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
Attachments
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
Also, please show where 10 Ohm R's are located (schematic/picture?).
Thx-RNMrash
Last edited:
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.
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
When I got the unit, I immediately drilled out those B&K connectors and put BNC's there, see pics.
Gary
Attachments
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
Thx-RNM
Nothing Special:
http://www.ebay.com/itm/3590S-2-501L-500-Ohm-Rotary-Wirewound-Precision-Potentiometer-Pot-10-Turn-/120985135227
http://www.ebay.com/itm/3590S-2-501L-500-Ohm-Rotary-Wirewound-Precision-Potentiometer-Pot-10-Turn-/120985135227
@ghg -- you show one end of 2C at ground, and one end of 0.5R connected to the output of the amp -- usually, these ends are connected together... I haven't seen this configuration for the T-T before -- are you sure that 2C is at ground?
Man, that 1616 sure is quiet.
Man, that 1616 sure is quiet.
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?
Just tune the notch to exactly -60dB and then add a couple of zeros to ARTA's calculated values. Don't forget to turn on the 400Hz HP filter in ARTA.
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?
>The spurious stuff in the plot is from the 1616 power supply?
I checked the EMU 1616. It uses the AK5394A ADC. That's a key part of how it gets the low noise. I just bought one on eBay to see how useful/practical it is and how funky the control software is.
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
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
Check my input at -- Active Twin-T filter forum regarding the use of a notch filter for similar purpose and other apps using an HP334A
THx-RNMarsh
THx-RNMarsh
- Status
- Not open for further replies.