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.
I was able to have some PCBs made, together with another DIYer.
The chassis case from an old CD player was stripped down:
Chinese R-Core power transformers purchased from diyclub.com.hk in Hong Kong:
Preliminary chassis layout:
Bread-boarding the 5687/E182CC tube output stage:
Testing High Voltage supply for tube output circuit:
Testing -15vdc and +/-5vdc supplies for the digital board:
The digital board component-filled: WIMA/ERO MKP metalised polypropylene. film caps, Sanyo Oscon PSU decoupling caps. Amplimo TM-3, 1:15 microphone transformers.
CS8412 pin 20 loop filter cap on underside of board: (3300pf bypasses 510R + 0.22uF in series.
20 ohm DAC I/V resistors, ‘basket-weave’ wound on vintage radio coil-formers:
E182CC tube output stage – later changed to 5687s in order to try to reduce gain a little.
In-system, with Teac P700 CD Transport:
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…..