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 Forum index » DIY Hardware and Software
Jurgen's Bergfors VCA build - DIY beginner needs help
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jurekprzezdziecki



Joined: Mar 22, 2016
Posts: 68
Location: warsaw

PostPosted: Tue May 10, 2016 1:55 am    Post subject: Jurgen's Bergfors VCA build - DIY beginner needs help Reply with quote  Mark this post and the followings unread

guys,

i have found a single VCA circuit which is Jurgen's Bergfors design.
it looks simple and sounds very good as a description says.

http://hem.bredband.net/bersyn/VCA/lm13600%20vca%202.htm

i have put this into Eagle for further PCB design. i would ask you to check if i made some mistakes - it's my first schematics in Eagle... so it was hard;Smile

there is no voltage values on the original schematics so i put +/-12V.
i have used LM13600 as an original but i know that 13700 could be used as well.
ther are power rails outside the IC - i don't know what voltage shoud be used - i put bipolar +/-12V as well.

also... this circuit uses only a half of LM13600 - so what to do with a second part of the LM13600? it's just unconnected? should be grounded?

i have chosen a standard 3,5 mm mono jacks... just for something on the PCB. i think the best would solder them with wires to the board separately.

when all errors will be removed i will put it on breadboard:)


LM13600 Bergfotron VCA 2.png
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AlanP



Joined: Mar 11, 2014
Posts: 746
Location: New Zealand
Audio files: 41

PostPosted: Tue May 10, 2016 2:08 am    Post subject: Re: Jurgen's Bergfors VCA build - DIY beginner needs help Reply with quote  Mark this post and the followings unread

jurekprzezdziecki wrote:

also... this circuit uses only a half of LM13600 - so what to do with a second part of the LM13600? it's just unconnected? should be grounded?


I'd say use the second half for a second VCA Smile
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jurekprzezdziecki



Joined: Mar 22, 2016
Posts: 68
Location: warsaw

PostPosted: Tue May 10, 2016 2:10 am    Post subject: Re: Jurgen's Bergfors VCA build - DIY beginner needs help Reply with quote  Mark this post and the followings unread

AlanP wrote:
jurekprzezdziecki wrote:

also... this circuit uses only a half of LM13600 - so what to do with a second part of the LM13600? it's just unconnected? should be grounded?


I'd say use the second half for a second VCA Smile


thanks for your replay. i don't want to make it to complex, it's my first project Smile
do you mean to make a second channel of this VCA?
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LFLab



Joined: Dec 17, 2009
Posts: 497
Location: Rosmalen, Netherlands

PostPosted: Tue May 10, 2016 6:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Nope, a second VCA (was my suggestion on Muffs as well Very Happy ).
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wackelpeter



Joined: May 05, 2013
Posts: 461
Location: germany
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PostPosted: Tue May 10, 2016 6:25 am    Post subject: Reply with quote  Mark this post and the followings unread

i'm not sure if i did build it correct or wrong nearly 2 years ago, but i wasn't able to mute the signal totally... it was almost present and with some CV it got amplified more...

maybe try this on breadboard first... i've exchanged mine with 2 others VCA's...

But as i said, i'm not sure if i did some mistake, as these where some of my earlier modules and now the stripboards are plundered...

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jurekprzezdziecki



Joined: Mar 22, 2016
Posts: 68
Location: warsaw

PostPosted: Tue May 10, 2016 6:43 am    Post subject: Reply with quote  Mark this post and the followings unread

LFLab wrote:
Nope, a second VCA (was my suggestion on Muffs as well Very Happy ).


got it:)) just reading!
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jurekprzezdziecki



Joined: Mar 22, 2016
Posts: 68
Location: warsaw

PostPosted: Tue May 10, 2016 6:44 am    Post subject: Reply with quote  Mark this post and the followings unread

wackelpeter wrote:
i'm not sure if i did build it correct or wrong nearly 2 years ago, but i wasn't able to mute the signal totally... it was almost present and with some CV it got amplified more...

maybe try this on breadboard first... i've exchanged mine with 2 others VCA's...

But as i said, i'm not sure if i did some mistake, as these where some of my earlier modules and now the stripboards are plundered...


thanks! i will test it on breadboard first for sure.
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jurekprzezdziecki



Joined: Mar 22, 2016
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Location: warsaw

PostPosted: Wed May 11, 2016 8:04 am    Post subject: Reply with quote  Mark this post and the followings unread

just showing a progress with the project Cool

i have changed the schematics a lot for a better legibility and added a PSU sub circuit with supply coupling. so next thing is to put it on the breadboard!

thanks a lot guys! especially Jarnos (LFLab)Smile


LM13600 VCA2 Bergfotron rev.5 final.png
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steved



Joined: Oct 07, 2015
Posts: 18
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PostPosted: Wed May 11, 2016 8:21 am    Post subject: Reply with quote  Mark this post and the followings unread

i built Bergfors VCA -1 (basically the same VCA )

( http://hem.bredband.net/bersyn/VCA/lm13600%20vca%201.htm )


i don't have any issue with totally muting the signal.

I have made two of these and am able to tune the CV offset / offset to get great results.

I am new to electronics..but i like to experiment - i left the second half of the 13700 disconnected for simplicity and everything sounds great.

I made my PCB using Fritzing - wish i used eagle.

good luck!
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jurekprzezdziecki



Joined: Mar 22, 2016
Posts: 68
Location: warsaw

PostPosted: Wed May 11, 2016 12:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

steved wrote:
i built Bergfors VCA -1 (basically the same VCA )

( http://hem.bredband.net/bersyn/VCA/lm13600%20vca%201.htm )


i don't have any issue with totally muting the signal.

I have made two of these and am able to tune the CV offset / offset to get great results.

I am new to electronics..but i like to experiment - i left the second half of the 13700 disconnected for simplicity and everything sounds great.

I made my PCB using Fritzing - wish i used eagle.

good luck!



thanks a lot for the reply. i new t electronics as well, it is my first project actually. i leave a second half of 13600 unconnected as well but if everything will be ok i will make a second channel of VCA.

you said 13700 - so you change the IC? i know they are similar but there is a difference, right? can i change them as well with no consequences?

can i import eagle schematics to Fritzing?
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steved



Joined: Oct 07, 2015
Posts: 18
Location: usa

PostPosted: Thu May 12, 2016 8:36 am    Post subject: Reply with quote  Mark this post and the followings unread

yes i used 13700 not 13600.
there is a difference, i think it is something with the bias current, but from what i read it doesn't make a difference in most circuits.
I could be wrong.
I use 13700 in VCF and VCA without any issue. 13700 was stocked on mouser but no 13600

i dont think you want to go from Eagle to Fritzing -
Fritzing is real easy to learn and start with, and easy to outgrow.

hope this is helpful - like i said, i am new and don't really know what i am doing ha
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LFLab



Joined: Dec 17, 2009
Posts: 497
Location: Rosmalen, Netherlands

PostPosted: Thu May 12, 2016 11:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Oh yeah, stick with Eagle for sure, it's a learning curve for sure, but totally worth it if you are progressing into more complicated circuits.

I've never used 13600 myself, I think, but they should be interchangeable (13600 is a slightly lower spec, could indeed be the bias current Steve mentioned).
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jurekprzezdziecki



Joined: Mar 22, 2016
Posts: 68
Location: warsaw

PostPosted: Fri May 13, 2016 5:47 am    Post subject: Reply with quote  Mark this post and the followings unread

ok, so i will try to change the op amp just on the breadboard, let's see.
yes, eagle is very complex.. overhelming in some way but it's great indeed.
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jurekprzezdziecki



Joined: Mar 22, 2016
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Location: warsaw

PostPosted: Fri May 13, 2016 5:50 am    Post subject: Reply with quote  Mark this post and the followings unread

last thing - the pots used in the project should be logarithmic, right? not linear?
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jurekprzezdziecki



Joined: Mar 22, 2016
Posts: 68
Location: warsaw

PostPosted: Sun Jun 05, 2016 11:07 am    Post subject: Reply with quote  Mark this post and the followings unread

hi guys,

i have build the VCA on breadboard and after some troubles works good.
the only problem is CV modulation. i can't get it work as expected.

the problem is, that a pot (R7) responsible for allows CV modulation only when full down (counterclockwise position). it's not working with any range. every step clockwise gets signal input cut / mute completely.

i don't know how to fix it.

any advices?

i have attached the final schematics - please look

[img][/img]


LM13600 VCA2 Bergfotron rev.7.png
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steved



Joined: Oct 07, 2015
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PostPosted: Mon Jun 06, 2016 4:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

what are you feeding it for CV?


(i dont know if this is the right way to do it, but)

i tune mine in like this:

I send the envelope in to the cv input alone, and turn the cv offset to the point where i can not hear any pop when i hit play a note.

I next plug in my audio and turn it up until it starts to bleed with out CV input.
then i play with the two knobs until it works just right.
For me i run at +-12 v..
ill try and link my version of the schematic.. looks same as yours i think..

hope this helps. you may want to build one of the single transistor VCAs along with this so you can play around more!

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