Variable High-Pass Filter.... (Pro Question)

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Blue Bear Sound

Blue Bear Sound

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Anyone know of a transparent, high-slope, variable, 2-channel high-pass filter.... especially for infra/subsonic filtering?

Bruce
 
blue bear i APOLOGIZE (did i spell that right?) for making this post. i dont mean to be rude nor do i wish to disrupt your post in anyway.......but i dont know what the hell your talking about.

can you please explain to me what it is that your looking for? i know its a stereo hi pass filter but you lost me on the other stuff....i hope i didnt ruin your thread by this post.



czar
 
That's why I put "Pro Question" in the subject!!! ;)

Sorry guys, but the description is clear, to some... in basic terms, it's a high-pass that filters infrasonic frequencies below 20-30hz, but I want the slope frequency to be variable and the slope to be at least 12db/octave - 18db/octave would be better....

I was told a company called Filter Queen apparently used to make such an outboard unit, but it's been discontinued.......

SOMEONE must know of such a thing!

Bruce
 
Bruce,

The only one that comes to mind is the API215L. The hipass is sweepable in 12dB/Octave in a range of 20 to 600Hz. The lopass is 6dB/octave and the range is 500 to 20kHz.

I hope this helps:

http://store.yahoo.com/mercenary-audio/21sweepfil.html


I don't think this is exactly what you are looking for, but you are working at the extreme ranges here. If this is a one-shot deal, I hope your client has a good budget.
 
Yikes! 2 channels for $1000... and it's a console module to boot - not likely that I can use it standalone..........

I didn't think I was asking too much!! ;) :(

Thanks for the tip though, Sonic....
 
Bruce, if the API cuts the mustard for you, buy the 4 space rack, load two if them in it, and then 2 preamps for a stereo pair and you have the best shit in your whole setup. :) Never heard the EQ's, but everyone else loves them, but I have heard the Pre's and they smack bootie like ya like. Big time.
Good idea, good idea.....
Check Atlas Pro Audio for some decent API prices, but email them, dont look at posted prices. See if you can find Nathans address.
 
I worked with API eq's in the SAJE desk last month... Sweeeeeeeeet!! :cool:

But then again, my reference is the evil digital VS1880-eqs and the A&H GL3300...
 
It was a joke. I forgot the smileys! Bruce, perhaps we need to talk about proper mic usage hmmmmmm? :D :D Akai has something I do believe but again it might not meet your needs. I think musicians friend carries it.
 
Bruce,

That API look of dubious design to me. A “passive” filter with transformer coupling and discreet circuitry running on a single 16V supply. Looks like they’re going for some kind of “vintage” sound. I wouldn’t do it that way if I were designing a sharp transparent filter. Plus it only goes down to 20Hz. That’s not really infrasonic.

The Rane AC22 is easily modifiable to your needs. http://www.rane.com/ac22.html I see them online for about $330 US. It’s a 1U rack mount cassis and shouldn’t be too hard to use as a standalone. The mod would just take less than a half hour of simple replacement soldering and about $40 in extra parts. Rane makes decent stuff and it should work pretty nicely for you. I can help you out with the appropriate components (I have test equipment to match capacitors). I’d even be willing to do the mod if you don’t feel up to the task (and of course, if you feel comfortable sending me your equipment). But it’s really simple.

HOWEVER this a fairly specialized application and it just cries out total DIY. Man I could post a circuit for you that would be absolutely amazing. My favorite AD797 op-amp is perfect for this application. It’s so quite and so linear with less than –120dB THD and 60mA output current it’s about the closest thing you can get to having just a straight wire in your signal path. Say a 10-80Hz 24dB/oct state variable filter with a killer +-18V toroidal transformer based supply , hand matched film and foil caps, 0.5% resistors, and 797’s throughout. Ahhhh, it could be a thing of beauty........

Sorry, Bruce. I got a little carried away there :). Seriously, the modified Rane is a good way to go. Of course my custom design would be way better ;).

barefoot
 
Hey you without shoes! (hmmm.... I'm sounding like Green Hornet!)

Thanks for the info... just out of curiousity, what would you charge for your little box?

What I need -
- 2 linked channels (ie, 2-channel but controlled by a single set of controls.)
- variable frequency on the hi-pass filter
- level control on the amount of cut
- steep slope 12db/octave or better, 18...
- +4 dbu gain structure, unbalanced is ok...

I think that covers it!

Bruce
 
API gear - very VERY dubious stuff watch out!! ;) :rolleyes: <-again)

Tubedude, that is an often used way, and gives you some very high end gear for a reasonable price. The API pre's and EQ's are outstanding.

However, the best possible (sounding) piece of gear that would give you what you want would likely be the PSEQ-1 , which has an HPF with a corner frequency continuously variable between 10 and 220 Hz. It also tests (10K Ohms parallel, .001 mfd) a high boost / cut range balanced noise floor of -98dBu
 
I know... sad eh? Worth it though.
The EQ on the PSEQ is the same as the one on the CS-1 strip, and the CS-1 is simply the best, cleanest, most transparent preamp I have ever used, bar none. I was very excited when the AMEK 9098 PurePath arrived, which was in my opinion the only strip with pre's that outdid the Grace's. Then I got a prototype of the CS-1, which simply blew the 9098 away.
One of the main things about this EQ / pre / compressor is the incredible transparency throughout, especially in the regions where other such gear fails, extreme low and high.
The disadvantage - its so clear, clean and "noiseless" that you hear everything in your chain, immediately.

In an ideal world - without money involved, you'd have a studio with at least 2 CS-1's in the rack :( (I'm working on the second one, one will have to do for now).
 
Not being nit-picky here, but from what I understand and have gathered over the last 6 months, the PurePath and the 9098 have different pre's in them. Supposedly the PurePath sounds a little better. I've been thinking about the dual 9098 for quite a long time, though I havent gotten to hear it. Its accessable to me on a "plan" because, since its Harman stuff, my local shop can get it. Gonna wait on the RNMP and see what happens. :)

Also, sjoko, what did you mean "API gear - very VERY dubious stuff watch out!! "
What is so questionable about this setup? You mean for the need that Bear was calling for, I guess. :) Love the pre's.
 
LOL I was being very sarcastic in response to one of barefoot's usual "I know a bit of theory about stuff but I don't have a clue whats the real world is like" remarks:

Quote:
Bruce,

That API look of dubious design to me. A “passive” filter with transformer coupling and discreet circuitry running on a single 16V supply. Looks like they’re going for some kind of “vintage” sound.

I thought that was real funny - API - dubious design - going for some kind of vintage. :p

The 9098 is excellent, as is the PurePath. I have had and used both, I really couldn't say that the purepath was a better pre. Slightly different, by a small margin, thats all. In any case, they are serious assets to any rig.
The only reason I don't have them anymore is because I had the chance to get to use the CS-1, which in my opinion is the "ultimate" there is at present.
 
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