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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Thu Aug 14, 2014 1:23 am Post subject:
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Seek help
Serge resonant eq? |
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dingebre
Joined: Aug 10, 2008 Posts: 270 Location: Salt Lake City, UT USA
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Posted: Wed Nov 12, 2014 2:12 am Post subject:
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Good news, the GIC and Inductor versions are both finally working. I ordered PCBs today. If anyone is interested in buying a set, email or PM.
GIC - $70.00 per set (A little expensive, but they are 4 layer PCBs to minimize noise and hum)
Inductor - $50.00 per set (Will work with either the large or small core 5 Henry inductors Carsten has made)
A couple of quick comments on construction. I'll put more detail together if people buy the PCBs.
A set consists of 4 PCBs, a top, middle, and bottom PCB adn an I/O PCB which mounts to the bottom filter cell PCB. They have PCB mounted pots, Panasonic EVU-E2JFK4D54, DigiKey P3U0503-ND. You will most likely need to trim the shaft a little depending on the knob you use. the HP and LP pots are not PCB mounted and can be any smallish panel mount pot. I've calculated the values for the capacitors which are on the silkscreen. There are two choices, one for an "exact" cutoff frequency, one that pushes the cutoff either up or down about 6% to mimic what it appears Moog did (as well as Jurgen Haible on his version).
The construction is not bad. The calibration is the problem, here. Ideally, you want the overall "Q" to be about 3.7 (per Yves Usson's testing of an original 914). The trimmers will adjust that, but it's not so straight forward to tell. I've just set my trimmers to point to about 10:00 or 11:00 and the result is very pleasing. you don't want too high a "Q" or you lose some of the harmonics between the cells. Too low and you miss the nice resonance when the input attenuator is fully CW.
Be warned, both versions are kind of pricey to build. For the inductor version, you need a set of Carsten's inductors. for the GIC, you need 29 of the best, lowest noise, op amps you are willing to buy. I ended up using the OPA2227, about 4.50 each for 10-99 pieces. Probably way overkill. Jurgen used an MC4558 at about $0.40 depending on the exact one you pick.
So, enough for now. Please feel free to contact me if you are interested. I've got about 2 weeks til the PCBs are in. In the mean time, I'll work on a BOM and some construction notes. _________________ David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.
dingebre@3dphysics.net
http://www.xmission.com/~dingebre/Synthasystem.html |
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dingebre
Joined: Aug 10, 2008 Posts: 270 Location: Salt Lake City, UT USA
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dingebre
Joined: Aug 10, 2008 Posts: 270 Location: Salt Lake City, UT USA
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dingebre
Joined: Aug 10, 2008 Posts: 270 Location: Salt Lake City, UT USA
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synthcube
Joined: Dec 21, 2011 Posts: 64 Location: boston
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dingebre
Joined: Aug 10, 2008 Posts: 270 Location: Salt Lake City, UT USA
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Posted: Mon Jun 15, 2020 9:01 pm Post subject:
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Update 6/15/2020
I updated the web site's 914 FFB pages. Please see the website for details.
Basically:
1. I have re-done the inductor PCB design to work with CineMag inductors. They did the inductors for the Moog modular reissued systems. Please PM me if you want to use them.
2. I found a couple more errors on the Norlin schematics and have offered some corrections. They are very simple. Change a resistor on the I/O PCB, eliminate a couple of capacitors with jumpers and eliminate some resistors on the I/O PCB.
3. On the inductor, I recommend increasing the LP filter capacitors to 1.22uF with a 1uF and a 0.22uF.
4. On all versions, I recommend changing the HP filter capacitors to 2nF with two 1nF capacitors.
Again, details on the web page:
http://analoguerealities.com/projects/fixed-filter-bank-914
I added more photos, added more information regarding calibration, and other stuff. _________________ David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.
dingebre@3dphysics.net
http://www.xmission.com/~dingebre/Synthasystem.html |
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