PCM63 max compliance voltage

regal · 22nd July 2008, 02:30 PM

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 µV

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

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

22nd July 2008, 02:30 PM	#1
regal diyAudio Member Join Date: Jan 2004 Location: MD	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 ?

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22nd July 2008, 08:19 PM	#2
Bernhard diyAudio Member Join Date: Apr 2002 Location: Munich	IIRC it has a built in diode that causes clipping... PCM56: 1000000 µV

23rd July 2008, 01:50 AM	#3
wildmonkeysects diyAudio Member Join Date: Jan 2002 Location: socal, merka.	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

23rd July 2008, 02:38 PM	#5
regal diyAudio Member Join Date: Jan 2004 Location: MD	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.

24th July 2008, 12:26 PM	#7
regal diyAudio Member Join Date: Jan 2004 Location: MD	see the link Mr Tent posted above.

24th July 2008, 12:49 PM	#8
Juergen Knoop diyAudio Member Join Date: Jan 2007 Blog Entries: 3	aah sorry is 0,05% distortion is a typical performance? regards

24th July 2008, 12:53 PM	#9
regal diyAudio Member Join Date: Jan 2004 Location: MD	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.

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