Cheap motor caps(MKP) vs Electrolitics

[rvrazvan]

I'm waiting for the OPT's for my Borbely 6c33 SET and i'm thinking about using MKP caps allover the amp. The only way of doing this without going into bankruptcy is to use motor run caps. Cheap ones. I'll use 20 uF caps in a headphone amp meanwhile.

So any experience with motor caps in the PS and other places in the amp(by-pass caps)?

[kevinkr]

Originally Posted by rvrazvan

I'm waiting for the OPT's for my Borbely 6c33 SET and i'm thinking about using MKP caps allover the amp. The only way of doing this without going into bankruptcy is to use motor run caps. Cheap ones. I'll use 20 uF caps in a headphone amp meanwhile.

So any experience with motor caps in the PS and other places in the amp(by-pass caps)?

Generally work pretty well in PSU applications, just make sure you get motor run and not motor start types.

[mige0]

If you already used it you projects you should have some experience already - no?

I use those cheap MP types it in *all* my PSU applications - though - I use it only in parallel to the 'lytics (SS type amps) and in parallel to them a cheap EPCOS "naked" MKT 100nF foile and in parallel to them a cheap Russian MICA of some pF or nF
Values are not any critical IMO, but type is.

This gives me the best sonic results so far.
Good attack, no 'lytics "smear / lag", "natural" and "transparent" sound.

Best
Michael

[rvrazvan]

The headphone amp is not ready so i have no clue about the sound .
have you used the for by-passing the cathode resistors?

[mige0]

No, currently I am back to solid state.

Besides that, I certainly would give it a try - those paper caps are bulky but cheap - luckily in valve amps there are not that many needed.

For signal apps most prefer exquisite (and veeery expensive) paper oil types though - i doubt the price is justified...


Michael

[rvrazvan]

i do not affort big expensive oil caps. And i think i could still benefit alot from the type of the cap. i hope i can use just Wima MKP10 for the smaller values and motor MKP for the rest . no lithics

[trobbins]

Although not with the same hi-fi intent, I've used MKP's as the first filter cap in restored amps that use CLC filtering and a valve diode. I have access to second hand 2.2uF to 10uF from old UPS and switchmodes operating at 240VAC, and the caps typically have a DC voltage rating of about 760VDC. An electrolytic in that first capacitor position not only typically sees a high peak voltage exceeding 450VDC, but also experiences high ripple current and can't be very high in capacitance, making it an arduous position that is best served by a metallised poly.

[mige0]

Originally Posted by rvrazvan

i do not affort big expensive oil caps. And i think i could still benefit alot from the type of the cap. i hope i can use just Wima MKP10 for the smaller values and motor MKP for the rest . no lithics

I'd suggest you to bypass the small value caps (MKP or possibly even better MKS) with the same MKT and MICA I suggested for the big metallized paper caps in power supply - you will have to find out yourself what sonic pattern suites you best.

The funny thing seems to be that the sonic pattern added / removed with the parallel caps of a certain make remains pretty stable in different applications - I mean - a PSU cap is only "sort of" in the signal path compared to a cathode bypass cap.

If you cant identify any sound difference - I'd suggest to use a cheap single cap solution

For testing sonic differences I do not recommend A/B testing but rather give yourself a few days towards a week to familiarize with the presentation - than change.
Go back and forth as often as you need to identify the difference or to come to the conclusion that it makes no difference for you at all.

This procedure takes longer (in the first run) than flipping a switch but the benefits are that you will also pick up distracting sonic patterns more easily -probably not so obvious at a first glance - good for long term confidence once you made up your mind.


Michael

[ratbagp]

I've used motor run caps in power supplies for some time and like them. They are especially useful for voltages above the usual electrolytic limit of 450 - 500 vdc.

Mounting them can be a pain and I now use Goop to glue them to a piece of metal that I then mount to the chassis. The Goop holds them quite securely if you give the glue a day to set under pressure. If you need to remove the capacitor you can with a bit of force. You can find Goop at most hardware shops.

This link is good for inexpensive used motor run caps.
Surplus Center

Of course, I have no connection with the seller.

ray

[00940]

I'm using such 20uF/450VAC mkp caps from ICAR both at the input of my HV power supplies and as output coupling caps. They're both rugged (and thus make great input filter caps) and good sounding compared to electrolytics (and thus make great output caps).

Of course, the problem is to find the room to fit those caps into your amplifier. They weight a ton too. For comparaison, the small film cap is a 10uf/400VDC solen and the electrolytics 220uF/200V caps... (in a proto of an headphones amplifier, see: http://www.diyaudio.com/forums/headp...sed-ecl84.html )