Poor Man's Monitor Controller/Headphone Amp

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This is the last(I hope) revision of the i2c attenuator board:
http://cl.ly/3O2v0w443I1N2S250g3M

I've decided to add pga2311 chips to the digital part of the proto board as well. I'll see how they work and if I see any noticeable differece.

I could have chosen +-15V version of pga, but I've ordered parts late at night and somehow missed it. Now, question:

- Can I run pga2311 of 3.3V rails? Datasheet says 5V, but I figured out I'll ask before putting one more regulator on the pcb.

- If pga2311 runs on 5V and msp430 on 3.3V rails, will I have any problems with logical levels in SPI interface?

- When using SPI interface, can I select Chip enable for both pga's and send data only one time since data for both of the chips is always the same(balanced configuration)? (seems logical)

My schematic:
http://cl.ly/1D150y3s1E070H010S0i


PS I haven't figured out what pins of the msp430 should be connected to the spi data and spi clock
 
Well, I didn't finish what I planned to do today, but the pga4311 variant seemed so compact and elegant that I could not resist doing a board like this: (work in progress)

http://cl.ly/0U2M47122b0P0K2T1o3b

It will drive few hundred meters of cables or make your headphones happy ;) I'm planning to do the lme49600 optional.
 
I know I am probably boring everyone to death, but a quick question about ground planes. Here's my current situation:
http://cl.ly/1p3Y1M1p3j35030b2K3s

Should I have another ground plane on the top layer? Because of the power supply star thingy the parts of the bottom ground plane are not connected together and I could lay another one on the top layer and fix it with a little bit of via magic. Any possible problems with that solution? That's how it would look like:
http://cl.ly/1x3Z1Y1L3m2b2A3h0U2K
 
michal_k said:
This is the last(I hope) revision of the i2c attenuator board:
http://cl.ly/3O2v0w443I1N2S250g3M

I've decided to add pga2311 chips to the digital part of the proto board as well. I'll see how they work and if I see any noticeable differece.

I could have chosen +-15V version of pga, but I've ordered parts late at night and somehow missed it. Now, question:

- Can I run pga2311 of 3.3V rails? Datasheet says 5V, but I figured out I'll ask before putting one more regulator on the pcb.

- If pga2311 runs on 5V and msp430 on 3.3V rails, will I have any problems with logical levels in SPI interface?

- When using SPI interface, can I select Chip enable for both pga's and send data only one time since data for both of the chips is always the same(balanced configuration)? (seems logical)

My schematic:
http://cl.ly/1D150y3s1E070H010S0i


PS I haven't figured out what pins of the msp430 should be connected to the spi data and spi clock

The 2311 will need a 5V, but you can interface 3V3 into it. (SPI).
You may want to use some voltage translation on the SPI, just to ensure that there's no surprises.

Depending on the MSP430 you are using, I suggest using the USCI port, that'll tell you exactly which data pin to use (and the clock pin). The CS (chip select pin) is a simple GPIO toggle. (not part of the peripheral)

Cheers

Rochey
 
thanks Rochey!

I'm 99% done right now. That's how board looks like:
http://cl.ly/3V052S0I3s2Z3y3k1n2n

I still need to figure out how to connect 4 pin XLR for balanced headphones cable and lay down nice ground planes. As always, comments most welcomed.

EDIT: The board is now finished. I'll place an order on Monday and let you all know as soon as I get the prototype.
http://cl.ly/1U412O0Z0W2d3r2S0L27
 
Rochey said:
The 2311 will need a 5V, but you can interface 3V3 into it. (SPI).
You may want to use some voltage translation on the SPI, just to ensure that there's no surprises.

Not necessary; TFDS says logic high input is > 2V and input low is < 0.8V, standard TTL levels which any 3.3V micro can do.

-a
 
Thank you Andy - I'm well aware of what TFDS says.

I like the Err on the side of caution. If you already have 5V in the system, then 3 transistors won't hurt.

/R
 
michal_k said:
I know I am probably boring everyone to death, but a quick question about ground planes. Here's my current situation:
http://cl.ly/1p3Y1M1p3j35030b2K3s

Should I have another ground plane on the top layer? Because of the power supply star thingy the parts of the bottom ground plane are not connected together and I could lay another one on the top layer and fix it with a little bit of via magic. Any possible problems with that solution? That's how it would look like:
http://cl.ly/1x3Z1Y1L3m2b2A3h0U2K

Not boring, I get to learn from your questions.
 
Hi, just to let everybody know I didn't forget about this project. I've received PCBs - first time I used national plant rather than chinese manufacturer. All I can say is wow, quality is beyond amazing compared to chinese products.

I could already report how it works if only I didn't forget to order opamps  :eek:

Anyway, I'll take some photos tomorrow with a day light and stuff.
 
Pictures time:

I've soldered almost everything, still waiting for opamps to arrive:
2012-03-05%20at%2012:58.png

Analog part hooked up to the power supply: no smoke, no explosions, looks good:
2012-03-05%20at%2012:58.png
 
http://zwod.technoservice.com.pl/en/

not cheap but I highly recommend them. Great to deal with as well.
 
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