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.
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.
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
)
Cheers,
Bruno
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
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 don´t listen to sinewaves, thus you can´t say it will be better when playing music by looking at those curves. You can´t 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.
Carondimonio said: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
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.
tschrama said:
-60dB 1kHz sine from CD, amplified with OP27 after DAC.
Analyzer bandwith set to 10 kHz, picture shows 1kHz & K2-K9.
Noise floor on all players around -64dB ( 1kHz signal set to 0 dB on analyzer )
Harmonics around -55dB for TDA and around noise floor for PCM.
Vertical scale 10dB / div.
Quoted value of the datasheets for BB PCM chips is always without adjustment. And chips are very different. Some are very good, some very bad, independent of J or K markings and I am afraid this is because of parameter chancges due to aging.
A K-chip may turn into crap after years of use and vice versa.
till said:
As mentioned before PCM chip performances vary a lot.
I am looking for the golden ones
If You would be right, the bad chips must look good from heavy filtering but they do not. Same with unadjusted pots.
Also there is no reason for heavy filtering because it is 4xfs like TDA.
It does not matter if we listen to sine waves or music, there are also pure tones in music where low distortion is important.
Tell me a reason why music will not be distorted when sines are...
Thanks Bernard.. but this seems toooo good to be true..
the BB chip is quoted to have -35dB THD at -60db out/1KHz.. You say you can adjust that to -64dB?? How the hell is that possible..? How can you adjust a 16 bit DAC from -35dB to -64 dB THD?
The TDA5141 has a quoted THD of (around) -40dB, and is among the best ever made.. Yet you measure -55dB THD?? That surely isn't possible??
Offcourse I could be wrong.. but maybe there slibbed a error in your measurement methods?
Don't wanna be hard on you m8, but your results a extraordinairy, i'm just very interested
the BB chip is quoted to have -35dB THD at -60db out/1KHz.. You say you can adjust that to -64dB?? How the hell is that possible..? How can you adjust a 16 bit DAC from -35dB to -64 dB THD?
The TDA5141 has a quoted THD of (around) -40dB, and is among the best ever made.. Yet you measure -55dB THD?? That surely isn't possible??
Offcourse I could be wrong.. but maybe there slibbed a error in your measurement methods?
Don't wanna be hard on you m8, but your results a extraordinairy, i'm just very interested
I fear you look on it from the wrong point. Maybe because you fell in love with the spectrum analyzer toy...
Let say distortion is the difference between what you put in and get out. You look whats coming out of a system and say the more it looks like a sine, the better it is. But what you feed into the system is far from beeing a sine, you only belive in it would be a sine. But a -60db 16 Bit PCM signal is far from beeing a sine, thus the system you call good because it gives you a fine sine output does lie. In case you feed in a signal that is not a sine by definition, you can´t say if there is more difference beween input and output caused by the circuit that makes it look more like a sine, or that what makes it look more like a staircase or whatever. It depends on the specific wavefom. Also: in case you look at -60dB sine whats coming out of the DAC and tell the quality by THD measurement, what you measure ist the filtering and not the DAC chip.
till said:
So tell me why not !
BB publishes the same kind of measurements for their modern DACs like I do, -60dB signal with spectrum analyzer.
Philips does the same thing but simple THD.
And: What is a complex waveform ?
In the end it can always be traced back to a sine with harmonics and nonharmonics which are sines again.
What is the difference to convert a sine or a lot of it ?
By the way, I hear the difference with music too.
you convert only the lower one and filter out everything else?
Maybe measurement is done this way because its easy to measure. But it not necessarily tell you something.
Die Grundannahme das das Signal jeweils einem Sinus ähnlicher als einer stufenartigen Wellenform wäre, und folglich möglichst als solcher generiert werden soll, muss nicht unbedingt richtig sein.
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