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-   -   PCM63 max compliance voltage (http://www.diyaudio.com/forums/digital-source/126770-pcm63-max-compliance-voltage.html)

regal 22nd July 2008 02:30 PM

PCM63 max compliance voltage
 
Couldn't find the max compliance voltage for the PCM63 in the datasheet, I heard PCM1704 is 25mV, same for TDA1541.

Is 25 mV a good number to use for the PCM63 ?

Bernhard 22nd July 2008 08:19 PM

IIRC it has a built in diode that causes clipping...

PCM56: 1000000 V ;)

wildmonkeysects 23rd July 2008 01:50 AM

A while back Lynn Olson (if I may paraphrase) looked for spurs up out of the noise floor, and found 75 ohms or less to be ok.

My ears were/are happy with a 50 ohm "i/v" load feeding a Lundahl LL1674 amorphous core 1:8. Lowish output voltage, but very good sonics.

Share and Enjoy,

WMS

Guido Tent 23rd July 2008 02:31 PM

Quote:

Originally posted by wildmonkeysects
A while back Lynn Olson (if I may paraphrase) looked for spurs up out of the noise floor, and found 75 ohms or less to be ok.

My ears were/are happy with a 50 ohm "i/v" load feeding a Lundahl LL1674 amorphous core 1:8. Lowish output voltage, but very good sonics.

Share and Enjoy,

WMS


Hi,

We have encountered long ago that 50 ohm might be some max value, consider the fact that the current output of the PCM DACs is not so good, and diodes start conducting a bit already at much lower voltages. Doede has done some measurements:

http://www.dddac.de/pcm63/DAC_I-V_Resistor.htm

We know use less than 1 ohm in our IV converter for the PCM1704

best

Guido

regal 23rd July 2008 02:38 PM

Yes my experience with the PCM1704 showed excessive sibilance at more than 10 ohms.


I am designing a new tube DAC around the PCM63, if 50 ohms sounds as good as 5 ohms then I don't need to spend the $'s on expensive step-up transformers.

Juergen Knoop 23rd July 2008 09:37 PM

Quote:

consider the fact that the current output of the PCM DACs is not so good
I always thought that DACs don't have current outputs but switched resistors or caps and they need to be fed into a perfect (virtual?) ground in order to sum correctly.
Is there measured data confirming that simple resistors or transformers can do the job?
regards

regal 24th July 2008 12:26 PM

see the link Mr Tent posted above.

Juergen Knoop 24th July 2008 12:49 PM

aah sorry
is 0,05% distortion is a typical performance?
regards

regal 24th July 2008 12:53 PM

I am thinking its high, trying to discern the max compliance voltage to minimize this.

With the PCM1704 its a known 10ohms/25mV's. The sound definately improves when you get under 10 ohms.

samoloko 2nd September 2009 11:36 AM

Quote:

Originally Posted by wildmonkeysects (Post 1567638)

My ears were/are happy with a 50 ohm "i/v" load feeding a Lundahl LL1674 amorphous core 1:8. Lowish output voltage, but very good sonics.

Share and Enjoy,

WMS

would you please give detail about that setup


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