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It is called a Kailin Phono Box and it uses one 12ax7 per channel and has a MM and a MC switch on it..To look at this thing,it has a nice cast aluminum panels but inside would be considered a joke until I heard this thing..I hooked it directly into the Mc225. I also hooked it into rebuilt a pair of Supratek preamps and in both cases this little phono stage was hanging in there unbelievably well..It was natural and dynamic and accurate..Now,here is the kicker..This thing has a buzz noise like interference grounding and it's apparent and controlled with volume but it isn't filter hum but it still sounds wonderful even with the annoying buzz..When I took it apart,I noticed it is using 6,3vac between pins 4,5,and 9..I may try and add a DC source to raise the filament because that is the only way I think I can get rid of it..I have no idea what's inside that sealed box but what really amazes me is the gain of this thing..I used a stepup transformer running with the mac mc225 and this phono stage should not sound this good..Even going thru the Supratek and then into the Mc225,it had the buzz but it had that incredible posture that really presents the music quite well..I'm using my Koetsu Rosewood and Premier MMT arm.Is there any info on these?
Honest amplification is better than excessive 2nd order distortion anytime.
Edits: 03/25/14Follow Ups:
I dealt with some buzz in the RCA classic hybrid circuit that Eli and I tend to promote. Try some quieter tubes and the spiral LPS as Eli suggests. If it still buzzes, see if the filament supply is floating. If so, try grounding to the B+ supply. That may help.
Other fixes (that may be too much work) could include elevating the AC heaters or converting them to DC regulated. In the case of the RCA hybrid MOSFET follower, we also needed to tweak R6 in the RCA schematic because the second cathode was now directly grounded, and then increase the coupling cap to compensate so that the RC constant was maintained. This also served to reduce gain slightly, which helped residual hum as well.
Try the Sovtek 12AX7LPS. See if a hum bucking heater helps.
Does the "beast" use a SMPS? Those things are know to cause noise.
Eli D.
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