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Pseudo .5 291 Bandpass Filter Board |
J3RK
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 Posted: Thu Sep 29, 2011 11:41 am Post subject: Pseudo .5 291 Bandpass Filter Board |
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Hello,
Just thought I'd move discussion of this to a new thread. I've got a board around 75% laid out now. (first pass, so there will need to be some optimization, fixes, and I'm planning some additions/mod-space) I plan to order prototypes within the next couple of weeks.
Basically it's a single 291 bandpass filter. I'm looking into tapping/mixing other responses now too.
I've decided to do one filter per board using a smaller board. They'll be stackable with thru-power header like the .5 258 boards. This should also help with putting multiple boards into smaller formats. I'm planning a quad-board module myself that can be used as a resonant eq, or formant filter.
Anyway, I'll start updating this thread with any major progress, and hope to have a final design ready within a month or so.
Here's the basic BOM:
| Code: | Bill Of Materials
=================
QTY PART-REFS VALUE
--- --------- -----
Resistors
---------
2 R1,R45 47k
1 R2 2.2M
4 R3,R8,R12,R31 6.8k
2 R4,R13 33k
4 R5,R15,R25,R32 10k
1 R6 5.6k
2 R9,R14 10M
2 R18,R19 4.7k
4 R20,R21,R28,R29 1.5k
1 R22 1M
2 R23,R26 15K
1 R24 68R
5 R27,R33,R34,R48,R49 1k
1 R30 4.7M
1 R35 100k
1 R36 220R
2 R38,R39 62K
2 R42,R43 68K
***MODS***
R24=33R
R27=100R
Capacitors
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1 C1 1000pf
2 C2,C5 .022
1 C3 220pF
1 C4 15uF
1 C6 470pF
1 C7 47pF
1 C8 .47
***MODS***
C2,C5=.047
Integrated Circuits
-------------------
1 U1 TL071
1 U2 TL074
1 U3 TL072
Transistors
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2 Q1,Q2 2N3904
***MODS***
Q1,Q2=2N5089 (sounds a little nicer to me anyway)
Diodes
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1 D1 DIODE-ZEN 3.9V
1 D2 1N4148
Miscellaneous
-------------
1 Q 100k UI
4 CF,CF CV,WIDTH, 10k
1 FM 50K
4 VT1-VT4 OptoCoupler
1 WIDTH TRIM 5k |
2 10uF or higher electrolytic caps for power filtering.
4 .01uF bypass capacitors (labeled BP1-BP4) *
***Errors***
There are two small silk-screen errors on the board unfortunately. On the left side of the board where the controls attach, there are two resistors labeled R21. The top one should actually be R43.
* There seems to be a "bonus" bypass cap on the board. You can populate it or not. (it's an unlabeled cap) Just drop a .01 in there if you feel like it. The original layout didn't have bypass caps at all, so they are optional.
** This is a silly one, but basically the "Q" header at the top-left of the board, is more or less useless. This was on the schematics that I was working from, so I included it. The real resonance/Q trim is the 5K WTrim pot, which will adjust the resonance for the Width control. This is really something that I feel is best left to a trim-pot. Just set it the way you like it, and you're good. I'm actually not sure what the original intent of the 100K pot on the input is. While it does make very slight changes to the signal, it's definitely not audible, so it's entirely optional.
Also, here is the schematic for those interested:
http://home.comcast.net/~r3cogniz3r/291diagram.jpg
Last edited by J3RK on Tue Mar 13, 2012 12:31 pm; edited 10 times in total |
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giorgio
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| Posted: Thu Sep 29, 2011 11:46 am Post subject: |
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cool. this may be the extra filter I'm looking for for my DIY synth, especially if a highpass output could be tapped.
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Last edited by giorgio on Thu Sep 29, 2011 8:23 pm; edited 1 time in total |
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PF
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| Posted: Thu Sep 29, 2011 1:24 pm Post subject: |
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yes, yes, yes....... please.
4 boards.
Last edited by PF on Sat Oct 15, 2011 3:02 am; edited 2 times in total |
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rico loverde
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| Posted: Thu Sep 29, 2011 1:31 pm Post subject: |
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Luka
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| Posted: Thu Sep 29, 2011 1:32 pm Post subject: |
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great - i really like my 291s
i would like to have a bank of them
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KNYST
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kdub
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| Posted: Thu Sep 29, 2011 2:03 pm Post subject: |
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| yes! x4 sounds good to me. I was thinking about building a cgs serge resonant equalizer, but I think a j3rk pseudo 291 is first in order. |
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boothnavy
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| Posted: Thu Sep 29, 2011 3:22 pm Post subject: |
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Uh huh, yup.
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negativspace
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gwaidan
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| Posted: Thu Sep 29, 2011 7:26 pm Post subject: |
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| Count me in for at least 2 PCBs |
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decaying.sine
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| Posted: Thu Sep 29, 2011 8:25 pm Post subject: |
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I'll take around 4!
Actually, I'll just take 2-4 of anything, come to think of it!
Thanks J3RK.
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toppobrillo
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| Posted: Thu Sep 29, 2011 9:08 pm Post subject: |
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Ill take a couple!
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gigasturtz
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| Posted: Thu Sep 29, 2011 9:32 pm Post subject: |
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| yes please! |
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diophantine
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| Posted: Thu Sep 29, 2011 9:35 pm Post subject: |
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Awesome! Count me in for 4.
Last edited by diophantine on Thu Oct 06, 2011 7:49 pm; edited 1 time in total |
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Peake
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| Posted: Thu Sep 29, 2011 10:20 pm Post subject: |
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Yes, please include the lowpass and highpass outputs! Check that EM thread as one of them, IIRC the LPF, is out of phase.
Very cool!
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patchdub
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Isaiah
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| Posted: Fri Sep 30, 2011 1:47 am Post subject: |
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Sounds tempting!
Will the PCBs be Euro compatible (Voltage/PSU Header etc)?
How big will they be?
If they were small enough that you could parallel mount/stack 2 or 3 behind, say, a 14HP panel, that would be great!
Cheers! |
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rosch
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| Posted: Fri Sep 30, 2011 1:54 am Post subject: |
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edit: i'd take at least 2, maybe more
great project, J3RK
Last edited by rosch on Fri Sep 30, 2011 9:39 am; edited 1 time in total |
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