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Old 19th July 2015, 09:00 PM   #1
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Smile Capacitor/resistor value suggestions for dc blocking/high pass filter

Hello

I was wondering if anyone is able to suggest appropriate capacitor and resistor values for the construction of a new output stage (DC blocking/high pass filter after DAC) for a cd player going out to a standard line level preamp input?

And also (for an alternate more specific project) appropriate values going out to a 50K ohm preamp input?

Cheers
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Old 19th July 2015, 09:48 PM   #2
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Every commercial CD player either already has a coupling cap at the output or employs a DC servo to eliminate any DC on the output. Beyond that, for a simple coupling cap application where DC blocking is the only goal, the sky's the limit, use as large value that will physically fit. Most preamp inputs will have at least a 10 kohm impedance, and a corner frequency of around 2 Hz will eliminate any negative frequency or phase response effects. So using 10 kohm and 8 uF will give you a 2 Hz corner frequency.

Mike
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Old 20th July 2015, 04:21 PM   #3
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Quote:
Originally Posted by Michael Bean View Post
Every commercial CD player either already has a coupling cap at the output or employs a DC servo to eliminate any DC on the output. Beyond that, for a simple coupling cap application where DC blocking is the only goal, the sky's the limit, use as large value that will physically fit. Most preamp inputs will have at least a 10 kohm impedance, and a corner frequency of around 2 Hz will eliminate any negative frequency or phase response effects. So using 10 kohm and 8 uF will give you a 2 Hz corner frequency.

Mike
Thanks for the info...

Its getting clearer now!!

You see i had modified a stage in the past with 22k resistors and 3.3uf caps going out to my preamps 50k input, and the volume level/gain in comparison to my other players was significantly less……do corresponding values have such effect on volume?
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Old 20th July 2015, 08:25 PM   #4
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On my Oppo DV-980H DVD player which uses the Cirrus CS4361 DAC, I bypassed the opamp output stage by following the diagram in the datasheet for the CS4361 (fig attached). I used 7.5uF which I had onhand instead of the indicated 3.3uF, and I used 1nF for 'C'.
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File Type: jpg CS4361 DAC connx diagram .jpg (338.6 KB, 15 views)
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Old 20th July 2015, 11:03 PM   #5
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Quote:
Originally Posted by Fidelogos View Post
Thanks for the info...

Its getting clearer now!!

You see i had modified a stage in the past with 22k resistors and 3.3uf caps going out to my preamps 50k input, and the volume level/gain in comparison to my other players was significantly less……do corresponding values have such effect on volume?
Like this?

072015.JPG

22k in parallel with 50k is a little over 15k total with 3.3uF cap gives a Fc about 3Hz, so you're good to go.

Mike
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