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
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
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Thanks, E-MU 1616m stock, just used the line in at the back.
Schematic: http://www.diyaudio.com/forums/equi...on-audio-range-oscillator-21.html#post3116055 see Post #204
You may checkout R32/R33 easy, just the two resistors after the + - PS terminals.
Schematic: http://www.diyaudio.com/forums/equi...on-audio-range-oscillator-21.html#post3116055 see Post #204
You may checkout R32/R33 easy, just the two resistors after the + - PS terminals.
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
When I got the unit, I immediately drilled out those B&K connectors and put BNC's there, see pics.
Gary
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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
I also use a banana to BNC adapter that plugs right into the Euro sockets without any problem and is secure.
-RNM
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?
I'll fit mine up with this as well.
The spurious stuff in the plot is from the 1616 power supply?
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