Need help with this I/V stage replace...

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rfbrw

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Joined 2001
Lyra said:


Not nesseserely....balanced.
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Not sure what you mean by this statement but if you mean to contradict me that's fine by me.


According to Õàëÿâùèê I should not use R-2R parallel or balanced. Parrallel or balanced R-2R DAC will kill a sound. Better use trim circuit for tuning LSB.
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That's one opinion amongst many not the word of God. There are many topologies and as many opinions about them and I've yet to see a dac design written on a tablet of stone.


Whatever I have to do to gain maximal sound quality.
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What constitutes maximal sound quality is something only you can judge. Consider the easiest modification and go on from there.


What is the purpose with the SM5828 shift-register anyway ?
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To delay the data by half the sample time. It can be considered an additional 2x oversampling using linear interpolation.


What will happen with the sound if I bypass this ??
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It removes the delay and the attendant oversampling. It turns it into a balanced dac without a balanced output.

ray.
 
Lyra

Lyra

Member
Joined 2003
rfbrw said:

Not sure what you mean by this statement but if you mean to contradict me that's fine by me.
ray.
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What i ment was that my final CDP dosn't have to operate with balanced DAC's if it would be easier to make it play right/good in unbalanced mode.
The ZAPFilter could make the signal out balanced anyway if i want.....

All the best!
Lyra
 
Lyra

Lyra

Member
Joined 2003
Re: MSB trim......

Jocko Homo said:
You will need a test CD with a test tone, about -60 dB, and a 'scope.

Adjust the MSB trim for the lowest distortion, which can be seen on a 'scope.

Do not do it with a 0 dB signal, as you will find in most service manuals. It will be wrong. Trust me on this one.

Jocko
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I burned some test tones (1000Hz/-60dB sinus) on a CD using <Test Tone Generator>, and <Nero>.

BUT..... when I play this CD in the player, hook on the ocilloscoop on the players output...... I don't se any difference when I turn the potmeter.
I marked the pot's with a thin marker before I begun testing, so I could find "my way home again" just in case.

Shouldn't this distortion be clear when looking on a osilloscop ?
My osilloscop is old, but I can see the sinus-signal perfectly clear on the screen.

What am I doing wrong ?
Wrong frequence ?
Wrong curve ?
Anything....!?

Lyra
 
R

rfbrw

Member
Joined 2001
Ahhh the tyranny of measurements. Give JH a call. He's the AD1862 guru.
As for the CF37606, the D.A.T.A Master Type Locator and Discontinued Devices databooks list it as a gate array i.e. a custom chip. Finding data will be difficult but you could test it to find out what it does.
 
Bernhard

Bernhard

Member
Joined 2002
The benefit of measurements.

rfbrw said:
Ahhh the tyranny of measurements.
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Both channels distortions look very similar, this is very unlikely to happen normally , and in combination with the fact that the MSB adjustment does not work (why then they put it there ??? ), it strongly points into the direction that some of those DSP chips are to blame.
 
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rfbrw

Member
Joined 2001
Re: The benefit of measurements.

Bernhard said:


Both channels distortions look very similar, this is very unlikely to happen normally , and in combination with the fact that the MSB adjustment does not work (why then they put it there ??? ), it strongly points into the direction that some of those DSP chips are to blame.
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This suggests that you have not really understood the function of the adjustment.
 
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