Good Idea or Bad Idea?

[cpd]

For x-mas my wonderful wife got me a Pro-Ject Debut Carbon Esprit turntable. It is currently sitting behind a door in my TV stand and is taking up a lot of real estate in the stand. It is connected directly to my Denon 2805 phono input. There is a slight hum in the phono stage, audible only at medium to high volume which I believe is due to interference from all of the other cables and wires behind that stand. That is my belief because the hum is present even when the TT is off and when I move the cable further away from the other cables the hum decreases. But that is not the point of this post, as I am working with Pro-Ject on that issue.

A while ago my wife decided to turn our upstairs family room into our bedroom so I dutifully moved our home theater downstairs to our formal living room. I have convinced her to reverse that decision! When I get everything back upstairs I will have an opportunity to isolate the TT from the rest of my components by putting it on a stand in a closet. To do so I believe I need to buy a phono pre-amp and place it in that closet as well. The plan would be to then connect the TT to the pre-amp (including the ground), and the pre-amp to a 2-sided RCA wall plate in the closet. From the wall plate I would run approximately 20 feet of interconnect to another 2-sided RCA wall plate near the TV stand location. From there it would be about 5 more feet of interconnect to connect to a non-phono input on the receiver.

This would hopefully isolate the TT from any interference caused by proximity to other cables. It would also free up valuable real estate in my TV stand. What I don't know is if I am just inviting more problems by increasing the cable runs and introducing so many connections.

Thoughts on that?

 

[markw]

You should place the phono preamp as physically close to the turntable as possible. By raising the level of the signal there, you will have less chance of picking up and amplifying any extraneous hum with that extended length of interconnect.

 

[slipperybidness]

You should place the phono preamp as physically close to the turntable as possible. By raising the level of the signal there, you will have less chance of picking up and amplifying any extraneous hum with that extended length of interconnect.

+1

To address your current problem: Have you tried to use SHIELDED RCAs?

I had a similar problem on my TT. I bought some RCA cables that are marketed for car audio amp installs (twisted pair and good shielding). That solved my hum problem.

 

[cpd]

You should place the phono preamp as physically close to the turntable as possible. By raising the level of the signal there, you will have less chance of picking up and amplifying any extraneous hum with that extended length of interconnect.

Yes, the plan is place the preamp on the same stand as the TT in the closet with a very short cable run. My hope was raising the level there would fend off interference. What I don't know is if I would be taking one step forward by doing that and two steps back by sending the line level down 25 feet of interconnect with two connections in between.

 

[cpd]

+1

To address your current problem: Have you tried to use SHIELDED RCAs?

I had a similar problem on my TT. I bought some RCA cables that are marketed for car audio amp installs (twisted pair and good shielding). That solved my hum problem.

I did try using some shielded audio quest component video cables i had laying around (with one color disconnected). Although it was hard to tell, I believe it lessened the hum, but it was still audible.

The other problem is I want the TT out of the stand entirely. I will not be able to sell my wife on a separate stand next to the TV stand (so it is either in the TV stand or in the closet).

 

[slipperybidness]

Well, the bottom line is that long runs of RCAs (ie unbalanced) are always a hit or miss proposition.

If your environment is noisy, then you're hosed. If not, then you're golden. Unfortunately, the only way to know if it will work is to try it and see.

At least you are on the right track of putting the phono pre as close to the TT as possible. Long lines on a pure phono signal (ie before the phono pre) is definitely a bad idea. Not just interference concerns, but also cable inductance/capacitance concerns (I can't remember which off the top of my head and too lazy to go look it up).

 

[cpd]

Between the wall plates the cable will be routed through a crawl space. I would probably purchase some well shielded BJC RCA's and I could also run the cable through some form of conduit to further shield against interference. Does anyone know if such a conduit exists?

I am not very educated in this area. Does balanced cable solve the issue? Eventually I will be upgrading my AVR and would consider something with balanced inputs.

 

[cpd]

Nevermind the question about balanced cables and the noise issue - apparently that's the whole point