Motor caps - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 28th November 2005, 01:23 PM   #1
diyAudio Member
 
croccodillo's Avatar
 
Join Date: Mar 2005
Location: Bergamo
Default Motor caps

I've read in some threads here that somebody uses polypropilene motor caps in their projects: are those capacitor good enough?
I'm trying to build a para-feed SE amplifier, so I could use such a cap for output stage (I have lot of them).

Ciao,
Giovanni
  Reply With Quote
Old 28th November 2005, 01:28 PM   #2
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
Quote:
polypropilene motor caps in their projects: are those capacitor good enough?
They are excellent! Some of the best you can get IMO. The only things possibly better are some of the paper in oil motor caps.
  Reply With Quote
Old 28th November 2005, 02:12 PM   #3
diyAudio Member
 
tubemaster's Avatar
 
Join Date: Sep 2005
Quote:
Originally posted by Bas Horneman
The only things possibly better are some of the paper in oil motor caps.
Hello,

btw. where can you get paper-in-oil motor caps for power supply use?

Thanks
Michael
  Reply With Quote
Old 28th November 2005, 02:23 PM   #4
diyAudio Member
 
croccodillo's Avatar
 
Join Date: Mar 2005
Location: Bergamo
Just an idea: I work for a company that produces microwave ovens for medical applications; into every microwave oven (yes, also the one you have on your kitchen desk) there is an high voltage (4500V), paper in oil capacitor, usually with a capacitance of about 1-2 microfarad.

Ciao,
Giovanni
  Reply With Quote
Old 28th November 2005, 03:03 PM   #5
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
Quote:
btw. where can you get paper-in-oil motor caps for power supply use?
Don't have an address for them really. Have some russian ones I got from e-bay. And there we have the big drawback of paper in oils. If you get NOS there is apparently a big difference in quality...not all paper in oils are created equal. (same for polyprop but I would guess less variation)



Giovanni's suggestion is a good one. Unfortunately most are indeed 1uF -2uF.
  Reply With Quote
Old 28th November 2005, 05:29 PM   #6
Sherman is offline Sherman  United States
diyAudio Member
 
Join Date: Feb 2004
Location: Chicago area
Quote:
Originally posted by tubemaster


Hello,

btw. where can you get paper-in-oil motor caps for power supply use?

Thanks
Michael
Try eBay. I got some very nice caps of 40uF, 55uf and 100uF for a very good price. Be sure to just search 'All Categories' as listers put them all over the place.

One important thing to note- get motor run caps and not motor start caps. Motor runs are designed for continuous duty. Also, motor caps will be rated for AC voltage. I've been told you can double that for DC use but I use the AC * 1.4 rule.
__________________
--Sherman
  Reply With Quote
Old 28th November 2005, 09:35 PM   #7
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
I am using salvaged Microwave oven caps in my Parafeed amp. I am using them for power supply filtering. They are rated at about 1500V and look very robust. If you use a CCS source in your design, it is surprising how little capacitance you can get away with in your power supply. The CCS, if good, will supply clean DC at a constant current, so all that heavy duty filtering you usually need for SE designs becomes largely redundant. I do however use two large filtering chokes.

Shoog
  Reply With Quote
Old 29th November 2005, 12:27 AM   #8
speaker is offline speaker  United States
diyAudio Member
 
speaker's Avatar
 
Join Date: Mar 2004
Location: USA
What is the prevailing wisdom as to why motor run caps are good? I've also seen them used as tweeter highpass filters. Do they have an especially low ESR & DF or other factor? I understand the reliability aspect but what else attributes to their suitability?
  Reply With Quote
Old 29th November 2005, 09:27 AM   #9
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
Quote:
What is the prevailing wisdom as to why motor run caps are good?
Excellent question.

My answer is : I don't know.

But like you said reliability is good.
And there is anecdotal evidence that the oil "dampens" leading to good sonic qualities. Why else would a lot of "boutique" caps use oil? Maybe someone in the know can shed some light on this.

The paper in oil thing ...once again...just speculating here..is a tone thing...paper also has better di-electric qualities compared to teflon. But this can only be said of paper with a certain type of "dryness" I suppose.

Last but not least..if using older caps with oil in putting them in your amp will save them from being dumped in some landfill where they will pollute groundwater with heavy metals.
  Reply With Quote
Old 30th November 2005, 07:26 PM   #10
jsn is offline jsn  United States
diyAudio Member
 
jsn's Avatar
 
Join Date: Sep 2004
Location: The Atomic City
This is the closest thing I have seen to quantitative proof that paper in oil is a good thing:

http://members.aol.com/sbench102/caps.html

I really like polypropylene in oil caps becuase they are inexpensive, easy to get as motor run caps, and relatively easy to work with.

Here is an amp that uses a bunch of inexpensive 10uF poly-in-oil caps:

http://boozhoundlabs.com/monkey/

I also like these for speaker crossovers. You can sometimes get good deals on low voltage (200V or so) Russian surplus PIO caps on eBay.

To me the sound of oil caps in general is clearer, more relaxed, and perhaps tonally a bit darker. Of course meaningfully describing sound is a hard thing to do, so ymmv.

High voltage, low value oil caps like those mentioned in microwave ovens would make great coupling caps, and really great parallel feed caps.

jsn
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Motor run Caps Question Fat Daddy Tubes / Valves 4 3rd May 2008 10:55 PM
dual value motor run caps wicked1 Tubes / Valves 4 6th February 2008 09:37 PM
ESR of motor-run caps? JoshK Tubes / Valves 12 14th December 2007 03:17 AM
AC Motor Start Caps for PS use gilid Tubes / Valves 44 28th June 2004 11:35 PM


New To Site? Need Help?

All times are GMT. The time now is 01:25 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2