Non oversampling DAC with TDA1543

It's already 5 years ago when I made the nonoversampling DAC. I was realy not sure about conclusions in article writen by Mr. Kusunoki . But after years of using NONOS DAC I realy like this sound and I have not problems with alaising - using only simple LC filter at the output of DAC. Without additional filter or output buffer. Also my audio chain is a good filter ;-)

As CD transport I used CD-ROM drive - not the best solution. I modified old TESLA CD player MC911. The most parts in this type are Philips, the CD unit is CMD 4, decoder SAA7210, filter SAA7220 and the DAC is TDA1541.

I used the DAC schematics with four TDA1543, ... is well known DAC from internet.

Working point of TDA1543 is dependent on supply voltage and the output current. Optimal adjustment of power supply is 8,6 to 9,0 V. Minimal THD can be achieved by the value of R5 ( output current ) I reached about 0,007 % THD at 440 Hz on 0 dB = 1,2 Vrms output voltage. For 2 Vrms is value 680 Ohm of R8 and R9 needed.

The best sonic results I get with power supply with the NiCd batery ( 7 pieces of Sanyo N-1250SCRL ). But this is very unpractical. In fully charged state has the battery 9,6 V - too much for TDA1543 I think, for long time I have tested 9,2 V.

The line voltage in area where I live is very stable 238 V +/- 3 V without peaks and riplles. So I can use this simple power supply. In most cases is this power supply not recomended !
If the supply voltage is more then 8 V, then the TDA1543 must be cooled.

A wanted to compare the NON and OVERsampled sound, so I made this simple switch with multiplexer 74HC157. All necessary signals I found on SAA7220 chip. Pins 1, 2, 3 are nonoversampled WordSelect, Clock and Data from dekoder SAA7210. Pins 18, 16, 15 are 4 times oversampled signals. Enable pin on 74157 multiplexer is used to dissabling non vallid audiosamples. Of course, the better way is mute the analog signal.

When I switch from OVERsampling to NONoversampling, the reduction of noise is remarkable, the highs are clearer and brighter. The overal soundstage is better. I get more detailed sound, suddenly I hear background intruments and vocals that got lost with OVERsampling. I remaind me at first hours wits this DAC - I enjoyed whole night hearing of "new sound".

O V E R sampling DAC measuring.

This is a typical waveform of oversampled square signal.

Right is the spectrum of 440 Hz sinus signal 0 dB. I think, that filter SAA7220 adds distortion and noise in audible range of frequency comparing to nonoversampled spectrum.

N O N oversampling DAC measuring

The Square waveform of signal 1kHz 0 dB. Also the slave rate is a litle bit better.

Right is the spectrum of 440 Hz sinus signal 0 dB in audio range - to 20 kHz. I can't measured this spectrum in range 20Hz - 200kHz. But I now, there would be the alaising frequency products - serious problem for dolphins, dogs and vampirs, they shouldn't use this DAC ;-)

The last time a spend enough time with tweaking CD players, this is time and money consuming process often with inexpressive result. This DAC is very cheap ( I don't use SP/DIF to I2S converter ) and the result is surprising good. The overal concept is very promising. I will try make DAC with 12 pcs TDA1543 ... and I did

17.10.2005