PMD-100 options?

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I don't think you need it if you're using a 20 bit PCM63P, but if you're using the PMD100 to feed 16-bit DACs I'd probably use it.

Rigging a PMD100 to turn dither on/off should be pretty simple to do - tie the DITH pin one way with a resistor, and switch it the other way with a toggle switch or something. Then put on some music and toggle the switch back and forth and see what you prefer.
 
While the PMD-100's dither is non-adjustable, the PMD-200 offers a choice of several dither modes from none to maximum. In addition to having different gross magnitudes, the dither modes also use different algorithms to produce their dither. We ran in the factory default of minimum dither. (The no dither mode is disrecommended for listening purposes by Pacific Microsonics.) Comparing the different available dither modes would be an interesting future experiment.

http://www.jeffchan.com/audio/filter-comparison.html
 
Taken from below link:

"While the PMD-100's dither is non-adjustable, the PMD-200 offers a choice of several dither modes from none to maximum. In addition to having different gross magnitudes, the dither modes also use different algorithms to produce their dither. We ran in the factory default of minimum dither. (The no dither mode is disrecommended for listening purposes by Pacific Microsonics.) Comparing the different available dither modes would be an interesting future experiment. "

http://www.jeffchan.com/audio/filter-comparison.html
 
I'm running in sw mode and can switch between the various modes. I cannot recall that i've heard a difference too. Depends on the rest of the chain, including my ears.

But i could measure a difference.

Witout dither.
 

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With max dither, same settings on the 7L5.

centre of the screen is 50kHz and it's 10kHz per division.
So you see 0 to 100kHz. Peek at 0 kHz is not there in real live, comes from the SA.

Top is at -40dB and it's 10dB per division. So -40 to -120dB on the screen. But don't think this thing is calibrated after decades.....

But you can clearly see the difference: Much more noise outside the audio band, but a few dB less within the audio band.
 

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When starting upgrading the player I found something interesting. The Rotel RCD-971 has a jumper for turning the dither on or off. It is located close to the PMD-100 chip.

I did not notice it before, because it is not in the schematic, there dither is permanent connected (10k to +5Vd), but in layout you can se the jumper...

So, everyone can easily test the dither influence...


As I have made a discrete I/V stage without filter, directly after the PCM63, I have disided for the non-dither, perhaps because of the increased HF noise might upset my system further down...



:)
 
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