Using a Velodyne sub, mounted in hte opposite corner of the TV/AV rack. Sub is wired w digital coax, going through the attic. The sub is plugged into a Panamax "max sub", as well the coax is ran through the max sub. ALL the A/V equip is connected to a MAX8 or sumn like that in the A/V rack.

If I run the coax through the max sub, I get a humming noise in the sub. (Similar to when you touch the sub RCA connector going to the amp) If I bypass the RCA connections on the max sub, (power is still connected to max sub) then the hum goes away.

Any ideas?

Ground issue?

If you use cable as a feed , 99% of humming noise is coming thru cable. Make sure you have 100% perfect ground on your cable feed.I have sometimes problems with it in Chicago area . Just my 0.2 cents Rob

sounds like a ground loop to me on the sub side

Subs have weird grounding schemes. Don't run it through the Panamax.

The most recent weird grounding scheme I ran into was when I was connecting a sub at a store where I had just fixed their demo switching board. I connected speaker wires to the high level inputs.

When I connected the left ground, the sub hummed. Note: it hummed when I connected the ground -- and it has a two-wire power plug. This means no ground loops. When I connected the left hot, the hum stopped.

Here's where it gets weird. The left and right speaker wire are connected to the same ground at the output of the power amp, right? I connected the right channel ground and the sub started to hum -- with the left channel ground and hot connected! As soon as I connected the right channel hot, the hum stopped.

Subs have weird grounds. Do what it takes. DON'T clip off the third prong of a grounded plug, though.

just to clarify, it doesnt hum when the POWER is run through the Panamax, only the RCA cable. Im using a SINGLE RCA/coax coming from the amp, going into the Panamax "max sub". Fron there it goes to a Y adapter, and then into the L and R sub line level inputs.

Thanks for the tips

Yeah, but if you have plugged the power cord of the Panamax into the wall, THAT will cause any problem that might be grounding. Power going through the Panamax shouldn't cause any problems anyway, just its connections to power ground.

equipment and sub are in different outlets, correct? other side of room?

with stuff we use we only connect left side of sub power amp via rca so i am not familiar with y connector and right and left configuration.

but if other equipment is on its own "panamax" and the sub is on its own"panamax" part of problem is your configuration, ground loop central. the potential for ground thru the 2 different panamax outlets is jacked up. not to mention outlets may not be on same "phase". what you have hear is a can of whoop ass.

remove panax's and hook directly to wall see if problem goes away. onluy hook left rca up see if problem goes away. if not ....punt

ed

Ive heard this explained before, but I think it was more with the Max in wall, like behind a Plasma. It was suggested that the max in wall be home run (110v) back to the main rack/surge protector. Reasons were the same, ground loop issues. But for the "Max sub", the whole POINT of the piece is REMOTE protection of the sub. If they expect you to home run 110 back to the main surge, why would you even NEED the max sub? Youd just home run 110 to the main surge, and be done with it.

doesnt matter..you are basically treateing both set of equipment seperately with seperate protection and filtering then you connect the 2 via an rca cable...what would you expect? i would expect a major ground hum.... the 2 grounds have diferent potential and now you have a can of hoop ass.....

ever notice the hum bars in a plasma or projector....this is caused by same problem...... thats why we always make sure our power is good and clean.

all our projo's and plasma power goes back to the rack with zero grounds outside the plug to our filtering equipment( same as our audio equipment...yeah its not pretty but we eliminate all kinds of issues....

or try a ground lifting rca plug

ed

So what are you suggesting? Just to NOT USE the RCA connections, and only protect the power? Or to home run the power for the "max sub" back to the Panamax power strip in the A/V rack, which defeates the purpose of the "max sub" in the first place?

dont use the sub max if it gives you greif. or use ground lifters on the rca cables. or home run the power

ed

When you plug the rca into the max sub you are connecting the braid to the ground in the max sub. If the outlet from the head end is on a defferent circuit or phase you are now having a ground loop. I would use the max sub for power, but not for the rca. By running it into the max sub you are grounding the sub cable to a different ground potential that the head end equipment causing the hum. To double check this left the ground from the max sub. If it goes away it is a ground problem. Then I would suggest using the Jensen transformer for line level audio if you still insist on using the max sub to protect the sub cable.

Mike

i say punt.........tell the customer his stuff sucks and it all needs to be replace.......
then resell him the same equipment without the sub max...problem solved and you made a ton of extra cash.

Good sales strategy ceied I gotta try that one! I stopped selling panamax a long time ago in lieu of Surgex.

Frank,
If I read your description correctly, the hum dissapears when you remove the signal line from the Panamax...

Run the signal straight through and just use the Max Sub for the power in this application. Obviously, there is some sort of transformer couple to ground or something in that Max Sub that the preamp section of the Velodyne disagees with.

I run line level all over the place for local source plates, subs, etc. and NEVER put it through any sort of surge protection device. Maybe if the lines were running outdoors that would be a recommended practice, but within a home they will be fine...

If a house takes a hit strong enough to get into the line level cabling that is run strictly inside the house, then the insurance company is definitely involved at that point!!

Next time, just use a Max 2 on your remote subs (if you can't home run a Max In-Wall kit to the rack mounted Panamax)

Don't bother buying the special one with the line level protection if it interferes with the subs you sell...