Thanks Tam Lin, I remember your advices regarding computer for my 24x pcm63p-y dac. unfortunately i will not use this dac (wadia) with computer. after 18years of use computers i moove back to disc transports(cd transport and dvd-audio transports) so in hardware i just reverse data with 74hc86, reclocking at the same LE and clock? ? i didint thought it was so simple. i want to try balanced wadia. all wadia i have is single ended.
The problem is that with binary arithmetic, there is a difference between inversion and negation.
Inversion is a logical operation that is applied the each bit individually. The rule for inversion is invert every bit.
Negation is an arithmetic operation and is applied to the value of the data represented by the collection of bits. The rule for negation is invert every bit and then add 1 to the resulting binary number.
When you invert the number 0, you get -1.
When you invert the number 1, you get -2.
And so on...This is not the behavior you want to create a balanced signal.
When you negate the number 0, you get 0.
When you negate the number 1, you get -1.
And so on...This is the behavior you want to create a balanced signal.
A problem with negation is that certain input can lead to binary overflow and the wrong result. Recognizing and correcting overflow with a hardware implementation is not simple, but is easy with software.
You should also know there is no value in using a pair of DACs to create a balanced signal, even if you do the proper negation of the input. One DAC will be converting a positive number while the other is converting a negative number. It is unlikely the two DACs will be sufficient matched to make it worthwhile.
Inversion is a logical operation that is applied the each bit individually. The rule for inversion is invert every bit.
Negation is an arithmetic operation and is applied to the value of the data represented by the collection of bits. The rule for negation is invert every bit and then add 1 to the resulting binary number.
When you invert the number 0, you get -1.
When you invert the number 1, you get -2.
And so on...This is not the behavior you want to create a balanced signal.
When you negate the number 0, you get 0.
When you negate the number 1, you get -1.
And so on...This is the behavior you want to create a balanced signal.
A problem with negation is that certain input can lead to binary overflow and the wrong result. Recognizing and correcting overflow with a hardware implementation is not simple, but is easy with software.
You should also know there is no value in using a pair of DACs to create a balanced signal, even if you do the proper negation of the input. One DAC will be converting a positive number while the other is converting a negative number. It is unlikely the two DACs will be sufficient matched to make it worthwhile.
This is implying at hardware invertsion od the data word. Since there is no "software" burned into the pcm1704.
So If this hardware way is working for PCM1704 the same way should work with other PCMs with same input format. I would try the same logic for booth data lines original and inverted. To have same very small delay of data lines.
another question: will this improv the sound?
OR it is just to match balanced input in the preamp, without bying expensive line transformer?
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I can recommend to lave like it is. And add balalnced line transformer at the end.
The didgital hum will not "cancel" itself with ditaly balanced DACs but maybe just higher?
It is not like in analog signal...
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If You have 24x parallel dac end, current dac output, I persume that You are using Riv simple conversion, (because of the very high amount of Io for any other way easily to convert to voltage). Exept in case that every DAC chip has own OP or other circuit for IV conversion...
thera are already -180deg output and should be corrected with transformer. Because Riv +Io conversion shifts voltage signal to -Vo...
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The advantage is that the output resistance of that paralleled dac end is so low, that You practicaly can use a "poor" transformet to get excellent results. Does not deserve higher primary inductance, low number of turns, low wire resistance in prim and sec, low caacitances, low lackage ind, etc etc
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It could be classic repeaing coil 1+1 : 1+1.
cheers
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