Capacitor Size

Larger is always better......why is that in question?

The reason caps had been able to shrink in size is do in part to over etching the aluminum foil to increase its surface area. When you do that, less foil is needed and the body of the cap can shrink. Up until recently, when compared to their larger cap brethren, the smaller etched aluminum cap did not sound as good. I tried this experiment with the same manufacturers cap, just different case size. It was missing the relaxed quality of the larger cap. Note that both caps had been broken in. Although caps now still vary sonically from manufacturer to manufacturer, I believe the days of over etching the aluminum are over especially if the cap is designed for audio applications. You will note that caps designed for audio applications are usually a bit larger in case size for the same value.

The smaller value Electrolytic capacitors like 10KuF to 25kuF are smaller than caps from 20 to 30 years ago. The big 50000uF/125V,76000uF/100V,51000uF/160V caps cannot be made smaller than 3 inches in diameter and 5.9 inches long.
Even in the 1980s and 1990s these caps were same size as today.

yep, Atmasphere is correct. The new caps for a given microfarad value and voltage are usuall considerably smaller than caps from 10 years ago let alone older caps out of 1970s or 1980s vintage gear. sounds like your repair guy is being honest with you.

Your technician was on the level. Its a general rule of thumb that electrolytic capacitors (the kind found in power supplies) decrease in size in newer versions. It was that way in the 1970s and is still true today.

Are you asking about power supply aluminum electrolytic caps or film capacitors???

It actually sounds good, to be fair. But the fact is, I didn't have it in my possession w/ the original caps long enough to be able to notice a significant difference. Further, my speakers are very limited in the lower frequencies, so any improvement there is impossible to judge.

I actually don't have any complaints about the sound, save for the fact that a high frequency problem has arisen, which means the amp will need to be serviced (the right channel emits a lot of spitty hiss, for lack of a better way of putting it, while there is no source playing. I assume it's a capacitor problem of sorts).

Maybe when it goes in for service, I'll ask the tech to have a look-see for me.

Incidentally, despite the original tech informing me that the new caps are physically smaller, I only recently looked under the hood, as a result of the right channel, upper frequency issues (wanted to see if i could spot anything obvious). I was pretty surprised to see just how MUCH smaller the new caps are, however, which is what raised the question in my mind in the first place.

How does the amp SOUND?

I know that the capacitors he used were not particularly expensive/ high end, as he stated that they would still be an improvement over the old ones.

I've physically tried to look at the capacitors' specs, but can't read what it says on the cap b/c of the way they are mounted.

I'm going to try to dig up the old paperwork to see if that tells me anything.

I've re-capped several vintage amps recently, and the new electrolytic caps are indeed smaller in most cases. So no, as long as he used a quality brand of capacitor from a reliable supplier, you should be good to go. Happy listening!

The type of capacitor matters also. For example a paper in oil(PIO) cap will be larger in size than most poly film caps. Caps that are made with damping considerations may be larger and heavier such as the Duelund capacitors.

Depends entirely on the brand. More voltage spec usually means a bigger cap. Old vs. New is not the issue. Have a look at a V- Cap or a Mundhorf. Both anything but small, and current production. The small caps today that are good are Rel Theta or their polystyrene RT. Both are very good for the price. Quality matters. I hope the quality of caps is good you had installed. The quality does matter, but they have to fit. If a V-cap will fit they are the best imho. The amp has to be good enough to benefit though. A trashed antique with old wiring etc. will see a smaller benefit than a full restoration. Jallen

A cap is a cap. They come in various sizes depending on manufacturer. Caps are measured in mfd and they're marked on the cap for tolerance. I do know that the caps currently made today go out of tolerance much quicker than older caps. I would have had him test the caps on his meter and prove that they needed to be replaced.