Resistors and capacitors physical size ?

[uki]

Hey guys !

I have seen online some electrolytic capacitors, some of the caps are about this size 18*25 mm with this value 47µF/500v,  the filter caps on tube amps are usually way bigger with same value.

Same with about resistors, I have bought some 1w resistors and they are small as 1/4w(1/2w) usually are, I've asked the guys in the store and they said it really is 1w,  see pic.

I would like to know if the physical size does make difference ?

[sluckey]

I would like to know if the physical size does make difference ?

Absolutely. How big would your cellphone be if it were built with 1/2 watt carbon comps. Miniaturization in electronics is very desirable.  Weight reduction is also a big goal in many electronic oriented industries. Maybe not so much in the small, dark corner of the tube guitar amp world.

[HotBluePlates]

Physical size may tell you more about the manner of construction than anything else.

I recently used some 1/2w wirewound resistors in a new build. But because the resistance value was low (100-500Ω), the physical package was tiny. It was on par with some 1/4-1/8w resistors I've seen.

A short length of resistance wire on a small former probably resulted in smaller size than found in a metal film resistor with a bigger former, a longer length of resistance material and a heavier coating, where the metal film resistance is 10-100kΩ.

[PRR]

> 18*25 mm with this value 47µF/500v

8uFd 450V e-cap used to be 1"x3" (25mm*75mm).

The stuff gets better. "Better" often means smaller. If not pocket-size, then to reduce the amount of costly metals etc needed.

Those high-Watt resistors work because of higher temperature materials. Some of the microscopic 2W parts must run (at full rating) hot enough to burn paper. Conservative design requires you to allow just as much *air space* around the teeny-part as you would for any 2W part, since that's how the heat gets out.

In general most teeny-parts are as-good or built-better than anything Leo had in 1959. Old carbon-comp and old e-caps drifted and failed a lot; that's why Leo went from haywire P2P to neat eyelet boards where parts were easy to replace.

[pompeiisneaks]

Yeah I've even seen caps getting smaller as I've done this for only about a year.  Doug's first batch of Illinois caps were one size, in a recent build, I got 4 of the same cap, all the same size (I think 47uF at like 350V) and two were longer and slightly thicker than the other two.  It's basically something that they keep improving and I'm sure Doug's likely mostly out of the larger ones and only has the smaller ones in stock now.  Same performance in a smaller package.

~Phil

[uki]

Thanks guys !!