Valve DAC from Linear Audio volume 13

Jump to Latest
#962
My birthday treat - beautiful music by a consumate musician and an excellent DSD256 recording - it sounds wonderful via my Valve DAC - a real treat!

EUDDR1801-1-500x500.jpg


For this recording Sonodore microphones were used to bring the music to the Horus Analog to DSD 256 Converter from Merging Technologies. Eudora notes that “Of course, no DXD conversion and processing was applied, this is a pure DSD256 recording.”
Click to expand...

I purchased the DSD256 download from NativeDSD - well worth browsing their collection, albeit a little expensive. I have a couple of other DSD256 recordings from them and they're also excellent, both musically and recording wise.
 
#969
nautibuoy said:
Marcel. any thoughts on using Silk Transformer Volume Controls instead of the Lundahls on the output to Valve DAC?

SACThailand
Click to expand...

My first thought was that they are not suitable for vegans, but that was a mistake, as SILK apparently refers to their winding technique rather than their insulation. There may also be a relation to Tai chi, Silk reeling - Wikipedia

Anyway, if I were to try them, I would connect the primaries in series and use the right schematic of post #837, https://www.diyaudio.com/forums/att...-volume-13-a-filter_alternative_1v_750ohm-png , but without R3 and C9 (and obviously with the Lundahl replaced with the transformer volume control). That's assuming that 1 V RMS is enough to drive the main amplifier to full power.
 
Last edited:
#977
The output impedance of the DAC is about 11.2 kohm (differential, 5.6 kohm per side), as set by the anode resistors, so it's an LC filter with very different termination impedances. It is designed to have a third-order Butterworth roll-off at 42.9 kHz, but I don't know to what extent the winding capacitance of the transformer and C9 disturb that. The insertion loss is dominated by the transformer.

The thing is that I originally designed the filter for Jensen transformers, see post #182, https://www.diyaudio.com/forums/dig...-linear-audio-volume-13-a-19.html#post5868091 Ray preferred Lundahl, so I changed it into the circuit of post #215: https://www.diyaudio.com/forums/dig...-linear-audio-volume-13-a-22.html#post5872031 However, Jensen claims that the standard application circuit for their transformer has a flat input impedance well above the audio band, but Lundahl doesn't specify at all what happens with the input impedance of their standard application circuit at ultrasonic frequencies.

I later tried to guesstimate the parasitics of the Lundahl transformer from the rather sparse information in the datasheet and to come up with a filter that is both compensated for and as insensitive as possible to transformer parasitics, see post #837, https://www.diyaudio.com/forums/dig...-linear-audio-volume-13-a-84.html#post6328063 . No-one has tried those filters yet, though, while Ray has listened to his version of the filter of post #215 and is very happy with it.
 
#978
diyAchim said:
Probably a daft question - but why wind your own inductor?

Would a standard component between 1.5mH and 2mH not do largely the same?

Here's a list of components that where specified at 25kHz or 100kHz:
Inductors
Click to expand...

The reason I chose to wind my own inductors is that Siemens/Epcos/TDK provide enough information to calculate the distortion of a homemade inductor on a potcore, while standard inductors generally have no clear distortion specs. It would certainly be interesting to see how well or how poorly standard inductors work, though - when they have an air gap and are designed to saturate at currents far above the few milliamps of signal current that come out of the DAC, distortion could very well be a non-issue.
 
You must log in or register to reply here.
Top Bottom