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pcm5242 vs pcm1794a

Hemant Nile
Prodigy 40 points
Other Parts Discussed in Thread: PCM5242, PCM1794A, TPA6120A2, OPA2134, TL072, OPA4134, PCM1792A, PCM2706C, TMS320C5533

Hi,

I am planning to design a portable USB-DAC, I can't decide which dac chip to use.

ti pcm5242, ti pcm1794a , wolfson wm8741 ,akm AK4490EQ or ess SABRE9018AQ2M

pcm5242

1. its new and has programmable minidsp core

2. readymade design is available, only usb to i2s needs to be designed

3 low dynamic range (114db) than others

pcm1794a

1. old but many referance designs are available

2. good dnr(129db)

Any advise on the selection is most appreciated

I plan to use ti tpa6120a2 opamp, for no other reason than its in the referance design.

Everything will be USB powered.

USB to I2S

1. tenor te8802l   24/192khz , but I don't know where to buy it and I can't find much information about it

2. CP2114   16/48khz   It has internal EPROM and I2C support

3. pcm2707c   16/48khz  

Can I use Purepath studio to code minidsp on pcm5242 using above chips?

any suggestions on the design are most welcome.

thank you

  • 0
    TI__Mastermind 27990 points
    Hi Hemant,

    You laid it out pretty well, another thing to add is that the PCM1794A is a current output DAC so extra components for I/V conversion will be needed. The advantage as you stated is that the PCM1794A has better performance. The PCM5242 is a newer design and recently released so support beyond the released documents will be stronger behind the PCM5242.

    As for the USB to I2S, PPC uses a specific driver to package I2C commands into USB packets and then have the TAS1020 interpret them with its firmware as it is not a standard, I don't think that the other chips will be able to communicate with PPC for I2C commands.

    Justin
  • 0 in reply to Justin Bohr
    Prodigy 40 points

    thank you for the reply.

    I guess I will use pcm1794a unless ti comes up with new dac chip.

    can you recommend opamps for I/V conversion ?

  • 0
    Expert 1720 points

    Hi Hemant,

    If you plan to use PCM5242 with TPA6120a2 that in datasheet exists their recommended connection. With PCM1794a I used for I/V conversion resistor with TL072. It is not ideal solution, probably OPA2134 will be better.

    In datasheet of TPA6120a2 is recommended combination of PCM1792a with OPA4134 for I/V conversion and filtering.

    With all these combination you must solve troubles with volume settings.

    USB to I2S

    PCM2706c and PCM2707c are good simple USB to I2S chips, but they have limitation for 48kHz and software volume control doesn't work on I2S output.

    Today doesn't exists simple chip for higher sample rates for USB to I2S conversion. Best convertors use XMOS or Atmel processor. TAS1020B from TI has NRND status and TI recommend to use TMS320C5533. It may work, but I haven't experience with him.

    For volume control you need some processor which convert USB volume commands to the I2C commands for DAC. You can also use analog volume control, but it is not practical to have portable USB DAC with 4 gang potentiometer because there is differential connection from DAC to the amplifier.