Active filter board GB

[BobEllis]

You tease! (ceramic caps? )

[JensRasmussen]

I know - sorry......

It was what I could do i 10 minutes....

\Jens

[BobEllis]

I have heard from everyone who expressed interest on the WIKI, EXCEPT:

Harryeng
Herm
Cobra2
vgeorge
t3447ml
gmikol
saml
still4given

If you are still interested, please let me know.

Keep those payments coming - 142 boards paid so far.

[illusionxx]

Bob,

i`ve just paid via paypal but same here as in capslock`s case. The money has to be transferred to my paypal account first before it will be credited to your account. The bank transfer has been authorized and it usually takes two business days.

illusionxx

[BobEllis]

No problem. Thanks for keeping me up to date.

More than half paid already - 176 of 330.

[Ed LaFontaine]

For those who need a better understanding of

"Sallen-Key"

filters, a search is helpful. That is how I found the following suggestions in this link:

http://www.elecdesign.com/Articles/I...leID=7486&pg=1


Until now, the choosing of resistor and capacitor values has been left without mention. Theoretically, any values of R and C that satisfy the equations may be used. But practical considerations call for certain guidelines to be followed. Given a specific corner frequency, the values of C and R are inversely proportional to one another. By making C larger, R becomes smaller and vice versa.

In the case of the low-pass Sallen-Key filter, the ratio between the output impedance of the amplifier and the value of filter component R sets the transfer functions seen at frequencies well above cutoff. The larger the resistor's value, the lower the transmission of signals at high frequency. Making R too large may result in C becoming so small that the parasitic capacitors, including the input capacitance of the amplifier, cause errors. The best choice of component values depends on the particulars of your circuit and the tradeoffs you're willing to make.

Here are some general recommendations for capacitors and resistors: You should avoid capacitors with values less than 100 pF. If at all possible, use an NPO type. X7R is okay in a pinch, but avoid Z5U and other low-quality dielectrics. In critical applications, even higher-quality dielectrics, like polyester, polycarbonate, Mylar, etc., may be required. As for resistors, values in the range of a few hundred to a few thousand ohms are the best bet. You also should choose metal-film resistors that possess low temperature coefficients. Finally, use 1%-tolerance capacitors and resistors, preferably those of the surface-mount variety.

[gmikol]

Jens--

The board rendering looks cool!! But I have a question...

What are P1 and P2 (the black rectangles) on the board? I don't see them on the schematic.

Can you post a final schematic?

Thanks again for your work in putting this together.

--Greg

[BobEllis]

Jens should be asleep, so I will answer. Those are the level adjust pots for each output. You can get away with just one for your higher sensitivity driver, but this way gives more flexibility for 3+ways.

Jens posted the schematic here: http://www.diyaudio.com/forums/showt...411#post854411

[gengis]

Money sent.

Thanks to both Jens and Bob.

[BobEllis]

The schematic linked to in my last post is NOT the final version , but it is close to give you an idea of what it looks like. Component designations and the connection to make a bandpass have changed.

We'll get the final version posted shortly.