capacitors, capacitors, capacitors

[CarlSeibert]

A friend and I are both building Pearl IIs. A sizable portion of the cost is capacitors. I don't have enough experience to have a well developed gut feeling for value or any favorite brands.

There are basically three flavors we have to chose: big-ish electrolytics that smooth power, caps in the RIAA network that are between the signal and ground and two coupling caps, smack dab in the signal path -one is two paralleled film caps of small-ish value and right at the output we have what is specified to be a 22uF electrolytic, bypassed with a film cap.

There's an armload of these things, so just buying the fanciest boutique brands all the way through doesn't seem like a smart option.

So, advice? Brand preferences? Should everything that touches the signal path be the same brand or price range? Or should I go all out for the two coupling applications? There are 22uF film caps (at ghastly prices, I'm afraid) so would it be a good idea to dispense with the electrolytic there?

I've actually heard and respect stuff that you guys have designed and built, so I have a baseline to weigh advice here that I wouldn't have on some other forum where I have no idea who's deaf and who's not.

I'll attach the schematic in case anybody wants to be specific.

Pearl_II_SCH.pdf

[deepak]

Cool, do update us on what you think of the Pearl 2 when it's finished. I don't know if this will be of much help, but I preferred the Pearl 1 with MKPs in the RIAA section vs Solens. Though I believe the MKP one was also using PRP resistors ( )

[CarlSeibert]

We'll be using PRP resistors, 'cept for a couple values they don't have.

I think Wayne built the prototype with MKPs.

Anybody have any thoughts on those scary looking coupling caps?

MIT Multicaps look intriguing. They're expensive, but not heart attack inducing expensive. Has anybody used them or heard them?

[Pars]

I've used these Erse caps before in a preamp, and liked them. Probably not the last word in anything, but 22uf caps will get quite pricey. Not sure what kind of footprint you have available on the board, if they are board mounted as well. I would think these would be better sounding than any electro. I know Nelson likes Elna Silmic IIs for electros. For the PSU, I would probably use Panasonic; FMs if possible, or TSHAs if you need a snap in.

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[dsavitsk]

There is no need for the output cap to be 22u. Most preamps have a input impedance of 50K or higher for which 1u is enough. Even under the worst case scenario if your preamp has a 10K Zin, 4.7u is plenty high. One thing you might do, though, is increase R18 from 100K to 1M or so. It is in parallel with the input of the next stage, and does nothing at 100K but increase the size of cap you need.

Second, the parallel 0.1u interstage couplers are unnecessary. There is some thought that paralleling identical caps is a good thing (it is the theory behind the multicap) but with most modern caps the benefits are less than they were in the past. But, you'll do fine with a single .22u cap there.

As for recommendations for coupling, there are a number of "cap review" sites around. If you don't want to spend a lot of money, I think I'd look around for some Vitamin Q's, or maybe some of the Russian PIO or teflon stuff. If you want to spend more, I like the new Jupiters and the Mundorf SIO's the best of things I've tried. I also like Cardas caps, but even among capacitor marketing which is over the top and silly, Cardas seems especially over the top and silly. The best middle of the road option to my ear are the Dynamicaps which I think are a nice step up from Auricaps and their ilk. But, there are lots of things I've not tried.

For the RIAA stuff, what you really need is precision. Unless they are too big, I like the Wima film and foil (FKP) caps available from Mouser. Otherwise, the Wima MKP's are OK, too. I've used sonicaps in this spot, too , which worked OK.

MKP, by the way, just means metalized polypropylene, so Solens are MKP, too.

[deepak]

In that case when I said MKP they were Mundorf M-Cap MKP

[luvdunhill]

I've been on a recent polyester film cap testing spree (gasp) and am planning on using them in a phono preamp. Currently, I really like:

Siemens / Epcos SilverCaps, which are rather unique in that they are not coated. Datasheet:

http://www.epcos.com/inf/20/20/db/fc_2009/MKT_B32560_564.pdf

Evox MMK, similar to some of the Wima lines, nice and compact sizes. Datasheet:

http://www.kemet.com/kemet/web/homepage/kechome.nsf/file/MMK%20Series/$file/F3294_MMK.pdf

In general I prefer polystyrene _box_ caps though, but am trying something different in this particular design.

[FrankCooter]

The great cap divide is between the paper in oil traditionalists and the film/foil modernists. Since you guys are building two units, why not build one one way and the second the other? When you're finished , pit the two against each other and let us all know the winner.

Doug is absolutely right (as usual) about the size of the output caps. A value of around 5 uf is plenty. I'd also follow his advice about the RIAA caps.

Electrolytics are all bad. Blackgates, no longer available, were the best of them. In tube circuits, many of us use motor-run oil in paper types. The Cerefine types, also no longer in current production, were considered a less expensive alternative to Blackgates. These occasionally show up on Ebay. Many here now use Panasonics for power supply filters.

[CarlSeibert]

Doug - Thanks for pointing that out, "that" be several things, actually . When I was thinking MKP, I was thinking of the Wima. I'll look and see if the FKPs will fit.

The lower value output cap would make things a lot easier. More money available for shopping, or trying a couple things.

Frank - That's just what we're going to do. We started out thinking we were going to do them identically, but we've drifted a little. We'll try to keep the differences controlled so we can compare and reach some valid conclusion when they're up and running.

Thanks guys!