DVD RCA outputs->Active Monitor TRS inputs=HUM

[danieljoelle]

I have a set of M-Audio SP-5B active monitors (power supply built in to each one) that I'm trying to use for DVD playback along with my TV (normally use them for video editing).
So: DVD player RCA outputs are connected to the TRS (1/4" Tip/ring/Sleeve) inputs of the monitors. I get a significant HUM with this setup. (I've read the HUM FAQ, but I'm still unsure of the cause.) There is no standalone amp in the system.

I've tried putting one of these

http://www.musiciansfriend.com/srs7/g=live/search/detail/base_pid/180613/

in the path between DVD player and monitors, but that results in a LOUDER hum. (this device changes unbalanced to balanced)

I'm considering using one of these:

http://www.musiciansfriend.com/srs7/g=live/search/detail/base_pid/180634/

Am I on the right track?

Thanks,
Newbie Dan

 

[markw]

Just a WAG, but have you ever considered the simple approach?

First off, are the inputs to the speakers a mono 1/4" plug? If so, all you need is a cheap mono 1/4" phone plug to female RCA phono jack adapter. From then on, all you need is a simple RCA plug/RCA plug cable.

I do believe a Tip/Ring/Sleeve configuration is used for a balanced connection, which it sounds like you ain't dealing with. The output of the DVD is most certainly unbalanced and, I believe, the input to the powered speaker is as well.

But, then again, if he speaker input is truly a balanced connectoin, then you need to convert tha TRS balanced input to an unbalanced one. Again, Check Rat Shack.

 

[danieljoelle]

Thanks for the reply,

Originally, I bought RCA to TS (1/4" mono) cables at Rat Shack. (Couldn't find RCA to TRS -1/4" stereo - cables.) That's when I first noticed the HUM. Then I moved on to the CLEAN BOX I (unbalanced to balanced converter, RCA to XLR), with no change (actually it got worse). See the first link above.

The speakers (active monitors) do, in fact, have balanced XLR and TRS input jacks (using only one or the other, of course), and I am using balanced cables.

Now I'm wondering if it's a ground loop problem (I'm not an electronics wiz, more of a hobbyist video editor), and that's why I'm considering the CLEAN BOX II, which looks like a ground loop isolator.

Dan

 

[danieljoelle]

Today, tired and frustrated, I bought a ground loop isolator at Radio Shack.

What do you know: It works like a charm:

http://www.radioshack.com/product.asp?catalog_name=CTLG&product_id=270-054

How safe it is, I don't know. A $17.00 solution in the end..

I did bookmark that site, LarryP, to further educate myself.

Let me know if you think I'll fry something using this!!

Thanks,

Dan