Psu iii mod

[bob orbell]

Hi all, read here for something I found interesting. Many of you will know my basic system but here is a reminder, two WD PSU III's, one Phono III, one Aikido CF Pre, WD KT88 all are as basic kits apart from KT88, this has the better power supply parts, OK, for quite a few years I have been powering the Phono and Pre from two separate power supply's, both supply's have high voltage regulators (home made ) the Phono runs at 250 volts the Pre 200 volts, for a long time I have not been too happy with the sound of vinyl, so I did a few tests on the scope and found the HT reaching the Phono had small spikes on the line, at around 100 Hz , a test with the pre was just a straight line , so I removed the snubber capacitors that I had fitted to the choke ( two 220uF 1000 volt back to back with CT to 0 volts ) no change, I then removed the choke and bridged the circuit, the scope now showed a straight line, so connected back into the system and vinyl now sounds bloody good, smoother more detail and better separation of instruments, even sibilance had been reduced, so why ?, I have read that a choke needs to draw a min of current before the power supply woks correctly, otherwise it reverts to pulse charging of the following capacitors, so is this the reason my vinyl has not sounded good, the Phono draws very little current. If anyone ells is using a phono on its own, it may well be worth trying the power supply with the choke removed. Comments please. Bob