Cap choice for analog stage filters?

[barrows]

I was wondering what type/brand of caps people like, and why, for the filter in the analog stage of DACs. Considering values from 500 pf to 15 nF or so. Polypropylene film/foil, vs polystyrene film/foil, vs. silver mica, vs. ?
Wima, Amtrans polypropylene film/foils, vs. REL polystyrene, vs. silver mica, vs. Vishay Sprague orange drop polyester film, vs???

 

[merlin el mago]

1st choice Teflon, 2nd Silver Mica, 3rd VISHAY-RODERSTEIN MKP-1837.

 

[qusp]

Teflon first, evox/rifa PFR range film and foil, SMD PPS film (evox/rifa, Wima or panasonic films), Amtrans polypropylene film. then Vishay MKP-1837.

forget wima, in the size you are looking at the evox rifa PFR film and foil are better in every way, like being able to use a little mundorf supreme in a small 5mm lead package. close anyway. not so easy to find though and the range of capacitance is limited, but your 500pf->15nf is covered. (only up to 22nf)

wima are OK, but not worth the attention they get on this forum IMO, I think its the pretty red colour

 

[barrows]

Thanks...

qusp. A mini Mundorf Supreme sounds great to me. Unfortunately an internet search did not result in much luck for me, unless I want to purchase 1000s of them.
I am looking for 1 nF and 10 nF, any ideas on sources? I only need a handful, perhaps 16 of each or so...

 

[qusp]

OK i'm about to go buy some more myself, so i'll be back with a link, cant think of it off the top of my head

 

[qusp]

here ya go they have a good range of other caps there too. for example the legendary rifa PHE169 low Z PSU cap. probably the best power supply cap available. so I just linked to the rifa page, you'll see them there as the small blue leaded caps like wima or vishay size box caps. they have ampohm copper foil and film caps there too for output caps if you are keen. another good value. all others in this physical size are metalized polypropylene, not true film and foil

damn, they dont have the values you need, but maybe ask them. sorry I just new they had them and that they came in those sizes. they will order them in for you perhaps, they do that with their other caps

 

[qusp]

you'll be able to find something there though, polypropylene caps are pretty much a specialty. they have the sprague orange drops which is one I forgot to mention

 

[qusp]

well they have the .47nf there which may be close enough for your 500pf, but 15nf is a nogo, but ask them about ordering it for you. is this for a sabre? pretty much datasheet values

 

[barrows]

Thanks

qusp, I had found these guys-I will go ahead and see if they can get the values I need. I have some polyester orange drops (Vishay-Sparague) here as well-but these are steel leaded, I really would like to avoid steel leads.
For a future Legato board build, and some mods on other stuff...

 

[john curl]

I would use polystyrene, if possible. Polypropylene, if necessary. REL RT polystyrene is an almost perfect cap for this application.

 

[jcx]

I haven't found any polystyrene that explicitly state that they are extended foil construction - some of the NOS boxed types?

the common "jelly roll" fused polystyrene/foil will be inductive at frequencies where DAC switching glitches, clock feedthru components are expected

most of the current production Boutique audiophile polystyrene are physically too large (high parasitic inductance/low SRF), as well as too high in value

 

[barrows]

Thanks...

John Curl, I was considering the REL RT, and think that I can get them to fit where I need them. I have heard from a few other folks that polystyrene film/foils are the way to go.

 

[chipzahoy]

Hi Barrows,

I just ordered some 1nf REL RTs to replace the Panasonic Z-series filter caps on the Legato. I'll let you know how it goes. I'm still not sure whether to add PS caps to C1-C4 or leave them empty though.

 

[barrows]

chipz...

The RTs are pretty large. Are you planning to mount them on the underside of the board? I am going to try the smaller REL RTE. I think pretty soon I will order up a new Legato board.

 

[john curl]

RT polystyrene is extended foil, I am fairly sure, due to its measured self resonance and method of attaching the leads. However, REL RT is a fairly large cap and cannot easily replace surface mount or similar sized caps, without a lot of trouble.

 

[jcx]

I realize the glare from JC's halo makes it hard to see other poster's points - but the Blowtorch thread recently touched on caps again - and someone pointed out that extended foil polystyrene are available

LCR EXFS series boxed polystyrene should be superior in very high frequency performance to the Boutique caps - which should be important in a DAC output circuit

It was also pointed out in those discussions that for microphonics mass production caps made on high speed winding machinery could be better than the “hand wound by virgins” Aduiophile caps of the same materials

 

[barrows]

Thanks...

JCX. I appreciate your concerns about avoiding potential inductance for high frequency filter circuits. The REL RTE are a "box" style cap, but I do not know if they are wound or stacked internally. These are small caps though, and I doubt that they are hand wrapped by either angels or virgins!
Do you have a source for the caps you are referencing?

 

[jcx]

I didn't see the picture - you would think it would be simple enough to include the words "extended foil"

LCR COMPONENTS|EXFS/HR 1000PF +/- 1%|CAPACITOR, 1.0NF 63V CAPACITOR | Newark.com

 

[john curl]

I just spoke to the owner and designer of Reliable Cap. The RTE's look OK to me, AND they do have a smaller footprint. Bas says ALL normal caps from Rel are EXTENDED FOIL. End of story.

 

[jcx]

viewing the rel cap site Reliable Capacitors it is NOT clear - the "RT" series is the only polystyrene listed - and doesn't go down to 1nF

some audio Boutique distributors have the 600 V RTE boxed caps - at ~$8 a pop - you get the 5 pc min of the LCR EXFS for the price of 1 RTE

but I don't see RTE speced on RelCap's site

I would be perfectly happy using current production, fully speced extended foil ps caps but "the story" isn't complete re REL from what can be seen online