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Old 27th April 2014, 12:54 AM   #1
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Default what is so unique about PCM1795?

Ive seen couple of products are using pcm1795 instead of 1792A supposed to be the flagship of TI DACs. What is so unique about this chip is there any sonic advantage?
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Old 27th April 2014, 03:10 PM   #2
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Cheap.
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Old 27th April 2014, 03:24 PM   #3
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TDA1387 is cheaper and bound to sound better with the right implementation. That's assuming your requirements aren't for >16bits.
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Old 28th April 2014, 06:48 PM   #4
Rochey is offline Rochey  United States
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[First, a disclosure - I work for TI. I'm a PCM audio product definition engineer. I am completely biased. ]

While they are based on a similar architecture, the PCM1795 and PCM1792A are different.

Looking historically, the PCM1796 and PCM1792 were based on similar designs, but the digital interpolation filter and current segment engine on the PCM1792 are larger and more complex than the 96. (hence it's 9dB better performance)

In 2009, we launched the PCM1795, which used the same analog section (current sources, voltage references etc) as the PCM1796, but with a new digital interpolation filter that could support 32bit data.

It was found that with an equal amount of averaging as a competitors device, that the analog back end in the PCM1796 could actually show analog content at levels equivalent to the 25th bit.

As a consequence, the PCM1795 was born as a potential replacement for the PCM1796.

s3tup also makes a good point, compared to the PCM1792, the PCM1795 is a lower cost product. That has been a strong part of it's success. At 123dB dynamic range, it is still considered an excellent DAC and remains a strong part of our portfolio.

(and now for the pitch... because you knew it was coming! )

The PCM5142 was based on a similar architecture to the PCM1792. Whilst it has lower performance, it integrates WAY more than the PCM179x, and throughout the many, MANY hours of listening tests at our Golden Ear customers. (if I hear another Diana Krall song, I may go nuts), many of the experienced customers compared it tonally to the PCM1792.

I stop by this forum every once in a while. If I see more on this thread, I'll comment on my next pass through
Y'all are always welcome over on TI's e2e forum too. (TI E2E Community)

Cheers

Dafydd Roche
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Old 28th April 2014, 07:35 PM   #5
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Hi Rochey, since you've came here... Ain't the PCM5102 is the same as PCM5142 minus miniDSP core?
PCM5102 sounds good AFAIK.
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Old 28th April 2014, 07:36 PM   #6
Rochey is offline Rochey  United States
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yes, it's based on the same design, the PCM5142 integrates the miniDSP, and a very very convenient i2C/SPI port, that allows you access to the real easter eggs.
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Old 28th April 2014, 08:10 PM   #7
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Thanks!

I've heared of "i2C/SPI", "ESS90XX" and "easter eggs" before (in the same project), it was some kind of horror story to program it with "partially correct" datasheet.

So "easter eggs" and "i2C/SPI" in the same sentence are kinda spooky
Yet DSP feature is rather sweet...

Too bad the tiny DSPs a-la TAS3108 are gone Yes, quite a niche product since these simple audio tasks could be easily done in SW. Yet you have these "Lip Sync" chips still being produced...
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Last edited by s3tup; 28th April 2014 at 08:13 PM.
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Old 28th April 2014, 11:41 PM   #8
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The PCM5142 does sorely need an update to the datasheet because as it stands, it and it alone, isn't enough to get the most out of the chip. Help is required.

That aside I was informed a couple of months ago that TI have a new DAC chip on the horizon with a miniDSP core and similar-ish performance to the PCM1792. The estimated date of arrival was around now, is this accurate or has it been delayed?

I do like my PCM5142s and in the systems I've put them in, they do sound very nice.
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Old 29th April 2014, 02:22 AM   #9
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Quote:
Originally Posted by Rochey View Post
[First, a disclosure - I work for TI. I'm a PCM audio product definition engineer. I am completely biased. ]

In 2009, we launched the PCM1795, which used the same analog section (current sources, voltage references etc) as the PCM1796, but with a new digital interpolation filter that could support 32bit data...

Cheers

Dafydd Roche
Hi,

Judging from the PCM1795 interpolation filter's stop-band rejection spec. of -98dB, versus -130dB for the PCM1792A, the PCM1795 filter coefficients have less precision despite it accepting 32-bit wide audio data. Seems a counter-productive design decision.

On a tangentially related feature design question, does the PCM1795's digital volume attenuator operate with 32-bit precision, or in other words, with a 32-bit attenuator quantization noise floor?
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Old 29th April 2014, 03:01 AM   #10
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Quote:
Originally Posted by Rochey View Post
[First, a disclosure - I work for TI. I'm a PCM audio product definition engineer. I am completely biased. ]

While they are based on a similar architecture, the PCM1795 and PCM1792A are different.

Looking historically, the PCM1796 and PCM1792 were based on similar designs, but the digital interpolation filter and current segment engine on the PCM1792 are larger and more complex than the 96. (hence it's 9dB better performance)

In 2009, we launched the PCM1795, which used the same analog section (current sources, voltage references etc) as the PCM1796, but with a new digital interpolation filter that could support 32bit data.

It was found that with an equal amount of averaging as a competitors device, that the analog back end in the PCM1796 could actually show analog content at levels equivalent to the 25th bit.

As a consequence, the PCM1795 was born as a potential replacement for the PCM1796.

s3tup also makes a good point, compared to the PCM1792, the PCM1795 is a lower cost product. That has been a strong part of it's success. At 123dB dynamic range, it is still considered an excellent DAC and remains a strong part of our portfolio.

(and now for the pitch... because you knew it was coming! )

The PCM5142 was based on a similar architecture to the PCM1792. Whilst it has lower performance, it integrates WAY more than the PCM179x, and throughout the many, MANY hours of listening tests at our Golden Ear customers. (if I hear another Diana Krall song, I may go nuts), many of the experienced customers compared it tonally to the PCM1792.

I stop by this forum every once in a while. If I see more on this thread, I'll comment on my next pass through
Y'all are always welcome over on TI's e2e forum too. (TI E2E Community)

Cheers

Dafydd Roche
Well Sir if you are a TI guy then I ask you one very important question that why are you reducing the quality of your product? Example NRND for PCM1704? Its only good DAC out there with signed magnitude R2R.

We want to know why do you stop such incredible products out of your product line.

Considered that you have great Sigma delta dacs but you should have one super performing product in your line.
If its possible put this statement to your managers. There are lots of people who are even ready to make it public news on blogs and forums that TI is stopping quality products like PCM1704.

If you have the ability do try to increase the standards as they are premium products.

I will tell you why.
Duelund Capacitor: 700 USD
Mundorf Mlytic / Jensen 4 pole caps: 100USD
Van Den Hul 3T cables atleast 1000 USD cable
Speakers few thousands or tens of thousands of dollars.

So when people are able to spend that much what makes Texas instruments stop such product which is sold for 60USD. Don`t you think that such equipment cannot perform without great DACs out there?

If possible tell this to your management if you can build a DAC chip costs 200USD and the Industry will pay for it.

one word Texas Instruments has great value in the market dont loose it by discontinuing great products like PCM1704.

See this link about THE REVIEWS..

Audio Converter - Audio DAC - PCM1704 - TI.com
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