TEAC UD 701N

Oldfart

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Nov 22, 2020
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Just announced on their Japan website is this upgrade to my UD 505NT. Instead of using the top of the range dual AKM DAC chips, it employs delta sigma upconversion of PCM to high speed 1 bit DSD. Adopted by Marantz for the SA10, KI ruby and latest CD players, PS Audio Directstream DAC, MBL and dCS ring dacs, I guess this approach has considerable merit. Would appreciate the thoughts of owners of any of the above as I have no experience other than the half way house software upconversion option on the NT 505 PCM to 512DSD. I prefer upsampled 8 times PCM but fine margins.
UD 701N
 
It would appear that the employment of delta / sigma converter and other changes are going to mean a significant increase in price. Will be interesting to see how this one gets on or whether price will be it's undoing.
It does look very interesting though imust admit.
 
D

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I have the Rubies but couldn't offer any opinion as to whether the DSD approach has any merit, I just let my ears be the judge... they sound damned good to me, probably the best I've ever heard in my lounge.
 
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Oldfart

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Nov 22, 2020
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Hi Doug,

sounding damn good is vindication in my book. Ken Ishawata always said the final product development was done by ear and his was better than most. I’m sure he didn’t go down the delta sigma route without very good reason. Glad you are enjoying the Rubies.

Agree. Price will indeed be critical, Al Ears. The NT 505 would undoubtably be much more expensive if built in Japan alongside big brother Esoteric. Punches above its price, imho - just have to ignore the built in Covid epicentre sticker. Will wait for reviews, but looks very promising. My guess will be a 50% hike so £2250RRP. Esoteric grandioso streamer over 10 times that!
 

Wil

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May 8, 2020
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The key aspect is the word "discrete":
"Instead of using a generic DAC IC, we incorporated a newly-developed TEAC ΔΣ (Delta Sigma) discrete DAC comprised of discrete circuitry that uses FPGA incorporating our original algorithms."

Chip-based Delta Sigma converters have been commonplace for a long time e.g.:
If you don't want to read [Caulfield's] whole interview, I'll excerpt just this as teaser:
"The big variable, however, is your DAC. If it's a chip-based Sigma-Delta converter, as are the majority of DACs, then supplying it with a DSD/PDM bitstream previously converted to DSD/PDM in a processor with greater resources will potentially sound more analog and pleasing. You're giving your DAC a bit of help through choosing an optimal format and resolution ahead of time. This can take processing load off of your DAC possibly achieving a more pleasing outcome. You really have to do some listening comparisons to determine what will work best for you and your DAC."

KI himself said to WHF, in 2009, about the "need for current" which CMOS chips lack.

In-house discrete circuitry DAC designs will, at least, enable higher current…

E.g. from today's WHF Features:
"3. dCS Ring DAC

OK so it doesn't look like a cute piece of jewellery but, as is often the case in engineering, there comes a point at which the performance of an existing technological approach cannot practically be improved. When this happens, progress means trying something different. And that, says the Cambridge-based digital specialist dCS (Data Conversion Systems), is essentially what happened when it developed the Ring DAC.

Although off-the-shelf silicon DAC chips can be bought for relatively little online, dCS wanted more than someone else's best efforts.

So dCS engineers did it themselves. The Ring DAC is a bespoke digital signal processing engine designed by and unique to dCS. This DAC (early model pictured above) is a clean-sheet solution running code written and regularly refined by the firm. It uses a network of FPGAs (Field Programmable Gate Arrays) programmed to run dCS firmware and handle all digital filtering and digital-to-analogue conversion.

Why go the long way around rather than buying in from reputable semiconductor suppliers? In 2014, dCS director of product development, Chris Hales, said, "Because we’re in control of the digital signal processing we can improve it. For example, the mapping algorithm – which is pretty crucial to the way the Ring DAC works – is something we change if we see fit. The filtering is completely under our control, so we’re not at the mercy of what’s in the chip that you buy, we can change it arbitrarily to whatever we want. We can even do that retrospectively and put that into products already into the field.”


Doing a digital converter the dCS way is far more expensive than buying in off-the-shelf DAC chips, but the results are undeniable – dCS DACs sound unlike anything else on the market because, well, that really is what they are."
 
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Wil

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May 8, 2020
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