Pass Diy High Low Pass Please

[macka]

I recall this popping up somewhere as yet untried.

Ian

[Fred Dieckmann]

"To someone who's just starting out, the question of Q could be an entire thread on its own."

You are trying to reinvent the wheel......

The topology for the Sallen Key filter is extremely well documented for anybody that wants to read it. If people will go read the links in this thread they will find this out. Mr. Pass's monumental achievement is to make all this modular and adjustable for the non techo-nerd user. Hehas written a novel in how to use the crossover in the excellent manual, a manual so explicit that you could damn near reverse engineer the design. The slopes for the different Qs would allow someone to figure out the Qs needed in a hour of Spice simulation. This is not a molehill but it surely ain't no mountain.

The links again for something to read before Grey Day:

http://www.borbelyaudio.com/xover.pdf

http://www.passlabs.com/pdf/XVR1MAN1.PDF


http://www.t-linespeakers.org/tech/...Sallen-Key.html

I believe the Q calculation are fast and loose in this reference and you may want to look at the following for exact calculations. Don't be put off by the derivations of the equations. The actual caculation for the values of Fc and Q are very simple.

http://www.web-ee.com/primers/files/Sallen_Key.pdf

For a Spice text file (and most free student Spice programs should handle a GIU version of a circut this simple):

http://www.ecircuitcenter.com/Circu...1/opsalkey1.htm

A good collection of filter design links:

http://www.circuitsage.com/filter.html

Filter pro from TI( One that I like to use that is pretty simple and has good documentation):

http://focus.ti.com/analog/docs/sam...vigationId=9742


Since you find it such a mountain to climb, why not call it the Everest? After all the rest of use are wondering if we will ever see it......

See you at the top,
Fred

[macka]

I don't think that's the context Grey was refering to.

It seems Fred is only interested in the end result, not the how and why. I've never seen a project in waiting cause so much anxiety, when the real value is in the journey.

No diy article would be complete without a coverage of the key elements of filters and the rational behind the choices involved in crossover networks.

Here is nice bunch of articles on the Rane Audio reference pages that are very understandable without needing a PHD in astro physics.

http://www.rane.com/note134.html

http://www.rane.com/note107.html

http://www.rane.com/note119.html

But this is my favourite references:

http://www.linkwitzlab.com/frontiers.htm#F

http://www.linkwitzlab.com/filters.htm

And some light reading for Fred:

http://www.linkwitzlab.com/publications.htm

Ian

[jam]

So you guys want a cross-over................

Single-ended, classA and all that good stuff. Here is something I pulled up from...........

[jam]

........and now for part two.

Have fun and enjoy.

[jam]

You should be able to figure out the rest.

Regards,
Jam

[macka]

Looks like the practical application of Borbelys 2 part article of Jfet buffers.

http://www.linkwitzlab.com/filters.htm

http://www.borbelyaudio.com/ae699bor.pdf





Ian

[jam]

J-fet's could be replaced with mosfets if you are so inclined and there are ways to improve the current sources...........

[Fred Dieckmann]

"It seems Fred is only interested in the end result, not the how and why. I've never seen a project in waiting cause so much anxiety, when the real value is in the journey. "

You are kidding right? I provided some links for people that might like to see how to calculate the cut off frequency and determine the Q of a circuit. Read the Borbely article and the Pass labs manual and you will be pretty well armed to go build a filter with some good op amps (or even discreet op amps) or even with followers like the design JAM dug up by Mr. Mega ( I will have to ask him were he found that....) that could be done with tubes, BJTs, op amps, or mosfets.

First we were waiting on permission from Mr. Pass, then a name, and now documentation on how a filter works and how to adjust it. I think the references explain that pretty well.

He said he had a design and PCB... where's the beef? I agree that it is the
journey and not the destination! I was hoping that we might get to go somewhere besides being led down the garden path. If he has been up the mountain, bring us something. It doesn't have to be written in stone and he can revise it as he goes.

THOU SHALT NOT COVET THY NEIGHBOR'S CROSSOVER.

THOU SHALT NOT BEAR FALSE WITNESS ABOUT THY CROSSOVER.

[Fred Dieckmann]

Originally posted by jam
J-fet's could be replaced with mosfets if you are so inclined and there are ways to improve the current sources...........

Damn I was thinking the current sources could be replaced by mosfets........ I built one with all Zetex mosfets but I can't find a picture. Heres one of the Welborn Labs crossover.