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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]
LeftyLogic
sammy123 wrote:
So has anyone been able to squeeze precision pots for the frequency? I have been looking and the smallest i see are about 3/4" at the base. Probably too tight to wire in place of a pcb mounted 9mm alpha with Barcodes panel. It would be nice though because the tuning on this is tough...not that it needs to be perfect, but small adjustments are difficult.

I'm not sure about Barcode's panel, but I did some measurements on my design, and it looks like there should be room for 10-turn pots that are up to 7/8" in diameter! (assuming that the other pots are 16mm instead of 9mm)

Seth
thetwlo
CJ i'll sort that for ya. you solder my smt caps i buy you caps? silly less than a dime. fuck it, happy to send caps to cj anyway, pm me your addy.
sammy123
LeftyLogic do you have source for 10 turns that size?
LeftyLogic
sammy123 wrote:
LeftyLogic do you have source for 10 turns that size?

7/8" seems to be a pretty standard size for 10-turn pots, and it looks like jameco carries them for pretty cheap: http://www.jameco.com/1/1/50319-3540s-1-103-vp-3540-wirewound-potentio meter-ohms-10-k.html

I'm thinking I might have to grab a few at some point for one of my builds! It's peanut butter jelly time!
Zaibach
After weeks of sourcing parts and building, my twin Living VCOs are finally complete! It's just beautiful... I owe Jurgen Haible and everyone involved big time! thumbs up I have to give Logicgate credit for my panel design and for the choice of knobs, which I more or less 'copied' because I liked it. I was not tight on space, since I started a new rack, so I just made use of two 42HP Doepfer blind panels. It's not perfect (the writing and symbols are not quite aligned right) but anyway, sounds great. I even 'crafted' a mixer (switchable between 8 inputs/2 outputs or 4 inputs/1 output each) especially for these.

I used single-turn pots for frequency, and I've got to say that it is quite possible to tune the three oscilltors to unison without too much trouble, but it is a bit unnerving sometimes, because you touch one knob accidently and you have to tune again. I was thinking about multiturns but I was tight on money. If I would build it again, I would definitely use multiturns...

qfactor
fuzzbass wrote:
re ca3046 ... I have twice obtained them from ebay seller iseetheworld and in both cases received good OEM Harris chips. They are working in my TTSH. As with all ebay transactions, you take a risk. But this was my experience.

Treat these chips with care, they are fragile and especially heat sensitive. Socket them.


Just got a bunch of these (10, in fact) from this ebayer, as you've suggested!
Got them in record time, for US$17
Now, hopefully they all turn out real!! eek!
But since you've gotten them twice from him before, should be "safe", eh?! d'oh!
Mindarp
I have a pile of bc558 and bc548. Will these work ok with this build?
LED-man
Zaibach wrote:
After weeks of sourcing parts and building, my twin Living VCOs are finally complete! It's just beautiful... I owe Jurgen Haible and everyone involved big time! thumbs up I have to give Logicgate credit for my panel design and for the choice of knobs, which I more or less 'copied' because I liked it. I was not tight on space, since I started a new rack, so I just made use of two 42HP Doepfer blind panels. It's not perfect (the writing and symbols are not quite aligned right) but anyway, sounds great. I even 'crafted' a mixer (switchable between 8 inputs/2 outputs or 4 inputs/1 output each) especially for these.

I used single-turn pots for frequency, and I've got to say that it is quite possible to tune the three oscilltors to unison without too much trouble, but it is a bit unnerving sometimes, because you touch one knob accidently and you have to tune again. I was thinking about multiturns but I was tight on money. If I would build it again, I would definitely use multiturns...




from where you get the TRI/SIN signal ?
Zaibach
Quote:

from where you get the TRI/SIN signal ?


The Tri to Sine converter is on the driver pcb. So you have to wire a triangle out from the LVCO to the panel, as well as to the converter on the driver pcb, and then the resulting sine back to the panel.
Randy
I'm having a bit of trouble finding the 100nf SMT 0504 caps. There seems to be all sorts of 100nf caps and different sizes but that combination seems to be tricky. And I'm not that familiar with SMT/SMD stuff, which doesn't help.

Anyone aware of a seller on eBay that might have these, or which part number on Mouser would work?

Thanks

Randy
bsmith
typo - use 0805... I ran into this earlier in the thread too..
https://www.muffwiggler.com/forum/viewtopic.php?p=1698136#1698136
Randy
bsmith wrote:
typo - use 0805... I ran into this earlier in the thread too..
https://www.muffwiggler.com/forum/viewtopic.php?p=1698136#1698136


I went through the thread and of course missed that! Thanks.

Randy
bsmith
and if you are wanting to go the smt route for the tempco....
http://www.mouser.com/ProductDetail/Panasonic/ERA-S33J102V/?qs=%2fha2p yFaduiamcDwRD0o%252bQMOomQv6GK8d7nJwl%252bk7XjidcJ1MaHlKg%3d%3d
qfactor
Tayda sells the 100nF SMDs too at 1 cent a piece! thumbs up
Part #: A-3511
Benjamin AM
Sorry to bring this up so late in the game. I found that the Barcode BOM v1.3 had some values that did not work my build. I feel I should share my experience in case anyone out there has had the same issue. In regards to the PWM section of the circuit, resistors R39 and R36 were troublesome for me. I came to this conclusion because I felt that the PWM wasn't working as advertised because the pulse wave was cutting out even before full CW and CCW. This circuit is not supposed to be like this. The diodes are supposed to protect the pulse from completely shutting off. This means to me that the gain and bias on the transistor at the summing stage of the PWM circuit is to high. So all that I did to change this was return R36's value to the suggested value by Haible(750k opposed to the Barcode BOM 1.5M). Then the PWM mixer resistor(R39) back to the original value 1M, instead of Barcode BOM value(510k). I also found it nice to return one of the biasing resistors(R33) back to original value 20k. Now all is good for me.
R33=20k
R39=1M
R36=750k
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.
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