by cartoonweirdo » Sat Jan 24, 2009 12:00 pm
I first need to make a distinction and say that all NOS electrolytic caps (also known as power supply caps, filter caps, or cathode caps) are TERRIBLE!! this is because the electrolytic goo in them dries out over time (even in use, but especially when sitting around) and by the time they qualify for NOS they are useless.
I have tried many of the vintage caps you have listed and have found that they sound much better than bad modern caps but about as good as good modern caps.
You are of course going to ask what the good and bad ones are, but to me that's subjective. Also, coupling caps of any brand are right for some jobs but suck in others. The thing is that you are looking for your guitar amp to have a certain sound, or tone. Many things contribute to that tone, and filter caps seem to be somewhere between 3rd and 5th in importance.
In my experience, bad filter caps will make a guitar amp sound farther away, less warm, overly bright or bassy, plastic or artificial, and etc etc. Good ones will sound full, rich, more present, and more magical. Since none of these parameters can be measured by anything but your ears you will have to solder caps in and out of your amps to hear the difference for yourself.
I recieved a great afternoon of education listening to an old fender head (chosen for ease of changing caps) through it's stock speaker cab with different caps. You can try changing to all one brand or you can mix and match (especially cool in the tone stacks). I know what my personal favorite for that head was (new mallories) but all the caps sang in different, and useable, ways. This information, of course, is also interactive with the individual irons, tubes, speakers, or circuit. For instance a set of caps will be overly bright and ringy if the "wrong" 12AX7 is in the circuit. A duller tube will make them sound "right".
I know this sounds hard to figure out (it can be) and pretty subjective (it is) but general trends do emerge eventually, and you would be best served as a repairman or a builder to be aware of those trends and use them to your best interests.
Good luck,
Carl