Wow thanks for the quick response. The table is new with the wiring upgrade. I always do the reconnect dance and usually it has solved the problem. It seems I might need to find a preamp doctor in Alaska to take a look, or try tapping the thing to deal with the humming. I wonder about just leaving it on when I finally get it working properly--it can't cost anything compared to the 2 adcoms sitting there sucking up juice 24/7. I almost sounds like an internal ground is unhooked. I thought I would try to run a wire from the unit's ground post to see if that would work.
apt holman problems
I recently bought a rega 25 and tons of albums -- the good news. The bad news occasionally the right channel cuts out and I reconnect everything and will try some connection cleaner. Now a hum has begun in the phono stage, seems worse on phono 1 than two. I don't have a manual, but might it be a ground issue? Is it worth trying to fix or is it time to get "tubed." Other components are Adcom 5500 monoblocks with Vandersteen 2ce's. thanks.
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Manual is at https://www.hifiengine.com/manual_library/apt-corporation.shtml Does hum only come when channel cuts out? That sounds like cable. If hum in both channels, the turntable to pre-amp separate ground wire is suspect as others wrote. This ground is a separate wire, not the shield of the RCA interconnects. Post on back of pre-amp to ground on turntable. What is Holman's current company? |
Also, even on pre-amps that are encased in solid metal on all six sides, do not have a pre-amp too close to a power amp. Even if the power amp is off, some keep the power supply on standby, generating an electromagnetic field that can cause hum. I had this problem, and ended up moving the pre-amp a foot from any amp, and the problem went away. Especially true if your pre-amp has an MC input, and is the kind where there is just a phono input select, meaning it picks up signal from both the MC and MM inputs all the time! For that, put an all metal shorting plug in to the unused phono inputs. This advice is for all pre-amps. |
That preamp is old enough that I would replace the filter capacitors in the power supply before anything else! Electrolytic capacitors (which are used in the power supply) really are only good for about 20-25 years- after that probably about 50% of them are failing. You're well past that point! When they fail they can start to draw current, and this can lead to power transformer failure. Plus, there's really no way the preamp is performing correctly; it will sound instantly better with new power supply filter caps installed. |
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