Harrison Ford Filter Feeler

[G-Sun]

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

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

The only thing different is C3.

and here is the corresponding for the low-pass:

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

The difference is R1 and R2 who is omitted.

 

[emrr]

http://groupdiy.com/index.php?topic=44444.msg567566#msg567566

Site may be of use:

http://sim.okawa-denshi.jp/en/Fkeisan.htm

 

[bruce0]

Quick photo of work in progress.  Everything seems to fit nicely.  Now on to the psu, wiring, etc...

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]

I just wired up each channel nicely to the DB25.  Pretty easy to do.

 

[mdmitch2]

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.

 

[G-Sun]

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]

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

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/

 

[G-Sun]

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) ?

 

[G-Sun]

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.

 

[Harpo]

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

 

[G-Sun]

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

 

[dandeurloo]

Pots arrived yesterday.  ;D  Now I am waiting on the Knobs.  They will probably be another few weeks. 

 

[Marcocet]

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).

 

[dogma]

yes i laughed when i saw this. Street is $2350!

 

[12afael]

woah!

 

[kdramsey]

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.

 

[mutetourettes]

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....

 

[dandeurloo]

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. 

 

[dogma]

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?

 

[dogma]

Hey dan is there any update on the kit availability and therefore the cost would be known too?