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Old 10th February 2011, 06:50 AM   #2961
Draki is offline Draki  Macedonia
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My December-bought DCX stopped working after a month: upon switch-on, the display screen would lit but remained blank, and the LED segments on input channel A and output channel 1 were all lit - the unit was "frozen" like that.
The dealer replaced it with a new unit.
However this second unit behaves similarly after switch-on: sometimes the display is lit but without any data on it, and no LED segments lit/ sometimes the display (w/o any data) and the LED segments are all lit....... However this time - for now at least - the next switch-on will bring it back to normal.
Any similar experiences? What may be the culprit? I am about to implement the mods (Oettle src/clock and direct outs) but would like to solve this first.
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Old 10th February 2011, 07:14 AM   #2962
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I was wondering if anyone had replaced the ADC's for ASRC's to accept I2S in various flavours, and does it make sens to do so or is optical just as good.
Connecting I2S directly to the DSP would require major surgery, and it would only be able to handle 96khz 24bits.

Does anyone know why one of the ADC's of the DCX inputs (left and right) are tied together? I know it is a mono configuration but why tied them? doesn't make sens to me
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Old 10th February 2011, 09:05 AM   #2963
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Quote:
Originally Posted by egberttheone View Post
I was wondering if anyone had replaced the ADC's for ASRC's to accept I2S in various flavours, and does it make sens to do so or is optical just as good.
Connecting I2S directly to the DSP would require major surgery, and it would only be able to handle 96khz 24bits.

Does anyone know why one of the ADC's of the DCX inputs (left and right) are tied together? I know it is a mono configuration but why tied them? doesn't make sens to me
I've never understood that either. This is the ADCs that receive the C-channel input. For one, the tying together doubles the already low load on the driving opamp. That can't be good for the distortion performance.
It may have to do with how they switch the ADC outputs around to the switch matrix and DSP. Tying together probably saves them a switching pin, but I haven't checked that in detail.

jan didden
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Old 10th February 2011, 01:47 PM   #2964
sek is offline sek  Germany
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Input C is intended for measurements and other auxiliary purposes only. It therefore has a cheaper ADC than the main inputs (AK5383 as opposed to an AK5393 for inputs A and B).

I always thought that feeding both input channels of that ADC saves the DSP precessing power and eases code development efforts for spreading the monaural digital stream across multiple signal paths during the auto-align process.

I would imagine that leaving one channel muted would create more work and new problems with a now funny digital signal during software development.

Or maybe a DAC like this behaves odd in the digital domain with one channel "empty"?

Last edited by sek; 10th February 2011 at 01:51 PM. Reason: clarifications...
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Old 10th February 2011, 02:33 PM   #2965
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I never knew that input C was for auxiliary purposes only.
But upgrading the DAC would make it a fully functional input, just like A & B or am i wrong ?

ps. I was thinking maby one of the channels is used for the measurments, it was maby developed in software like this and the hardware is later cut down to overcome costs.

Last edited by egberttheone; 10th February 2011 at 02:35 PM.
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Old 10th February 2011, 02:41 PM   #2966
sek is offline sek  Germany
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Quote:
Originally Posted by egberttheone View Post
I never knew that input C was for auxiliary purposes only.
But upgrading the DAC would make it a fully functional input, just like A & B or am i wrong ?
According to Asahi Kasei, the AK5383 is pin compatible to the AK5393, yes. The 5383 isn't that bad, though.

Quote:
I was thinking maby one of the channels is used for the measurments, it was maby developed in software like this and the hardware is later cut down to overcome costs.
Simple as that, I guess. I assume the algorithms were developed first and the requirement for a stereo measurement signal somehow made it into the hardware specification.

No need for any magic to explain it.

My two cents.
Sebastian.
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Old 11th February 2011, 09:16 AM   #2967
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I dont think a stereo measurment signal.
I think they use for example Left as a audio input and Right for the measurement input.
It could be easly tested by removing the 2 resistors.
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Old 11th February 2011, 03:35 PM   #2968
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OK I finally got to try out my new DCX. Trying it drive it with a new Gemini CDMP-1400 player. Using the XLR outs from the player I hardly get enough power to light the -30DB lights on the input to the DCX. Assuming I what to run the inputs to the DCX as high as posible what would be the best way to fix this, without adding a preamp? Andy
Would bypassing the electrolytic caps on the input provide any gain?
Maybe I could use some step up transformers?
Should I try and modify the output of the 1400 player?
Andy
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Old 11th February 2011, 04:02 PM   #2969
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Maybe I could use some step up transformers?
It seems may of the over the shelf transformers have limited bandwith.
200Hz to 15KHz. Are thare any that will cover 20Hz to 20KHz?
What inpedence should I use 200 ohm to 100 ohm?
Andy
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Old 14th February 2011, 11:41 AM   #2970
Legis is offline Legis  Finland
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Balanced passive out modded DCX's THD, using digital input and balanced output, is nearly non-existent.

For quick comparison to the last weeks's measurements:

Unbalanced output, THD@-1dB = ~0,011%
Balanced output, THD@-1dB = ~0,0006%

Unbalanced output, THD@-10dB = ~0,004%
Balanced output, THD@-10dB = ~0,0003%

Also the IMD-measurements dropped at the same extent.


Here are the graphs (-4dB was taken with 24 steps per octave, others 6 steps pe
r octave)


Click the image to open in full size.
Click the image to open in full size.

Click the image to open in full size.

Last edited by Legis; 14th February 2011 at 11:44 AM.
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