GK-2 cutoff frequency for SS section - diyAudio
Go Back   Home > Forums > Commercial Sector > Manufacturers > AKSA

AKSA Builders of market proven kits and modules at sound quality to rival the best in high end

Reply
 
Thread Tools Search this Thread
Old 30th January 2013, 11:09 AM   #1
Jens A. is offline Jens A.  Denmark
diyAudio Member
 
Join Date: Dec 2009
Location: Copenhagen
Default GK-2 cutoff frequency for SS section

Hi Hugh,

When I created the SS output on my GK-2, I used a 1 uF teflon cap. When we discussed this prior to my implementation, I remember you said it should just be between 1 and 10 uF.

Just out of curiosity - what would the cutoff frequency (- 3 dB point) for the SS output be with the 1 uF cap?

It is looking into the Ground Sound filter's 20 k input impedance.

I do not feel there is a problem, but since I have already implemented a very steep (48 dB/octave) sub filter at 10 Hz in the Ground Sounds, there is no need for additional sub filtering, and if that turned out to be the case I would simply change the SS output cap value to ensure I do not "get too much of a good thing"

Cheers,

Jens
__________________
"Life is too short for over-expensive hi-fi pretending to be high-end"
  Reply With Quote
Old 30th January 2013, 01:08 PM   #2
diyAudio Member
 
Osvaldo de Banfield's Avatar
 
Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Simple: the -3dB roll off frequency is when the reactance of the capacitor (1/(2 * pi *frequency * capacitance)) equals load resistance. In this frequency, phase angle between voltages becomes 40 degrees and voltage across loads becomes .7071 of the input voltage.

If you get a calculator, then F 0 1/(2 pi capacitance [microfarads] * resistance[mega-ohms]) will give frequency in hertz.

Fortunately, this calculae is independent of capacitor brands and personal tastes. Is as is.
Good luck.
__________________
LW1DSE
  Reply With Quote
Old 30th January 2013, 01:59 PM   #3
Jens A. is offline Jens A.  Denmark
diyAudio Member
 
Join Date: Dec 2009
Location: Copenhagen
Quote:
Originally Posted by Osvaldo de Banfield View Post
Simple: the -3dB roll off frequency is when the reactance of the capacitor (1/(2 * pi *frequency * capacitance)) equals load resistance. In this frequency, phase angle between voltages becomes 40 degrees and voltage across loads becomes .7071 of the input voltage.

If you get a calculator, then F 0 1/(2 pi capacitance [microfarads] * resistance[mega-ohms]) will give frequency in hertz.

Fortunately, this calculae is independent of capacitor brands and personal tastes. Is as is.
Good luck.
Errr, well, yes ...

Unfortunately, I'm not much of a mathematician and have never used a scientific calculator, so for me this is not simple.

So what is "F 0 1"? And what "resistance" are we talking about?

Cheers,

Jens
__________________
"Life is too short for over-expensive hi-fi pretending to be high-end"
  Reply With Quote
Old 30th January 2013, 02:54 PM   #4
diyAudio Member
 
Osvaldo de Banfield's Avatar
 
Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Quote:
Originally Posted by Jens A. View Post
Errr, well, yes ...

Unfortunately, I'm not much of a mathematician and have never used a scientific calculator, so for me this is not simple.

So what is "F 0 1"? And what "resistance" are we talking about?

Cheers,

Jens
OK, it was a typo I would write f= 1/ 2 * pi * Capacitance * resistance, and it gives you frequency. Resistance must be considered the equivalent resistance to any ground before the capacitor in the way of signal flow. Example:
lets consider a 1 microfarad ( F, or 10E-6) farad and a 20Kohms load.

So the "corner" frequency, say, the frequency at which the signal after the cap is -3dB (.7071 times) respect to the signal before the cap will be:

f = 1 / ( 2* pi * 20000 ohm * 10E-6F) = 15.91Hz.

Then, at about 16Hz, it is considered the lowest frequency your circuit will pass without "severe" attenuation and or distortion.

It is independent if the load resistor is a single 20000ohm or two 40000 in parallel, or or two 10K in series, or any other combination of resistances that gives you 20000ohms as result.

Aclareta: 1E-6 means .000001 in scientific notation, or 1/1 million or 1 millionth part of any measure.
__________________
LW1DSE
  Reply With Quote
Old 30th January 2013, 04:09 PM   #5
Jens A. is offline Jens A.  Denmark
diyAudio Member
 
Join Date: Dec 2009
Location: Copenhagen
Quote:
Originally Posted by Osvaldo de Banfield View Post
OK, it was a typo I would write f= 1/ 2 * pi * Capacitance * resistance, and it gives you frequency. Resistance must be considered the equivalent resistance to any ground before the capacitor in the way of signal flow. Example:
lets consider a 1 microfarad ( F, or 10E-6) farad and a 20Kohms load.

So the "corner" frequency, say, the frequency at which the signal after the cap is -3dB (.7071 times) respect to the signal before the cap will be:

f = 1 / ( 2* pi * 20000 ohm * 10E-6F) = 15.91Hz.

Then, at about 16Hz, it is considered the lowest frequency your circuit will pass without "severe" attenuation and or distortion.

It is independent if the load resistor is a single 20000ohm or two 40000 in parallel, or or two 10K in series, or any other combination of resistances that gives you 20000ohms as result.

Aclareta: 1E-6 means .000001 in scientific notation, or 1/1 million or 1 millionth part of any measure.
Hmmm - I am afraid I still do not understand. If "1 /" means "1 divided by" then I cannot see how you get to the result shown. If I divide 1 by the result in the brackets, I get less than 1.

But I probably do not understand the notation ...

Anyway, since we do not know the resistance, I guess we can just as well wait for Hugh

Cheers,

Jens
__________________
"Life is too short for over-expensive hi-fi pretending to be high-end"
  Reply With Quote
Old 30th January 2013, 04:44 PM   #6
diyAudio Member
 
Osvaldo de Banfield's Avatar
 
Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Quote:
Originally Posted by Jens A. View Post
Hmmm - I am afraid I still do not understand. If "1 /" means "1 divided by" then I cannot see how you get to the result shown. If I divide 1 by the result in the brackets, I get less than 1.

But I probably do not understand the notation ...

Anyway, since we do not know the resistance, I guess we can just as well wait for Hugh

Cheers,

Jens
Go to the windows calculator, and in the menu "view" click scientific, you will see the calculator expands.

Then, in the numeric right keyboard type (or in the calculator drawing press with the mouse the number) 2, then the asterisc that operates as a multiplier sign, with the mouse click the "pi" button, the * again, then type the value of the resistance load in ohms, the *, then the capacitance in farads (Again, 1F is .000001F). Then, press equal button.

Once did it, press with the mouse, the 1/x button, and you'll get the value I post in the previous msg, (15.91xxxx) with lots of decimal numbers. In practice, only the first or two first digits are of interest.

But, if you don't know the load impedance form the output of the cap to ground, all this thread is meaningless.

Cordially, Osvaldo .
__________________
LW1DSE

Last edited by Osvaldo de Banfield; 30th January 2013 at 04:56 PM.
  Reply With Quote
Old 30th January 2013, 06:26 PM   #7
Jens A. is offline Jens A.  Denmark
diyAudio Member
 
Join Date: Dec 2009
Location: Copenhagen
Quote:
Originally Posted by Osvaldo de Banfield View Post
Go to the windows calculator, and in the menu "view" click scientific, you will see the calculator expands.

Then, in the numeric right keyboard type (or in the calculator drawing press with the mouse the number) 2, then the asterisc that operates as a multiplier sign, with the mouse click the "pi" button, the * again, then type the value of the resistance load in ohms, the *, then the capacitance in farads (Again, 1F is .000001F). Then, press equal button.

Once did it, press with the mouse, the 1/x button, and you'll get the value I post in the previous msg, (15.91xxxx) with lots of decimal numbers. In practice, only the first or two first digits are of interest.

But, if you don't know the load impedance form the output of the cap to ground, all this thread is meaningless.

Cordially, Osvaldo .
Ah, that's how to do it! Thanks

Not all in vain - once Hugh tells us what the resistance is, I'll use your calculation to adjust my cap value, if necessary

Thanks,

Jens
__________________
"Life is too short for over-expensive hi-fi pretending to be high-end"
  Reply With Quote
Old 30th January 2013, 06:38 PM   #8
diyAudio Member
 
Osvaldo de Banfield's Avatar
 
Join Date: Dec 2011
Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Quote:
Originally Posted by Jens A. View Post
Ah, that's how to do it! Thanks

Not all in vain - once Hugh tells us what the resistance is, I'll use your calculation to adjust my cap value, if necessary

Thanks,

Jens
Congratulations, guy!!!
__________________
LW1DSE
  Reply With Quote
Old 30th January 2013, 07:53 PM   #9
andyr is offline andyr  Australia
diyAudio Member
 
Join Date: Nov 2003
Location: Melbourne (Oz, not Florida!)
Hi Jens,

There's an easier equation to remember/use - although it's a slight approximation. This is: 160,000 / R * C (where C is in microFarads).

But, yes, this gives the -3dB roll-off of the R-C pair but you need to remember that the effects of the roll-off (in terms of phase) will extend up to 10x the -3dB frequency ... so in Oswaldo's example, this would be 159Hz.

Which is much too high.

The output cap in the GK-1/GK-2 is 1uF, so when combined with the 43K input impedance of my Lifeforce/Maya amps, produces approximately 4Hz - much better!

So, in your case - looking into the 20K input impedance of the Ground Sound filter - I would use 2.2uF as a minimum.


Regards,

Andy

PS: Don't forget that if you are using the "Sub out" facility to feed your bass drivers or subs, you also need to put an output coupling here (whose value depends on the Zin of the amp driving them).

Last edited by andyr; 30th January 2013 at 07:57 PM.
  Reply With Quote
Old 30th January 2013, 08:46 PM   #10
Jens A. is offline Jens A.  Denmark
diyAudio Member
 
Join Date: Dec 2009
Location: Copenhagen
Quote:
Originally Posted by andyr View Post
Hi Jens,

There's an easier equation to remember/use - although it's a slight approximation. This is: 160,000 / R * C (where C is in microFarads).

But, yes, this gives the -3dB roll-off of the R-C pair but you need to remember that the effects of the roll-off (in terms of phase) will extend up to 10x the -3dB frequency ... so in Oswaldo's example, this would be 159Hz.

Which is much too high.

The output cap in the GK-1/GK-2 is 1uF, so when combined with the 43K input impedance of my Lifeforce/Maya amps, produces approximately 4Hz - much better!

So, in your case - looking into the 20K input impedance of the Ground Sound filter - I would use 2.2uF as a minimum.


Regards,

Andy

PS: Don't forget that if you are using the "Sub out" facility to feed your bass drivers or subs, you also need to put an output coupling here (whose value depends on the Zin of the amp driving them).
Hi Andy,

This whole thread is in fact about the "Sub Out" (= SS output)

The capacitors I am talking about are on the SS output, as recommended by Hugh, but they may need to be a somewhat higher value anyway.

Let's see what Hugh says!

Cheers,

Jens
__________________
"Life is too short for over-expensive hi-fi pretending to be high-end"
  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
Erse crossover cutoff frequency? rms1 Multi-Way 4 7th January 2013 04:42 AM
Does Potentiometer affect cutoff frequency clm811 Solid State 6 21st October 2011 11:27 AM
Frequency Cutoff habsrock93 Full Range 2 21st August 2007 02:32 PM
Crossover cutoff frequency ? Fradbut Multi-Way 3 22nd January 2007 10:31 AM
Reasonable low frequency cutoff markkanof Multi-Way 5 12th June 2002 11:14 PM


New To Site? Need Help?

All times are GMT. The time now is 01:08 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