Top critical review
97 people found this helpful
Good preamp / bad power supply
on October 10, 2008
I purchased the PP400 preamp for my new receiver which does not have a phono input (preamp), like most others in the same situation. The preamp is very nicely packaged. There is too much HUMMM. My background is electronics so I know what the reason is from the start. I had suspected it to be the case even before I purchased it. I cut the cord between the power supply and the preamp and inserted a filter circuit in between. So much for the warranty! For those who can understand it, the circuit is just a one transistor capacitance multiplier. The ripple (hum) was reduced from 50mv to under 2mv. The solution is not perfect but now I can live with it. I found that experimenting with grounding also help to reduce hum. Try attaching the ground wire to different points on the receiver chassie. Be sure to reduce the volume as you move the grounding around so you will not blow out the speakers or your ear drums.
I am rather surprised, after reading the other reviews that not more hum complains were launchased. With that much hum on the power supply, hum is unavoidable. I am giving a full 5 stars on the preamp itself. The lack of filtering on the power supply dropped the rating to 3 stars overall.