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Old 22nd October 2012, 02:29 AM   #1
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Default New DAC design Comments/Critiques?

This is a design I came up with before I go and create the board figured I'd post here for comments and critiques.

The Idea is Optical S/PDIF input into a CS8416 configured in hardware mode. The output directly feeds into the PCM1792A which is being controlled by the ATTINY88 via SPI. Volume is controlled at the DAC lvl with the rotary encoder and the volume level is output via the LEDs. Then I used the reference design from the TPA6120A2 (which is U6 on the SCH) datasheet for the rest.

The board will input +12V generated from a wall-wart and the 3.3V is generated from a regulator and the +/-5 and the +/-12 are from 1W CUI regulators.(VWRAT2 is the series).

Also I know there are some errors small errors in the schematic (like U6 not labeled and the grounds are missing at the output of M1, M2 are missing) I originally drew the schematic schematic in eagle and just finished transferring it to DIPTRACE which i recently found and prefer over eagle.
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Last edited by dmgash; 22nd October 2012 at 02:40 AM.
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Old 22nd October 2012, 03:42 AM   #2
qusp is offline qusp  Australia
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I see you have basically lifted the dac->4134->6120A from the reference design. I highly recommend you look at other implementations of the tpa6120A, the series resistance on the output (R39, R40), outside the feedback loop is a BAD idea, as it will directly add to the output impedance. I would also look at opa1644 to replace 4134. it depends what headphones you plan to drive, but if they are in any way low impedance I would make some changes
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Old 22nd October 2012, 10:16 PM   #3
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Quote:
Originally Posted by qusp View Post
I see you have basically lifted the dac->4134->6120A from the reference design. I highly recommend you look at other implementations of the tpa6120A, the series resistance on the output (R39, R40), outside the feedback loop is a BAD idea, as it will directly add to the output impedance
From the datasheet
"RO is a series output resistor designed to protect the amplifier from any capacitance on the output path,
including board and load capacitance."

Also why would you recommend that op-amp over the 4134?
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