capacitor question (p3a)

[jewilson]

I would not use resistor or signal capacitor purchased from Digikey. The Resistors metal film resistors have non-ferrous metal leads and the signal caps are not so hot either. Their power supply and decoupling caps or OK.

Checkout http://www.percyaudio.com/Catalog.pdf he sales the some of the best caps, many different bands and all types of films.

For resistors buy type RN55D or RN60D by Vishay, Reliable Capacitors or great just stay way from Solen.
www.mouser.com sales vishay resistors

[elizard]

Originally posted by jewilson
I would not use resistor or signal capacitor purchased from Digikey. The Resistors metal film resistors have non-ferrous metal leads and the signal caps are not so hot either. Their power supply and decoupling caps or OK.

Checkout http://www.percyaudio.com/Catalog.pdf he sales the some of the best caps, many different bands and all types of films.

For resistors buy type RN55D or RN60D by Vishay, Reliable Capacitors or great just stay way from Solen.
www.mouser.com sales vishay resistors

When you're strapped for cash, ordering for a few different places means big $$$, so i don't have that option (and being a student, i'm always strapped for cash).

That's why i specified everything be from digikey.

Also, digikey is nice b/c all the customs and taxes are included in the price automatically.

[jewilson]

Not living North of the US I do not normally think about that problem. However, I just do not like to lower quality parts knowing that I will want to rebuild the hardware later and that always happens.

Grab a magnet and run it over you Digikey metal film resistors, it should not pick them up if the lead is truly non-ferrous metal. The lead material will end up degrading the sound. In addition, the Vishay RN55D or 60D are cheap from Mouser.

As for as caps use polystyrene, then polypropylene Teflon is very expensive. beware that all film cap are not created equal just there polypropylene.

[sam9]

Re the P3A input cap: any variety of metal film that will fit in the holes and which has the right value will function. To the extent there is a resulting tonal difference it will bw minor. Most of us won't hear it even if its there. A bipolar electroltic would work too, but you want the lowersr ESR you can get - one way to get it is to go with higher working voltages.

Just to see if I could, I once used two 22uF tantalum caps with ploarity back to back - the two negative leads were soldered together the air. Ugly but it sounded just like a second P3A that used a metel poly cap. The point is that there is a certain latitude in how you do this.

An other consideration is the the capacitance value. The lower the value the higher the roll of frequency. 4.7uF is fine for most purposes, but if really need the amp flat down to 20Hz, 10uF is a better choice. You can go higher but its kind of pointless. By the same token, if these amps are going to power small or moderatly sized satellite speakers that go with a sub, 2.2uF is fine and it will be easier to find one that fits on the board.

[elizard]

hmm, maybe i'll check how much the whole mouser order would cost me ....

[jewilson]

Electrolytic cap work best at 80% of there working value. Most cap are underated and will work at their rated voltage. Having said that I have had some several premature failures runing electrolytic at there maximum working voltage bit only after years of operation.

If you use an electrolytic at say like 35% of it rated voltage you will lose volume and performance for the cap. This does not seem to be true for film caps.

[elizard]

so, then using the 35 should be ok since the rails will be about 30V?

[jewilson]

Yep, that should be OK

A while back when I worked at TI one of the inspection processes used was to check the leads with a magnet. These resistors with non-ferrous metal leads can increase distortions, of course in some location they will not.

[sam9]

This won't helpyou much, but I struggle with the same thing --trying to get everything on one order. Usually digikey is the best option, but sometimes it's mouser.

[elizard]

Originally posted by sam9
This won't helpyou much, but I struggle with the same thing --trying to get everything on one order. Usually digikey is the best option, but sometimes it's mouser.

yeah, i'm trying to set up the mouser order right now

i can get everything from digikey no problem, i already have my order made up

but, i guess i'll do a mouser order, and compare the prices ..
i'm also using vishay/dale resistors, so .. we'll see

if the prices are close, then i'll go mouser, if they're off by more than about $15-20, then i've no choice but to go with the cheaper.

the digikey order, btw (excluding the PS caps which i have at home) is about $60

although i do like the no-minimum quantities w/ mouser (on the items i saw so far)