Output level of Sony cdp-395 - diyAudio
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Old 3rd January 2013, 06:19 PM   #1
ytsoc is offline ytsoc  Romania
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Default Output level of Sony cdp-395

Hello ,
I got this player and the output seemed kinda low.
So i put a 1khz tone on a cd and i measured 0.7v peak to peak output.
Is this normal? The specs say it has 2 volts output .
I removed all circuits after the buffer stage and the results are the same, replaced op-amps , nothing changed.
I don't know what else could be at fault that is common to both chanels
I do have an osciloscope .
Here is the output stage:
Click the image to open in full size.
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Old 3rd January 2013, 06:22 PM   #2
DF96 is offline DF96  England
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Problem with the muting circuit?
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Old 3rd January 2013, 06:23 PM   #3
Mooly is offline Mooly  United Kingdom
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It depends what level the tone is on the CD

A 0db tone should be playing back at around 5 to 6 volts peak to peak. Check the calibaration of your scope too.

I doubt you have a real fault with the player.
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Old 3rd January 2013, 06:30 PM   #4
ytsoc is offline ytsoc  Romania
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Quote:
Originally Posted by DF96 View Post
Problem with the muting circuit?
removed everything after the buffer output(even the output caps)

Quote:
Originally Posted by Mooly View Post
It depends what level the tone is on the CD

A 0db tone should be playing back at around 5 to 6 volts peak to peak. Check the calibaration of your scope too.

I doubt you have a real fault with the player.
test tone is indeed at 0db, scope is ok(but even if it was faulty , compared with a technics tuner, and pc , the cd-player sounds a lot weaker)
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Old 3rd January 2013, 06:37 PM   #5
Mooly is offline Mooly  United Kingdom
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Have a look at the signal with the scope on the output of the first two opamps (the TL082's). That should be the same amplitude as you would get at the final output sockets.

If it really is a 0db tone then that suggests a problem somewhere but I find that hard to believe I've never ever once had a low amplitude problem from any player. If the player has an unknown history or hasbeen worked on then check that BOTH feeds to the differential amps are present. That is the signal on those two red arrows going to each opamp. A normal music CD should have peaks approaching 2.5 volts (5 volts peak to peak). Try it.
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Old 3rd January 2013, 06:42 PM   #6
Mooly is offline Mooly  United Kingdom
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It just so happens I have a similar-ish player on the bench at the moment,
Sony CDP790 and KSS240 Restoration Project

and so I know what the levels should be. The 2 volts you quote will be 2 volts RMS (a kind of standard for many players) which is 5.66 volts peak to peak at 0db.
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Old 3rd January 2013, 06:43 PM   #7
ytsoc is offline ytsoc  Romania
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output voltage p-p at output pin of first op-amp is about 1.5v then after R369 drops to 0.7volts.

Here are some scope shots:
inverting input of first op amp:
Click the image to open in full size.


non inverting input of same op amp
Click the image to open in full size.


output of first op amp(1.5V)
Click the image to open in full size.

input/output of buffer(second op amp)
Click the image to open in full size.
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Old 3rd January 2013, 06:48 PM   #8
Mooly is offline Mooly  United Kingdom
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That doesn't look right. The output of the first opamp looks incredibly noisy.

Let me just look at mine... 5 minutes
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Old 3rd January 2013, 06:57 PM   #9
Mooly is offline Mooly  United Kingdom
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OK. The output of the first opamp on mine is around 5.8 volts peak to peak. It looks absolutely clean and clear.

The signals on the two input pins of the first opamp also look clean and clear and are around 1.2 volts peak to peak.

If you want pictures it will have to wait 'till tomorrow but they are just a perfect clean and clear sinewave.
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Old 3rd January 2013, 06:58 PM   #10
ytsoc is offline ytsoc  Romania
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welp, since up to the input pins of first op amps we only have passives can i assume that the DAC is toasted?
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