B&K 1607 notch filter activated

Status
Not open for further replies.
B&K 1607 notch filter activated & Victors oscillators

I decided to activate my B&K 1607 notch filter. Fortunately, I did not have to draw the whole schematics ( no service manual available ). A quick view inside showed the balance pot being in series with the 0.5xR arm ( see Pic_1 ). So, there was no problem to attach an opamp outside the B&K box ( see Pic_2, Pic_4). The choosen R2 R1 values give a h2 insertion loss of ca. 0.3dB, good enough for me. I had to replace the single turn Balance pot of the B&K, a 10 turn Bourns did it, much better control of notch depth.

The measurement chain:
Victors 1k oscillator driven by a 26mA current source, R32/R33 replaced by 10 Ohm resistors, a trick presented by 1audio. Vout: 2,67V rms -> E-MU 1616m(ASIO) -> Arta gives -10dB.

After notch filter insertion ARTA gives:

h2 = ca. -151 +10 -5( notch gain ) = -146dB
h3 = ca. -157 +10 -5( notch gain ) = -152dB

Well done, Victor
 

Attachments

  • PIC_1.jpg
    PIC_1.jpg
    195.8 KB · Views: 544
  • PIC_2.jpg
    PIC_2.jpg
    225 KB · Views: 537
  • PIC_3.jpg
    PIC_3.jpg
    264 KB · Views: 522
  • PIC_4.jpg
    PIC_4.jpg
    135.1 KB · Views: 525
Last edited:
Very nice modification. Its easier than I though it would be. What changes, if any, have you made to your E-Mu 1616?
Also, please show where 10 Ohm R's are located (schematic/picture?).

Thx-RNMrash
 
Last edited:
What is the value of the balance pot? It seems like this would be an easy retrofit inside and run the opamp from a pair of 9V batteries. The only remaining issue would be the common ground and dealing with those B&K connectors, neither of which is insurmountable.
 
Pot 500 Ohm; you just have to break the pot connection to ground and put a switch there ( passive/active mode ), no grounding problems, as I run the opamp from two 12V SLA batteries.

When I got the unit, I immediately drilled out those B&K connectors and put BNC's there, see pics.

Gary
 

Attachments

  • IMG_2404.jpg
    IMG_2404.jpg
    144.4 KB · Views: 483
  • IMG_2405.jpg
    IMG_2405.jpg
    144.4 KB · Views: 174
The 500 Ohm rheostat is large in diameter and feels like fine wound wire. I want to find something without greater inductance and doesnt add any distortion. What make, model, brand of pot did you use?

Thx-RNM
 
Now you got me fired up to do it..... I removed the original 500 Ohm and replaced it with a 10 turn from Beckman Inst/Spectral that i had in my parts bin and am using the turns counter for a knob which can lock the setting.

I also use a banana to BNC adapter that plugs right into the Euro sockets without any problem and is secure.

-RNM
 
Perfect, now a new teaser:

Switched the E-MU 1616m to 48kHz and tweaked the notch depth a little bit,
so Victors 1kHz gives now h2 ca. -150dB, h3 -153dB ( see the math #1 )

BR

Gary
 

Attachments

  • PIC_5.jpg
    PIC_5.jpg
    205.3 KB · Views: 267
I checked a 1K 10 turn pot and no measurable inductance or capacitance of significance below 100KHz. A good wirewound pot with a good contact material should have the lowest distortion of any pot.

I'll fit mine up with this as well.

The spurious stuff in the plot is from the 1616 power supply?
 
Well, think so, 50Hz power line, but the switch mode PS of the E-MU has a nasty 60 kHz ( switching f ) spike too, tomorrow I'll fire it up using 4x12V SLA's.




>The spurious stuff in the plot is from the 1616 power supply?
 
Well, hopefully you will get the 1616m, NOT the 1616 -> lower quality AD/DA.

1616m:
ADC - AK5394 (AKM)
DAC - CS4398 (Cirrus Logic)

1616:
ADC - PCM1804 (TI)
DAC - CS4392 (Cirrus Logic)


And the spike at 63 kHz is bad, time to build a linear 48V/18W PS.


Gary
 
Status
Not open for further replies.