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lingDAC - cost effective RBCD multibit DAC design
lingDAC - cost effective RBCD multibit DAC design
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Old 12th July 2018, 04:08 AM   #1
abraxalito is offline abraxalito  United Kingdom
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Default lingDAC - cost effective RBCD multibit DAC design

I've been working on DAC designs using TDA1387 for several years now, both in helping modify existing designs and coming up with my own solutions.

'lingDAC' has satisfied me in listening to such an extent that I feel its worth sharing the whole design here as I feel I'm close to reaching the end of the road with what's possible when beginning with the TDA1387 (famous last words!).

A few bullet points to introduce this DAC :
  1. designed for Red Book CD source material hence 16bits and 44k1
  2. no-oversampling design means no digital filter is used
  3. a steep analog filter is used instead of the digital filter to kill images
  4. the design is aimed at reaching the best SQ, not best measurements
  5. lowest possible BOM cost commensurate with still sounding good
  6. designed as a board stack for maximum DIY flexibility, boards are 5*5cm

I need to tidy up the schematics before posting them, I'll add them to this post as they're rendered presentable.


Returning later I see I'm told I'm unable to add attachments to this post so guess new info will go into subsequent posts.
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Last edited by abraxalito; 12th July 2018 at 09:20 AM.
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Old 12th July 2018, 08:58 AM   #2
DRONE7 is offline DRONE7  New Zealand
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Old 12th July 2018, 09:25 AM   #3
abraxalito is offline abraxalito  United Kingdom
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Here are the three boards required to build a lingDAC - from the left the DAC, filter-I/V and buffer stages. A fourth board for power supply is in the works, the aim being to be able to run from a very cheap USB 5V wallwart. For now the first two boards need a 9V supply and the third, 7V.
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File Type: jpg 3board_spread.jpg (160.0 KB, 527 views)
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Old 12th July 2018, 12:51 PM   #4
BesPav is offline BesPav  Russian Federation
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Please, let us know analog filter order and approximation function.
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Old 12th July 2018, 01:38 PM   #5
abraxalito is offline abraxalito  United Kingdom
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The order of the analog anti-imaging filter is 5 - that is two inductors in series positions and three capacitors in shunt. Its not a standard textbook function, rather somewhere between Chebyshev type 1 and Cauer (Elliptic).
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Old 12th July 2018, 02:53 PM   #6
rickmcinnis is offline rickmcinnis  United States
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I have been wanting to return to digital but not wanting to spend a fortune.

ABRAXALITO is always a step or to ahead so I want to build one of these.

Looking forward to your revelations!
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Old 12th July 2018, 03:02 PM   #7
randytsuch is online now randytsuch
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I was very fortunate as Abraxalito sent me one of his first lingDACs a couple of months ago.

I have been slow to try it out (Sorry Abrax), but am getting close now. Real life and laziness have slowed progress :/

I received the three main boards, and have put together a power supply using three lifepo4 batteries. Power supply is about 90% finished, just need to actually hook up the batteries to it now, but it does have three working 3.3V regs.

So PS will output 10V, and then Abrax included diodes on my power input to drop it down to around 8V to power the three boards.

Lately have been making some changes to my digital playback system which has a soekris r2r dac, the original 1021 with a bunch of mods mostly related to power.
Been spending some time listening to it as my baseline.

Hoping to hook up the lingDAC this weekend, then will let it break in some and then compare to my soekris.

Randy
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Old 12th July 2018, 04:07 PM   #8
sumotan is offline sumotan  Indonesia
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Congrats Abrax,
Im an old man, soldering those smd parts is going to kill me. Lol
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Old 12th July 2018, 05:01 PM   #9
wcwc is online now wcwc  United States
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Looks interesting.
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Old 12th July 2018, 05:50 PM   #10
rickmcinnis is offline rickmcinnis  United States
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Quote:
Originally Posted by sumotan View Post
Congrats Abrax,
Im an old man, soldering those smd parts is going to kill me. Lol
I am hoping he might find a way to offer populated boards!!!

(thanks for your note sumotan - still trying to figure out which way to go - but have long wanted to try something from the mind of abraxalito)
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