[moeburn]

Oh yes

 

[IEATTEFLON]

oh no.

 

[BlazerFRS]

I assume you'll be making your own board w/ surface mount components?

 

[Teerawit]

1) Man, that's a beautiful case.

2) PPA? Man, that's be so much more beautiful. Good luck.

 

[moeburn]

Quote:

Originally Posted by BlazerFRS I assume you'll be making your own board w/ surface mount components?

Of course I'd make my own board, and I can cram regular size resistors and caps no problem. I've found one particular capacitor at my local surplus store that is very high quality and made very short and fat, but if you want to save height, you could always go axial instead of radial.

 

[mono]

Some of us (Ok, maybe just me), dont' feel a Pimeta needs 4 giant electrolytic caps to begin with, that it is zero benefit over some smaller ones. I think if you used 4 x 100uF surface mount tantalums and a NiMH battery you might be able to avoid electrolytics completely.

 

[moeburn]

Quote:

Originally Posted by mono Some of us (Ok, maybe just me), dont' feel a Pimeta needs 4 giant electrolytic caps to begin with, that it is zero benefit over some smaller ones. I think if you used 4 x 100uF surface mount tantalums and a NiMH battery you might be able to avoid electrolytics completely.

Provided you could ever find 100uF tantalums...

 

[mono]

What's hard about finding 100uF tants? Supposing you have confirmed the amp is stable the voltage rails aren't drifting, you don't necessarily need caps with a voltage rating high enough to cover the V+_to_V- voltage difference because they're only at 1/2 that, between the rails and vGnd.

While it could be argued that it's a safety margin to have them overrated, should the virtual ground collapse, having a virtual ground collapse is not a scenario one would expect to face once they'd confirmed it stable, no shorts, etc, (before adding those caps). If we want to consider some fluke accident that starts having crazy effects on the voltage rails, then I argue that among all vulnerable parts, the lower cost of the caps makes them a lesser concern compared to opamps or buffers.

Anyway, keeping this in mind suppose you want 24V rail-rail, 12V rail-vGnd. Choose a 16V cap. here's one, $1 ea., If you can't find something, parallel a couple 47uF caps, or don't use surface-mount, you can get 4/$1 16V/47uF here,

I'm not suggesting those I linked are any better than alternatives at Digikey et al, only that they're even available at surplus parts 'sites too, and sometimes at lower cost. Some many be higher impedance though, but that's part of why a Pimeta has the film caps. You may not even need 100uF, that was just a value I threw out there, could be more or less and since you're making your own board you have control over what/where/how-many.

 

[moeburn]

Wow, the largest non-polarized cap the two stores have near me is 1uF, and they're both pretty big (250v). I'm not a fan of ordering online because I never order enough to compensate for shipping costs.

 

[mono]

"Non-polarized"? You don't need non-polarized.

I don't know about all online 'sites, but some might throw a dozen tants in an envelope and ship for a buck or two if you asked them. If you're buying all the parts for a Pimeta though, might it be just as cost-effective to shop online at lowest prices? Often local shops cost more per part.

 

[moeburn]

Quote:

Originally Posted by mono "Non-polarized"? You don't need non-polarized. I don't know about all online 'sites, but some might throw a dozen tants in an envelope and ship for a buck or two if you asked them. If you're buying all the parts for a Pimeta though, might it be just as cost-effective to shop online at lowest prices? Often local shops cost more per part.

?

I was under the impression that electrolytic was the only type of polarized cap, since the store near me calls the tants "non polarized tantalum capacitors". Apparently I'm wrong. I'll look at some of the other stores and see if they have any regular tants, thanks for clearing that up.

 

[Sinbios]

I know the solid tants I used in my sound card are directional...

 

[mono]

Quote:

Originally Posted by moeburn ? I was under the impression that electrolytic was the only type of polarized cap, since the store near me calls the tants "non polarized tantalum capacitors". Apparently I'm wrong. I'll look at some of the other stores and see if they have any regular tants, thanks for clearing that up.

Of the common types "most" of us are using, only the ceramics and films are non-polarized, except of course those electrolytics that are specifically non-polarized. Tantalums generally (always?) aren't (they are polarized), are are definitely subject to fail if polarity is reversed.