Micronas DAC3550A - interesting noise problem

[Peter Neal]

Hi,

I'm using a Micronas DAC3550A (built around the reference design at the back
of the data sheet) and I have an interesting problem.

If I play audio to the left channel only I get crystal clear sound output on
the left channel and seemingly random high frequency noise of about 1v
peak-peak on the right. If play audio to the right only, the situation is
reversed and I get crystal clear sound from the right channel and 1v
peak-peak noise on the left.

If I play audio to both channels I simply get noise on both channels, again
of about 1v peak-peak (which completely drowns the audio).

I'm pretty sure what I'm seeing isn't cross talk between the two channels as
the noise is constant, even when the audio on the second channel is quiet.

I am at a loss trying to understand how this could happen - can anybody shed
any light?

Cheers,


Pete.

 

[Dejan Durdenic]

"Peter Neal" <no@email.specified> wrote in message
news:c5Osc.179$ir2.141@newsfe1-gui.server.ntli.net...

Hi,

I'm using a Micronas DAC3550A (built around the reference design at the
back
of the data sheet) and I have an interesting problem.

If I play audio to the left channel only I get crystal clear sound output
on
the left channel and seemingly random high frequency noise of about 1v
peak-peak on the right. If play audio to the right only, the situation is
reversed and I get crystal clear sound from the right channel and 1v
peak-peak noise on the left.

If I play audio to both channels I simply get noise on both channels,
again
of about 1v peak-peak (which completely drowns the audio).

I'm pretty sure what I'm seeing isn't cross talk between the two channels
as
the noise is constant, even when the audio on the second channel is quiet.

I am at a loss trying to understand how this could happen - can anybody
shed
any light?

Cheers,


Pete.

To me it seems that your timing of the audio stream is shifted by one bit so
that the MSB of the
left channel is actually LSB of the right one...If you play only left
channel, it works with one bit
less resolution and if you play right only, it's LSB actually changes MSB of
the LEFT channel.

regards

 

[Peter Neal]

"Dejan Durdenic" <no_spam@nospam.com> wrote in message
news:c90cs5$3b7$1@ls219.htnet.hr...

"Peter Neal" <no@email.specified> wrote in message
news:c5Osc.179$ir2.141@newsfe1-gui.server.ntli.net...
Hi,

I'm using a Micronas DAC3550A (built around the reference design at the
back
of the data sheet) and I have an interesting problem.

If I play audio to the left channel only I get crystal clear sound
output
on
the left channel and seemingly random high frequency noise of about 1v
peak-peak on the right. If play audio to the right only, the situation
is
reversed and I get crystal clear sound from the right channel and 1v
peak-peak noise on the left.

If I play audio to both channels I simply get noise on both channels,
again
of about 1v peak-peak (which completely drowns the audio).

I'm pretty sure what I'm seeing isn't cross talk between the two
channels
as
the noise is constant, even when the audio on the second channel is
quiet.

I am at a loss trying to understand how this could happen - can anybody
shed
any light?

Cheers,


Pete.



To me it seems that your timing of the audio stream is shifted by one bit
so
that the MSB of the
left channel is actually LSB of the right one...If you play only left
channel, it works with one bit
less resolution and if you play right only, it's LSB actually changes MSB
of
the LEFT channel.

Fabulous - that's solved it! Now playing crystal clear stereo audio.

Many thanks for your help.

Cheers,


Pete.