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Old 5th October 2004, 09:33 PM   #1
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Default tda1541 vs. PCM56

Hi,

upper graph is Philips CD880 , lower graph is Denon DCD1500II with PCM56 and accurate distortion adjustment.

Click the image to open in full size.
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Old 5th October 2004, 10:29 PM   #2
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And ?
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Old 5th October 2004, 10:47 PM   #3
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both non oversampling, both same I/V stage and filters ???
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Old 6th October 2004, 06:36 AM   #4
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And ?

As always this is with -60dB signal. TDA is clearly distorted while PCM is much better and distortion is below noise floor.

It simply means that in low level music passages you will hear the difference.

Both standard implementation as in the CDP.

The difference between the chips is that PCM allows for adjustment and TDA does not.

This adjustment makes a big big difference.
The PCM might look worse than the TDA when unadjusted.

Also some ( even unadjusted ) PCMs are better than all TDAs I have seen.

Strangely some PCMs already measure very good in a circuit without adjustment pot, while others perform even better with adjustment.

It is very very difficult to do the adjustment with a standard pot, 10turn pots are necessary.

Also there is temperature drift, best is to wait 12 hours before doing it.
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Old 6th October 2004, 07:23 AM   #5
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Hi all,

Quote:
Till wrote:
both non oversampling, both same I/V stage and filters ???
That' s exactly the point:
as a matter of fact, you did not test the performances of the DAC chips alone, but of the two chains oversampling(if any)/DAC chip/I-V converter/analog filter...
What about the jitter in the two players?
Did you use exactly THE SAME CD (I mean, swapping it from one player to another)?

Don' t get me wrong, I' m not saying that there' s no differences between the two chips, I just mean that the differences you measured are probably not due to the DAC chips only.

Anyway, it is interesting... guess I' ll look for some PCMs and try to build a DAC unit (but before I have to finish my TDA1541A
)

Cheers,

Bruno
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Old 6th October 2004, 08:03 AM   #6
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Hi Bernhard,
Would you have the circuit diagram of the DAC section with the PCM56.
I got one chip from an old CD player. I'd like to try it out.
Also the circuit of the IV converter you used.

Thanks,
Ashok.
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Old 6th October 2004, 08:25 AM   #7
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Quote:
Both standard implementation as in the CDP.
so it does tell nothing - except there is harder filtering at the PCM and it will be better reproducing sinewaves at low levels. But usually you donīt listen to sinewaves, thus you canīt say it will be better when playing music by looking at those curves. You canīt state the distortion of a complex musical signal will be smaller with the PCM, from these curves!

Other way we could say the PCM (in this implemetation of course) does lie more, as there is nothing like a that low distorted -60dB information on a CD...

try the same with a square wave and some autocorrelation...

By the way.I still prefer the AD1865 - but tests are only soundwise.
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Old 6th October 2004, 09:21 AM   #8
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Very interesting Bernard. Could you put some objective numbers to go along with your photo, (Volt out, THD, bandwidth, freq, sample freq, clock freq...IV opamp)? How do these compare with the quoted value of the datasheets?
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Old 6th October 2004, 02:14 PM   #9
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Quote:
Originally posted by Carondimonio
Hi all,



That' s exactly the point:
as a matter of fact, you did not test the performances of the DAC chips alone, but of the two chains oversampling(if any)/DAC chip/I-V converter/analog filter...
What about the jitter in the two players?
Did you use exactly THE SAME CD (I mean, swapping it from one player to another)?

Don' t get me wrong, I' m not saying that there' s no differences between the two chips, I just mean that the differences you measured are probably not due to the DAC chips only.

Anyway, it is interesting... guess I' ll look for some PCMs and try to build a DAC unit (but before I have to finish my TDA1541A
)

Hi Bruno,

I have tested all combinations of TDA /B & SAA A/B chips with and without os in different players like Philips CD304mkII, CD880, CD960 and PCM56 /J/K in Denon DCD1500mkII, DCD3300 and a Kenwood.

Always for the PCMs a good chip was a good chip in every player and achievable results with PCM are clearly better than TDA .

CD was always the same.
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Old 6th October 2004, 02:47 PM   #10
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Quote:
Originally posted by ashok

Would you have the circuit diagram of the DAC section with the PCM56.
Also the circuit of the IV converter you used.

I did not follow the tracks on the pcb to get the schematic, look for the data sheet.
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