Harrison Ford Filter Feeler

Emailed.

Cheers

I got mine up and running over the weekend!  They sound great and it was a super easy build.  Now I just need to get some cool knobs for it.  Anyone find any cool knobs?

I put my first board together and realized a heavy basscut with the HPF-pot in CCW position. Are we sure that the HP filtercaps are right? Anybody else expierienced that?
Changing C1 and C2 to 1uF helps a lot, but there´s still an unnatural LF-boost going on with the filter engaged and HPF pot CCW.

AARRGGGHHH, stupid me, wrong pots installed. I´d better shut up now and learn to read

Sorry if this is in the wrong place. Is there a build thread?

Anyhow
I just got boards from Dan. Thanks that was quick!
but
I'm out of tl074s 
and
Prior to getting these boards I lashed this filter together with ne5534's and they sound great although the range is a little bit awkward I'm using the 50k C taper pots, perhaps I wired those backwards and pinched the range or I need to change a few resistor values.  I'll do some comparisons now that I have these new boards.
So
has anyone tried these with different opamps like LME49740 for example.
edit:
rats 49740 is not a jfet input... getting pretty hard to find a quad opamp in a dip.
maybe I'll have to order soic to dip adapters for the mc33079's I have
end edit:
I'm thinking I might order these instead of the 074's (or maybe both and try it out)

Thanks
Sleeper

The not so low bias current of NE5534 will make your pots scratchy after some time. If you don´t want to go the TL074 route then try TLE2074, they should sound cleaner and have higher output current. Make sure that they don´t oscillate!

Thanks Jensenmann- good point, I've already heard a bit of voltage on the pots now and again.
I'd been looking at this- sslG hi pass

Clever how they nested the pots.
Not clever how they need to use triple pots

I'd like to put some of these into the pre's I use for drums and they have a +-20volt supply thus my aversion to the 074s.  I'll be skipping the INA and the DRV parts.
Hmmmm
That tle might be the ticket. 
It wouldn't kill me to turn the voltage down to 19volts
Thanks Again
Sleeper

I had a better idea I thought I would share...
I made a small adapter pcb that converts 2 dip8 opamps into 1 dip 14.
Now I'm going to use the opa2604's I have on hand.  I've got a fet input and I don't need to change any voltages
It has to be raised a bit to clear the .1uf caps or I might mount the caps on the bottom of the board. Either way, I'm set.

After some more fiddling with the right pots installed I didn´t like the pot law. There´s too much going on in a too small angle. I swapped the pots to the solderside of the PCB and voila, much better. Unfortunately Dan´s panels don´t work that way. Aaaarrrrgggghhhh again.
What I still don´t like is the upper corner frequency of the LPF when the filter is supposed to be out of the way. It sounds a bit harsh to my ears. So I changed C5 to 22nF and C4 to 6,8nF. Same thing with the HPF, changed C1 and C2 to 220nF (C1 does not have any effect on that, though). Now there´s more control at the lowest end, too. Another improvement was replacing the TL074 with a LT1058 which worked stable in the stock circuit, no matter what signal I threw on it. And finally I changed the LP filtercaps from MKS to FKP and polystyrene, just for esoteric reasons  ;D

Is x1 to be shorted/jumpered in pairs if not in use?
(x1 is the unbalance in/out)

It's really a tight fit in a 1U case, right? Anybody got smaller pots than 16mm?
It seems like it's not 1 mm left..

My BOM with sourcing here:
https://docs.google.com/spreadsheet/ccc?key=0AmEgFUTJT9ZtdENwNHQ4QmlEU2YybTJ6dmhqNi1TYXc
AML, Farnel, Elfa

A little tight but not too bad

Thanks for the BOM!

Marcocet said:

A little tight but not too bad
Thanks for the BOM!

Click to expand...

You're welcome

Had to file down the edges of my case (Par-metal) to make it fit.
(Not to mention a bad made nut in one of the handels -needed to make a screw shorter, without a proper clamp ..that's not the easiest thing I've done    )

Anyone know the min/max lowcut and min/max highcut when using 47k pots?
(or should I be able to calculate it myself?)

Marcocet said:

The 4mm knobs seem to be damn near impossible to source in the US.

Click to expand...

I'm having a hard time sourcing 4mm shaft pots as well.
Tried these: http://no.farnell.com/jsp/search/productdetail.jsp?SKU=1282397
But they don't fit (and don't look like that picture).

Maybe that axis convertor is the way to go? .. expensive to have all these shipments.

That's why I went with the AML for the pots and switches and mouser for everything else.  It all works and everything fits nicely.  The only thing I'm waiting on are knobs. They are on a long back order from selco.  In the meantime plenty of other things to do.

 

Canford UK have these 4mm Sifam knobs:

http://www.canford.co.uk/Products/21549/58-901_SIFAM-S111-004-COLLET-KNOB-115mm-diameter-4mm-shaft-black

You can get different coloured caps for these too although Canford only have black. And Canford postage ain't cheap.

grubbyliver said:

Canford UK have these 4mm Sifam knobs:

http://www.canford.co.uk/Products/21549/58-901_SIFAM-S111-004-COLLET-KNOB-115mm-diameter-4mm-shaft-black

You can get different coloured caps for these too although Canford only have black. And Canford postage ain't cheap.

Click to expand...

Thanks! Sure looking nice
A couple of others:
http://www.canford.co.uk/Products/58-801_REAN-C104-COLLET-KNOB-103mm-diameter-4mm-shaft-black
http://www.canford.co.uk/Products/58-911_SIFAM-S151-004-COLLET-KNOB-155mm-diameter-4mm-shaft-black

I've now finished 2 channels. Working fine

I've tested the frequency-response, as follows:

- MDA testtone-generator, pink noise
- Reainsert out ADA8000, ch 1 + 2
- Harrison ford filter, ch1 for adjusting lowcut, ch2 for highcut
- Reainsert in Rme Hdsp 9632, ch 1 + 2
- Waves Paz, frequency analyser

I've used the 47k dual rev log pots from AML.

Hard bypassed:


Bypassed:


Engaged, all min settings:


LowCut 9 O'clock, HighCut 15 O'clock


LowCut 12 O'clock, HighCut 12 O'clock


Both full:


Mda testtone:


Comments:
I don't know why ch 2 is returning 2,7db lower than ch1. Could be some flaw in my ADA8000.
Looks like the locut goes from 65-4k Hz, and the highcut goes from 14k-125Hz.
I'd prefer it to be something like 20-600Hz and 22k-1k hz.