‘Adagio’ TDA1541A non-oversampling DAC

When I first listened to DACs, I concluded quite quickly that ‘multi-bit’ DACs sounded more like music to me, than ‘bitstream’ DACs – more dynamic & ‘alive’.

The TDA1541 was originally developed by Philips (in 1985) as a high performance stereo DAC.  The ‘A’ version was manufactured between 1989-1995.  It was (is still?) regarded as one of the best sounding DACs ever made.  This chip was used in almost 100 different CD players (eg. Philips, Marantz, Naim, Sony, Luxman, Meridian, Arcam, Cambridge, Pioneer, Quad, Rotel).

The original ‘non-oversampling’ approach was proposed by R. Kusunoki almost 20 years ago.  His analysis was that ‘oversampling’, using a digital filter, creates time-distortions and obscures the potential of the 16bit/44.1kHz  DAC.

This ‘Adagio’ DAC was designed by Thorsten Loesch (around 2002) – a TDA1541A DAC, non-oversampling, digital filter-less, with vacuum tube analogue output stage. The receiver chip was the Crystal CS8412.

Adagio DAC 2a

 

I was able to have some PCBs made, together with another DIYer.

DAC build 011

DAC build 010

The chassis case from an old CD player was stripped down:

DAC build 003

DAC build 009

Chinese R-Core power transformers purchased from diyclub.com.hk in Hong Kong:

R-core TXs 004

Preliminary chassis layout:

DAC 251210 001

Bread-boarding the 5687/E182CC tube output stage:

DAC SRPP 002

Testing High Voltage supply for tube output circuit:

PSU-tube

HT PSU & heater circuit adapted from my Phi-42 phonostage (thank you Diego).

DAC 080111 003

Testing -15vdc and +/-5vdc supplies for the digital board:

DAC 170111 001

The digital board component-filled: WIMA/ERO MKP metalised polypropylene. film caps, Sanyo Oscon PSU decoupling caps.  Amplimo TM-3, 1:15 microphone transformers.

DAC-240111-01

IMG_1915

AudioNote TRANS-279 digital interface transformer, was used at the SPDIF input.

Completed chassis:

IMG_6846

CS8412 pin 20 loop filter cap on underside of board: (3300pf bypasses 510R + 0.22uF in series.

IMG_1917

20 ohm DAC I/V resistors, ‘basket-weave’ wound on vintage radio coil-formers:

IMG_1922

E182CC tube output stage – later changed to 5687s in order to try to reduce gain a little.

IMG_2977

Completed chassis:

DAC 310111 c

In-system, with Teac P700 CD Transport:

IMG_2051

 

The sound:

Surprisingly, is a little ‘bright’ tonally.  Further work needs to be done.  Tweak the output stage a little more, to reduce gain.  Remove the cathode bypass cap.

To be continued…..

 

 

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4 thoughts on “‘Adagio’ TDA1541A non-oversampling DAC

  1. I have been on a similar path, using parallel TDA1541a, am loading the secondary of the transformers instead of the primary, the transformer and the i/v resister contribute a lot to the sonic signature of the DAC, I use a 5 position selector switch to audition resisters to pick one that sounded best in my system, some transformers I tried do sound bright, tube output stage is 6AH4 choke loaded, the sounds is fantastic.

    • Hello Ka – thanks for visiting. Am interested in more details of your design. After some years of non-use, right now my DAC is on the bench, troubleshooting a PSU problem! Looking forward to listening again. There is also a bit too much gain for my system. Will report back with an update soon.

      • Hello Owen-My DAC board is the one offered on DIYaudio many years ago by tubelover, only minor tweaks on the board with a snubber on the power transformer’s secondary before the rectifiers, most experiments were done with the i/v resisters transformers and output stage, the transformers are unfortunately not available anymore, it is an obscure military surplus, the i/v resister is composed of two different types of resisters in parallel to get the synergy I prefer for my system, I have compared my unit to many others including some very expensive commercial DACs, in A/B listening test most of my friends prefer mine.
        Just a thought you may try to bypass the Sine x/x filter on your DAC, it may eliminate the brightness you hear since it lift the upper frequencies to compensate NOS.
        You can see my system profile in Audiocircle under username shooter.

    • Yes exactly my thoughts too, the analogue output filtering may be too severe & I will bypass it for starters.. (Most of my listening is vinyl & I have neglected finishing this project.) Cheers.

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