Ok, Cap me
Apr 8, 2006 at 6:58 PM Thread Starter Post #1 of 9

Regus

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Ok having successfully built the dddac with the the basic components Doede ships with his kits it is time to start tweaking it, and while I can tell capacitors apart and do the math I am fairly clueless about audiophile capacitors - I see the words Black Gate everywhere I look and people talk about paper and oil capacitors as something good too, but beyond this...

Now there are a number of 100uF and 100nF capacitors on the boards that I figure could do well with a replace to something reasonable and then there is the output capacitors which as I understand it are the most important ones.

What should I try? I am willing to shell out the cash and buy several different sets to learn something about the subject...
 
Apr 8, 2006 at 7:13 PM Post #2 of 9

Xakepa

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Check Tangent's website, or google "high-pass filter".

Output caps are the ones you care the most. Depending how much capacitance you need there to avoid roll-off there are different choices and types. If you need more than 10-20uF, Black Gates could be for you - otherwise they are not the best solution...just the best compromise size/quality.

Film caps is a vast territory: quality-wise, sizewise (from 1/2" up to Coke can size), pricewise (up to $400 per piece). However, that's the best one can get
 
Apr 8, 2006 at 11:36 PM Post #4 of 9

Regus

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Ok things are starting to come together for me now - and the prices are almost scary
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Now reading around I seem to get some relatively low farad suggestions - Tangent's formula suggest as little as 1.9 uF (i measured the input impedance on my two amps to somewhere between 40 and 50 kOhms) the ecp site says 4.7 uF is common(?) - but they both talk about phase distortion and place that at something like 8-10 times the break point frequency, but my calculations lead me to conclude that around 15 uF is required for the breakpoint frequency to be 10 times less than 20 Hz (I suspect Tangent's handwritten PDF might explain this but I gave up trying to make sense of it).

Now 4.7 uF doesn't seem completely insane (phase distortion shouldn't surpass 68Hz) and the prices are fairly likable, wheras 15 uF and upwards make my flat seem cheap.

I'm thinking of ordering two auricap 4.7 uF and two Jensen paper oil 4.7 uF and see where that brings me. (has anyone bothered to tell parts connexion, that the internet shopping cart has been invented and comes in some very cheap but perfectly usable versions?
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Apr 9, 2006 at 2:41 AM Post #5 of 9

Xakepa

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Reg, I think you got it wrong.

Looking at the specs of your DAC, I see output caps (C2-C5 on page 5), and designer suggest in the footnote that it's the most important tweak component, recommening 470uF oil caps.

These are the ones you have to choose, and 100-470 seem to be the ballpark...I mean uF, not feet.

Black Gates are a good economical option here. 100nF shunt you can leave behind I guess. There's a discussion on shunting caps several topics below, and it doesn't seem to be a great idea.

Good luck!
 
Apr 9, 2006 at 3:54 AM Post #6 of 9

dsavitsk

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Quote:

Originally Posted by Regus
Now reading around I seem to get some relatively low farad suggestions - Tangent's formula suggest as little as 1.9 uF (i measured the input impedance on my two amps to somewhere between 40 and 50 kOhms) the ecp site says 4.7 uF is common(?) - but they both talk about phase distortion and place that at something like 8-10 times the break point frequency, but my calculations lead me to conclude that around 15 uF is required for the breakpoint frequency to be 10 times less than 20 Hz (I suspect Tangent's handwritten PDF might explain this but I gave up trying to make sense of it).

Now 4.7 uF doesn't seem completely insane (phase distortion shouldn't surpass 68Hz) and the prices are fairly likable, wheras 15 uF and upwards make my flat seem cheap.



I think your calculations are off. First choose your 3db point. 2Hz is a good choice as it is 1/10th of 20Hz and it is conceivable that your speakers reproduce 20Hz. Then run the calculation considering that your amp has an input impedence around 50K, and your dac has an output resistor of 100K in parallel, thus you can consider the impedence seen by the cap to be about 33K.

So, C = 1/(2 * pi * 2 * 33000) which is about 2.4uF. The reason that 4.7uF is common is that it is common to see an input impedence of 10K.

Quote:

Originally Posted by Regus
I'm thinking of ordering two auricap 4.7 uF and two Jensen paper oil 4.7 uF and see where that brings me.


A fool and his money. I think you are expecting magic from these caps that just doesn't exist. They do not make a circuit better, they simply do less damage than other caps. Also, if you just got this working in the last couple of days your existing caps (not to mention the transformers, chips, and PS caps) are not broken in yet and will continue to change in sound for at least a few days if not longer. If it were me, try the auricaps first as they are known for clarity and are not crazy expensive. If you feel that you need more sparkle on the top, then maybe try PIO's. But really, if the auricaps don't do it for you, try a different dac. Also, keep in mind that a lot of these caps sound better, or at least different with a high voltage applied to them. They may not sound their best with the 3.85V from the dddac.

Quote:

Originally Posted by Xakepa
These are the ones you have to choose, and 100-470 seem to be the ballpark...I mean uF, not feet.


You are off by several orders of magnitude. The dddac pages suggests 470nF, though this will give a high 3dB point and is likely too small. Those are also very very expensive caps. I doubt this dac can produce sound that makes them worthwhile (the TDA1543 is just not that good of a chip), but even if it can you will need really good upstream components to hear the difference. Differences from one high end cap to another are not like differences between opamps. They are very subtle when they are there at all. This is real golden ear kind of stuff.
 
Apr 9, 2006 at 5:14 AM Post #7 of 9

Paragon

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Quote:

Originally Posted by Regus
I'm thinking of ordering two auricap 4.7 uF and two Jensen paper oil 4.7 uF and see where that brings me. (has anyone bothered to tell parts connexion, that the internet shopping cart has been invented and comes in some very cheap but perfectly usable versions?
smily_headphones1.gif
)



Wow.. $100 for some capacitors?! How much was that DDDAC?
Why not go for some cheaper Solen/Aeon and see if that does anything for you?

How about going capless? I have some singles!
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Apr 9, 2006 at 12:33 PM Post #8 of 9

Regus

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Quote:

Originally Posted by dsavitsk
I think your calculations are off. First choose your 3db point. 2Hz is a good choice as it is 1/10th of 20Hz and it is conceivable that your speakers reproduce 20Hz. Then run the calculation considering that your amp has an input impedence around 50K, and your dac has an output resistor of 100K in parallel, thus you can consider the impedence seen by the cap to be about 33K.

So, C = 1/(2 * pi * 2 * 33000) which is about 2.4uF. The reason that 4.7uF is common is that it is common to see an input impedence of 10K.



Ok I supose I managed to ignore the output resistor a little too much
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And while I see the C = 1/(4pi * f) formula I don't understand why it is correct, Tnagent also uses this formula f = 1/(2pi * RC) for finding the corner frequency and with those values we get 1/(2pi * 33000 * 0.0000024) = ~2
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Hmm ok you win, I must have been tired yesterday and had a zero too much in there somewhere.


Quote:

Originally Posted by dsavitsk
A fool and his money. I think you are expecting magic from these caps that just doesn't exist. They do not make a circuit better, they simply do less damage than other caps.


And the difference between improving and doing less damage is...?

I am not that far gone, I do understand that they will not turn my dac into a television set
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I admit I have absolutely no idea what they will actually do and how great a difference they will actually make. But I do understand this: Education may be free in my country but learning never is - the only way I will ever learn what caps do and do not do is by spending the money and trying some different ones out.


Quote:

Originally Posted by dsavitsk
Also, if you just got this working in the last couple of days your existing caps (not to mention the transformers, chips, and PS caps) are not broken in yet and will continue to change in sound for at least a few days if not longer.


I realize that, and I will wait patiently before actually changing anything around, but I sincerely doubt that I will not be able to tell the difference between a pair of 2 cent electrolytes and some quality caps - I could be wrong of course - never happened to me before but there is a firs time for everything
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Quote:

Originally Posted by dsavitsk
Also, keep in mind that a lot of these caps sound better, or at least different with a high voltage applied to them. They may not sound their best with the 3.85V from the dddac.


There seems to be a lot of controversy on that subject, and without a higher voltage output to compare with there is little chance of me actually determining whether or not I think it is true.


On and end note when I ordered the kit from Doede I was hoping it might be better than my E-MU 1212m, I was not expecting anything major and certainly not a revelation - but when I had finished it and listened for the first time my jaw dropped I felt like I was experiencing hi-fi for the first time all over again - I am very very impressed with this DAC.

But of course as all things go when I got over my initial bafflement I started to notice the ups and downs, amongst other things I find it a little lacking in bass punch and I am not a basshead at all - it is very tight but just a little too weak I figure a better PSU and some more burn in time will take care of this.

I think it can be tweaked to go where I want it to be, the flaws (if you can call them that) are all minor things that could be just a little bit better.

And my reason for ordering more than one set of caps at once is that not living in the states and the states seeming to be the only place where things like this are actually sold (which I supose should worry me) the shipping costs are not trivial nor are the shipping times.

That coupled with the fact that I intend to actually try and learn something makes it sensible to order 2 or 3 sets.
 
Apr 9, 2006 at 12:51 PM Post #9 of 9

Regus

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Quote:

Originally Posted by Paragon
Wow.. $100 for some capacitors?! How much was that DDDAC?
Why not go for some cheaper Solen/Aeon and see if that does anything for you?

How about going capless? I have some singles!
icon10.gif



About $460... not counting the time i spent building it...

And it may well be overkill, but that is the problem you see I don't know and there really is only one way to find out...

But point taken, I will try out some cheaper ones too, atleast that is cheap learning...
 

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