Harrison Ford Filter Feeler

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Now, this must be close to correct for the highpassfilter:
fil92.gif

http://www.electronics-tutorials.ws/filter/filter_6.html

The only thing different is C3.

and here is the corresponding for the low-pass:
fil90.gif

http://www.electronics-tutorials.ws/filter/filter_5.html

The difference is R1 and R2 who is omitted.
 
http://groupdiy.com/index.php?topic=44444.msg567566#msg567566

Site may be of use:

http://sim.okawa-denshi.jp/en/Fkeisan.htm
 
minor_glitch said:
Quick photo of work in progress.  Everything seems to fit nicely.  Now on to the psu, wiring, etc...

8264122744_b59b3144cf.jpg

Looks nice.  I noted nice TASCAM punches on back panel.

Ian (ruffrecords) has some DB25 summing PCB's, and if you leave the resistors off they have a jack so they can just be DB25 interface PCB's which might work well for you.
 
dandeurloo said:
Looks great!

I wanted to let you guys know I am going to start stocking pots and knobs for these.  That will make it much easier.  Once I get those in I may do full kits. 

The Knobs and Pots are ordered!

Very interested in a full kit for this.
 
emrr said:
http://groupdiy.com/index.php?topic=44444.msg567566#msg567566

Site may be of use:

http://sim.okawa-denshi.jp/en/Fkeisan.htm
Thank you very much Doug!
 
G-Sun said:
fil92.gif

http://www.electronics-tutorials.ws/filter/filter_6.html

fil90.gif

http://www.electronics-tutorials.ws/filter/filter_5.html

Highpass:
(from Harrison Ford Schemo, attached)

fc_min = 2pi / sqrt((pot+R6)*(pot+R3)*C1*C2) = 2pi / sqrt((47000+390)*(47000+390)*0.1^2*10^-6) = 1,32
fc_max = 2pi / sqrt((0+390)*(0+390)*0,1^2*10^-6) = 161

Lowpass

fc_min = 2pi / sqrt((R4 +pot)*(pot+R5)*C5*C4) = 2pi / sqrt((47000+390)*(47000+390)*0.047*10^-6*0.012*10^-6) = 5582
fc_max = 2pi / sqrt((0+390)*(0+390)*0.047*10^-6*0.012*10^-6) = 678384

This is still wrong..

http://web2.0calc.com/
 

Attachments

  • harrisonfordfilter.jpg
    harrisonfordfilter.jpg
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Now, trying the link from Doug:
http://sim.okawa-denshi.jp/en/OPseikiHikeisan.htm
http://sim.okawa-denshi.jp/en/OPseikiLowkeisan.htm

I get

Highpass:
fc_min = 33,6Hz
fc_max = 4080Hz

Lowpass:
fc_min = 141Hz
fc_max = 17183Hz

:) :) :)

Now, these figures are "better" than my visual readings. Hm.. what to trust most?
I could live with locut_min 33hz and hicut max 17kHz.

Yet, modding seems better.
Could I just take e.g. C1 and multiply value with 4
and e.g. C5 dividing by 4?
without screwing some other elements of the design (that I don't understand) ?
 
So, setting

C1 to 0,47uF i get
highpass_min = 15Hz
highpass_max = 1,9k

C5 to 0,012uF
lowpass_min = 280
lowpass_max = 34k
Edit:  WIMA - MKS2 0.015µF
min: 250
max: 30k

Looking good to me.
 
G-Sun said:
Highpass:
(from Harrison Ford Schemo, attached)

fc_min = 2pi / sqrt((pot+R6)*(pot+R3)*C1*C2) = 2pi / sqrt((47000+390)*(47000+390)*0.1^2*10^-6) = 1,32
..........
is not what the formula said, for example
fc_min = 1 / ( 2*PI() * SQRT( (47000+390)*(47000+390)*100e-9*100e-9) ) = 33.584
 
Harpo said:
G-Sun said:
Highpass:
(from Harrison Ford Schemo, attached)

fc_min = 2pi / sqrt((pot+R6)*(pot+R3)*C1*C2) = 2pi / sqrt((47000+390)*(47000+390)*0.1^2*10^-6) = 1,32
..........
is not what the formula said, for example
fc_min = 1 / ( 2*PI() * SQRT( (47000+390)*(47000+390)*100e-9*100e-9) ) = 33.584
Ah.. thanks! Now I can have peace of mind :)
 
Looks like Harrison liked our idea :) Another big thanks to everybody involved in this, particularly 12afael, Jens and Dan! I haven't been around in a while and it looks like people have figured out all my screwups. Maybe it's time to go back and mod some of my original ones (which still work great btw).

832cimg.png
 
Just finished a pair of prototype units for 500 series.  I added a few extras to suit my needs including the ability to turn each band off separately.  The other feature is a -6dB per octave slope for a more gentle cut. It is interesting that Harrison added a meter to their 832c filter... I was thinking about adding a signal present led and possibly a makeup gain knob.

image_zps8088f40c.jpg


image_zps594cb1e6.jpg


 
I find myself intrigued by this circuit - I reckon i'll be building it unbalanced too, and I'm going to try and use that fourth Opamp stage (which is, I think, unused, right?) for a little variable all-pass filter... might combine two channels' worth for a two-stage all-pass that can work on one of the channels rather like the ibp... is that nuts? all my filters in one basket....
 
UPDATE:

Kits are almost in stock.  I am just waiting on a few more parts to show up.  They will be for 8 channels to go along with the chassis.  Still working out pricing.  I need those last parts to get here to figure that out. 

 
As there is so much room with the studer 169 I've been thinking of putting them both in a 500'slot and see if they fit. What do you guys think?
 
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