Passive EQ Capacitors?

Hi,

Any capacitor recommendations for passive eq?

-Is there a preferred composition?

-Voltage rating? (Are high volt caps less than ideal in a passive circuit?)

-Most importantly, availability? (Sourcing a complete set of "ideal" caps for a Pultec - all having the same composition, volt rating and manufacturer - appears nearly impossible.)

Thanks,

Ron

Hi Ron,

I can't offer an answer to your questions, but I'm curious if you are asking because there are problems with the Pultec you built?

Thanks
-E

Ron and I were having an email conversation about this, and it's a question we were wondering about. It seems nearly impossible to get all of the caps for a Pultec from the same manufacturer at the same voltage. It's possible to get all the values in Panasonic polypropylene caps from Digikey, but not in the same series or voltage rating. They'd have to be part ECQP series and part ECWF series. http://sethglassman.com/0847.pdf is a link to the catalog page pdf. Is lower voltage more important for passive circuits? Does any of this matter in a big way?

Thanks

In gerneral, go for polypropylene wherever you can fit it. For some of the bigger caps you may need to go for polyester (mylar). As far as voltage rating goes, it's not really a big deal...it will be hard to find caps with a rating less than 50V though.

Good luck

Kris

Oh, I forgot to mention, if you want all the caps from one manufacturer, perhaps try Solen www.solen.ca. Also, MIT multicap would probably work as well...spendy though!

Cheers,

Kris

if you want all the caps from one manufacturer, perhaps try Solen www.solen.ca. Also, MIT multicap would probably work as well

Click to expand...

I checked most of the Hi-Fi cap makers (all the ones that I could think of:Kimber, Multicap, Hovland, Solen, Auricap, TRT, Jensen, Cardas, etc..) and none of them had all of the values. A few had most of the values, and that's what led to this question: If the caps are not all reasonably matched in terms of materials, voltage, or maker, are they likely to sound different enough to be a problem? Maybe there's no answer except to try it and see.

Thanks

Why do they need to be of the same voltage rating? Since there's no DC across them--we are talking about the filter section, right?--it ought not to matter.

Some of the values are difficult to find. For my Pultec boards I used Siemens Stackfoil caps for the "standard" values (they were the only type I could find that fits the boards). For the special values (12n, 18n etc.) I used old Philips "tropical fish" caps...

Best regards,

Mikkel C. Simonsen

You should try to stay in the same manufacturer/type for each section/band of the EQ. Try using ceramics/npo for the highs, paper for mids and polypropylenes for lows. Or try to get your best combination.

[quote author="NewYorkDave"]Why do they need to be of the same voltage rating? Since there's no DC across them--we are talking about the filter section, right?--it ought not to matter.[/quote]

Hi Dave,

Thanks for your reply.

Personally, I thought there might be a performance issue as some folks are talking about 600v caps in the passive section. You're saying then that these would make no difference when compared to say, 100v?

(I ended up using sprague 100v orange drops, unfortunately they're polyester, but Mouser had all but just 3 or 4 values.)

Could everyone contribute some more sources for these small caps?

Thanks,

Ron

Hey,

I found all, except 4, of the orange-ish Caps for my Pultec at either Mouser and Digikey.

I am putting together an excell spread sheet for parts numbers now and I should post it ASAP.

The EQ sounds great ! I am going to build another one soon.
Putting the Pultec in series with my Distressor makes my tracks sing.

The Voltage values do not matter. Except the higher voltage ones might get too big to fit on the PCB beside one another.

_Chuck

Oh yeah I forgot to mention the other 4 I couldn't find I found at a local electronics store called Norvac Electronics. They have a 800 number on the web somewhere.

-Chuck

Here are the digi-key part numbers. These are not for the gyraf version, btw, but the PTP:

P3503-ND CAP .0033UF 630V POLYPROPYLENE  
P3506-ND CAP .0056UF 630V POLYPROPYLENE  
P3508-ND CAP .0082UF 630V POLYPROPYLENE  
P3510-ND CAP .012UF 630V POLYPROPYLENE  
P3511-ND CAP .015UF 630V POLYPROPYLENE  
P3512-ND CAP .018UF 630V POLYPROPYLENE  
P3514-ND CAP .027UF 630V POLYPROPYLENE  
P3518-ND CAP .056UF 630V POLYPROPYLENE  
PF2683-ND CAP .068UF 250V METAL POLYPRO  
PF4224-ND CAP .22UF 400V METAL POLYPRO  
PF4334-ND CAP .33UF 400V METAL POLYPRO
PF4824-ND CAP .82UF 400V METAL POLYPRO  
PF4155-ND CAP 1.5UF 400V METAL POLYPRO

I'm not sure what the difference is between Polypropylene and Metallized Polypropylene. Could it be that the plain ones have separate foil and film layers, and in the metallized the foil is bonded to the film?

[quote author="jrmintz"]I'm not sure what the difference is between Polypropylene and Metallized Polypropylene. Could it be that the plain ones have separate foil and film layers, and in the metallized the foil is bonded to the film?[/quote]
Yes. The "plain" ones are the best, but the metalised ones are smaller.

Best regards,

Mikkel C. Simonsen

I was lucky enough to have a boatload of caps, different types in the same values, so I got to plug and play different ones to get the best in each band.
I found that the square Wima's gave the best sound.
You will have different resultsd than the schematic because of tolerance, inductor value variation, and transformer differences, so be preparedto rip out what you thought was the best value in order to get a smooth transistion from one band to the next.
cj

That makes a lot of sense, CJ. Thanks.

No problema, and I am sweeping the 2622 for response at this moment.
:guinness:

[quote author="jrmintz"]I'm not sure what the difference is between Polypropylene and Metallized Polypropylene. Could it be that the plain ones have separate foil and film layers, and in the metallized the foil is bonded to the film?[/quote]
Film/Foil is where a foil of either tin, aluminum or copper is sandwiched between a film of mylar, polyester, polypropylene, paper/oil, and who knows what else. Then they roll it up.
Metalized is where they just spray some metalized materal on the film, then roll it into a cap.
Opinions are all over the place on what's better, me, I think that whatever works best in the circuit is the best cap in that instance. Sometimes the high end stuff is the best, sometimes the cheaper stuff sounds better. Mica is a better cap than ceramic, but in the treble position of a tube guitar amps tone stack I much prefer ceramic for the flavor it lends to the tone.
Kelley

I'm working on another Gyraf Pultec and I'm looking for info about the voltage of the caps in the EQ section (the 0.0033, 0.0068 ones......)

Is 50VDC caps sufficient for the EQ section????

Some things to think about with plastic film caps

The higher the voltage the thicker the plastic

The thicker plastic has more area for electrons to get "stuck" DA, old name soakage

The type of plastic can have a tone and I believe the way the plastic film is made even with the same base materal can change the tone

I find I use the plastic and voltage rating of a film cap kind of the same way one uses different alloys or windings with a transformer.

Polypros have little or no tone

PET caps are were the fun is! wound, stacked, grade of PET, voltage rating (film thickness) affect the DA it seems The DA seems to be the sound of the cap. Even with an AC signal there is a DC component in some signals.

Also the DC difference between both ends of the cap can stress the dielectric of some cap types.

Sometimes when I build something like a microphone I don't use the "best" cap because it might be to clean. Look at the old tube microphones a lot had electros to the transformer. What do electros have???

when I get to building thew 1081 boards I have I will have to decide what caps for the filter networks.