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Old 22nd January 2014, 08:33 AM   #2281
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Join Date: Sep 2009
Hi All,

small update on the progress over here.

After changing the op-amp to OPA2211 and removing the caps everything works - more or less.

2 Issues though:

I still get a faint hiss, similar to the one before changing the op-amp, the level is much lower though. Should I try to tame it fitting those caps back or would anyone suggest another path to follow ?

Second, more annoying issue:

When hooking up an amplifier with DC blocking cap everything works fine.

When I try to put a DC blocking cap (4,7uF MKP) ahead of my R/C lowpass in line with the signal, I can't get any output.

The RC is a 1K resistor in series and 3300pF to ground.

Any thoughts on that matter ?

Cheers,

Max
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Old 27th January 2014, 10:16 AM   #2282
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Join Date: Sep 2009
Some update,

in finally I managed to get the DAC working byloading the output (positive to ground) with a 10K resistor.

Then I have my 1K/3300pF LP filter and finally the 4,7uF DC blocking cap, which I will skip later as I have one in each amp I am using.

This is until now the only way to get rid of the high pitched noise on the output, turn on/off thump has been reduced to acceptale levels as well.

I admit than 10K is a lot, I am loosing to much output level, but at least it works.

What's the minimun load I can apply without getting into current out mode ?
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Old 27th January 2014, 10:53 AM   #2283
Bunpei is offline Bunpei  Japan
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The current [mA] of 4 channels in parallel is;

AVCC [mV] / ( 195 + R_load [ohm] )

How much current can you accept based on your idea?
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Old 27th January 2014, 12:53 PM   #2284
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Bunpei,

I am actually using all 8 channels, but thanks for your input.

Could you kindly develop your thoughts ?

Cheers,

Max
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Old 27th January 2014, 12:57 PM   #2285
peufeu is offline peufeu  France
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Location: Lyon, France
Can you post scope trace of "high pitched noise" ?

ES9018 is not supposed to need a load to run. If it does, I'm interested since I plan on using it.

Can you post pictures/schematics of your output filter ?
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Old 27th January 2014, 01:18 PM   #2286
Bunpei is offline Bunpei  Japan
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The current [mA] of N channels in parallel is;

AVCC [mV] / ( 50000/64/N + R_load [ohm] )
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Old 19th March 2014, 06:46 PM   #2287
miero is offline miero  Czech Republic
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Location: Prague
Has someone noticed huge noise after the filter rolloff frequency with I2S source?

Building an open embedded audio applicance.

I might have something incorrectly configured, but the I2S timing seems to be alright:
Building an open embedded audio applicance.
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Old 22nd March 2014, 08:04 AM   #2288
Bunpei is offline Bunpei  Japan
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I tested white noise plays via I2S.
No abnormalities above 22.05 kHz were observed in my environment.
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Old 22nd March 2014, 08:21 AM   #2289
miero is offline miero  Czech Republic
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Bunpei, thanks for the checking. I need to do more diagnostics...
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Old 22nd March 2014, 12:06 PM   #2290
peufeu is offline peufeu  France
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miero, you should start a topic, show schematics and photos...
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