Ich habe Reinout meine brandneuen amorphen Strom-Spannungs-Wandler gegeben, damit er diese in seinem DAC ausprobieren soll. Es scheint, daß sie ihm gefallen haben:My favorite source is the analogue pick-up/turntable. I have a very nice oversized platter. It is that large that I had to construct my own 18” tone arm. Fitted with a Van Den Hul Colibri cartridge I have a wonderful analog source.
But not all music is available on vinyl. And the CD is a very practical to use format. So I want my digital source also of high quality. Till recently I had a Krell cd-player: serious stuff but not really the last word in digital presentation. I switched to a Bel Canto CD2-player which gave a more natural presentation of the music (but missed Krell’s effortless bass-performance).
In essence is the Bel Canto a superb transport with a somewhat simple internal DAC; it simply begs to be upgraded by an external DAC.
Years ago on www.diyaudio.com there was a thread on an open source DAC. All participants could enter their input in improving the final DAC-board. Finally it became a well-designed non-oversampling parallel TDA1541A DAC-board. For the following gainstage you had the option for a opamp-version (AD844) or a tube version (6C45 SE or 6DJ8 SRPP).
All participant could order the pcb set (containing the actual DAC and the opamp/tube-version gainstages).
On the forum a lot of information was passed on the components choice. Everybody shared their knowledge. So I finally came up with a mix of Caddock resistors, Riken resistors, BlackGate NX HiQ-capacitors, Elna capacitors, etc.
That original DAC-board is no longer produced but on Ebay I noted some very interesting DAC-kits !
Two resistors really stand out: the I/V resistors at the end of the DAC. These resistors present the load to the TDA1541A’s and their value is critical. Too high and your soundstage will collapse (along with the musicality); too low and your output is minute. Theoretically the value should be somewhere between 22 and 68 ohm. At 36,5 ohm the DAC performed optimal. But that value is not commercial available. I dislike paralleling resistors so with the aid of 2 transformer bobbins and some copper wire 2 specific 36,5 ohm resistors were wound.
Where I really left the original design is after the actual DAC-board. In theory the parallel TDA1541A provide only 80 mV. So you need a gain stage of factor-25 to reach the common 2 Volt line level. For that reason the opamp and/or tube gainstages were provided. But I never liked those designs.
The last option for gain is a transformer. That transformer must cope with a very small input signal from a low impedance source; not the easiest of tasks ! I started with 1:25 step-up transformers (in the picture to be spotted as 2 blue boxes) and I immediately knew that this was the way to go. My Krell was already sold. The Bel Canto’s own internal DAC was completely blown away by the musicality of the DAC/transformer-combination.
Christof noted my DAC and the transformers. He liked the design of this I/V-conversion + transformer but told me the transformers could be done better…..
After some time 2 “DAC-transformers” arrived:
Serious oversized amorphous cores;
1:20 step up (but Christof told me the insertion loss of these trannies were really negligible);
Nice stainless steel cover.
Please note the size difference of the larger Silvercore’s and the original transformers (blue).
The size of the Silvercore represents also what their impact was on the performance: everything became bigger/larger. The soundstage grew in height and width, the bass became extremely low (and still articulate !). In overall their biggest impact was on the actual presentation of the music: instead of being a spectator you were drawn into the music.
I have never heard a bigger musical impact of a single component in my set before !
Happy listening !