[450]

I read through some parts of this thread and I realize this is still in the planning stage but what kind of DACs would this USB DAC compare with?

 

[steinchen]

We've already entered the prototyping phase. It started as an USB DAC but meanwhile got an SPDIF input too.

 

[ble0t]

Howdy

R42 = 100R
R38 = 75R

Sorry about leaving those out.

As for the PIC, I've bumped into some issues with it as of late (such as frying my development board accidentally). To be quite honest, I don't expect to have anything done until the holidays. I apologize for all the delay in that respect.

To use the USB portion, JP4 (the one right next to the PCM2707 crystal) needs to be set so that the multiplexer has a high voltage input i.e. have the jumper set so that it is on the two pins closest to the PCM2707 crystal.

Do all the voltages appear to be good as far as the power supply is concerned? Feel free to post as much commentary and results as possible. Thanks again for participating!

 

[steinchen]

just powered up the dac for the first time and the voltages does not seem right as far as I can judge this. to have a detailed look at the voltages I need a schematic where the IDs match the IDs of the silkscreen / BOM.

jumpers: what about / how to set the other jumpers (jp1 to jp3) ?

 

[threepointone]

I don't know how important this will be in practice, and i'm not exaclty sure what's what on the board, but shouldn't the digital and analog grounds be separate (except right at the power supply) to reduce noise being injected into the analog circuit? might want to consider this in the final design

 

[Clutz]

Quote:

Originally Posted by threepointone I don't know how important this will be in practice, and i'm not exaclty sure what's what on the board, but shouldn't the digital and analog grounds be separate (except right at the power supply) to reduce noise being injected into the analog circuit? might want to consider this in the final design

No - it causes more problems than it solves.

 

[ble0t]

There are a couple 'stages' of the power supply (LM317, LT1206, etc.), so which voltages look off?

As far as JP1 and JP3 are concerned, those are there to allow external input if the builder wanted to try supplying the clock and/or PCM179* from a different power supply. A quick look at the traces should tell you how to set those in order to take advantage of the built in power supply.

I'll try and get a fully updated BOM/Sch/Brd put together and post it as soon as possible.

 

[Clutz]

Hey ble0t - any updates?