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Old 15th June 2009, 02:52 PM   #1
schmike is offline schmike  Hong Kong
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Default PCM 1702 I/V Stage

anyone can told me how can i built the Tube i/V stage
I find out have a srpp circuit but i think it is out of phase
i want to built a same phase i/v stage using tube
the maxium i/v resistor for pcm 1702 is 1k
i can't find the good circuit
please help
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Old 15th June 2009, 06:34 PM   #2
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PCM56 DAC with 6SN7 output stage
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Old 16th June 2009, 04:30 PM   #3
schmike is offline schmike  Hong Kong
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THX
BUT It also is out of phase
I don't want to use opt or I/V TX for this output
srpp is 180 degree phase shift from the input
so the ciruit isn't the best circuit
anyone can give me a better circuit for me?
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Old 17th June 2009, 08:15 PM   #4
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Invert the digital signal.
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Old 18th June 2009, 08:06 PM   #5
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Quote:
Originally posted by schmike
THX
BUT It also is out of phase
I don't want to use opt or I/V TX for this output
srpp is 180 degree phase shift from the input
so the ciruit isn't the best circuit
anyone can give me a better circuit for me?
2nd option: invert the speakers

anyhow, there is no such thing as absolute phase
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Old 19th June 2009, 08:52 PM   #6
oshifis is offline oshifis  Hungary
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Well, I always believed that a sound pressure peak (like that caused by hitting a bass drum) at the recording studio should cause a sound pressure peak (as caused by the outward movement of the loudspeaker diaphragm), at least at low frequencies. The phase shift of crossovers makes this nonsense at higher frequency. Is the absolute phase detectable by the human ear or not - this is another question, but IMHO absolute phase does exist up to the loudspeaker terminal. The reference is the signal at the microphone terminal (speaking about a single omni mic). A pressure increase induces positive voltage at the hot terminal.
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Old 19th June 2009, 09:15 PM   #7
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Quote:
Originally posted by oshifis
Well, I always believed that a sound pressure peak (like that caused by hitting a bass drum) at the recording studio should cause a sound pressure peak (as caused by the outward movement of the loudspeaker diaphragm), at least at low frequencies. The phase shift of crossovers makes this nonsense at higher frequency. Is the absolute phase detectable by the human ear or not - this is another question, but IMHO absolute phase does exist up to the loudspeaker terminal. The reference is the signal at the microphone terminal (speaking about a single omni mic). A pressure increase induces positive voltage at the hot terminal.

SPL is independent of polarity
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Old 20th June 2009, 06:28 PM   #8
oshifis is offline oshifis  Hungary
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Sure. Just swap the hot and GND (red and black) wires of the left speaker cable, leave the right unchanged. You'll be surprised
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Old 20th June 2009, 06:57 PM   #9
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Quote:
Originally posted by oshifis
Sure. Just swap the hot and GND (red and black) wires of the left speaker cable, leave the right unchanged. You'll be surprised

I do not deny the presence of differences in perceived sound when doing so, but please consider that one never knows if overall polarity is "correct" when connecting black to black and red to red. Polarity changes throughout many components.

And then, still, many multimike recordings make a mess out of polarity

so, "absolute" polarity does not exist
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Old 20th June 2009, 07:32 PM   #10
oshifis is offline oshifis  Hungary
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You are absolutely right, I must have misunderstood you, sorry for that. I meant absolute polarity does exist in theory, it could be realized in practice, but as you said many factors make it difficult to reach. A good example is a mixing console: nobody knows how many inverting stages are in series in the signal path.

BTW, on the recording side, is there any standard that dictates preserving absolute polarity during the recording process? I mean if the sound pressure increases in the studio (causing positive voltage at the microphone terminals), the binary word increases on the compact disc (causing positive voltage at the output of a noninverting I/V stage), or the groove goes up on the LP (causing positive voltage on the pickup terminals).
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