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 Forum index » DIY Hardware and Software » Jürgen Haible designs
Living VCOs
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Would you prefer one PCB with 3 VCOs a la JH-5A, or 1 VCO per PCB with more features
One PCB with Oscillator Driver and 3 VCO cores (like JH-5A - cheap!)
60%
 60%  [ 62 ]
1 PCB = 1 VCO (with many waveforms and inputs)
39%
 39%  [ 41 ]
Total Votes : 103

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jhaible



Joined: May 25, 2007
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PostPosted: Wed Oct 14, 2009 11:13 pm    Post subject: Re: Living VCOs
Subject description: Oops!
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numbertalk wrote:
davebr wrote:
I think the CW for the Detune controls is on the left in the wiring diagram. With CW on the left, CW rotation increases frequency.


Ah, I hadn't noticed this on mine since it this control covers such a small range, but you're right - I didn't catch this and mine are wired up backwards.


I guess I never noticed that myself, because I just use a tiny amount to create rich beating between VCOs. One VCO center, 2nd VCO a bit clockwise, 3rd VCO a bit counter-clockwise.

JH.

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Luka



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PostPosted: Mon Nov 02, 2009 2:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

jurgen would there be any issues if i droped in some dual matched transistors in place of the 550/560 pairs like 2sa798s and similar npn

would you have any recommendations for such

i started matching transistors for this but i dont really trust my DMM enough for this task and i have a bag full of 798s. so wondering if this is viable

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jhaible



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PostPosted: Mon Nov 02, 2009 2:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

Luka wrote:
jurgen would there be any issues if i droped in some dual matched transistors in place of the 550/560 pairs like 2sa798s and similar npn

would you have any recommendations for such

i started matching transistors for this but i dont really trust my DMM enough for this task and i have a bag full of 798s. so wondering if this is viable


Of course you can use matched pairs, but maybe there is some misunderstanding: There is no need to for matched transistors here! You don't have to select pairs of 550s or 560s here either! Just take them as they come out of the bag ...

JH.

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Luka



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PostPosted: Mon Nov 02, 2009 3:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

great, so is there really no performance boost at all from matching the transistors?


also i found metal can lm311H for cheap
are these suited to the task just as well as the dip versions

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jhaible



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PostPosted: Mon Nov 02, 2009 11:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

Luka wrote:
great, so is there really no performance boost at all from matching the transistors?


also i found metal can lm311H for cheap
are these suited to the task just as well as the dip versions


The only pair that should be matched is in the 3086 (or 3046) array.

I'm quite sure you could use that metal can comparator with a little bending of legs, but then again you might get a lot of money for these, one time, and DIP 311's are dirt cheap.

Thinking of it again: I have not actually tried a 311H, and comparators may self-oscillate when their input connections are too long - no idea if the bent legs of a metal can would make any trouble here. Probably not, but you will be able to tell us afterwards!

JH.

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cloudberry



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PostPosted: Wed Nov 11, 2009 4:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've been listening to the demos of these vcos and they sound wonderful! I'm looking at building my first vcos too (also looking at Thomas Henry, MOTM and Oakley), and am curious as to how accurate these 'Living VCOs' are? Are they accurate enough so they could be multitracked to create chords without, let's say, 'fruity' tuning? And (perhaps more demandingly!) would they hold their tuning well enough to use them live, with all that that entails....?


Thanks,


Cloudberry
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Funky40



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PostPosted: Sun Nov 15, 2009 6:43 am    Post subject: Reply with quote  Mark this post and the followings unread

I have since 3 Days the first time ever the possibility to play my Synth with a Keyboard.
WOW, what a different thing to play my JH triple VCO with the Keys instead of sequenzing.
i'm very happy with my triple VCO.
My minimal setup without attenuators for PWM and FM works fine for now.


after several Days of surching i found yesterday also my Weller solderstaion,
so i can go for final wiring of my second triple VCO which is waiting since three months.
I'm very curious how they will be playable as a two-voice. ( hopefully later 4-voice )
Great Module, thanks alot Jürgen !


@cloudberry
cannot answer you, but i'm optimistic Very Happy
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bennethos



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PostPosted: Tue Nov 17, 2009 6:57 am    Post subject: Reply with quote  Mark this post and the followings unread

My L vco board is fully populated, I will start the wiring soon.

I'm going to integrate it in my eurorack system.

As this is one of my first projects I'm going to follow the excellent guide on Dave Brown's site (I also used you're BOM David, thx !!!)

I saw he changed his frontpanel design a lot of times so I'm going to stick with his final design and try to convert it to eurorack...

I'll keep you posted Smile
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JoeMorris



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PostPosted: Thu Nov 19, 2009 4:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi,
just finally finished my living vcos board as first (semi-)functional unit of my quixotic attempt at building a keyboard synth (loads of other stuffed boards waiting to be tested too, thought Id start at the beginning)...

Two of the oscillator's sawtooths work perfectly and sound gratifyingly chunky already even now in their unadulterated virgin state, but both pulse outputs (Im doing this all via the amps on the driver circuit) sound quite a bit quieter than the saws and one of them seems to sweep in and out a little bit uncontrollably. (The other one sounds fine just quieter - I presume pulse/saw are supposed to be same volume?)

The third oscillator just seems to make a high pitched wine.

Anyone got any ideas as to where to start tweaking to get this right?

Cheers,

Joe
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bennethos



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PostPosted: Fri Nov 20, 2009 1:06 am    Post subject: Reply with quote  Mark this post and the followings unread

I would first measure ground to 15v ground to -15v , 15v to -15v to exclude shorts.

Then power up the vco and check the ic's, they should be cold and keep cold within 30-60 seconds. if they get warm there's a problem :p

You could also remove the ic's of vco3 and measure the pins to exclude shorts for the ic's and check for shorts with a multimeter (ground/v+) (I hope you didnt solder them fixed on the board.

Be sure to check the correct direction of you're ic's as well !.

What I would also do, the other 2 work fine, check the color codings of the resistors/compare them with the working vco's...

My hunch is that it's an IC problem.

What does the scope show ? for the high pitched tone ?


My board is also fully populated, soldered the minimum pots and tested it on the scope, everything seems to work fine Smile. I'm quite proud, as this is my first project :p

cheers
Benjamin
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studionebula



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PostPosted: Sat Nov 21, 2009 10:17 pm    Post subject: Can't get 1V/oct adjusted correctly Reply with quote  Mark this post and the followings unread

I've finished assembling my Living VCO module. I'm having trouble with the calibration. I can't get the 1V/oct scaling set up correctly. The oscillator frequency goes up by more than one octave per volt, even at the most extreme setting of the scaling trimmer.

The behavior is the same for each of the oscillators, so I think it's probably not a component error (unless I made the same mistake three times, which is entirely possible). The CV input voltages appear to be correct. The oscillators appear to behave correctly otherwise, e.g. they do go up in frequency as the CV increase, the PW control and trimmer work, both the saw and rectangular outputs look good on a 'scope.

Any suggestions would be most welcome. I'm kind of stumped at this point.

EDIT: I mis-stated the problem above. The frequency goes up by less than one octave per volt, at most.

Since making my original post I've checked the values of all of the resistors that I believe are relevant--basically every one from the CV inputs to the sawtooth output point. I have found no errors. I remain stumped. I'd really appreciate hearing from anyone who has completed one of these modules to know whether or not you encountered a similar problem. (I'm guessing that nobody has since I imagine it would have been mentioned already.)

--Adam
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The Peasant



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PostPosted: Mon Nov 23, 2009 2:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

I finished my Living VCOs yesterday, I had no problems calibrating the V/oct response. I did make some minor changes to the circuit.

I did not want to use the VCO driver section of the pcb on my project, so I carefully sheared it off from the three oscillators. It will need to have one trace repaired and then it will be used to add it's functions to a CV keyboard that my partner is building.

Instead of BC560C and 550C transistors I used some that are simply marked "BC560" and "BC550". I'm haven't compared specs, so I'm not sure what the actual difference is with these parts or what difference this might have made to the circuits.

I was unhappy with the upper frequency range that I could get even with the freq. trimpots all of the way up. I ended up changing the integrating capacitor from 2n7 to 1n0 and lowering R7, etc. to 250K.

I also adapted a saw to triangle waveshaping circuit from a MFOS VCO for each oscillator and added a version of Ian Fritz's sine shaper circuit (Thanks Ian!). This circuit takes it's input from the raw sawtooth output, directly connected to pin 7 of U1, etc. I built these on perf-board along with three of the output level boosters, like those on the VCO driver section, for the pulse wave outputs.

I'll attach the waveshaper schematic and some pics.

Take care,
Doug


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jhaible



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PostPosted: Mon Nov 23, 2009 3:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

The "C" suffix just means the highest current gain (beta) group. A is lowest, B is medium, no suffix could be anything (unselected).
I don't think this circuit, or most of my others, are particularly sensitive to beta; I just spec the "C" types because they are all the same price where I buy them, so I never try lower beta transistors.

JH.

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studionebula



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PostPosted: Tue Nov 24, 2009 10:20 am    Post subject: Re: Can't get 1V/oct adjusted correctly Reply with quote  Mark this post and the followings unread

I found the cause of the 1V/octave scaling problem I mentioned in my previous post. The problem was that I substituted a CA3086 transistor array for the CA3046. This is listed as a substitution on Dave Brown's Mouser BOM. I probably chose the CA3086 because that's what Bridechamber had in stock at the time, or something.

At first glance the two parts are viable substitutes for audio applications. Even looking at the Intersil web pages for both parts does not reveal the difference. The difference is in the HFE current gain parameter; the CA3086 has a gain of 100, while the CA3046 has a gain of 110. The Intersil web pages actually have a typo; HFE is stated as 100 for both. It wasn't until I did a parameter-by-parameter comparison of the PDF data sheets for the parts that I found the difference.

So, the current gain is lower in my circuit, and hence the current coming from the CV summing amp isn't sufficient to increase the oscillator frequency by 1V/oct. To correct this I reduced the value of the 51K resistor that follows the scaling trimmer pot. For my test I used a couple of clip leads to put a big resistor in parallel. With the resistance lowered I was able to get the oscillator to track at 1V/oct with no trouble. I have some 47K resistors on hand; I'll try replacing the 51K resistors with those.

My circuit analysis knowledge is fairly limited, so I'd be entirely happy to hear from anyone who would like to confirm or dispute my reasoning.
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jhaible



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PostPosted: Thu Nov 26, 2009 3:25 pm    Post subject: Re: Can't get 1V/oct adjusted correctly Reply with quote  Mark this post and the followings unread

studionebula wrote:
I found the cause of the 1V/octave scaling problem I mentioned in my previous post. The problem was that I substituted a CA3086 transistor array for the CA3046. This is listed as a substitution on Dave Brown's Mouser BOM. I probably chose the CA3086 because that's what Bridechamber had in stock at the time, or something.

At first glance the two parts are viable substitutes for audio applications. Even looking at the Intersil web pages for both parts does not reveal the difference. The difference is in the HFE current gain parameter; the CA3086 has a gain of 100, while the CA3046 has a gain of 110. The Intersil web pages actually have a typo; HFE is stated as 100 for both. It wasn't until I did a parameter-by-parameter comparison of the PDF data sheets for the parts that I found the difference.

So, the current gain is lower in my circuit, and hence the current coming from the CV summing amp isn't sufficient to increase the oscillator frequency by 1V/oct. To correct this I reduced the value of the 51K resistor that follows the scaling trimmer pot. For my test I used a couple of clip leads to put a big resistor in parallel. With the resistance lowered I was able to get the oscillator to track at 1V/oct with no trouble. I have some 47K resistors on hand; I'll try replacing the 51K resistors with those.

My circuit analysis knowledge is fairly limited, so I'd be entirely happy to hear from anyone who would like to confirm or dispute my reasoning.


Whatever the reason for the mistracking was, a difference in current gain it cannot have been. The circuit is making use of the exponential voltage controlled current source operation of these transistors, not of the approximately lienar current controller current sourec operation.
Maybe one of these chips was just faulty.
Glad it works now! But 3046 and 3086 schould be pretty equivalent here.

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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studionebula



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PostPosted: Fri Nov 27, 2009 1:41 pm    Post subject: Re: Can't get 1V/oct adjusted correctly Reply with quote  Mark this post and the followings unread

jhaible wrote:


Whatever the reason for the mistracking was, a difference in current gain it cannot have been. The circuit is making use of the exponential voltage controlled current source operation of these transistors, not of the approximately lienar current controller current sourec operation.
Maybe one of these chips was just faulty.
Glad it works now! But 3046 and 3086 schould be pretty equivalent here.

JH.


Thanks for your reply. The module still does not work correctly. I was unable to improve the tracking problem by changing resistors--which now makes sense, since you have told me that the use of the CA3086 is probably not the source of the problem.

I am still unable to get any of the three oscillators to track correctly. I doubt the problem is a faulty chip, since all three oscillators behave the same way (as I stated previously).

I guess my next step will be to remove the PCB from the panel altogether and try to get it working correctly on my bench with test leads and a power supply. Maybe I made some sort of wiring error with the jacks, although I don't see how this could affect the tracking. But I can't think of anything else to try and I'm pretty frustrated at this point, so I'll try that.

--Adam
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jhaible



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PostPosted: Fri Nov 27, 2009 2:15 pm    Post subject: Re: Can't get 1V/oct adjusted correctly Reply with quote  Mark this post and the followings unread

studionebula wrote:
jhaible wrote:


Whatever the reason for the mistracking was, a difference in current gain it cannot have been. The circuit is making use of the exponential voltage controlled current source operation of these transistors, not of the approximately lienar current controller current sourec operation.
Maybe one of these chips was just faulty.
Glad it works now! But 3046 and 3086 schould be pretty equivalent here.

JH.


Thanks for your reply. The module still does not work correctly. I was unable to improve the tracking problem by changing resistors--which now makes sense, since you have told me that the use of the CA3086 is probably not the source of the problem.

I am still unable to get any of the three oscillators to track correctly. I doubt the problem is a faulty chip, since all three oscillators behave the same way (as I stated previously).

I guess my next step will be to remove the PCB from the panel altogether and try to get it working correctly on my bench with test leads and a power supply. Maybe I made some sort of wiring error with the jacks, although I don't see how this could affect the tracking. But I can't think of anything else to try and I'm pretty frustrated at this point, so I'll try that.

--Adam


If the tracking is wrong in all 3 VCOs, maybe you have a problem in the oscillator driver?

JH.

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studionebula



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PostPosted: Fri Nov 27, 2009 2:55 pm    Post subject: Re: Can't get 1V/oct adjusted correctly Reply with quote  Mark this post and the followings unread

jhaible wrote:


If the tracking is wrong in all 3 VCOs, maybe you have a problem in the oscillator driver?

JH.


That's entirely possible, although I made voltage measurements to verify that the correct CV was arriving at the CVs_* inputs for the oscillators. However, I currently have the PCB entirely disconnected from the panel and am running it with a bench power supply and one potentiometer connected to the Freq_3 header. I have a CV attached with clip leads to the CVs_3 header. In this configuration I am able to correctly adjust the scaling of the third oscillator! Very Happy So apparently there is a problem with my driver, or my wiring.

I think that the problem could also be due to the power supply in my modular cabinet. I measured it the other day and its voltages are a little bit high, e.g. about +15.2V. Is it possible that this could be the cause of the scaling problems? I have my bench supply set to +/-15.0, of course. As an experiment I raised the levels to +/-15.2 and noticed that the scaling became more difficult to adjust. Do you think that it is possible that this could be the source of the problem? Obviously now that I have found the problem with the supply I will recalibrate it, but unfortunately that will be somewhat time-consuming to do since I have to take the back off the cabinet to reach the trimmers, and I will probably also have to recalibrate my four other VCOs. Rolling Eyes

In any case, thanks for your help. It looks like I'm finally closing in on the problem.

--Adam
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jhaible



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PostPosted: Fri Nov 27, 2009 6:19 pm    Post subject: Re: Can't get 1V/oct adjusted correctly Reply with quote  Mark this post and the followings unread

studionebula wrote:

I think that the problem could also be due to the power supply in my modular cabinet. I measured it the other day and its voltages are a little bit high, e.g. about +15.2V. Is it possible that this could be the cause of the scaling problems?


No.

JH.

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dingebre



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PostPosted: Sat Nov 28, 2009 11:48 pm    Post subject: Doh! Reply with quote  Mark this post and the followings unread

I'd thought I'd share an maybe provoke a smile or two.

I hate trouble shooting. I triple check every resistor, orientation, solder joint, and wire. Despite my obsessive, neurotic behavior...

I got the first of two boards and panels wired. Putting it in a FracRack format requires very dense wiring and I have to be extra careful. I know I checked the pin-outs on my multi-turn "frequency" pots.

OK, I turn it on and nothing, then very funky, distorted saw and pulse waves, then nothing. Finally, I seemed to have a stable output, but I was not convinced. It crapped out again. The negative power was shorted on VCO-3. Then on VCO-1, then not. I was going nuts. I checked every wire, solder joint, orientation; I wiggled every wire and sometimes it would do it, sometimes not. I HATE trouble shooting.

Turns out I wired all the pots so that when the wiper was clockwise, it shorted the -15 supply to ground. As I was tweaking and twiddling, I'd randomly leave one or another pot close enough to shorting that just handling the module would cause it to short.

sheesh....

Back to serious discussion...

David

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studionebula



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PostPosted: Sun Nov 29, 2009 12:19 pm    Post subject: Tracking problem solved, I guess Reply with quote  Mark this post and the followings unread

David, if that mis-wiring error gets a "Doh!", try this on for size: I don't think that there was ever anything actually wrong with my module. I think it was all my error.

Over the past couple of days I completely disassembled the PCB from the panel and tested each oscillator individually, adding connections as I went. I also tested the master section separately. In the end I was able to properly set the 1V/Oct scaling for all three VCOs, with no changes to my original assembly.

So, why did I have such trouble in the first place? I'm not entirely sure, but I know of one actual mistake I made. When I bought the trimmer potentiometers, I used the Mouser part numbers from Dave's BOM. I didn't look closely at the description for them and somehow got it in my head that they were 10-turn units. They're actually 19-turn pots. I was starting my calibration by turning them to one extreme and then counting five turns to put them at the center of their range, or so I thought. Instead, obviously, I was putting them at about 25% of their range. The other difference between these pots and the Bourns pots I usually buy is that these don't make a subtle click when you reach one end or the other of their travel. Hence I was keeping track of the number of turns I'd made while attempting to calibrate the circuit, and after around five turns in either direction I assumed I'd reached the end of their useful rotation. This was a bad assumption, obviously; instead I was using only about half of their range.

That was just a silly mistake, obviously. I will say, though, that these VCOs seem more difficult to calibrate than the MOTM oscillators I've built. That's not a criticism--just an observation that another part of my problem was my own expectations and perhaps a small lack of patience. Rolling Eyes

So, thanks again, JH, for your answers to my queries because they helped me narrow the search for my (nonexistent) problem. I'll post a photo of the finished module soon, but first I want to finally bolt it into my cabinet and see how it sounds!

--Adam
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dingebre



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PostPosted: Sun Nov 29, 2009 3:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

ahh commiseration makes the brain freezes so much easier to endure Smile

I will only add that looking at a 20 Hz wave with DC coupling on a scope is not a good idea...

David

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PostPosted: Mon Nov 30, 2009 6:05 am    Post subject: Re: Doh! Reply with quote  Mark this post and the followings unread

dingebre wrote:
I got the first of two boards and panels wired. ....

.......
I HATE trouble shooting.
David


i got the second Module wired.
-------> Nothing ! Sad ( i have CV out of the Driver as far i could see yesterday very late )
Me too HATE Troubleshooting !


I wired with the first module as a reverence........guess must be a short somewhere.
To quote David onemore: "Back to serious discussion... " Laughing
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Funky40



Joined: Sep 24, 2005
Posts: 875
Location: Swiss
Audio files: 1
G2 patch files: 5

PostPosted: Mon Nov 30, 2009 11:39 am    Post subject: Reply with quote  Mark this post and the followings unread

success Very Happy
The wiring of the amp stages was mixed up.
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dingebre



Joined: Aug 10, 2008
Posts: 270
Location: Salt Lake City, UT USA

PostPosted: Fri Dec 04, 2009 11:32 pm    Post subject: Vibrato Depth Sensitivity Reply with quote  Mark this post and the followings unread

I've not seen this discussed, so I assume I have something wrong.

The vibrato depth is very sensitive. I see no effect on the scope (looking at the output of the driver) until about the 3:00 position. Then it increases very rapidly. If I put an open jack into VJK to break normaled ground, the control starts to show an effect at about 12:00 position, but still increases very rapidly.

I replaced the two transistors and the LM13600 (I tried an LM13700, too) and no change. I've checked the resistors (but may still have an incorrect one installed).

The pot wiring checks out. The emitters of Q23-Q22 gives an even sweep of voltage. The collector of Q22 saturates at -14.00 VDC at about 12:00 position of the pot then decreases as I turn it higher.

I'm not sure what the frequency span is supposed to be, but the rate seems to work fine.

Does anyone else see this behavior?

Any ideas where/what to check?

Thanks.
David

_________________
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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