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 Forum index » DIY Hardware and Software » YuSynth
Problem with the EMS Filter
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aka.kike1



Joined: Aug 06, 2014
Posts: 11
Location: croatia

PostPosted: Sat Mar 14, 2015 2:09 pm    Post subject: Problem with the EMS Filter
Subject description: Frequency pot doesn't work
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Hi everyone

I have build ems filter (discrete version).

The filter worked fine, i needed to change the value of R41 to 220K. i trimmed it and everything was OK,

Next time when i powered the synth the frequency pot didn't work.
Everything is going trough the filter, when i play with resonance pot i hear
slight difference?

What it could be?

Maybe the CA3046?
I had spare TL074 and replaced it, nothing happen.

Can anyone offer something i could try, I have already ordered new CA3046.
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Sebo



Joined: Apr 27, 2007
Posts: 542
Location: Argentina

PostPosted: Sun Mar 22, 2015 6:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

I had the same problem. I built my EMS VCF a few years back, after deal with the resonance and input overdrive problems the filter stops working. The cutoff pot only works between 50 and 200 Hz. After a long time I finally get the time to look at it. I changed the CA3040 and the filter start working again, but after a month or so it fails again...
Now I'm trying to figure what's wrong in the circuit, and why the CA3046 stops working...

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aka.kike1



Joined: Aug 06, 2014
Posts: 11
Location: croatia

PostPosted: Mon Mar 23, 2015 1:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank you Sebo for the reply, I think mine stopped working when i plug in the velocity from my mididac into resonance cv input but i don't know for sure. Maybe it didn't work before that, who knows!?
I had bought the cheapest CA3046 from ebay, so now I have ordered Intersil.
I will change it and see will it work and how much.
I will post on that.
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Snaper



Joined: Feb 28, 2014
Posts: 135
Location: Hungary

PostPosted: Mon Mar 30, 2015 7:08 am    Post subject: Reply with quote  Mark this post and the followings unread

Sorry about hijacking your thread, but have a question about the freq pot, so I decided not to create a new one for it.
I've finished my lovely EMS, with the suggested (in the Yusynth-Euro thread) +-12V mods.
After applying the "680k - to 220k" mod , the resonance is here Very Happy
But.
The freq pot is still a bit "odd".

I've recorded a sample :

https://soundcloud.com/encoder909/ems

Basically I'm just tweaking the freq pot. As you can here, it react slowly for the fast movements (end of the recording) and seems that something wrong with it. there is no, erghm..."true lowpass" here?
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Snaper



Joined: Feb 28, 2014
Posts: 135
Location: Hungary

PostPosted: Tue Mar 31, 2015 12:08 am    Post subject: Reply with quote  Mark this post and the followings unread

Snaper wrote:
Sorry about hijacking your thread, but have a question about the freq pot, so I decided not to create a new one for it.
I've finished my lovely EMS, with the suggested (in the Yusynth-Euro thread) +-12V mods.
After applying the "680k - to 220k" mod , the resonance is here Very Happy
But.
The freq pot is still a bit "odd".

I've recorded a sample :

https://soundcloud.com/encoder909/ems

Basically I'm just tweaking the freq pot. As you can here, it react slowly for the fast movements (end of the recording) and seems that something wrong with it. there is no, erghm..."true lowpass" here?


Update!
Changed the CA3046 (got a bunch) until I found one which is sounds OK. (Seems they are very different. Tried RCA and Harris, finally, used a Harris one.)
They key is that this filter is very sensitive to the input.
Actually, because lack of panel space, I did not used the attenuator for the inputs (only for CVs).
After run this thru an attenuator modul the filter starts to "shine", and everything seems to work correctly.
All in all, it is a very uniques sounding stuff, and also very very sensitive.
I think this will be one of my fav filters Very Happy
Thanks Yvess!
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