Capacitors in Series - phase changes? - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 23rd January 2007, 10:05 AM   #1
diyAudio Member
 
GeorgeBoles's Avatar
 
Join Date: Mar 2004
Location: Australia
Default Capacitors in Series - phase changes?

Hello folks,

I am aware that putting capacitors in series produces an overall capacitance of 1/Ct = 1/Ca + 1/Cb + ... etc., and had never thought about it any more.

But what happens to the phase of a signal which passes through, say, three capacitors in series - is it changed by only 90 degrees (as it would be for a single capacitor, as if they were all working together as one), or is it retarded by 90 degrees three times over - (once for each capacitor)?

Your advice would be helpful if multi-amping my soon-to-be-borne Linkwitz Orions with different sorts of power amplifier, or if I fiddle with more or fewer capacitors in the signal chain, say in my Nelson Pass "NS10" type pre-amp... depending on what is in my spares box or what is cheap at my supplier.

All advice gratefully and gracefully received.

Regards,
George.
__________________
My Website - borne out of frustration, but expanded for fun.
DIY HiFi, Combat Flight Sims & some stolen antiques
  Reply With Quote
Old 23rd January 2007, 10:13 AM   #2
diyAudio Member
 
GeorgeBoles's Avatar
 
Join Date: Mar 2004
Location: Australia
Default And effect on voltage handling capability

Also, while I am at it, I read somewhere on this forum that it was unsafe to simply put two capacitors in series and expect them to handle twice their rated voltage, e.g. using two 35V rated capacitors in series in a power supply to cope with 50V rails, because the voltage may NOT be shared equally between them,

In this discussion, there was a diagram showing how to ensure that the voltage was split between the capacitors, I think by placing resistors in parallel with each of the capacitors and letting the resistors split the voltage.

Can anyone either point me to the thread, or point me in the correct direction.

Regards again,
George.
__________________
My Website - borne out of frustration, but expanded for fun.
DIY HiFi, Combat Flight Sims & some stolen antiques
  Reply With Quote
Old 23rd January 2007, 02:46 PM   #3
Formerly "jh6you". R.I.P.
 
Babowana's Avatar
 
Join Date: Jul 2006
Default Re: Capacitors in Series - phase changes?

Quote:
Originally posted by GeorgeBoles


I am aware that putting capacitors in series produces an overall capacitance of 1/Ct = 1/Ca + 1/Cb + ... etc., and had never thought about it any more.

But what happens to the phase of a signal which passes through, say, three capacitors in series - is it changed by only 90 degrees (as it would be for a single capacitor, as if they were all working together as one), or is it retarded by 90 degrees three times over - (once for each capacitor)?

The phase shift is always a relative value.
For example, when we have a low pass RC filter (lag-network) of an amplifier, we could consider the phase shift.

Let's say, we are using three caps having the same value (Ca) in series, the total capacitance is calulated as Ca/3.
And, if we compare the phase shift between R-CaCaCa (three caps in series) filter with R-C (one cap of Ca/3) filter, the phase shift is maintained the same.
But, if we compare the phase shift between R-CaCaCa (three caps in series) filter and R-C (one cap of Ca) filter, the phase shift is different. In this case, the phase shift is increased in R-CaCaCa filter according to the number of caps in series. Each additional phase shift is less than 90deg and the increase rate is non-linear.

The same principle is applied to the high pass filter, but the phase shift is decreased when there is the phase shift.

Sorry I'm bad in writing . . . somewhat drunk . . .
  Reply With Quote
Old 23rd January 2007, 03:59 PM   #4
Formerly "jh6you". R.I.P.
 
Babowana's Avatar
 
Join Date: Jul 2006
Default Re: Re: Capacitors in Series - phase changes?

Quote:
Originally posted by Babowana


The phase shift is always a relative value.
For example, when we have a low pass RC filter (lag-network) of an amplifier, we could consider the phase shift.

Let's say, we are using three caps having the same value (Ca) in series, the total capacitance is calulated as Ca/3.
And, if we compare the phase shift between R-CaCaCa (three caps in series) filter with R-C (one cap of Ca/3) filter, the phase shift is maintained the same.
But, if we compare the phase shift between R-CaCaCa (three caps in series) filter and R-C (one cap of Ca) filter, the phase shift is different. In this case, the phase shift is increased in R-CaCaCa filter according to the number of caps in series. Each additional phase shift is less than 90deg and the increase rate is non-linear.

The same principle is applied to the high pass filter, but the phase shift is decreased when there is the phase shift.

Sorry I'm bad in writing . . . somewhat drunk . . .

I was wrong. It should have been:

The phase shift is always a relative value.
For example, when we have a low pass RC filter (lag-network) of an amplifier, we could consider the phase shift.

Let's say, we are using three caps having the same value (Ca) in series, the total capacitance is calculated as Ca/3.
And, if we compare the phase shift between R-CaCaCa (three caps in series) filter with R-C (one cap of Ca/3) filter, the phase shift is maintained the same.
But, if we compare the phase shift between R-CaCaCa (three caps in series) filter and R-C (one cap of Ca) filter, the phase shift is different. In this case, the phase shift is decreased in R-CaCaCa filter according to the number of caps in series. Each phase shift is less than 90deg and the decreasing rate is non-linear.

The same principle is applied to the high pass filter, but the phase shift is increased when there is the phase shift.
  Reply With Quote
Old 23rd January 2007, 04:50 PM   #5
diyAudio Member
 
Join Date: Sep 2004
Location: UK
Consider a black box containing two 2uF capacitors in series.

The outside world can only see a single 1uF capacitor.

What parameters of capacitance could produce a difference in phase shift between the black box and a single 1uF cap?

None.

Yes, the DC voltage across each one will depend on the effective leakage resistances of the caps. Swamp this with a parallel resistor to define the voltage share.
  Reply With Quote
Old 23rd January 2007, 10:28 PM   #6
diyAudio Member
 
GeorgeBoles's Avatar
 
Join Date: Mar 2004
Location: Australia
Default Many thanks, I am happy now.

Many thanks to you both, Babowana and Cliff.

You have solved my problem.

Regards,
George.
__________________
My Website - borne out of frustration, but expanded for fun.
DIY HiFi, Combat Flight Sims & some stolen antiques
  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
Phase Linear 700 Series II - 60Hz Hum craigstrat Solid State 6 28th September 2008 02:45 AM
Phase Linear 200 Series 2 IrishboyM4 Solid State 23 28th May 2008 03:04 AM
Phase Linear 400 Series 2 Repair rwagoner Solid State 50 1st September 2007 03:01 AM
Can Speakers be Wired Out of Phase in Series ralph-bway Multi-Way 5 7th May 2005 02:33 AM
Is a series-XO the only way to always have both speakers in phase? Bricolo Multi-Way 11 31st March 2003 08:40 AM


New To Site? Need Help?

All times are GMT. The time now is 10:53 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