Help with active XO

[ben62670]

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]

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]

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]

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]

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]

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]

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]

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

 

[AndrewT]

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]

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/2007/12/bi-amp-active-crossover-using-gainclone.html