Harrison Ford Filter Feeler

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Marcocet

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Joined
Sep 27, 2004
Messages
241
Location
Brooklyn, NY
It looks like 12afael, Jens and I finally have a production version of this PCB ready and we're about to place an order for ourselves. Essentially it's a clone of the classic Harrison sweepable filters. The board runs on +/- 15v, has extremely few parts, and is tiny enough to fit a bunch in a rack case. It could also easily be built into a 500 series module. The hardest parts to source are the 47k Rev Log pots, which are available at Audio Maintenance (thanks Colin!).

I'm not trying to run a shop or anything, but if anybody would like a few boards I can figure out a price and add them in to our order. Please feel free to PM me or email me at strangeweathersound @t gmail.



EDIT:

Boards are sold out. Here's the BOM. I've attached an excel copy too for those who are that way inclined.

5 10k         R1, 2, 6, 7, 9
4 390         R3, 4, 5, 8

9 0.1u         C1, 2, 6, 7, 11, 12, 13, 15, 16
1 100p         C3
1 0.012u C4
1 0.047u C5
2 100u C8, 9 electrolytic
1 10u         C10 electrolytic

2 50k Dual Lin LOPASS, HIPASS Audiomaintenance.com
1 ESWITCH 2 pole switch Audiomaintenance.com

1 INA134P IC2
1 TL074P IC1
1 DRV134PA U$1

http://strangeweatherbrooklyn.com/sales/HarrisonFilterBOM.xls


schematic here
 

tmuikku

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Dec 24, 2008
Messages
481
Location
Finland
Hi!

which pot it uses, the conductive plastic or this cheaper carbon pot? http://www.audiomaintenance.com/acatalog/om-01-028_extended_info.html

have you prototyped it already? 8) the pushbutton seems to come very close of those potis, is there room for switch cap and knobs? Just kicking the tires since I'm interested!

It seems eight will fit into 1u case?
 

coriolis

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Joined
Jan 24, 2009
Messages
31
Location
Aarhus, Denmark
I'm not familiar with these - are they hi/lo shelf filters with selectable freqs? Or? Got a schem or a pic of an original unit?
I'm certainly looking for something simple like this, so might be interested...

C
 

mitsos

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Joined
May 4, 2007
Messages
2,886
tmuikku,

just a guess but switch is probably on one side and pots on the other side of the PCB.  BTW, if it fits Omegs then they are ALL conductive plastic. According to their website, that's all they make.  I've even brought this up to Colin once, but didn't really understand the reason he gave me for selling them as carbon. Anyway, bottom line is that all Omegs are cond plastic.

There was another thread with info about these in the drawing board:

http://www.groupdiy.com/index.php?topic=44444.0
 

benlindell

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Feb 28, 2009
Messages
631
Location
NYC
If the price is reasonable I'd love to grab up 8 of them, I can never seem to find enough highpass filters in the studio.

are the 12db/oct filters?
 

Marcocet

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Joined
Sep 27, 2004
Messages
241
Location
Brooklyn, NY
I'm expecting them to land in the $4-5 each territory, but don't hold me to it quite yet. It all depends on how many people are interested.

Yep, they're 12db/octave filters.

Mitsos got it. Switch mounts on the bottom of the board.

I'll get together a BOM but if I remember they weren't more than $25 each in high quality parts, excluding the pots.
 

benlindell

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Feb 28, 2009
Messages
631
Location
NYC
What does the switch control, sorry if it's obvious, I just glanced at the PCB, is it a bypass for both filters or just the lowpass?
 

Marcocet

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Joined
Sep 27, 2004
Messages
241
Location
Brooklyn, NY
benlindell said:
What does the switch control, sorry if it's obvious, I just glanced at the PCB, is it a bypass for both filters or just the lowpass?

Both, but it's not true bypass. If you want that you can wire it up off board.

 

jackies

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Joined
Oct 19, 2006
Messages
735
Location
DC
So do we just post here, or have to email you with the desired number of boards?
It's 8 for me btw...
:D
 

Marcocet

Well-known member
Joined
Sep 27, 2004
Messages
241
Location
Brooklyn, NY
jackies said:
So do we just post here, or have to email you with the desired number of boards?
It's 8 for me btw...
:D

Either one's fine :) You are now on the list. I'll close it in a week or so and contact everybody for payment.
Thanks!
-marc alan

 
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