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Removing / replacing output caps on a DAC
Removing / replacing output caps on a DAC
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Old 10th November 2017, 05:36 PM   #1
ig983 is offline ig983
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Default Removing / replacing output caps on a DAC

Hi everybody!

I need some help, I`d like to make some changes to my DAC but I`m afraid I`d screw something up.
Can you please tell me if my thinking is correct?
I have a Cambridge Audio DACMagic that is connected through balanced out on the DAC to unbalanced RCA in on my amp. I chose this because it for whatever reason sounded better then when connected DAC RCA out to amp RCA in.

And now I`m looking to get some higher grade output caps for the DAC and when I opened it, I saw it uses a total of 8 caps - 4x 0,1uF and 4x470uF.

My budget doesn`t allow for 8 quality caps so I was thinking - can I take out these 8 caps and just place one cap on each signal line?

In my limited understanding, it should be the same since its already not balanced

Right? Or am I missing something important.

I`ve attached the DAC schematic with marked caps if it helps
Thanks
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Old 10th November 2017, 08:17 PM   #2
wwenze is offline wwenze  Singapore
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You should be looking at C299 and C48 for the right channel, and their counterparts for the left channel.

It's an electrolytic and a polypropylene in parallel, you may choose to replace only the electrolytic if you want.
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Old 10th November 2017, 08:24 PM   #3
kaputt is offline kaputt  Germany
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Maybe it would make more sense to get rid of the capacitors alltogether and install a servo to null out dc? What's the point in replacing one 470uF elco for another?
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Old 10th November 2017, 10:15 PM   #4
ig983 is offline ig983
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Hi!
Thank you for your replies.

@wwenze - I`m using balanced out, doesn`t the signal pass through C38 for left and C97 for right channel?


@kaputt - a friend of mine replaced his caps with Mundorf and the sound is way better then whatever was inside. I`d like to do the same but not have to change my XLR to RCA cables. Can I just remove all caps that are on the way (as I understand it, those are C1, C2, C38, C39, C40, C41, C42, C97 ) and place two 0,1uF caps for C38 and C97? Would that work?
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Old 10th November 2017, 10:50 PM   #5
rayma is offline rayma  United States
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Quote:
Originally Posted by ig983 View Post
Can I just remove all caps that are on the way
and place two 0,1uF caps for C38 and C97? Would that work?
Maybe, but it depends on what the input impedance of your amplifier is.
If it's high (100k or more) perhaps 0.1uF will work, or else a larger value of film cap.

The unbalanced output has an extra op amp stage (a balanced to single-ended converter),
and also another DC blocking capacitor, that the balanced output does not need or have.
That's why you may prefer the balanced output.

If you end up doing this, you'll also want to disable the circuitry for the single ended output,
by removing R218, R219, and U61. These parts are in the right channel, similar for left channel.
This will further reduce the loading on the coupling capacitor, so a smaller uF value can be used.

Last edited by rayma; 10th November 2017 at 11:18 PM.
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Old 10th November 2017, 11:27 PM   #6
rayma is offline rayma  United States
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Quote:
Originally Posted by rayma View Post
This will further reduce the loading on the coupling capacitor, so a smaller uF value can be used.
A typo, I left out R100 and R101 (right channel) to be removed (or increased in value),
which allows a smaller blocking capacitor value.

Last edited by rayma; 10th November 2017 at 11:29 PM.
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Old 10th November 2017, 11:41 PM   #7
ig983 is offline ig983
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@rayma - that sounds great!
So I`m taking out R218, R219, R194, R195 and disabling U57:A, U57:B, U61:A and U61B.
What value cap do you think would definitely work?
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Old 10th November 2017, 11:45 PM   #8
ig983 is offline ig983
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Ok, so removing all of the above + R100, R101, R102 and R103
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Old 10th November 2017, 11:48 PM   #9
wwenze is offline wwenze  Singapore
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Oh ok, I misread the post.

With a balanced-to-RCA connection, usually only one of the balanced signal pins is used, so you can still halve the number of caps to be replaced.

470uF is a lot of capacitance; use a calculator to see how much is enough for you.
The 470uF is in parallel with a 0.1uF because film caps have lower impedance than electrolytic at high frequencies. If you are using a very big film cap, then you only need one capacitor.

R218/R219/U61 are not loading C40/C41

Keep R100 and R101. They provide a path to ground for DC. They also help reduce turn on pop in some situations. You may increase the value if you want, but remember that the effect of increasing their value diminishes once their value become comparable to load resistance.
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Old 10th November 2017, 11:50 PM   #10
rayma is offline rayma  United States
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Quote:
Originally Posted by ig983 View Post
I`m taking out R218, R219, R194, R195 and disabling U57:A, U57:B, U61:A and U61B.
What value cap do you think would definitely work?

First, we still have to know the input impedance of your amplifier to see if this will work.
It should be 100k or higher. Otherwise, the bass response will be reduced too much.
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