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

gadgadasvara · Post by **gadgadasvara** » Thu Jun 14, 2018 10:06 am

thank you for the quick response.
i did follow the silkscreen on my board, as you can see in my picture. but still no luck..any suggestion things that i should check with the multimeter?

oh, i'm using 1/4W 5% tolerance resistor, but when i check all the 100K resistor value with multimeter, it seems lower than 5%, the value can go as low as 68-70K.. do you think that can be the source of the problem..?

thanks.

ViSrop · Post by **ViSrop** » Tue Jul 17, 2018 3:03 pm

Hello, I usually find my answer in posts but I need help because of my beginner level in electronics.

I am not sure of my BOM, I took that of "Makers" BOM as an example but some components like "1KTC SMT" and ".1uF Ceramic" are obsolete and the "22pF Ceramic" is not recommended?
Can someone help me to find alternatives please?

And if a good soul feels the strength to check all my BOM I would be forever grateful

.

https://www.mouser.be/ProjectManager/Pr ... 521E2DA834

Thanks!

ovian · Post by **ovian** » Sun Sep 02, 2018 11:03 am

The closest I can find to match the now obsolete (667-ERA-S33J102V) mouser part given for the 1KTC SMT have a temperature coefficient of 3900 ppm or 4100 ppm verses the 3300 ppm of the original part given. Will the difference in temperature coefficient make any difference in operation? Do i need to find a part with the same 3300 ppm coefficient of the original?

Also if anyone has a part number for a smt tempco that fit the specs needed I would be eternal grateful.

thanks for the help.

negativspace · Post by **negativspace** » Tue Sep 04, 2018 8:04 am

Unfortunately I can't find SMT tempcos anymore, really... as for whether or not a ~3900ppm part is better than a 50-100ppm standard resistor, I'd guess so but it's just a guess.

I'm down to a couple of the tempcos, I need to work out an alternative myself.

ViSrop wrote: I am not sure of my BOM, I took that of "Makers" BOM as an example but some components like "1KTC SMT" and ".1uF Ceramic" are obsolete and the "22pF Ceramic" is not recommended?
Can someone help me to find alternatives please?

Go ahead and order the ones that are "not recommended" if they're in stock. That just means they're slated to be discontinued or at least no longer stocked, so you shouldn't plan to use them going forward in new designs.

Any 0.1uF ceramic will work, there's plenty of other options there. (Same goes for the 22pF.)

pulsepsycle · Post by **pulsepsycle** » Tue Sep 11, 2018 11:21 pm

Can I use a LME49720 instead of a LME49710. They seem nearly identical. Here in Holland I can only find the LME49720.

Karel

Jarno · Post by **Jarno** » Wed Sep 12, 2018 3:31 am

LME49720 is a dual and LME49710 is a single opamp, they are not interchangeable. Use TL071, I doubt it makes a difference.

negativspace · Post by **negativspace** » Wed Sep 12, 2018 11:20 am

^ Correct.

pulsepsycle · Post by **pulsepsycle** » Wed Sep 12, 2018 9:52 pm

Read the manual is what they say. And indeed! Thanks for pointing out. I've some other single opamps. I'll try those.

Phaedrus · Post by **Phaedrus** » Mon Oct 01, 2018 2:01 pm

negativspace wrote:I'm not sure I've seen a Mouser BOM posted for it, but let me know which parts you're having trouble finding and I'll dig up numbers for you.

Hi man. And thank you very much for repplying some time ago!
Im almost there with getting the components for making two VCAs, using the Mouser BOM that ViSrop posted on Jul 17, 2018.

(So thanks a lot ViSrop

)

I only need the 1KTC SMT's now. What Ive found closest to, as far as my limited knowledge goes, is this one:
https://www.mouser.dk/ProductDetail/279-RP73PF1E1K0BTDF

Can you or anyone else confirm that this will work?

Cheers.

woodster · Post by **woodster** » Tue Oct 02, 2018 2:02 pm

That is an 0402 sized one, I think it needs to be 0805 to fit the PCB ( I might be wrong there, it's been a while since I built mine)
0402 is tiny.

synthcube · Post by **synthcube** » Tue Oct 02, 2018 2:04 pm

we use this one in kits:

71-TFPT1206L1001FM

Phaedrus · Post by **Phaedrus** » Wed Oct 03, 2018 5:37 pm

I LOVE MW! - thank you guys.

The help is greatly appreaciated!

Ill get ordering some of those 1001's, then. :-)

Bartimaeus · Post by **Bartimaeus** » Wed Oct 03, 2018 8:57 pm

Bartimaeus wrote:I recently built a MA VCA. While the unit sounds good, it is SIGNIFICANTLY quieter than my other VCA's. I calibrated precisely (within <1mV) to the values listed in the manual, and while the response is good, it's really low volume.

Before I go swapping any resistors, does anyone have any advice? Should I have used a 10v Zener instead of a 5.1V?

More than a year later I gave it a look over and realized I used a 33K resistor in place of the 330R resistor

ghostfields · Post by **ghostfields** » Sat Feb 20, 2021 8:20 pm

polyot wrote: ↑
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

It turned out to be human error after all. No matter how sure you are, always recheck your parts.

what did your problem end up being? I just built one of these and have a similar situation, passes audio thru and offset works, was able to calibrate it fine but neither cv input does anything

MUFF WIGGLER

MUFF WIGGLER

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

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