Arcam phono board - problems

DD,

Good hunting, and I hope it is just a pin or grounding problem.

Jim S.

Spent a whole day today trying to get rid of this. Pulled all the cords, and opened the AV8. Connectors were seated, but the wires were bunched against a side wall. Rerouted the wires, put a techflex sheath around them for mechanical protection, roughed up the sheet metal by the grounding contacts, and re-assembled the unit. Hum was reduced, but still there. Pulled the bottom off my Thorens, resoldered what wires that looked sketchy, and re-assembled. Even better, but still a hum.

Unpacked a new project speedbox, and tried it out. Hum is significantly reduced. There is still some hum though when the old walwart AC transformer is connected to the circuit, even when that transformer is not connected to anything. And if I plug/unplug my frig the hum is affected. There is no hum when I run the turntable through the Rotel pre back in to another input. It is now dead silent, even at max volume. The internal Arcam board has just a touch of hum, more like a very low level purr. Only noticeable at high volume.

The music from the Arcam board sounds good, I think it is a touch better than the Rotel. But at higher volumes there is that purr. I suspect the Arcam phono board lacks sufficient filters for the transformer hum. Bummer.

I guess you gets what you pays for.

DD,

Nice to see you post the follow up. Sorry to see the hum is still there. Does sound like the Rotel has some power line filtering that squashes the the hum that the Arcam doesn't have.

And yes, sometimes you do get what you pay for. The boards were only $100 when I got my Alpha 10. But, I don't know if I could have lived with it if it produced a hum. Heck, I had a new transformer put in an Arcam CD player because I could hear the mechanical hum when I got close to it.

Jim S.

The saga continues . . .

I spent a fair amount of time online with the customer service folks at Needle Doctor last week. (I bought the speedbox from them, so I felt justified). They suggested that my cartridge might be incompatible with the phono board, and to swap it out if I had another one lying around. (I did and the hum got worse). I also borrowed a friend’s old Technics SL-D2 direct drive, with a Grado cartridge, which I learned is unshielded. Hum was way worse. (Although when input through the Rotel external preamp, no hum.)

I re-connected my Thorens, and the hum was back. I tried to short out the cartridge leads by connecting a wire between the red and green pins and another between the white and blue pins. The connection was unstable, but it seemed like the hum was worse, and definitely did not go away.

So I was back to where we started. It would seem the turntable wiring is suspect, but I did not think re-wiring the Thorens was worth the effort.

I was tired of all the hassle, so I bought the bullet and bought a new Project Xpression III from Needle Doctor. I’ll get it next week and report back. The Thorens goes on ebay. (I’m hanging on the the Rotel pre just in case . . . )