[IN STOCK] Eurorack 4hp THAT2180-based Audio VCA

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polyot
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Post by polyot » Sun Mar 22, 2015 9:12 pm

jflower wrote:I have troubleshot everything up until the 2180. I have a new 2180 that showed up a last week or so, but I haven't brought myself to de-solder the one on the board. I am seeing all the right voltages at the 2180.

jf
Bummer. That's about where I'm at. I really don't think I need to replace my 2180. I keep trying to follow the schematic and tracing voltages throughtout but I'm not getting anywhere. Already swapped out the TL074 since that seems to be what the CV hits, but nada. I don't have another of the smaller IC to test but that seems fine as well. Having built several much more complicated DIY modules without little to no issue, it's quite frustrating to get tripped up on a little 4HP one. :bang:

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Nantonos
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Post by Nantonos » Mon Mar 23, 2015 2:27 am

polyot wrote: Mine passes audio straight through to the output, with no effect of the offset or CV.
That seems to imply that:
- the 2180 works and is getting power
- the post-2180 current to voltage op-amp works and is gettig power
- there is no CV getting to the 2180 so it has unity gain.

From the 2180 datasheet:
If pin 2 (Ec+) and pin 3 (Ec-) are held at ground, the output current will equal the input current.
ondes | current rack
I am afraid a firmware change will not be able to turn a rather expensive 16-bit DAC into a 16-bit ADC, and flip all those op-amps :)

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cane creek
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Post by cane creek » Mon Mar 23, 2015 2:45 am

negativspace wrote:Oh boy, that's a task... I haven't done the Drummer but I've put together a few MSUs and a WCMS. (Never again... lovely module, but holy crap. :doh: )

Image
What module is that ?

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polyot
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Post by polyot » Mon Mar 23, 2015 10:25 am

Nantonos wrote:
polyot wrote: Mine passes audio straight through to the output, with no effect of the offset or CV.
That seems to imply that:
- the 2180 works and is getting power
- the post-2180 current to voltage op-amp works and is gettig power
- there is no CV getting to the 2180 so it has unity gain.

From the 2180 datasheet:
If pin 2 (Ec+) and pin 3 (Ec-) are held at ground, the output current will equal the input current.
Hmm. I'll double check when I get home but I'm fairly certain pins 2 and 3 measured at 0, which seems to confirm the above. So I'll have to trace from there and see where those go. Or could this still mean something could be wrong with my 2180?


Edit: NEVERMIND

:doh: It turned out to be human error after all. No matter how sure you are, always recheck your parts.
Last edited by polyot on Mon Mar 23, 2015 6:25 pm, edited 2 times in total.

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negativspace
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Post by negativspace » Mon Mar 23, 2015 10:37 am

cane creek wrote: What module is that ?
That's one of Clarke's West Coast Mini Synth panels.

arneborgan
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noob, TP and ground

Post by arneborgan » Mon Apr 27, 2015 9:47 am

Hi
Where I can find a ground point for the probing with TP?
thank you
a

jflower
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Post by jflower » Mon Apr 27, 2015 1:52 pm

I used one of the diodes near the power entry for ground.

Also, for the sake of closure, my build was plagued with a sketchy solder joint on the output wire. I think some of the wire insulation got messed up in the joint. Probing showed a connection to the jack since I was testing the wire, not the pad.

I also reseated the output opamp at the same time, but I'm fairly certain that had nothing to do with it. Time to build my next two!

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Post by arneborgan » Mon Apr 27, 2015 2:49 pm

Thank you
I ended up using the grounding on the jack inputs.

a

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antf4rm
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Post by antf4rm » Tue Jun 30, 2015 6:49 pm

This is an excellent sounding clean vca! And the overdrive potential is awesome. If you "uncalibrate" it, you can get a sweet overdrive sound.

:nana:

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negativspace
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Post by negativspace » Tue Jun 30, 2015 10:53 pm

Indeed! It exhibits... aggressive behavior when provoked. :hihi:

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woodster
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Post by woodster » Wed Jul 01, 2015 4:49 am

Interesting, I forgot about that trimming possibility.
I'll have to get some more then :hihi:
Last edited by woodster on Wed Jul 01, 2015 5:03 am, edited 1 time in total.

4floorsofwhores
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Post by 4floorsofwhores » Wed Jul 01, 2015 4:53 am

2 pcbs please with uk shipping
Careful now

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negativspace
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Post by negativspace » Wed Jul 01, 2015 1:44 pm

woodster wrote:Interesting, I forgot about that trimming possibility.
I'll have to get some more then :hihi:
:party:

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colorbars
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Post by colorbars » Tue Jul 07, 2015 11:05 pm

I built one a few months ago, plugged it in long enough to make sure it worked but it wasn't until today that I put it in my case and started using it. I'm getting something strange happening now that it's in case... Upon turning the power on (synthrotek 5A) the power drops out immediately then pops back on a second later. I disconnect the VCA from the bus and it turns on as normal. This is with no patch cords plugged in and it may be worth mentioning I have not done any calibration of the VCA. Any help would be appreciated. Everything seems to work ok, but the power drop upon turning the system on concerns me.

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negativspace
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Post by negativspace » Wed Jul 08, 2015 1:33 pm

That's a strange one... is it only the VCA that causes the drop? i.e. if you leave the VCA in but pull another module, does the behavior go away? It could be that the VCA is simply the difference between the supply being stressed and not.

Kinda grasping at straws here... if that's not obvious.

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flyingMono
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Post by flyingMono » Tue Sep 01, 2015 8:25 pm

Can anyone give me a part number to search for the potentiometers? I'm coming up blank...

never mind, found em.

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e.vil
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Post by e.vil » Sun Nov 01, 2015 11:48 am

honorable sirs.
are these multi-or single turn trimpots you are using?
and does it matter?

thank you

yours greatfully

chronic noob.

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humax5600
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Post by humax5600 » Sun Nov 01, 2015 12:39 pm

This one will do the job :
Specification 25 speeds

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e.vil
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Post by e.vil » Sun Nov 01, 2015 3:20 pm

humax5600 wrote:This one will do the job :
Specification 25 speeds

Oh god! yes!! thanks man!!! :hail:

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e.vil
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Post by e.vil » Mon Nov 30, 2015 12:18 am

good sirs.

I don't know if I am splitting hairs here.
But the beads i bought this time are bigger than the ones I got last time I bought ferrite beads. I had just taken a bom from somone else that time, but now I am sourcing everything myself proper.
Maybe it was a good thing so that I wouldo look them up and read about them and what they do.

I am just wondering.
should I buy new smaller beads or should I just use the ones I got? Will it make that big of a difference?

the ones I have now are
EMI Noise Filter Ferrite Axial, 60 Ohm @ 10 MHz

while the ones I have had l befor were half the size and i don't really know the specs of them

in advance, thank you guys for the help.

Image

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Neutron7
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Post by Neutron7 » Mon Nov 30, 2015 12:26 am

it is hard to know without the original ones, they could be bigger because they have a higher value, or because they are rated for higher current. i would not worry about it though.

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negativspace
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Post by negativspace » Mon Nov 30, 2015 12:57 am

Nah, that's fine. Doesn't have to be elegant, just has to fit. :hihi:

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e.vil
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Post by e.vil » Mon Nov 30, 2015 1:40 am

awesome! thank you guys :yay:

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zrknlzr
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Post by zrknlzr » Sun Dec 13, 2015 5:32 pm

hey folks,
i got a VCA Kit from thonk. The PCB 1.3 version.
Had no issue building it but got problems when trying to trim it.
The testpoint is on 2.39V and won't change at all when i adjust the zero trimpot.
How should i approach this problem?
▒▒ Euro, Serge, TTSH, Lunetta ▒▒

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negativspace
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Post by negativspace » Tue Dec 15, 2015 7:16 am

Definitely not right, you should only see a few hundred millivolts there. Does the voltage at the test point change as you turn the offset pot?

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