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Old 4th June 2005, 06:28 AM   #1
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Default Does digital data inverted results in analog signal inveted?

Hi guys,

I am trying to end of a DAC output with SRPP tube stage (phase inveted).

If I add a hex inverter, say 7404, to invert digital sdata of digital receiver and feed into DAC. Would the analog output inveted??

If it is inverted, then final output from SRPP stage will be in normal phase..
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Old 4th June 2005, 09:48 AM   #2
bocka is offline bocka  Germany
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Hi Tubeee,

yes, analog output will be inverted.
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Old 4th June 2005, 01:37 PM   #3
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Default Yes...

...but you will have one LSB error
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Old 4th June 2005, 02:02 PM   #4
guido is offline guido  Netherlands
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Default Re: Does digital data inverted results in analog signal inveted?

Quote:
Originally posted by Tubeee
Hi guys,

I am trying to end of a DAC output with SRPP tube stage (phase inveted).

If I add a hex inverter, say 7404, to invert digital sdata of digital receiver and feed into DAC. Would the analog output inveted??

If it is inverted, then final output from SRPP stage will be in normal phase..
Depends on the dac, or better the coding of the data. With two's complement coding (e.g. the way a tda1541 is usually used) that works. Check your dac's/filter/receiver datasheet.

Why invert anyway? Do you care that much about absolute phase? I wonder if you can hear the difference
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Old 4th June 2005, 03:25 PM   #5
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Thank you all guys,

It will be installed in a 8412-1541 so I think it will work.

The reason I want to reverse phase is that there are many recordings were done by wrong phase and I would like to check what's difference in reverse phase.

By the way, there is a track demonstrating "in phase" and "out of phase" sounds in a CD "Test & Burn-in CD" published by Sheffield/XLO. It is designed to fine tune the "toe in" angle of speakers. Does anyone experienced this? Will the "in phase" turnning into "out of phase" when inverted phase is applied by DAC?

Bernhard, I know the one bit of LSB error. It had been discussed but I don't think it will be an issue since all bits are shifted.
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Old 4th June 2005, 11:49 PM   #6
guido is offline guido  Netherlands
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That test cd is probably between channels in and out of phase.
To figure out if you have swapped one of the speaker cables.
At least on my test cd.

Inverting the dataline will invert both channels. Something else.
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Old 5th June 2005, 12:01 AM   #7
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Default be aware...

Tubee...

you must take some care when phase is the matter.

Sheffield Labs CD and many others offers phase test track regarding phase between channels, when phase of right channel is reversed to the left channel, and this way you will listen to a significant difference between in phase/out of phase signals. In phase signals is a MUST BE in this case.

At other side, phase regarded by the data signal as you asked, will invert both channels at same time, resulting in a IN PHASE signal anyway.

One thing is to invert the phase between channels and is completely different from inverting phase signal overall, and IMHO, we hardly heard the difference (overall data inverting), unless you have a very good room, loudspeakers, and confident amplifiers... and very good ears too.


Got it?

Best regards...

Euclides.

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Old 5th June 2005, 12:11 AM   #8
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Default LSB error

uhmm..
I was concerned about this error when inverting the digital to get balanced analog signal out... but, when analised at osciloscope and DVM, I realised 1 LSB error is so small voltage error that op. amp. offset error will mask, even precision OP.amp. like AD797.
So, you can adjust this small LSB error summing with offset voltage error at adj pins...

(my DAC is 20 bits precision, PCM1702)


Am I misunderstanding this??
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Old 5th June 2005, 12:13 AM   #9
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some DACs are using Gray coding with just one bit changed beetween neighbour values to get rid of peaks coused by non equal change of state. In 'normal' coding when 0111 1111 1111 1111 changes into 1000 0000 0000 0000 15 bits are changed and imagine how it looks if they don't do it simultanously. Assuming neighbour value change is most probable Gray coding make sense. Than inverters will destroy the wave. Anyway if you want to experiment with phase why not simply put speakers out of phase?
regards
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Old 5th June 2005, 12:18 AM   #10
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I agree....

but maybe he wants to change it from the seat, and try to hear the difference at the touch of a button,hehe...

but if the code is BTC ( binary two´s complement), no problem beyond the 1 bit error.

Regards to all.
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