Hey NYCDave, are these cool?

[sismofyt]

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3732745907

 

[NewYorkDave]

Yeah, those are cool, if you need a constant-impedance lowpass filter. I was looking at that auction, myself. I wouldn't spend too much on them, since there's really nothing magic about them and you could build your own if you needed to.

 

[sismofyt]

He'll only ship inside the US. I thought about bidding as well..

Passive hi/lo filtering is quite high up upon my DIY list! Maybe you'll give me a hand?

 

[NewYorkDave]

I have the catalog page with the specs for the Langevin HP and LP filters, and I believe an internal schematic is included. The component values are not shown on the schematic, but could be figured out with simple math.

Do you have Tremaine's Audio Cyclopedia? There's complete design data therein for this sort of filter.

 

[sismofyt]

No I don't have that one, shame on me

The math ain't difficult, I allready made some. But I'm sure you know some ninja tricks :green:

 

[sismofyt]

Tremaine's book is 127$ at amazon :shock: :sad: :? What edition should I look for?

Any good place to pick it up?

What about Audio Anthology Vol. 1-6?

 

[NewYorkDave]

I have both the first and second editions. (These are the only ones Tremaine wrote; the later editions, subtitled "Handbook for Sound Engineers" borrowed heavily from Tremaine, but are not the same book). Both editions are great, but the second edition is the one that almost everyone is referring to when they say "I read it in Tremaine..." It's also a lot easier to find. The first edition has more tube stuff, but the second is a more comprehensive all-around reference. It even includes some hip early transistor stuff from Langevin, Electrodyne, et. al.

You will pay out the ass if you buy a copy of the Audio Cyclopedia from a dealer; but if you're patient and keep looking, you can find one at a reasonable price. I bought my second edition on evilBay for about $40, believe it or not. Here's a second edition that's currently on evilBay:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=39996&item=5707239125&rd=1&ssPageName=WDVW
(The seller is a bit full of it, though, when he says "this is a very, very rare book." The second edition was in print till the late '70s, so there are many copies floating around).

Tremaine published a couple of other books, called Passive Audio Network Design and Attenuators, Equalizers and Filters, but almost all of the material was reproduced in the second edition of the Cyclopedia.

 

[NewYorkDave]

Oh... I got off on a tangent and forgot why I came back to this thread in the first place. I've scanned the catalog page for the Langevin HP and LP filters:
1.75Meg PDF

As you can see, it's a simple L-C "T" filter (one for each switch position, presumably).

Looking at the filters on evilBay, however, they appear to be fixed frequency with selectable attenuation, which tells me it's probably a bridged-T filter.

The design data for both types are in the "Equalizers" and "Wave Filters" chapters of Tremaine, in case someone else is inclined to scan and post it. As for me, I'm out of time for today and have to be going now...