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 Forum index » DIY Hardware and Software » YuSynth
Question about vco capacitor
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capicoso



Joined: Nov 19, 2012
Posts: 127
Location: Argentina

PostPosted: Wed Jan 09, 2013 1:14 pm    Post subject: Question about vco capacitor
Subject description: mica
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Hello. I'm building the vco. And here i have problems finding the silver mica capacitor 1%. So far i found silver mica 270pf BUT +-10% not 1%. NP0 ceramics 220 or 270, or polypropylene. The silver mica one is still the best even with 10% tolerance?
thanks
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isak



Joined: Dec 13, 2009
Posts: 731
Location: Israel
Audio files: 18

PostPosted: Sat Jan 12, 2013 3:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

You can use styroflex as well Wink
http://www.ebay.com/itm/Polystyrene-Styroflex-Capacitor-Made-by-Philips-listing-is-for-2-pieces-/271128402472?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item3f20831a28


Q...
What you will be using, the OPA2137P or OPA2137PA?
I want to build the vco as well and I'm not sure about this IC.
The OPA2137P is more expensive then the OPA2137PA, don't know why tho...
Any help will be thankful.

Cheers,
Isak E.

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capicoso



Joined: Nov 19, 2012
Posts: 127
Location: Argentina

PostPosted: Sat Jan 12, 2013 5:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

isak wrote:
You can use styroflex as well Wink
http://www.ebay.com/itm/Polystyrene-Styroflex-Capacitor-Made-by-Philips-listing-is-for-2-pieces-/271128402472?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item3f20831a28


Q...
What you will be using, the OPA2137P or OPA2137PA?
I want to build the vco as well and I'm not sure about this IC.
The OPA2137P is more expensive then the OPA2137PA, don't know why tho...
Any help will be thankful.

Cheers,
Isak E.


Hello, thanks for your time.

Yes i can, but at my local stores i couldn't find either. So my options are 10% mica, np0 or polypropylene.

I'm going to use LF442. I couldn't find 2137 here and someone that built like 3 or 4 vco told me that CA3240 is cheaper and it works the same. Or Lf442 also works.
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isak



Joined: Dec 13, 2009
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PostPosted: Sun Jan 13, 2013 12:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Really?
I have some 442's, I wander what will be the deference using 442's or tl072 like Yves recomands.

EDIT:
Yves, what will be preferred instead OPA2137, TL072 or LF442?


Cheers.

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elmegil



Joined: Mar 20, 2012
Posts: 1535
Location: Chicago
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PostPosted: Sun Jan 13, 2013 10:27 am    Post subject: Reply with quote  Mark this post and the followings unread

The question of film vs NP0/C0G caps comes up pretty regularly, and I have never seen any convincing reason why film would be preferrable. I still use them because I have a stock, but the long term plan is to get more stock of the C0G's....
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capicoso



Joined: Nov 19, 2012
Posts: 127
Location: Argentina

PostPosted: Sun Jan 13, 2013 11:00 am    Post subject: Reply with quote  Mark this post and the followings unread

elmegil wrote:
The question of film vs NP0/C0G caps comes up pretty regularly, and I have never seen any convincing reason why film would be preferrable. I still use them because I have a stock, but the long term plan is to get more stock of the C0G's....


Yeah, i searched and that's why i ask about the NP0 caps ( i didn't know about their existence)I guess i'm going to use NP0. They're way cheaper and in the datasheets they look goood

but my main question now is if it has to be 1%
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yusynth



Joined: Nov 24, 2005
Posts: 1234
Location: France

PostPosted: Sun Jan 13, 2013 12:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

Any precision dual AOP will do. The important is that it has a low bias.

Concerning the cap, the important is the temperature coefficient which must be kept low (500ppm maximum), in general silver mica and styroflex are offering that. The 1% tolerance is not really important unless you want to built plenty of VCOs and you want them to behave the same.

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capicoso



Joined: Nov 19, 2012
Posts: 127
Location: Argentina

PostPosted: Sun Jan 13, 2013 4:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well my idea would be having various VCOs. If i use NP0 then i think i'll have to match them to 1%. When you say they'll behave different, you mean they'll be tuned differently? Or...?

thanks
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yusynth



Joined: Nov 24, 2005
Posts: 1234
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PostPosted: Mon Jan 14, 2013 12:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, "tune differently"
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