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J.Haible's Living VCO for Eurorack [Build Thread]
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page Previous  1, 2, 3, 4, 5 ... 23, 24, 25  Next [all]
Author J.Haible's Living VCO for Eurorack [Build Thread]
Benjamin AM
I noticed an error on the Barcode PCBs. The FM and PWM inputs are connected incorrectly. Currently, the inputs are routed to the middle leg of the panel pot. It should be set up so the inputs are connected to the CW leg of the pots, the summing resistor is on the middle leg and ground is on the CCW leg. This way the pot functions as an attenuator rather than gain control(current setup).
Benjamin AM

This I s how I reworked the PCB without cutting any traces. For the PWM circuit, I unsoldered one side of R38(connected to CW leg of PWMPOT) and added a length of wire to route the loose side of the resistor to the pad labeled as "PWM". You will notice in the picture that I did this with green wire and used some white heat shrink for a little protection. Now R38 is connected to the middle leg of PWMPOT. The PWM input then has to move to the CW leg of the pot. I did this by wiring the PWM input jack directly to the board. Fortunately there are two holes for 9mm and 16mm accomidations. Simply use the free hole and wire directly to the input rather than using the normal connection(MTA header in photo). In the photo you might notice that I made this connection with yellow wire. As for the FM circuit, I used the same sequence. The only difference is that the FM summing resistor is R2. It should be re-routed to the "FM" pad and the input should be hard wired to the CW of FMPOT.
logicgate
@Benjamin

My fix was:

"Hey guys,

About the R39 fix:

It seems that the best way to find the correct value for your build is by using sockets at R39 and keep swapping resistors (between 820K and 1M) until you find the right for you, since the resistances of each build will be a bit different and the PW is very picky.


I say that because I used 820K on my other two LVCOs and found out that the square wave still disappears when PW pot is FCCW, so I guess I will need a higher value for the other two, but not much."
Benjamin AM
Yes, it was good advise. My value was for R39 would have been 2M without changing the overall gain of the summing circuit. I could have left it like that but I wanted the PWM input to be not as hot so I also changed the overall gain. I could have just adjusted R38 instead of R36 but there are more resistor value options when the overall summing gain is lowered. This worked well in all three of my VCOs.
Siri
For those having got the barcode pcbs, do we have to do the modifications benjamin just described?

And the "R39 fix"?

thanks,
Mindarp
I bought what I think are the right tempcos for this project, but mine are 1/4W. Is that all right? They aren't as beefy looking as some of the other builds I've seen. I'm assuming that others have used 1/2W.
sammy123
1/4 are what I'm using.
Mindarp
Thanks sammy123
sammy123
Actually I lied....mine are 1/8th. They are the kind Synthcube and Thonk sell.
sduck
There are several varieties of 1/4w tempcos - some look like big fat black things, some look like regular sized resistors. Either will work.
Siri
Siri wrote:
For those having got the barcode pcbs, do we have to do the modifications benjamin just described?

And the "R39 fix"?

thanks,


And also, what are the smt pads close to the R11 labelling for? I thought they would be for the smt version of the tempco but they don't look to be connected at the same place than the big R11 drawing?



EDIT : d'oh! Yes they are connected, it's for the tempco. w00t
qfactor
So is the SMT an alternative to using the through hole version (of the tempco)?
negativspace
Certainly appears that way. thumbs up
Randy
"After that, you can pretty much solder all the rest, besides the pots. I would start with the small capacitors, then the trimmers/pin headers for power and panel wiring/ big caps. You can see I used two film caps for C7 and C8, but you can also use Non-Polar Elecs. Actually, the original BOM of the Saw/Tri converter calls for them. I tested with both and I couldn't perceive any difference. "

The BOM doesn't mention the film/NP electrolytics here and the PCB markings hint the polystyrene looks like a film cap. Argh! I used film there and two normal MLCC caps for C7 and C8. Is it worth desoldering them?

Randy
Siri
correct me if i'm wrong... If I use the surface mount tempco, I should not use headers for the CA3046?
LeftyLogic
That's how I did it. SMT Tempco and no socket on the 3046. Although if you want better temperature stability you will probably want to put some kind of thermal goop in between the tempco and the IC, as they don't seem to make direct contact by themselves. (I'm not doing that on my builds though. In my opinion a bit of temperature drift is part of the charm.) hihi

Seth
latigid on
Many thanks for the BOMs:


J. HAIBLE'S OSCILLATOR DRIVER Barcode Edition v1.1
J. HAIBLE'S LIVING VCO CORE Barcode Edition v1.3


Do these take into account the fixes described above?
Phetus
Do the 550s and the 560s need to be matched?
Siri
LeftyLogic wrote:
That's how I did it. SMT Tempco and no socket on the 3046. Although if you want better temperature stability you will probably want to put some kind of thermal goop in between the tempco and the IC, as they don't seem to make direct contact by themselves. (I'm not doing that on my builds though. In my opinion a bit of temperature drift is part of the charm.) hihi

Seth


Thanks Seth!!

Phetus wrote:
Do the 550s and the 560s need to be matched?


I don't think so. Looking at these BOMs and J. Haible website and his own BOM, no mention of it, only mention of the matched resistors!
Phetus
Thanks! Just wanted to make sure i hadnt missed anything...
qfactor
In the version 1.3 Driver BOM, there's a 1M pot that was labelled as Log-based.
Can I use a Linear type instead? Any major issues if that's used? hmmm.....
Thanks
Randy
latigid on wrote:
Many thanks for the BOMs:


J. HAIBLE'S OSCILLATOR DRIVER Barcode Edition v1.1
J. HAIBLE'S LIVING VCO CORE Barcode Edition v1.3


Do these take into account the fixes described above?


Not from the versions I have, same as yours.

qfactor, where did you get a version 1.3 Driver BOM? On the version 1.1 I have, the 1M pot is linear.

Randy
Siri
@Randy

on this same thread, right here, where the latest BOMs are : https://www.muffwiggler.com/forum/viewtopic.php?p=1695437#1695437

When you download the driver BOM the title says V1.1 but if you go down down down you see "BOM revision 1.3" and if you go up again a little bit, on the 1M pot it says "1M Log Pot".

razz
Randy
Argh! I downloaded the originals and then didn't look around too much because I started sourcing components. Figured I'd go back through the thread but I wouldn't have re-downloaded the files because the titles where the same.

Suppose I better compare them, since I have already populated the boards. I wonder why the portamento pot needs to be log? I already ordered linear so I'll most likely just use that.

Thanks Siri.

Randy
qfactor
Yeah, I believe the differentiation would be that the later (updated?) BOM for the Driver has the "Total" component count column added to the list. The older one doesn't.
And yes, I'm confused too as far as which version this BOM really is! d'oh! because it's stated "1.1" at the top and "1.3" in finer print, at the bottom!! eek! . So just decided to call it the later version, like the BOM for the LVCOs seriously, i just don't get it

But I guess it wouldn't do too much "damage" to swap a Lin with a Log pot, eh?
confused
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