Mods done so far;
1) Replaced analogue output stage with output transformers and filters;
- Low pass filter on primaries (see diagram), using Teflon caps (Russian military surplus) and carbon film resistors (Kiwame 5W)
- Audio output transformers are Tamura GA80080 (from a Yamaha PM1000 mixing desk)
- Anti-ringing filter across RCA terminals, using Teflon caps (Russian military surplus) and carbon film resistors (Kiwame 5W)
2) Receiver chip PLL components corrected
3) Changed coax SPDIF input from RCA to BNC.
- moved the 75R terminating resistor from board, now soldered directly to chassis socket terminals, to help correctly terminate the 75R transmission line.
Opinion on sound quality with current mods;
- Sound is lovely and detailed, bass detail is a revelation. Highs are harsh and fatiguing when EI power transformer is used - toroidal is smoother.
Mods to be done;
4) Replace power supplies to chips.
Full system chain (for reference);
PC source;
- music - 16bit 44.1kHz flac files (ripped using EAC)
- playback software - foobar with WASAPI plugin
- output hardware - M2Tech's "Hiface" USB to SPDIF (BNC) adapter
SPDIF coax - Mark Grant Belden 1694A, 3m long
DIY DAC, modded as above
Analogue stereo interconnects - Mark Grant Canare LV61S
Amplifier - PrimaLuna Prologue 2 (KT88 tubes)
Speaker cable - QED Silver Anniversary (looking for tips here - thinking of trying Belden 5000UP)
Speakers - IPL Acoustics S3TL (DIY transmission line from IPL design)
Speaker stands - house bricks with felt pads
