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ben62670 12th December 2007 11:23 PM

Help with active XO
 
I am building an active XO, and it calls for 2 0.1uf caps, and 2 640k resistors. Are the resistors way to far out to operate properly?
The OpAmp is a TL082
My PS is 28VDC

Thanks Ben

AndrewT 13th December 2007 12:10 PM

Hi,
your resistor values sound a lot too high.
They are not E24 value.

It's more usual for audio frequency setting resistors to be in the range 7k5 to 15k.

ben62670 13th December 2007 02:09 PM

Thanks Andrew.
I got those numbers from an XO calculator, and they want me to use a 0.1uf cap, but I should probably substitute a 1uf cap.

Thanks Again
Ben

Edit
Would 2.2uf, and 29k work well?
These are the values I was given by winISD for 2500HZ.


AndrewT 13th December 2007 02:34 PM

Quote:

Originally posted by ben62670
Would 2.2uf, and 29k work well?
These are the values I was given by winISD for 2500HZ.

If you've read it right and given it the correct info then WINisd is telling lies.

I don't know which topology you are using, but for 10k expect somewhere around 2nF to 10nF to give 2.5kHz.

ben62670 13th December 2007 02:41 PM

I have read it correctly. It states 2.2uF, and .029 K ohms. Move the decimal point 3 places to the right, and I get 29K ohms correct?

Thanks Again

ben62670 13th December 2007 03:46 PM

OK I found a better program. Its called ESP
Elliot Sound Productions
a 12db Linkwitz-Riley would be?
10k, and 6nf
12k, and 5nf
or 15k, and 4.7 NF

Thanks for reconfirming that the information was way off WinISD gave me.

Ben

Sashi 13th December 2007 04:37 PM

Quote:

I have read it correctly. It states 2.2uF, and .029 K ohms. Move the decimal point 3 places to the right, and I get 29K ohms correct?
Nope...it's 29 ohms.

ben62670 16th December 2007 11:28 PM

Are ceramic disk bad for XO's? They are the only ones I can find locally.

AndrewT 17th December 2007 07:06 AM

Quote:

Originally posted by ben62670
Are ceramic disk bad for XO's?
use polystyrene or polypropylene for the smaller values. Try to find small polyester (MKT or MKS) for the larger values.
Don't use any ceramic, not even C0G/NP0.

gainphile 31st December 2007 08:57 PM

I just 'upgraded' my system with Rod Elliot's design, the 'P09' which is 24db/octave rolloff. It's using TL072 op-amps which sounded great - no noticable signal degradation.

for my 3.5kHz cutoff the calculator returned 39nF and 820ohms.

http://gainphile.blogspot.com/2007/1...gainclone.html

http://bp2.blogger.com/_COvnfAy4R9w/...0/IMG_3492.jpg


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