Polyester v polyprop?

[JamesHealey]

so i'm coming to design an amp for my self.. i'm wanting to stick to uk available parts so i won't be using orange drops i'll be either using metalized polyester caps by vishay or polyprop film by lcr. now what's the general consensus on what polyester and polyprop sound like?

[paulster]

If you haven't tried them yet I'd recommend trying the LCR PC/HV/S/WF 1500V series, although be warned that they're big.

I'm usually a fan of polyester caps for amps but I'm loving the LCRs in my Vox-type build.

For polyesters the MKT1813s are very transparent so that may have a bearing depending on what you want it to do.

[Cliff Schecht]

Polypropylene capacitors are stable and low leakage (I believe more so than polyester), great for circuits that require accuracy. They also do make great audio caps, you just need to be prepared to shell out real $$$ for the high end ones.

[Structo]

I was researching film caps the other day and I was surprised at how poorly polyester caps performed as capacitor dielectric.

It was basically the worst of the bunch including polyprop, polycarbonate, polystyrene and Teflon.

So the designers that chose polyester must have done so due to the tonal qualities of the material rather than temperature coefficient, frequency and voltage.

[JamesHealey]

yeah those are the one's i'm going to try paul.. i've used mkt1813 plenty of times they're great for cleans because of their transparent tone.. but they kinda sound shrill and somewhat brittle for distorted tones in my opinion.. much prefer orange drop pvc's for that application.. big fan of sozo but too expensive to import for every build i do.. trying to find readily available caps that sound good and aren't special order.. can get ps6's from audiocap but shipping is killer when you live near farnell trade counter..

[billyz]

I am certain it can be shown that Transistors are superior to Vacuum tubes as well. And in fact they are in many ways. For a reproducers of audio I want extreme accuracy and the least coloration possible etc. For that I would choose teflon or Polystryene, even the power supply caps. the best would be no caps at all. But, not in my guitar amp, where I want a tone pallet to color and shade the signal to Produce the sound I want to create.

That being said, not all Polyester is created equal, is it metalized or foil? for instance. I have tried Poly propylene and did not care for the tonality. However I love Polystyrene. Ceramic , as bad as it is, can do some wonderful things in the right application. So choose the caps based on your vision of the sound you are trying to achieve, not on the spec sheet.

Just some food for thought. There are no wrong caps or resistors.

[KellyBass]

I'm with billyz. I was checking out a high end tube bass preamp about a month ago and saw 8 cent ceramic caps laying right next to 15 dollar Hovland musicaps in a very critical part of the circuit. I guess the designer was looking for a little "fur" or something.

[paulster]

I'll add a big +1 to billyz's comments too.

Ceramics definitely have their place in guitar amps, and there are some really nice ones these days when it comes to getting a bit of fur!

[JamesHealey]

I quite like using Polystyrene instead of Mica in just about every application i've tried it in..

Ceramics tend to sound gritty and rough which I've found works really well in 18w Marshall type amps!

[FYL]

It was basically the worst of the bunch including polyprop, polycarbonate, polystyrene and Teflon.

Wow, a max -1% capacitance at 100 000 Hz, that's really bad. Now, what about those nice ±20% carbon comp resistors with a 400 ppm tempco?

[Cliff Schecht]

I was researching film caps the other day and I was surprised at how poorly polyester caps performed as capacitor dielectric.

It was basically the worst of the bunch including polyprop, polycarbonate, polystyrene and Teflon.

So the designers that chose polyester must have done so due to the tonal qualities of the material rather than temperature coefficient, frequency and voltage.

Look at the cost of each capacitor type as well. More often than not, the choice to go with a specific cap is cost-based as opposed to performance-based. As you start moving up in the dielectric types, the cost increases dramatically at a certain point. If you're doing a one off build, it's not such a big deal to spoil yourself and go with more expensive caps. But it makes sense for manufacturers to squeak by with the cheapest film caps they can get. When you open up a modern Fender amp, you'll see the cheapest film caps money can buy because they know people will bitch if they go to ceramic and it doesn't make sense to go better where you couldn't hear the difference anyways. I'll bet the most in-depth parameter they look at performance wise is voltage handling and cost.

I like FYL's comments too. The "worst of the bunch" is still better than the best ceramics!

Polystyrene is my favorite for low values, paper in oil for higher values. Ceramics do have a certain harshness that can add or subtract depending on application. Funny how such a (usually inexpensive) passive component can have such a substantial impact on sound..