Amp Hum both sides, No left side signal

Equipment: Pro-ject RM-9, Benz Ace Blue, Pro-ject Tube Box, Manley Shrimp, 2 Dynaco St-70's wired @16 ohms stepped down to 8 ohms. Synergetic Research, and Transparent Audio interconnects.

Problem: Constant hum through the speakers although turntable is grounded to phono pre amp (tube box.) Also when balance is moved to the Left, I get no signal? Can someone help me to properly connect my system... Please help!!! I have been working on this little system for over three years and I am finally at the point of seeing what this thing can do...


San Rafael, CA
I live in MN fly me out and we can work on it together.
Yo Leonard,

It sounds like there may be more than one problem. Best bet is to disconnect and unplug everything and then hook one item at a time back up and turn on the power and listen. So start by hooking the ST-70 amp to the left speaker and turn it on an listen for the hum. Next check the right speaker. If no hum, then turn off the amps and connect the interconnect to the input on the left amp (but not on the preamp); turn on and listen. Repeat with right amp.
Now try hooking up the interconnect to the left channel preamp output and turn on and listen for the hum. Now plug in the preamp and turn on and listen for the hum. No hum? Then you can turn on the preamp and the amp and turn on and listen for the hum. Turn the volume up about half way and try all the inputs. Repeat for the right channel.

Next step starts with disconnecting all four headshell wires from the cartridge. Connect the tonearm cable to the preamp phono input. Turn on and listen. Turn on the turntable and listen. No hum? Now connect those headshell wires to the left channel outputs of the cartridge only and turn on and listen. No hum? Play an old record. Now repeat for the right channel. If you get to this point and the hum is gone, then enjoy the music.

If the hum appears during the phono cartridge step, then it might be caused by a magnetic interference from the turntable motor or one of the power amp transformers being picked up by the cartridge. Re-locating the turntable might help or changing cartridges might be the solution.

Remember, no short cuts... Take everything appart like you are moving and rebuild the system piece by piece.
Thank you for the advise audio path, I will try all the above this evening. As for DIstephenson with the cost of living here I am lucky to have this little system... Nothing exrta to fly anyone out at the moment....
It is 9:30 PM and I followed your directions to a T as well as learned how to bias my amps. You were right no short cuts.. I now have my system working and I AM STOKED!!!!!

I have 2 years of vinyl collecting to listen to in the upcoming month or so.

thank you again,