capacitors like paper/oils and MKP mostly counts that higher voltage means thicker isolation, and this means better damping inside the capacitor. So, the higher the voltage, the better the sound. Disadvantage of course is that the capacitor also will be much bigger, and a bit more expensive…

Types of capacitors I have for sale are:

Electrolytic capacitors. Electrolytic capacitors are a sort of very fast batteries. They use a chemical process to store the energy. This gives them very high capacitance in small volumes. Drawback is that it makes them slow. They are very nice for reducing hum and for big energy storage, but not very suitable for signal purposes, because their bandwith typically goes upto about maximum 10-20 kHz.
For very good performance and sound in electrolytic capacitors I recommend the long life (LL) types, they are made with closer tolerances, can operate at higher temperatures (mostly 105 °C, ideal for tube amps), have longer life and sound very good. They also have bigger bandwidth, probably because of their better overall specs. Some of the Philips Long Lifes als have a Q code (special quality), these capacitors are even bigger, better and faster.
I mostly use Black Gate FK and K types for cathode decoupling and low voltage power supplies in transistor preamps. They sound real natural and clean. It is the best electrolytic capacitor for such purposes.
The best sounding capacitors for audio powersupplies, decoupling and speaker crossover filters are Paper/oil capacitors. These film capacitors use oil soaked paper as di-electric material and are therefore well damped and very smooth and natural in sound. They have very good (high!) bandwidth and electrical specifications.
Silver/mica capacitors are very good for coupling stages and filter purposes. The sound is very perfect, they almost have no sound at all! I use them whereover I can. Disadvantage is that they come only in small values, about upto 100 nF maximum.
The MKP capacitor also is quite good for audio. They are more sharp and more clean in sound, combining them with Paper/oils gives very good results.
Tantalum capacitors are very good, fast and reltively small capacitors. They operform very well in DAC powersupplies, and as bypass in heater supplies.
The MKS, MKT, Styroflex, Ceramic, and other types are not really good sounding in my opinion, but they can come in very handy for other purposes.
I also have a page with special purpose parts and capacitor related stuff. Here you find variable capacitors, feedthrough capacitors and stuff like clamps and mounting brackets.