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Old 27th February 2011, 04:56 PM   #1
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Join Date: Jan 2006
Location: Italy
Default DEM reclock with TDA1540

Did someone succesfully implement DEM reclock with old TDA1540 dac?
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Old 3rd March 2011, 01:18 PM   #2
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Join Date: Mar 2004
Location: Budapest, Hungary
I've just done latch signal (LE) reclockig, but I think DEM reclocking can be implemented the same way as with the TDA1541A. As for the latter, I coupled the Q and Q! outputs of a 74HCT74 to the DEM pins with 1nF capacitors each. The flipflop divided the master clock to 705.6 kHz (/16 division from 4.2366 MHz). It worked. I want to experiment with transformer coupling, instead of capacitor coupling.
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Old 3rd March 2011, 01:45 PM   #3
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Join Date: Jan 2006
Location: Italy
are you talking about LE reclocking between SAA7000 and TDA1540?
I haven't been able to get it working. Anyway, incredible, just today I was able reclock the DEM with the 1540. I use the dc coupled ECdesigns schematic with an about 1MHz signal (BCK, Q and /Q, obviously). I had to use four diodes (I think ECdesigns suggested this for multiple 1541 setups), 2K2 from the DEM pins to -17V and 15K. With scope waveforms are not as clean as with original capacitors, but it sounds excellent! I also listened to a -40db, or so, recording and it's ok. When I'll have finished last fine trim I will post final resistor value.

Last thing, Q and /Q signals can be supplied randomly on the DEM pins, or there's an order?
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Old 3rd March 2011, 02:33 PM   #4
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Join Date: Mar 2004
Location: Budapest, Hungary
I did LE reclocking as per the attached PDF.
I think Q or Q/ to which pins is not important,
Attached Files
File Type: pdf no_oversampling.pdf (27.8 KB, 544 views)
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