Hello, Jan, I am rapidly getting away from unbalanced interconnects as much as possible. In your example, it is difficult, but I would treat the disc playback system as an island and then run balanced audio off that island. My old RTS405 RIAA preamp has transformer outputs and that is securely bonded to the Technics turntable. Many A-D converters have good differential inputs. You can lift the shield at the input end and see if that improves things. I have been doing a bit more PA and musical instrument work with my older son who is a far better musician than I ever could be--and he's still learning. We have all sorts of audio transformers floating around and they get the hum out. On a positive note, I was pleased that both the $100 Steinberg USB audio interface and the Kurzweil PC3LE8 keyboard we bought this summer both have balanced interconnections. None of the stomp boxes that he wants have balanced interfaces. The nice thing, however, is his Ibanez electro-acoustic guitar's preamp has an XLR mic-level output. I do build him extra phantom blocking capacitor modules in a Switchcraft S3FM barrel to be safe. One thing we discovered was having a Mackie 1402 VLZ Pro mixer and a Yorkville C80P speaker plugged into the same power strip with 6' line cords (both grounded) and using a quality coaxial cable unbalanced interconnect between the two still caused annoying hum. Replacing the unbalanced cable with a balanced one (both ports were balanced) reduced the hum to below audibility from being annoying. I don't have any transformers in my studio (other than that built into my Studer A80s and A810s and the RTS RIAA preamp) and perhaps a few other pieces of equipment. Most of the gear is electronically balanced. I use Aphex 124A balanced-unbalanced converters to generate a balanced signal close to an unbalanced source and then run balanced into the A-D converter. There are good reference papers about hum and buzz (as well as one of the best source for audio transformers) at www.jensen-transformers.com. The Jensen ISOMAX with RCA connectors on both sides is pretty effective at breaking the ground loop as well. I have a couple of those that come in very handy--again in the field. Having at least one of these is a great troubleshooting tool. Radio Shack in the US has one that is a lot less costly and doesn't sound half-bad, but I wouldn't use it in the final configuration, but it's cheaper than the Jensen for testing. http://www.jensen-transformers.com/ci2rr.html http://www.radioshack.com/product/index.jsp?productId=2062214 As an aside, this product is an effective device when you have mostly mic inputs (with phantom power) to connect a playback device at a distance from your mixer. http://www.radioshack.com/product/index.jsp?productId=2062444 It is far better than the price would suggest as long as the input is the standard -10 dBV levels. It will also work with many guitar pickups. I think between me, my son, and the church, we have ten of these now. Cheers, Richard On 2011-08-29 3:56 PM, Jan Myren wrote: > HI! > > I have sometimes problems with "ground" hum from the power on my set-up. > The problems are most often with my 78 rpm turnable playback system > consisting of a Rek-O-Kut turnable, Pro-Ject pre-amp, Packburn 323A and > Rek-O-Kut re equalizer and de-hisser. It is not quite permanent. > BUT; when it sometimes appear it seems like it also make the music signals > sound distorted, especially at the end of the records. > > May such hum also have something to say for the music signals, like > distortion, maybe, or will it just cause that "famous" "ground" problems hum > sound from the loudspeakers? > -- Richard L. Hess email: [log in to unmask] Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX http://www.richardhess.com/tape/contact.htm Quality tape transfers -- even from hard-to-play tapes.