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Old 25th May 2009, 05:07 AM   #1
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Join Date: Feb 2009
Lightbulb USB-Powered Headphone Amplifier

Hi everyone,

This is my first amplifier design, so I appreciate any and all help.

I'm trying to squeeze a headphone amp into the Hammond 1455C80x with the TooleAudio BantamDAC. My main thread is over at head-fi,

http://www.head-fi.org/forums/f6/usb...lifier-387745/

and I've drawn info from these threads:

USB powered HIFI headphone amp/DAC

http://www.head-fi.org/forums/f6/usb...amp-ps-215585/

http://www.head-fi.org/forums/f6/usb...c-cmoy-219127/

Schematic:
Click the image to open in full size.

Layout:

Top and bottom layers:
Click the image to open in full size.

Top only:
Click the image to open in full size.

Bottom only:
Click the image to open in full size.

I'm taking the amplification stage from the AMB Audio Mini^3, which is basically a three channel, non-inverting amplifier using the AD8397 and OPA690. For the power supply, I'm boosting the 2.5W USB 5V to 12V with the isolated 1W DCP010512BP, which has a maximum efficiency of 89%. The voltage is filtered by a CLC LPF, regulated to 10V by the TL750L10 and then it's split by the TLE2426. Since the boosted voltage is isolated, the midpoint of the TLE is connected to USB V- (or earth ground) so that the rails sit at a measured +/- 4.72V. The amplifier draws max 50mA, so there is plenty of overhead for current draw.

Anyhow, the point of this thread is for design critiques and comments. I didn't design the amp in the traditional, "Create a transfer function, and create an amplifier to achieve that function," method. I more or less threw two existing projects together and consulted "Google, P. Eng." At the time of the writing of this thread, the boards are making their way to the prototypers via Canada Post, so we'll see what they come up with. Perhaps later I can provide close-ups of the board itself.

Prototypes of the Mini^3 oscillated because of board layout, so do you guys think I'm safe here? I won't have a chance to actually build the thing for some time as my place is being renovated, and I won't have access to a scope or signal generator until I get back to school in September. Now's the time to change things since the first round of boards have already been fabbed, so now I'm hoping to get feedback on the design.

So uhh, yeah, what do you guys think?
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