Not what you may want to hear but with such long ICs, you may want to consider balanced if your electronics will support it.
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You mention radio signals when you record. When this occurs, Is the Lynn turntable the source? I ask because improper ground at the turntable and /or phono stage often results in the reception of all kinds of RF signals, even ham radio and CB.
Try improving the grounds at the phono end of the system first. Then, you may be able to float the ground to your amps with no radio AND no hummmmmmmm.
My first guess is that some components are at different ground potential than the other components due to the isolated wiring / outlets. This is PROBABLY due to your house wiring producing a "ground loop". If that is the case, playin with your components will probably not correct this.
This type of situation puts different levels of voltage on the chassis of each component. The result is hum along with the potential for shock & damage to your equipment (especially digital gear). One of my friends experienced an EXTREME case of "ground looping" and was getting "bit" if he touched two different components at once. We measured the difference of ground potential between the two components / outlets as being FOURTY volts !!!!
You somehow need to tie the grounds together between the multiple outlets that you are using so that they all share a common path to ground i.e. "equal ground potential". I ran into this identical problem when going to mono-blocks and it drove me crazy for a while.
Short of doing this, you did not mention if you lifted ground at both amps, one amp and the front end, only at the front end or ungrounded the whole system. Try leaving the two amps grounded and remove ground at the front end and then vice versa. The fact that you have at least three outlets, all with their own circuit paths and possible varying levels of ground, may make it tough to deal with. Ideally, you only want ONE common point of ground for the entire system. How you achieve this could depend on your individual components and how they are wired.
Another quick and dirty test is to pick up an outlet polarity tester. These should be available at a local hardware store or a nearby Radio Shack. This is a very simple device that looks like the male end of a power plug with three different LED's and a chart printed on top of it. You simply plug this into the outlets and it tells you if they are wired in phase, if they have ground, etc...
Keep in mind that just because they show proper wiring and are grounded does NOT mean that they have a LOW resistance ground or that all grounds are "common" or tied in together. It is not uncommon for one electrician to ground the system at one spot ( electrical mains, ground rod, etc...) and then have another electrician ground new wiring at a different spot (cold water pipe, etc). This in itself can create a ground loop. Hope this helps... Sean
Sorry to be thick, but how do you "lift ground"?
I have a hum with a pair of EvO200.2's running as monoblocks into a Sunfire Theatre Grand. I never had any humming until I changed speakers (I replaced my Jamo E870's with a pair of Audio Physic Libra's). The Jamo's were biwired and the Audio Physics are not, that's the only difference between the non-humming and humming systems (although I have not gone back and replaced the Jamos to see if the humming persists).
The new speakers may just be more seseptable to the hum and not necessaraly the cause. I have to Rel Stentors 2's. Although they are the same model one is about three years older then then the other. When I got the second one it humed like crazy but the first one didnt. To make a very long story short it just turned out to be a ground loop from my cable tv that never affected the rest of the system.
Good Luck. I completely understand your frustation and I wish there was more I could tell you.