sine waves on nos dac

regal · 11th March 2007, 12:12 AM

I was running test tones from my computer to a NOS 1543 DAC. Up to 15khz sounded fine. Over that and it skews the output to a lower frequency. So 16khz sounds like ~10khz. The sound card is fine I compared it to a OS DAC which was fine.

Francis_Vaughan · 11th March 2007, 02:42 PM

Curious. Interesting that:
22.05kHz - 16kHz = ~ 6kHz
16 kHz - 6 kHz = 10kHz.

Sum and difference products like this require significant non-linear distortion to produce. However if you have a NOS DAC with a poor to non-existant reconstruction filter you can end up pumping a huge amount of ultrasonic energy into your amp. Energy with all the alias frequencies. Quite possible that some downstream component is cheerfully creating your 10kHz tone from these. Have you looked on an oscilloscope? What happens when you go to 17kHz in? What are you listening with?

regal · 11th March 2007, 05:59 PM

I have no access to a scope. This is a DAC-AH to a diy hybrid tube amp (millett.) Anything over 16khz gets distorted to a lower freqency.

janneman · 11th March 2007, 10:13 PM

Quote:

Originally posted by regal
I have no access to a scope. This is a DAC-AH to a diy hybrid tube amp (millett.) Anything over 16khz gets distorted to a lower freqency.

What type of reconstruction filter do you use? Are you sure you can hear those different frequencies accurately? How about the speaker? Do you have access to a freq counter?

Jan Didden

regal · 11th March 2007, 10:34 PM

I'm using headphones and comparing the tone to a OS DAC . The DAC-AH has no filter. It is quite obvious (the skew in tone.)

janneman · 11th March 2007, 10:38 PM

Quote:

Originally posted by regal
I'm using headphones and comparing the tone to a OS DAC . The DAC-AH has no filter. It is quite obvious (the skew in tone.)

Well, if you run that DAC without filter, all bets are off. The digital audio system REQUIRES both a filter before the ADC and after the DAC precisely to avoid aliasing, which is what you have.

Jan Didden

11th March 2007, 12:12 AM	#1
regal diyAudio Member Join Date: Jan 2004 Location: MD	sine waves on nos dac I was running test tones from my computer to a NOS 1543 DAC. Up to 15khz sounded fine. Over that and it skews the output to a lower frequency. So 16khz sounds like ~10khz. The sound card is fine I compared it to a OS DAC which was fine.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
tuning forks for pure sine waves?	cuibono	Everything Else	13	17th September 2008 05:39 PM
Sine Wave Generator with bulbs (Sine-lightenment)	Rodeodave	Everything Else	6	21st July 2008 01:19 PM
Sine wave testing on sub(s)	jol50	Car Audio	3	14th January 2008 06:10 AM
Sine and square waves percieved pitch, why?	baggystevo82	Everything Else	33	11th March 2005 05:18 AM
Hello everyone! waves	Howard	Introductions	5	23rd July 2003 11:36 PM

New To Site?	Need Help?
Register to Participate Search Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


<a rel='nofollow' href='http://www.diyaudio.com/openx/www/delivery/ck.php?n=aa5cb2e9&cb=597506' target='_blank'><img src='http://www.diyaudio.com/openx/www/delivery/avw.php?zoneid=3&cb=597506&n=aa5cb2e9' border='0' alt='' /></a>	We're saving for a new server - help us to serve you by Donating Today and become a friend with benefits! Ads on/off / Custom Title / 2009 Tshirt / More PMs / Bigger Images / Advanced printing

11th March 2007, 02:42 PM	#2
Francis_Vaughan diyAudio Member Join Date: Feb 2005 Location: Adelaide	Curious. Interesting that: 22.05kHz - 16kHz = ~ 6kHz 16 kHz - 6 kHz = 10kHz. Sum and difference products like this require significant non-linear distortion to produce. However if you have a NOS DAC with a poor to non-existant reconstruction filter you can end up pumping a huge amount of ultrasonic energy into your amp. Energy with all the alias frequencies. Quite possible that some downstream component is cheerfully creating your 10kHz tone from these. Have you looked on an oscilloscope? What happens when you go to 17kHz in? What are you listening with?

11th March 2007, 05:59 PM	#3
regal diyAudio Member Join Date: Jan 2004 Location: MD	I have no access to a scope. This is a DAC-AH to a diy hybrid tube amp (millett.) Anything over 16khz gets distorted to a lower freqency.

11th March 2007, 10:34 PM	#5
regal diyAudio Member Join Date: Jan 2004 Location: MD	I'm using headphones and comparing the tone to a OS DAC . The DAC-AH has no filter. It is quite obvious (the skew in tone.)

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)