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Old 18th December 2009, 01:50 AM   #1
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Default Capacitor types in chip amp (TDA2050)

Hello all,

I was wondering if you can help me go over what the types the capacitors should or could be in a standard TDA2050 amp. I am not looking for any expensive audiophile type of caps, but more of a cost/value type of cap. This is what I understand so far.

C1 electrolytic acceptable, polypropylene better
C2 electrolytic
C3,C4 ceramic
C5,C6 electrolytic
C7 polypropylene (is something else acceptable here?)

Is there a big difference between polypropylene and metallized polypropylene?
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Old 18th December 2009, 02:19 AM   #2
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C1 better not be electrolytic. Polyprop is prefered though some polyesters are quite decent. One can't generalise but if you have an option pick polypropylene.
C2 electrolytic is what is used most often and some put a small value polyprop or polyester in parallel say 0.1uF.
C3,C4 are available as small yellow box ( 63V ) type polyester caps. These are good and inexpensive.
C5 , C6 are elco's.
C7 can also be polyester and I'm not quite sure if it's type is audible unlike what you use at C1!
In my opinion C1 is the most critical cap in this circuit. C2 comes after that but it is also equally important to use a good one. Try shorting it out with a link and see how much dc offset you get. If it's less than about 0.2V at the speaker leads, you can safely listen to your system with or without C2 and determine how much it degrades the sound . You could also try different brands of elco's. Panasonic's are generally good but even cheaper types often can sound quite good. If your offset is less than 50mV ( with C2 removed) then you can remove C2 completely ! The offset will drift with temperature so you can run a test with the amp cold and when it's very hot. If the offset is less than 50mV then chuck C2 out !

All polypropylene caps have a metal layer. This is either a sputtered layer or a metal film. Metal film types cost more . Do they sound different? I think you should pick by the sound ,which you can only do by running the test in the location where you want to use it. The bias for 'possible ' better sound is towards metal film types. But I think one cannot generalise again.
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Old 18th December 2009, 03:21 PM   #3
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Thanks for the reply. It was very helpful.

My concerns lay mostly with the C1,C2 caps. To me they seem to be the ones that would affect the sound the most because they are directly in the signal path.

This is what I extracted from what you were saying:

C1 polypropylene
C2 electrolytic (possibly polypropylene or polyester in parallel)
C3,C4 polyester
C5,C6 electrolytic
C7 polyester

Last edited by davidallancole; 18th December 2009 at 03:49 PM.
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Old 18th December 2009, 06:44 PM   #4
mjf is offline mjf  Austria
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hello.
i often use mkt caps (polyester,mylar) as a good standard.
and for c2 a bipolar/non polarised elco (you can increase c2 to 47uf,this will give you a little more bass).
i do not use big ceramic caps with audio gear (c3,c4,should sitting near by the pins of the opamp).
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Old 19th December 2009, 06:50 AM   #5
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mjf - do you have a link to bipolar capacitors that you have used before? There aren't many options at Digikey for bipolars.
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Old 19th December 2009, 10:55 AM   #6
mjf is offline mjf  Austria
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Quote:
Originally Posted by davidallancole View Post
mjf - do you have a link to bipolar capacitors that you have used before? There aren't many options at Digikey for bipolars.
mine i got here

Passive Bauelemente | Kondensatoren | Aluminium Kondensatoren 4294955813&selectSubRange=Audio & bipolar 85*C#breadCrumb

(in canada perhaps this one: )
http://www.alliedelec.com

Last edited by mjf; 19th December 2009 at 11:03 AM.
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Old 19th December 2009, 07:27 PM   #7
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I'd get that C1 from here: https://www.hndme.com/productcart/pc/viewCategories.asp

Input filter caps (C1):
Nichicon ES 1uF is a solid performer, bipolar, so its "reversible" for more or less brightness.
The Elna Cerafine 4.7uF is also a solid performer (stripe towards source, normally).
*The larger figure, 4.7uF will operate the amplifier full bandwidth; however, you'd also need to increase the size of the NFB cap (C2) by the same proportion--If C1 is 4.7uF then C2 is 100uF.
*The smaller, 1uF (with 22uF at the NFB) can run full bandwidth if you multiply the values of R1, R2, and R3 by 4.55 times (22k * 4.55 = 100k).

Speaker output zobel:
For your C7, it specs only for polyester (because of the typically high ESR).
*otherwise the 2.2R load of R4 could be increased to 5R or higher figure to use ceramic or polypropylene caps at the zobel.

Last edited by danielwritesbac; 19th December 2009 at 07:38 PM.
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Old 21st December 2009, 04:45 AM   #8
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Thanks for the comments guys.

I went to chipamp.com to see what was used. I noticed they have a bipolar electrolytic for C2 on the LM1875 kit. I would suspect C2 to have as much influence on the signal quality as C1. Would it be all right to use a bipolar electrolytic as C1 then? Or has it been deemed that the C1 position has more influence over the sound. At the small cost of getting the bipolar, I will try both, but I was just wondering what everyone elses experience may have been.
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Old 21st December 2009, 05:45 AM   #9
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C1 has the biggest influence. C2 is the second most influential. The choice of a bipolar capacitor for C2 is necessary, because the feedback filter's high pass frequency is higher than the input filter's. A 22 F film capacitor in that place would be inadequately expensive and big, but you can achieve a sonic improvement in that place, by putting a small film capacitor in parallel to C2.
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Old 21st December 2009, 08:31 AM   #10
mjf is offline mjf  Austria
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[QUOTE
At the small cost of getting the bipolar, I will try both

good idea! so you can find the cap that fits to your preferences.
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