Electrolitics and Metal Film

[tman]

Hi

I was wondering as I see a popular mod for tubescreamers or in my case a Boss SD-1 is to replace the 1uF NP electro's with metal film.

What do metal film look like ?

Also does the cap which isn't present across the diodes 51pf does it sound better in or out

cheers ?

[erio fraga]

Take alook on pg 7 of the link bellow:

http://www.epcos.com/inf/20/20/db/fc_01/02830318.pdf


Regards

Erio

[Hal]

metal film capacitors are not very common, but are available from digikey...

they're made by panasonic, and are called "stacked metal film"

they are moderatly priced, at about $2.00 - $6.00 for 10 (depending on value).

They are also commonly used in DS-1 mods :-D (which i will be doing...in a couple weeks) :-D

[ildar]

On the same general path, what about tantalum caps to replace electrolytics? What about polarity issues?

[RDV]

I have a bunch of good ones for cheap! SPAM!

http://diystompboxes.com/sboxforum/viewtopic.php?t=20248

Regards

RDV(cheap cap boy)

[bobbletrox]

metal film capacitors are not very common, but are available from digikey...

they're made by panasonic, and are called "stacked metal film"

I'm pretty sure "stacked metal film" is just a fancy name for MKT caps.  Either way, they're both 'stacked' metalised poyester.  The only difference between the Panasonics and generic ol' MKTs to my knowledge is the size; i.e the Panasonics are dipped, where as MKTs are housed in little plastic boxes.  There are 1uF 63v MKTs that will fit into pedal mods no problem however.

There seems to be a mojo myth floating around about 'stacked metal film' caps.

[Eric H]

where as MKTs are housed in little plastic boxes.  There are 1uF 63v MKTs that will fit into pedal mods no problem however.

The nice thing about MKT-type caps is they were designed to be"circuit board friendly"  --the range of .001uf to 1uf, 50 or 63 volt, all slide right in to 5mm spaced holes.

-Eric

[tman]

Aren't they commonly know as polyester ?

Is there really a difference with Non Polarity electros you could just wire to together couldn't you ?

[bobbletrox]

Yep.  Metalised Polyester Film is what they really should be called.

The polarity of the capacitor hasn't got anything to do with the mod, it's the composition of the capacitor itself.  Electrolytics are argued to sound unpleasant, so mods such as the one's Keeley does replace them with film capacitors.

[erio fraga]

According basically to DIN 41 379, these are the classification of metallized and metal caps:

MKT  are caps which electrodes are metallized Polyester film, so the dielectric material is Polyester
MKP are caps which electrodes are metallized Polypropylene  film; the dielectric material is Polypropylene
KT are caps which electrodes are metal foils and the dielectric are Polyester film
KP are caps which electrodes are metal foils and the dielectric are Polypropylene film
MFP and MFT capacitors are constructed using a combination of metal foils and metallized plastic films.

The denomination “stacked-film” is related to a production technology in which large rings of metallized film are wound onto core wheels. A single stacked-film cap has an internal construction very similar to the ceramic multilayer cap structure.
In the traditional production technology (“wound caps tech”) you wind each cap each time. After, if flat final shape is deririble for space saving purpose,  the winding bobins are compressed.
Stacked-film technologie has a lot of advantages under the production point of view and besides confers some better capabilities to the caps than the tradicional technologie.
Stacked-film or flatted wound caps can be finished with insulating coatings or in plastic cases or even in metal cases to confer mainly more or less climatique resistence caractheristics.


Rgds

Erio

[Ge_Whiz]

The 51pF capacitor shouldn't affect the sound at all. It's there to prevent high frequency (RF) instability in the op-amp circuit.

[Paul Perry (Frostwave)]

I don't know.. 51pf is getting up to where it could roll of some top end. I think you have to let your ears be the guide, try 200pf, and see if it is different to you.

[brrt]

You could replace this cap with another value to discover its influence, but never really remove the cap, because of the earlier mentioned high frequency instability!

Brrt

[Peter Snowberg]

Erio,

Thank you very much for adding your information and that link! I just learned several things reading that Epcos data.

Take care,
-Peter