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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Sun Mar 16, 2008 2:22 pm Post subject:
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Well if it oscillates the problem comes definitely from Q12 or its polarization circuit.
The -3V seems a normal value (divider 680K and two 220K in parallel (R39 and R45 if the ouput (pin 7) of U1b is at 0V.
The sudden change to -1.3V is quite weird indeed... is U1b OK ?
Sounds like something misconnected : is the resonance pot connected to -9V on one side (CW) and to ground (CCW) ? _________________ Yves |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Sun Mar 16, 2008 2:31 pm Post subject:
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Could you try flipping the 2N3819, I know that one can find two brands that have opposite pin-outs , that's very puzzling when you check the datasheet from various constructor the pin-out can be reversed. ????
If this does not solve the problem try replacing the 680k by a 220K as in the original schematic. I changed this value to 680K because on my prototypes this change was necessary. _________________ Yves |
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Dave Kendall
Joined: May 26, 2007 Posts: 421 Location: England
Audio files: 3
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Posted: Sun Mar 16, 2008 7:57 pm Post subject:
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Quote: | could you try flipping the 2N3819, I know that one can find two brands that have opposite pin-outs , that's very puzzling when you check the datasheet from various constructor the pin-out can be reversed. ????
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Hi Yves.
That's very valuable information - thanks. I have a few EFM modules that use 2N3819s. On the datasheets I've got, the fairchild component has this - with the flat side of the TO-92 case flat down on the table , and the legs pointing towards you, it goes Source, gate, drain (left to right). The vishay part is the opposite! This *might* explain the failure of the S+H section on some EFMLFO5As to actually sample and hold. Fonik had this problem IIRC, and one of mine didn't do the business either....
I seem to remember reading somewhere that drain and source were often interchangeable? It seems that they aren't....
Can anyone confirm or deny this? The last few 2N3819s I have are unbranded. so, er, I might get into some trouble......
cheers,
Dave |
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etaoin
Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL
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Posted: Sun Mar 16, 2008 11:31 pm Post subject:
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yusson wrote: | Could you try flipping the 2N3819, I know that one can find two brands that have opposite pin-outs , that's very puzzling when you check the datasheet from various constructor the pin-out can be reversed. ???? |
Yeah, I knew about that one so I had already checked this. But I have a marked Fairchild FET, so there was little doubt.
Quote: | If this does not solve the problem try replacing the 680k by a 220K as in the original schematic. |
That worked! Seems to be fine now... _________________ http://www.casia.org/modular/ |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Mon Mar 17, 2008 12:05 am Post subject:
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OK then I will add a note on my page that the value of this resistor must be adapted to the 2N3819 used or may be is it due to the use of B brand which gives a lower gain. On my proptotype I used C brand which gives a higher gain and I add to increase the resistance from 220K to 680K in order to obtain a resonance range that spread nicely over the pot run.
Cheer Louis _________________ Yves |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
Audio files: 54
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Posted: Mon Mar 17, 2008 2:01 am Post subject:
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yusson wrote: | OK then I will add a note on my page that the value of this resistor must be adapted to the 2N3819 used or may be is it due to the use of B brand which gives a lower gain. On my proptotype I used C brand which gives a higher gain and I add to increase the resistance from 220K to 680K in order to obtain a resonance range that spread nicely over the pot run. |
Aren't you just seeing variations in pinchoff voltage from device to device? I have a bank of six VCAs made from FET-based variable resistors, and I had to select devices for the same pinchoff. But the response is so sensitive to pinchoff that I had to trim the bias points by hand to get even close to the same range on each channel. And this was with devices from the same batch. Look at the specified pinchoff voltage and you will see there is a huge range.
Ian |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Mon Mar 17, 2008 4:09 am Post subject:
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frijitz wrote: |
Aren't you just seeing variations in pinchoff voltage from device to device? I have a bank of six VCAs made from FET-based variable resistors, and I had to select devices for the same pinchoff. But the response is so sensitive to pinchoff that I had to trim the bias points by hand to get even close to the same range on each channel. And this was with devices from the same batch. Look at the specified pinchoff voltage and you will see there is a huge range.
Ian |
Yes that was my first hypothesis but I was not sure, Quote: | the value of this resistor must be adapted to the 2N3819 used | your info about FET from the same batch with such variations is very interesting indeed
Cheers _________________ Yves |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Tue Aug 12, 2008 6:24 am Post subject:
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I have updated (august 12th 2008) my diode-ladder filter page.
I just changed the value of R47 from10K to 39K which seems to give a better output level (at least in the range of the other yusynth VCFs anyway).
Cheers _________________ Yves |
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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 Sep 13, 2008 9:26 am Post subject:
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Hello Yves,
i see at Reichelt that the BC327 is available in different types.
BC 327-16 / -25 / -40
which one should i take ?
edit:
uhhh, the 2N3819 costs 20 times more at conrad then at Reichelt.
are there different Qualitys available ? something to care ? ( i have to Order at both places )
thanks |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Sat Sep 13, 2008 9:47 am Post subject:
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Hi
The brand of BC327 is not important you can pick any of these.
For the 2N3819, take the cheapest. Active components at Conrad's are well overpriced !
_________________ Yves Last edited by yusynth on Tue Sep 30, 2008 11:05 am; edited 1 time in total |
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numbertalk
Joined: May 05, 2008 Posts: 992 Location: Austin, TX
Audio files: 5
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Posted: Tue Sep 30, 2008 10:34 am Post subject:
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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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yusynth
Joined: Nov 24, 2005 Posts: 1314 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. _________________ Yves |
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numbertalk
Joined: May 05, 2008 Posts: 992 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: 1314 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 _________________ 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: 992 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: 1314 Location: France
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Posted: Sat Oct 18, 2008 9:14 am Post subject:
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You're welcome Funky40 ! _________________ 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: 1314 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 _________________ Yves |
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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: 1314 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 _________________ Yves |
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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: 1314 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!!!!! _________________ Yves |
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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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