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yusynth
Joined: Nov 24, 2005
Posts: 1166
Location: France
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 Posted: Tue Sep 30, 2008 11:11 am Post subject:
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| numbertalk wrote: | So this would be pin 2 of the CA3046, right? On the PCB you would just tap an output somewhere in the trace between pin 2 and R13 and would connect the positive lead of the cap to this side and then the negative lead to 0V, right?
| yusson wrote: | OK I checked the bubbly stuff in Autobahn and I understand what you mean.
I also checked the various EMS schematics I have and apparently I have two versions, one is a polarized cap connected to the base of Q4 (first transistor of the expo converter) which I considered as a design mistake and a second version where the very same cap is connected between the negative rail and ground which makes sense indeed. In my "clone" I suppressed this cap.
If you want to recreate this bug/feature of the old version you will have to add a 10uF cap between the base of Q4 and the 0V level. |
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Hi Paul
No it's pin 9 as a matter of fact, therefore you just need to solder a 10uF cap in parallel with R22 (1K)...
Here is a tip : for those of you who want to obtain a genuine EMS sound while using DOTCOM or YUSYNTH VCOs it is recommended to change the value of R8 to 27K. The output levels of these VCOs are much higher than those of an AKS and this makes a big difference in sound.
I have recently added a demo file on the diode VCF page... Check it out.
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numbertalk
Joined: May 05, 2008
Posts: 979
Location: Austin, TX
Audio files: 5
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| Posted: Tue Sep 30, 2008 11:30 am Post subject:
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Thanks Yves!
So if I wanted to wire this up through a toggle, does it matter which end of the cap is left floating when the switch is bypassed? Should I hard wire the cap between ground and the switch or to the lead out of pin 9 and the switch or does it not matter? I'm going to guess if it matters it would be to ground, so any signals or what not picked up would be shunted to ground. |
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yusynth
Joined: Nov 24, 2005
Posts: 1166
Location: France
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| Posted: Tue Sep 30, 2008 11:49 am Post subject:
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| numbertalk wrote: | Thanks Yves!
So if I wanted to wire this up through a toggle, does it matter which end of the cap is left floating when the switch is bypassed? Should I hard wire the cap between ground and the switch or to the lead out of pin 9 and the switch or does it not matter? I'm going to guess if it matters it would be to ground, so any signals or what not picked up would be shunted to ground. |
Yes the best is to leave the cap connected to the ground and insert the switch between the cap and pin 9.
As a matter of fact I have added this mod on the PCB that is used by Suit&Tie Guy for the Sea Devil filter 
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Yves
Last edited by yusynth on Tue Sep 30, 2008 12:41 pm; edited 1 time in total |
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numbertalk
Joined: May 05, 2008
Posts: 979
Location: Austin, TX
Audio files: 5
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| Posted: Tue Sep 30, 2008 12:36 pm Post subject:
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| Thanks! |
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suitandtieguy
Joined: Feb 05, 2007
Posts: 29
Location: Chillicothe IL USA
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| Posted: Sun Oct 05, 2008 7:46 pm Post subject:
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FYI currently the resistor changes i'm using for 10v p-p signal levels are the aforementioned 27K, but also the 2.2K shunt to ground is changed to 220 ohm, and the feedback resistor on the output opamp is changed to 15K instead of 10K.
i'm still fussing with it, but these values seem to work well. |
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Funky40
Joined: Sep 24, 2005
Posts: 875
Location: Swiss
Audio files: 1
G2 patch files: 5
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| Posted: Sat Oct 18, 2008 8:26 am Post subject:
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| Etaoin wrote: | | The filter works fine, but I only have a bit of resonance if I turn the res pot fully CW and put a large CV into the red mod input. With large enough CV, the res pot works as expected, with no CV, the res pot doesn't do anything. . |
Just wired the Yusynth Diode Ladder VCF
I had the very same Problem.
First thing i tryed was to change as mentioned above the 680K Res to 220K.
Now i have Resonance.
Seems to work fine now ! thanks for that Module Yves |
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yusynth
Joined: Nov 24, 2005
Posts: 1166
Location: France
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| Posted: Sat Oct 18, 2008 9:14 am Post subject:
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You're welcome Funky40 !
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Yves |
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stijn
Joined: Jul 21, 2008
Posts: 39
Location: utrecht, netherlands
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| Posted: Thu Nov 20, 2008 12:32 pm Post subject:
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Hi Yves,
I am about finished populating the board. The bom on your site states that 5 100nF caps are needed, but on the board (bridechamber) there is 6 needed. Is this correct? |
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yusynth
Joined: Nov 24, 2005
Posts: 1166
Location: France
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| Posted: Thu Nov 20, 2008 12:41 pm Post subject:
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Hi Stijn
6 is the right number , I forgot one on the BOM on my site , I will correct this ASAP
Have fun with this great filter.
Cheers
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stijn
Joined: Jul 21, 2008
Posts: 39
Location: utrecht, netherlands
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| Posted: Sun Dec 21, 2008 4:31 am Post subject:
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well I seem to have the opposit problem, my filter self oscillates all the time. resonance pot doesn't do anything. For the rest the filter is working fine.
Where should I look to solve this problem? |
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yusynth
Joined: Nov 24, 2005
Posts: 1166
Location: France
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| Posted: Sun Dec 21, 2008 4:52 am Post subject:
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Is C14 (100uF) polarised the right way (- to FET drain and + to R42/R40)?
On first analysis I'd say there is either a dead FET or a faulty polarisation of the Fet grid. Are you using a 2N3819 ? If so is it correctly placed that is as shown on the silkscreen ?
After check the voltage at the G pin of the FET, when tweaking the resonance pot this value must vary from 0V down to -2.4V (for R41=680K) or -5V (for R41=220K).
I all these are correct you may try increasing the value of R41
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stijn
Joined: Jul 21, 2008
Posts: 39
Location: utrecht, netherlands
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| Posted: Sun Dec 21, 2008 8:14 am Post subject:
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Hi Ives,
the polarization of the cap and fet are ok, the voltege at the G pin varies from 0,32 to - 0,47 V when tweaking the resonance pot (I am using a 22k resistor for R41). Oh and I am testing it with a +12/-12 V power supply. |
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yusynth
Joined: Nov 24, 2005
Posts: 1166
Location: France
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| Posted: Sun Dec 21, 2008 8:31 am Post subject:
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| stijn wrote: | | the voltege at the G pin varies from 0,32 to - 0,47 V when tweaking the resonance pot (I am using a 22k resistor for R41). Oh and I am testing it with a +12/-12 V power supply. |
It should vary from 0 to -2.4V !!!!! and 22K for R41 is way too SMALL !!!! It should be at least 220K!!!!!
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stijn
Joined: Jul 21, 2008
Posts: 39
Location: utrecht, netherlands
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| Posted: Sun Dec 21, 2008 8:41 am Post subject:
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| yusson wrote: | | stijn wrote: | | the voltege at the G pin varies from 0,32 to - 0,47 V when tweaking the resonance pot (I am using a 22k resistor for R41). Oh and I am testing it with a +12/-12 V power supply. |
It should vary from 0 to -2.4V !!!!! and 22K for R41 is way too SMALL !!!! It should be at least 220K!!!!! |
off course I mean 220k  |
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yusynth
Joined: Nov 24, 2005
Posts: 1166
Location: France
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| Posted: Mon Dec 22, 2008 3:49 am Post subject:
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OK 220K Then the voltage swing is weird it should stay below 0V and at least go down to -2.4V. Is some kind of voltage fed at the resonance CV input ?
Question : which version are you using the CA3096 version (U5) or the tranny version.
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Yves
Last edited by yusynth on Mon Dec 22, 2008 9:01 am; edited 1 time in total |
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stijn
Joined: Jul 21, 2008
Posts: 39
Location: utrecht, netherlands
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| Posted: Mon Dec 22, 2008 8:42 am Post subject:
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I have the descrete version. (bridechamber kit)
there is no voltage at the cv control for the resonance |
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stijn
Joined: Jul 21, 2008
Posts: 39
Location: utrecht, netherlands
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| Posted: Tue Dec 30, 2008 7:06 am Post subject:
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| Hi Ives, it turned out that the bridechamber kit has a PN4391 insted of a 2N3819 jfet, wich has a different pin out. So I desolderded it (wich was quite a hasle, are there any tricks fot this besides a solder sucker?) and flipped it but now I have no resonance at all, so I guess it's broken? |
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yusynth
Joined: Nov 24, 2005
Posts: 1166
Location: France
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| Posted: Tue Dec 30, 2008 7:48 am Post subject:
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| stijn wrote: | | Hi Ives, it turned out that the bridechamber kit has a PN4391 insted of a 2N3819 jfet, wich has a different pin out. So I desolderded it (wich was quite a hasle, are there any tricks fot this besides a solder sucker?) and flipped it but now I have no resonance at all, so I guess it's broken? |
I see, you should let know this to Scott Deyo because he provided you with a component that is not pin to pin compatible with the 2N3819...
It may not be broken but have a different pinch voltage than expected. As I explained on my page the characteristics of the pinch voltage of a JFET brand are very dispersed. JFETs are not as reliable in terms of charateristics as can be BJT transistors and picking two JFETs from the same batch may give very different results. Here it's even more different because you have a different brand of JFET...
What you can do is to take a 47K resistor and connect it in parallel with R41, and see if there is an improvement of the resonance control. If you recover the resonance control then try using other values in order to find the one that gives you full range. Otherwise, that is if with the 47K resistor you don't recover the resonance control, then your JFET is dead and replace it (preferably with a 2N3819 )
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chaorta
Joined: Jan 17, 2009
Posts: 10
Location: Chicago
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| Posted: Wed Jan 21, 2009 10:49 am Post subject:
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Here's a dumb question from a new DIY'er...i'd like to purchase this and build it. I do have building experience, and can SORT of read a schematic. My question is more mechanical...is the PCB small enough to fit in a Doepfer A100 case and will it run at +/- 12v, and if so, how would i go about making this happen?
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yusynth
Joined: Nov 24, 2005
Posts: 1166
Location: France
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chaorta
Joined: Jan 17, 2009
Posts: 10
Location: Chicago
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| Posted: Wed Jan 21, 2009 1:47 pm Post subject:
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Well that was easy, thanks 
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softfin
Joined: Oct 11, 2006
Posts: 264
Location: Far in the north
Audio files: 1
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| Posted: Sat Feb 07, 2009 10:51 am Post subject:
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| yusynth wrote: | Hi Chaorta and welcome
Concerning the PCB I can't tell you because I have no Doepfer case to check it. But may be if give the size of the PCB you can make yourself an idea. The PCB is 10 cm per 7.5 cm and has four fixation holes.
Concerning the power supply, yes it will run at +12V/-12V, for this you just need to remove some components : remove R3 (82ohm) and bypass its pads with a wire, remove U2 (78L12/7812) bypass with an insulated wire the left and rigth pads (leave the middle pad unconnected) and that's it (see the diagram below : left before mod, right : after mod, bypass wires shown in red) |
Finished my pair of diode ladders. I put them in my +-12V case, so I did the suggested modifications, but found the -9V was only about -7.25V, so I exchanged R4 with a 120ohm resistor and also replaced R50 with 5k trimmer as a voltage divider. I didn't measure the resistance of the trimmer when I achieved precise -9V, but it is probably around 2k.
These long awaited filters have this excellent spiky but pleasing character. The only downside seems to be CV bleedthrough which is louder than on my other filters. Is there any simple way to reduce it?
Btw, six diodes are reversed on the overlay with the color coded resistors.
Big thanks to Yves for this module! |
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yusynth
Joined: Nov 24, 2005
Posts: 1166
Location: France
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| Posted: Sat Feb 07, 2009 11:00 am Post subject:
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| softfin wrote: | These long awaited filters have this excellent spiky but pleasing character. The only downside seems to be CV bleedthrough which is louder than on my other filters. Is there any simple way to reduce it?
Btw, six diodes are reversed on the overlay with the color coded resistors.
Big thanks to Yves for this module! |
Did you match thorougly your diodes ? This is important to reduce the CV bleedthrough.
Concerning, the overlay error, this has been corrected on my site at least two months ago
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softfin
Joined: Oct 11, 2006
Posts: 264
Location: Far in the north
Audio files: 1
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| Posted: Sat Feb 07, 2009 1:48 pm Post subject:
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| yusynth wrote: |
Did you match thorougly your diodes ? This is important to reduce the CV bleedthrough.
Concerning, the overlay error, this has been corrected on my site at least two months ago |
I used the layouts I had archived some time ago, so I didn't notice the layout was already corrected. 
Regarding the diodes, I took a strip of factory packed diodes and measured them simply by putting +9V across each one and measured the voltage drop. All diodes had almost exactly the same amount of voltage drop, the difference in drop between diodes being 0.01-0.02V. That was also pretty much as precise a measurement as possible on my multimeter.
Should I match them more carefully, and if so, is there a more precise method you could recommend? |
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yusynth
Joined: Nov 24, 2005
Posts: 1166
Location: France
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| Posted: Sat Feb 07, 2009 2:54 pm Post subject:
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Yes you should... as a matter of fact they must be matched by pair within 2mV. The bleedthrough mostly comes for the unbalance between each side of the ladder. The principle of this kind of ladder is that the CV is canceled out by subtracting the left and right side of te ladder while the audio passes through because it is differentially transmitted by the input transistors.
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