life lesson on ceramic capacitors in signal path - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

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 21st February 2006, 05:39 PM   #1
mazurek is offline mazurek  United States
diyAudio Member
 
Join Date: Aug 2005
Default life lesson on ceramic capacitors in signal path

My active crossovers I built sounded sort of thin to me, really good on some things, not so much on others. I removed the 10 pf ceramic bandwidth limiting capacitors in the feedback path, and problem is gone. I had thought that their frequency of operation was so far outside of audio band that I was safe from their supposed problems. Luckily no oscillation, as I don't have room to install mica capacitors.

In retrospect, if I really need bandwidth limiting caps, I maybe should have chosen smaller resistor values to obtain larger capacitor values (and have more choice in quality capacitors).

By the way, In my opinion, I think modern rock/metal is the best way to find problems with speakers, my overpriced retail speakers and bad crossover all sounded great with acoustic material.
  Reply With Quote
Old 22nd February 2006, 02:58 AM   #2
jcx is online now jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
not all ceramic is bad, np0 or c0g are generally better than mica and approach film quality on measurable distortion and dielectric adsorption, with higher feedback R many op amps require some feedback C to cancel destabilizing parasitic C at their inputs, often only a few pF is required - don't even think about using hi K ceramics like Z5U in signal apps


generally harmonically "simple" music with single voice, few instruments gives best sound with distorting systems - challenging music is well recorded (without the compression common in Rock and other pop formats) and harmonically complex - classical orchestral music with real dynamic range is the hardest to get right

Rock/Metal usually relies on distortion in tube instrument amps as a part of the musical "voice" and may have further compression used to keep average levels high - its very hard to judge when such pre-distorted source is getting a little more added by your system - but the high average levels will certainly test your excursion limits and amp clipping levels
  Reply With Quote
Old 22nd February 2006, 07:29 AM   #3
klitgt is offline klitgt  Denmark
diyAudio Member
 
klitgt's Avatar
 
Join Date: Sep 2004
Location: Denmark
Default Re: life lesson on ceramic capacitors in signal path

Quote:
Originally posted by mazurek
My active crossovers I built sounded sort of thin to me, really good on some things, not so much on others. I removed the 10 pf ceramic bandwidth limiting capacitors in the feedback path, and problem is gone. I had thought that their frequency of operation was so far outside of audio band that I was safe from their supposed problems. Luckily no oscillation, as I don't have room to install mica capacitors.

Can you attach a diagram to visualize what we are talking about. It is an interesting topic that many can benefit from if they understand what it is all about. I think I have an idea but not quite sure

Cheers
  Reply With Quote
Old 22nd February 2006, 09:06 AM   #4
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
will polystyrene fit the space? even standing end on to the PCB.
__________________
regards Andrew T.
  Reply With Quote
Old 22nd February 2006, 01:34 PM   #5
mazurek is offline mazurek  United States
diyAudio Member
 
Join Date: Aug 2005
Can you get polystyrene in small values, and where?

Interesting comments jcx, appreciate the feedback. Too busy for a real reply today.

I attached a copy of the pcb for those interested, I will write up this project more thoroughly later, the documentation is not great.
Attached Images
File Type: png pcb.png (55.2 KB, 389 views)
  Reply With Quote
Old 22nd February 2006, 04:45 PM   #6
Nordic is offline Nordic  South Africa
diyAudio Member
 
Nordic's Avatar
 
Join Date: Sep 2005
RS components sells FSC Series Polystyrene Capacitors from 10pf upwards to .01uf, Capacitance tolerance 񶐱% or 1pF, 40V though, pretty expensive and 10 minimum per order
  Reply With Quote
Old 22nd February 2006, 05:49 PM   #7
Bobken is offline Bobken  United Kingdom
diyAudio Member
 
Join Date: Dec 2002
Location: UK
Hi,

If you have a choice here, go for extended foil polystyrenes as their end caps are attached to a greater area of the foil, and (generally) will sound better, too.

FSC-EX versions are extended foils, but you may not get them in the lowish values you are after. The FSCs mentioned above aren't very far behind them, though, in the sound-stakes.

Sonically, these extended-foils are one of the finest caps for small values, with only (non-magnetic leaded, which are rather rare) silver micas being close. So long as their slightly higher inductance (due to their rolled-up construction) isn't significant, and for most audio situations it won't be, I would choose these polystyrenes over all other caps, for relatively low pF values like compensation caps etc.

It was the accidental discovery of the obvious differences in sound between polystyrenes and ceramics (in a MC head amp) some 30+ years ago, which started me out on 'the road to ruin' of listening to all passive components in my entire system, and choosing accordingly!

Regards,
__________________
Bob
  Reply With Quote
Old 22nd February 2006, 07:11 PM   #8
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
Rapid sell from 10pF upwards in qty of 1. But post from UK will kill you. I'm sure someone local must offer a similar service.
__________________
regards Andrew T.
  Reply With Quote
Old 23rd February 2006, 12:55 AM   #9
diyAudio Member
 
TwoSpoons's Avatar
 
Join Date: Oct 2004
I can't believe you would delete some caps, not replace them, then blame the sound change on the fact they were ceramic. The sound change is because the caps are missing !
  Reply With Quote
Old 23rd February 2006, 02:00 AM   #10
diyAudio Member
 
Join Date: Dec 2005
Location: Kuala Lumpur
A 10pF ceramic will have a very good dielectric and is very close to an ideal capacitor.

I suspect that you have a stability problem somewhere.
  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
Tantalum Capacitors in Signal Path schnullimaus Parts 17 11th December 2013 08:39 PM
what is the difference between silver mica capacitors and ceramic capacitors ?? prorms Solid State 1 6th May 2008 12:38 PM
Good or bad to use parallel capacitors of same value in signal path... 2004ex Tubes / Valves 1 25th May 2005 11:38 AM
Aleph P 1.7: 2k pot is in the signal path? swede Pass Labs 14 29th December 2002 06:29 PM
15uf signal path capacitors for BOSOZ ralf Pass Labs 5 24th April 2002 07:51 PM


New To Site? Need Help?

All times are GMT. The time now is 05:27 PM.


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