What is better sounding I/V con. ? - diyAudio
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Old 12th July 2005, 04:32 PM   #1
Gasho is offline Gasho  Croatia
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Default What is better sounding I/V con. ?

What I/V conversion on BB PCM63K gives more natural , and transparent sound .

Active (AD847) , or passive with high quality , precision resistor (100ohm) connected from current output of DAC to ground?
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Old 13th July 2005, 04:39 AM   #2
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Passive.
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Old 13th July 2005, 05:12 AM   #3
Gasho is offline Gasho  Croatia
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Or transformer coupled.?
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Old 13th July 2005, 05:26 AM   #4
Gasho is offline Gasho  Croatia
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OK , my player is made with PDM100 HDCD dekoder , and it have some kind of relay (S301) . I donīt know is it some kind of gain switch or emphasisi filter or.......
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Old 13th July 2005, 08:30 AM   #5
zinsula is offline zinsula  Switzerland
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If you want to go with opamps, try this very inventive implementation of the AD844 (common base), which avoids the drawbacks of "standard" opamp I/V's:
http://users.verat.net/~rogic/1541/1...ev1_1b_sch.pdf

Read also all explanations on that website. Be aware that you can only use AD844 (and _very_ few others) with such an implementation. Not all current feedback opamps give access to the required circuit nodes.

And you'll need to make some mods, AFAIK PCM63 has not the asymmetric current range as TDA1541.
(I believe the circuit will be simpler in the PCM63 case)

Tino
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Old 14th July 2005, 07:29 AM   #6
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Default PCM63K

Gasho!

I would give a try to Pass D1 output (Pass uses PCM63 too...)

Regards,
Milan
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Old 14th July 2005, 07:30 AM   #7
Gasho is offline Gasho  Croatia
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I am going to do it passive. I will try 100ohm as reference , and +/- 10ohm variations. After that I will put a passive 6db/okt low pass filter (20KHz) than pass that signal to OP (output stage with gain).
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Old 14th July 2005, 07:58 AM   #8
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Default S301

I think, it is something with filter characteristics (probably)...
Would need mre time to study the schematics
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Old 14th July 2005, 09:02 AM   #9
Gasho is offline Gasho  Croatia
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Default Re: PCM63K

Quote:
Originally posted by mpopovics
Gasho!

I would give a try to Pass D1 output (Pass uses PCM63 too...)

Regards,
Milan
Hmm , I canīt find the data about that type of I/V conversion.

Probably that sistem work only if two DACs per channel works in balanced mode (on one DAC the signal is phase reversed in digital domain).
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Old 14th July 2005, 09:05 AM   #10
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Gasho,

That switch is the normal /hdcd mode filter. When HDCD is not active, you have to apply 6dB attenuation, which can be done internally in the pmd100, but You loose resolution, or externally in an analogic way, which can be seen on the schematics. [this is the proper, good solution]

By the way, thanks for the schematics!

Did You notice the tricky I/V solution applied here by Rotel? I have noticed that when I peeked into my one, and have a certain respect for it. Maybe it would worth a bit deeper digging into..
And, if You decide to go passive, your output resistance is just there, 100 ohm

Ciao, George
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