I have finally gotten my "Platinum" upgrade to work. And I do say "finally", because it has taken me 3-4 weeks to get my GK-1R back in reasonable working condition after implementing the Platinum caps according to Steven's recipe (apart from one exception).
I haste to add that none of the problems I ran into could be ascribed to any of Steven's advise, make no mistake!
The problems I ran into was hum, hum, hum, and yet more hum!!! Admittedly, I did complicate matters a little myself in that I replaced all signal wiring with my own Equilibrium Cable pure silver wiring at the same time as implementing the Platinum caps.
Anyhow, the first thing that happened after I had put my GK-1R back together, new caps, new wiring and all, I had HUUUUUMMMMMMM! Not devastingly loud, but still loud enough to be heard in my listening position, which is almost 6 metres away from the speakers. The hum was more or less independent of volume setting.
Hmmmm, I thought - this might be because I put the big 1 uF Platinum caps outside the board (in fact, I mounted them with Blue Tack astride two input relays each), causing them to pick up hum. However, moving the caps to the board did not help .....
Do you guys know in how many different ways ground wiring can be done on a GK-1R? Well, during the last 3-4 weeks I think I've tried them all!!!! Also tried various way of earthing (I've got true earth) the preamp. Nothing worked. Hugh and I had some email gander, but none of the things we could come up with worked .....
I won't bore you with all the details of the many things that were tried - suffice it to say that I believe that the main problem has been found. I turned out to be the output cap. Because I wanted to roll off the treble/mid section of my speaker system, which is driven off the tube output, I had reduced the output cap value from the 1 uF Auricap to a .047 uF Sonicap Platinum. Obviously, the latter is a very small size cap, even in the Platinum range, so we are not talking about hum intrusion into the cap (at least I don't think so).
I talked to a tube-knowledgable friend of mine today, who believes that the hum problem I experienced is likely to be caused by the change in the output impedance at the low end of the register, as it becomes easier for hum to be induced into the interconnect between the preamp and the power amp (in my case a LF55) and then possibly back into the rest of the preamp circuits. In my system, this signal wire has always been an unshielded one, which never created problems before. Whether this is the whole story, I don't know ....
I may try out shielded interconnects in this place, but until further notice, the original Auricaps have been reinserted and will stay, as the system is now hum-free
All the above being said, I'm not quite out of the woods yet. The process of eliminating the hum involved taking the Relay board out of the "loop" and running wires directly to input and output of the Analogue board. In theory, the Relay board shouldn't make any difference, but previous experience (from when I first built the GK-1R) shows that it may not be as straighforward as all that.
However, the main thing is that now I have music again! Those 3-4 weeks without music were scary!
I haven't had time to listen very much to the differences, but I second Steven's opinion that especially the 1 uF Platinum cap is worth the while. Bass certainly seems to dig deeper and have more slam. The Platinums also seem to render details in a most natural manner. I'll listen some more and report back later if I feel there is more to report. I should add that the improvement is worthwhile and quite pleasing.
If anyone runs into hum problems of the sort I've described above, please do not hesitate to contact me. I guess I've tried most of the things that can be done to remedy hum problems in the GK-1R over the last few weeks, poring over the GK-1R for endless hours.
But now there's lovely music, and all is bliss
