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Good capacitors for cmoy

post #1 of 8
Thread Starter 

I have already build cmoy with some cheap capacitors from local store.
Now i am willing to build one more but this time wiht metal film resistor and some quality c1 and c2 capacitor.
I have 2 question.
First , is it worthy to invest in capacitor that are costing 2-5 euro.
If i invest in expencive capacitor, would  i hear any sound difference.

If i should buy some expencive capacitors, can you recommend some capacitors.

Best caps in my local store are ULTRA LOW ESR elko Nipon Industrial Company, JAPAN, 220uF, 50V, 105°C, 10x16mm, RM:5mm  for 0.5 euro.
Are they worth any


I am using opa2134pa.



post #2 of 8

IMO- Yes  you should buy quality caps. The ones you suggested sound good with low  ESR and metal film resistors. I always use good spec components. like -polypropylene-polystyrene - and various quality resistors.Others in the sound science  will disagree and say--"they all sound the same" not as far as I and John Lindsay Hood/Cyril Bateman[ capacitor design engineer] and others  and many here who use them too     in the high quality amps they build .  There again I am a subjective along with 80% of the people here..I also have used the same family of chips in the past that you are using. You should not be disappointed with the reproduction.

Edited by duncan1 - 10/6/13 at 6:46am
post #3 of 8

OK, I will present a slightly different point of view, but one which IMO chimes with those of Bateman and Hood. We're specifically talking electrolytic caps here. I don't think anyone in the 'Sound Science' forum will disagree that electrolytics do distort, however the remedy for this is not, IMO, to buy some of the exorbitantly priced caps advertised on sale.


1. You don't need 50V capacitors. A cmoy won't have greater than 18V rail-to rail so a 25V cap will be fine, if you're running 9V with a rail splitter, a 16V cap will do. Lower voltage caps are smaller and cheaper.


2. Look at the temperature/time rating of the cap. A 3000 hour / 105°C cap is better than a 2000 hour / 85°C cap, purely in terms of how long it will last, but remember that a cmoy should not be running hot, especially if you don't cram it into a tiny box..


3. Electrolytic caps do cause distortion, this is a measured and measurable effect, but the best way to avoid it is to use an oversize capacitor. So in your case you could use a 3000 hour / 105°C cap (or better hours), rated 16V if you're running 9V with a rail splitter, and use 2200uF instead of 220uF. Because of the lower voltage rating the cap may well be no bigger than the 220uF/50V. The result is a smaller AC voltage across the cap, and consequently smaller distortion. Once the distortion is reduced to levels comparable to that arising from other sources, there is nothing to be gained by spending money to reduce it.


4. With regard to distortion, you only need to concern yourself with caps used for signal coupling (DC blocking) in the signal path. If the cap is bypassing the battery or power supply (opamp power pins), you can be a lot less fussy about the make, and you don't need to make them oversize.


Buy caps with a respectable name, Panasonic, Nippon, Vishay, Rubycon, etc. not 'no-name' caps, but don't spend out for the expensive caps like Black Gate, marketed as 'audio' types. If it says 'audio' on it, it's almost certainly a ripoff.


Many people like to buy high-priced 'audio' caps, as is evidenced by the wide variety on sale, but most engineers and others who trust measured performance parameters feel it is better to save the money and spend it elsewhere.



post #4 of 8

Of the working voltage of electroyltic caps that Cyril tested he found the lowest distortion on the 35 V range. Remember his own designed and built "cutting edge"[at the time ] but still good at =0.00001 % dis ability to display - Capacitors help in a specially designed jig to test with DC current flowing through them just to make thing    not only more harder but more to the point testing under near working conditions. Cyril published a series of articles on EE spread over a year.Nobody disagreed with him. Including DS.  

post #5 of 8
Originally Posted by duncan1 View Post

Capacitors help in a specially designed jig to test with DC current flowing through them just to make thing    not only more harder but more to the point testing under near working conditions.




If you're going to repeat things that you've read, you really must stop blathering and report the content accurately. DC current doesn't flow in capacitors, as any fool knows. With stuff like this in your posts nobody knows what to trust in what you have written and what significance to attribute to it.


Now I haven't read what Cyril Bateman wrote, but I know that DS has, and what I wrote is largely based on what he wrote, and that comparatively recently, and he suggests using lower voltage rated caps, quote "I tested 100uF 16V and 100uF 6V3 capacitors, and both types gave exactly the same results as the 1000uF 25V part in figure 2.17, with useful reductions in CV product and can size."


He also says "From (the) data, it appears that the AC voltage across an electrolytic capacitor should be limited to below 80mVrms if you want to avoid distortion. I would emphasize that these are ordinary 85°C rated electrolytic capacitors, and in no sense special or premium rated types."


Quotes from "Small Signal Audio Design."



post #6 of 8

I didnt bother replying to this post but as it is still on the go then in answer to it . Yes not through an "ideal " capacitor but tell me what electrolytic capacitor is ideal ?  You should know that electrolytic capacitors are far from ideal and show =RL-- leakage resistance while its starts off high it gradually reduces with age or damage . This was brought home to me many times in the valve/tube radios I repaired over a 45 year period the blocking capacitor from the anode of the previous stage to grid 1 =G1 of the next stage regularly leaked DC current this was enough to  stop the function of the radio changing these capacitors and by the way they were usually 0.1uf -350 V/ 450 V paper not electrolytic  was enough to bring the radio back to life . Theory as  many scientists will tell you doesnt always work in practice .

post #7 of 8
I have been into diy for quite a time...

The problem is cmoy design itself as the ground isnt that good

When we make a electronic circuit, we have to keep 5 things in mind

1. Intelligent idea
2. Proper implementation
3. Hand matching precision(accurate)
4. Properties of material
5. Quality of material

I have been using agdr audio super cmoy real ground.

I upgraded whole circuit with nice quality resistor and capacitor.

Dont just get over expensive caps or opamp..

If u wanna upgrade do it with good priced material which have decent quality and do it with all components

I use rhopoint gg102A resistor
Capacitors are Exotica TFT Cap by Reliable Capacitor and Black Gate Standard Elect Radial Capacitor.

With my resistor to be liquid helium treated.

Comparison was that lower masking of high frequency and low frequency and better drive handling, opamp stability so the amp has some headroom for auto quality improvement.

As signal is cleaner or less masked than normal material.

In one instance u cant find great difference but when A/B ing you would find a lot of difference.
post #8 of 8
I use opa1688 soundplus flagship by texas instrument as opamp...
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