VCA (NLC) XMIX EFM PCB

vladosh · Posted: Wed Mar 30, 2016 8:58 am Post subject: VCA (NLC) XMIX EFM PCB

This is Xmix and VCA from CellF NLC schematic , prolly the same Sims VCA posted here , in aaddition to the vca i added the xmix 2 channel mixer from wildcat from EFM , pcb is tested and working , should work prolly better on 12V and the VCA performance is so-so ..comparing to other VCA's i've built , so i don't know why i share it when it's not the best vca , i built it so here it is

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Ayab · Joined: Oct 27, 2015 Posts: 186 Location: London, UK

Hi,

Can anyone help me identify the IC's on this layout? Itching to get etching!

I have looked at the schematics referred to but they are the basis from which Vladosh has tailored the circuit himself.

Are these LM13700 and TL074?

Thanks for your help Very Happy

vladosh · Posted: Thu May 24, 2018 12:49 pm Post subject:

yes the IC facing down is TL074 ,i've built this VCA but was not so happy with it ,there were some clicking ,maybe because it was designed for 12V and i used 15V ,it's working but i like MFOS vcas better

Ayab · Joined: Oct 27, 2015 Posts: 186 Location: London, UK

Hello and thanks so much for getting back to me.

I have etched an MFOS dual VCA and will be populating it soon.

Do you have a simple way to make it into a Xfader?

Thank you also for your very interesting Synthhacks blog Very Happy

vladosh · Posted: Fri May 25, 2018 12:45 am Post subject:

i don't know how to convert it into fader ,you can find a xfade pcb layout on my blog but i'm not sure if i can recommend you that one ,i built it and it was working but there was minor bleed trough that was annoying ,maybe cause i made the vactrols myself .good luck with building

Ayab · Joined: Oct 27, 2015 Posts: 186 Location: London, UK

Hi - Thank you Smile

Will have a look for the Xfader on your blog. If I expect some bleed through it will be ok.

cslammy · Posted: Wed Jun 13, 2018 10:10 am Post subject:

For adding crossfade, The EFM crossfader may work, out of the wildcat. I haven't tried to build this but the circuit looks simple enough.

http://www.modular.fonik.de/files/EFMforum/orgEFMfiles/wildcat_001.pdf

Scroll down to Cross mix-inverter.

Ayab · Joined: Oct 27, 2015 Posts: 186 Location: London, UK

Thanks for the tip having a look at Fonik link now. Looks good, nice and simple from the parts layout. But there is no schematic or foil layout. Do you know where I can find one pls?

cslammy · Posted: Fri Jun 15, 2018 8:48 am Post subject:

cslammy

Hi again, I whipped up an eagle design for this.

As I said, it's not tested, but this is one of those "I can't see why it won't work" situations.

The ZIP file contains eagle 9.x brd and schem and the gerbers.

If anyone actually prints up the gerbers let me know if it works and I can make adjustments. I may run this the next time I do an easyeda run (it'd be $5 for 10 boards...) and if I get it working I'll post.

About the quickee layout: The xfade pot is 50K linear and to make this faster to conjure up in eagle I used a trimmer package, but you won't want to use a trimmer in real life, instead please solder your 3 pot wires to there (or you could wire in a VCA that passes DC if you want to "automate" this).

I could also do an eagle variation that uses a PCB mounted pot (you can get these cheap from small bear but it assumes certain front panel space requirements that may not work for you) if there is interest.

I image all the 47K resistors and 50K can be any value but should all be matched to at least 2% or better except the pot. Just a guess.

traces-wilcat xfade board 6-15-18.PNG

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schem-wildcat xfade 6-15-18.PNG

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EFMxfader-6-15-18take2.zip

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Ayab · Joined: Oct 27, 2015 Posts: 186 Location: London, UK

Wow that is great thank you Very Happy

Will try a home double sided etch for first time! : )

cslammy · Posted: Sat Jun 16, 2018 4:57 am Post subject:

No need for two sided ayab, I redid for single side. (I never had much luck fabbing 2 sided by myself....)

I include eagle sch and brd files.

Let us know how it goes! Very Happy

board xfade single sided.PNG

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EFMxfade-6-16-18 eagle single layer.zip

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brd and sch Eagle 9.x files for single sided xfade board. Based on EFM wildcat crossfader. Untested.

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Ayab · Joined: Oct 27, 2015 Posts: 186 Location: London, UK

Just seen this. You rock thank you Very Happy

gabbagabi · Posted: Sat Jun 30, 2018 4:46 am Post subject:

if anyone is interested-
and noone find an error-
ill pdf-it

regarding your schematic R2 must be higher in my opinion,
if u feed in two 10Vpp signals, u will get only 5Vpp signal out

after simulation i would suggest to try a value of 120k to 135K (two 270k parallel) then u get out a signal that is slightly under 10Vpp when the fader is full on one side, and slightly over 10Vpp in the middle

if u use all 100k, what i would do, this value is then of course 240k to 270k

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gabbagabi · Posted: Sat Jun 30, 2018 5:41 am Post subject:

and with this u should not have to worry about over/under shooting signals
beside the lower partcount

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Ayab · Joined: Oct 27, 2015 Posts: 186 Location: London, UK

Yes I would like to try and make the g.gabbi crossfader, thank you g.gabbi!

I will be running the Xfader on +/-12V do you think those resistor values would be ok?

gabbagabi · Posted: Tue Jul 03, 2018 8:50 am Post subject:

that means u try out my idea? and report back if it is working? and then i make a little pcb for it?

or u will try out the pcb of the efm xFader?

both will run smoothly on 12V.

Ayab · Joined: Oct 27, 2015 Posts: 186 Location: London, UK

I can try out both. I think crossfading is a useful functionality.

And yes I will let you know how it goes. Thank you.

gabbagabi · Posted: Wed Jul 04, 2018 10:31 am Post subject:

so i send you this,

please make double shure that i have done the mirroring right.
otherwise u could face problems with soldering the tl072. which is the reason why i use normally tl074, there it does not matter Smile

good luck,
would be a pleasure to have done something usefull

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xfader_part place.pdf

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