Counterpoint SA-5000 Upgrade
I mentioned in my previous post that I was pretty underwhelmed with the phono stage in my recently acquired amp. It had unacceptable background hiss and sounded harsh and edgy in the upper midrange, in other words like a transistor amp. Inspired by the Alta Vista website and comments regarding the much improved performance with the upgrades, and using my SA-3 as a prototype, I experimented with various gain blocks. But first I had to trim the filament voltage regulator to get the volts up from 5.7VDC. At the same time I upgraded the PSU power resistor, LV bridge rectifiers, and electrolytic caps on the main board.
I swapped out MF plate resistors with Mills WW, and coupling caps with Dynamicaps. Now improvements were already acknowledged, but I had to get rid of the SS stuff as it was far to complicated IMHO.
Both buffers and JFETs were removed from the phono stage and JFET from the line stage, as well as the MC cartridge stuff. I used 3mm LEDs in the cathode circuits, and set up the phono as a 2 stage common cathode amp and the line stage as a parallel triode, like the SA-5.
I can state with absolute certainty that this amp is now in a different league than before. It is impossible to tell if it is in circuit with line stage operation, and the phono is almost as quiet. The sound stage has incredible resolution with immense width and depth whilst portraying natural timbres,particularly so with vocals. The bass is wonderfully coherent with great extension. It also has heaps of gain.
It is still a work in progress, as I intend to bypass the balance and phase controls as well as replacing the rest of the chassis signal cable with 30 AWG (that's right 0.25mm )solid Cu-Ag plated Kynar wire.
This has been a very rewarding and worthwhile project.