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Old 29th September 2003, 02:28 PM   #1
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Angry TI PCM1792 vs AnalogDevices AD1955.

Ok, in listening tests, which one is better?

I really, really, really, hat the fact that TI rates their THD+N and most graphs in % and AnalogDevices rates their specs in -xxx dBFS.

It's like both of these companies are hiding something...
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Old 29th September 2003, 02:47 PM   #2
Electrons are yellow and more is better!
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If one company uses inches and another meters, you're right, there is something fishy going on.

Brian this is really simple:

0.1% = -60dB
0.03% = -70dB
0.01% = -80dB
0.003% = -90dB
0.001% = -100dB
0.0003% = -110dB
0.0001% = -120dB

Hope this helps.

The sounds vs the two chips, I don't think it is a huge difference(CD, 44/16), never listened to them though.
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Old 29th September 2003, 03:03 PM   #3
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OK, by your numbers, the Analog Devices' AD1955 has a better THD+N (much more important to me), which is what I prety much expected. Even though TI's dave has a better listed dynamic range.

I've always prefered their high end stuff over Burr-Brown / TI.
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Old 29th September 2003, 03:13 PM   #4
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Check carefully:

PCM1792, 44 kHz, 0.00025% (according to graph)

AD1955 48 kHz, 0.0003%

The difference is huge, don't you think?
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Old 29th September 2003, 03:47 PM   #5
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Ohhhh, Gigantic, BTW, I was comparing both DACs in Mono mode, 192Khz, 24 bit.

If I'm reading the graphs correctly:
TI @ 192 Khz THD+N = 0.001%, or - 100db.
AD @ 192 Khz THD+N = arrrrrrrg, ok, which graph do I use?
There doesn't seem to be a THD+N measurement for the 192Khz mode, unless it's still -110db.

However, both companies don't really 'fully' spec their mono mode.

Darn, gotta keep those .pdfs open... Ooops, just accidentally closed them again...
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Old 29th September 2003, 04:01 PM   #6
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It seems that 192 kHz is nothing TI wants to talk about. Notice also _how_ the measurements are done. I can't see any detailed desciptions of that. TI for instance has NE5534 as recommend opamp (unbelievable!).

Th AD1955 seems to be substantially better at 192 kHz but I think this is not the whole truth.
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Old 29th September 2003, 04:32 PM   #7
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what I have noticed when comparing AD to TI DAC´s: both are using the AudioPrecision System 2, AD states that they are using RMS mode, while the use of Averaging mode gives about 2dB better results, guess what mode TI is using....
(Hope it´s not nonsens what I write here, think it was PCM1738 and AD1955 datasheets...)
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Old 29th September 2003, 04:46 PM   #8
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It's not complete nonsense, however, the super crucial graph on the AD1955 sheet is the bottom left on page #11.

'Wideband FFT plot...'

Here, mono mode will have a profoundly larger margin in difference, more like another + 4-6 db because of the way the DACs are matched in an inverted fashion. With a similar test on the TI, it would probably stink on this test. The really high performance uncompressed SACD band doesn't appear to be one of their concerns.
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Old 1st October 2003, 11:37 AM   #9
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this thread was i looking for... anybody knows whether the ad1955 needs a seperate int. filter in mono mode? or is it performing the filtering also in mono mode?...
im wondering, besides this... pcm 1792/4 or ad1955.. although i think i ll stick with the ad, for entirely technical reasons - i cant have 14 opamps (propably opa627) on a board to get an s.e. out grom the pcm.... itd be a rather populated board.. (+2*28 caps)..
anybody used an ad1896?? seems nice to get rid of low pass filtering....
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Old 1st October 2003, 12:18 PM   #10
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Quote:
Originally posted by peranders
TI for instance has NE5534 as recommend opamp (unbelievable!).
It does seem rather odd, but I have been in contact with their application engineers and they highly recommended this approach to "enable datasheet level performance". Needless to say, I have my own view on how this can best be done.

Now, if you look at the PCM1794 which appears to be the same chip as the 1792, you will see that this chip is MUCH easier to use than the 1794 and the AD variant. My opinion is that these devices are all probably significantly better than previous chips (at least from data sheets) and whether one chooses one or the other is probably much less important than the actual implementation. Since the 1794 appears to be easy to use you can spend more time on the implementation and probably extract better results as a DIY'er

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