Until recently, my primary computer was a G4 PowerBook; and into its sound-out / “headphones” I had an audio line plugged; the other end of the cable split into a pair of RCA jacks (left and right channel) each of which went into the “AUX” left and right ports of my NAD amplifier.
The NAD amp therefore treats the computer as just just one more audio input device (akin to a CD player or whatever). From the amp, sound goes out to formidably large (if not necessarily audiophile-quality) speakers.
Worked fine.
I just recently acquired a MacBook Pro (yay me! for the first time ever I own an Intel-powered computer!) ( ::shakes off momentary residual dirty feeling:: ). It’s a nice piece of hardware. But when I plug in the same audio cable, some combination of the computer and the external audio system of cable, amp, more cable & speakers becomes… a #$%@#@ radio antenna.
I am not an audio person and there are a lot of things I don’t know about wiring and cables and interference and whatnot. The word “shielding” is floating up as something I’ve heard about but I will need some babytalk explanations of what I oughta do to get rid of this unwanted radio broadcast. What do I shield and how do I shield it, in terms and sentences aimed at audio-equipment ignorant persons?
got halfway through and thought, “shielding”…then saw you’ve already been down that path.
basically, you need a balanced cable (three wire) to cancel out the rf interference. I’ve never seen an 1/8" inch, but its be trivally easy to make. alternately, an 1/8" version of a DI box would work equally well, but necessitate more cable.
I’d offer direct links or upload a quick schematic but I’m on my phone and away from the studio. if you needme to later, just let me know.
I don’t think balanced cables are necessary here. It sounds like either the RCA cables or the mini-to-RCA adaptor is unshielded and simply needs to be replaced with better quality. Try just picking up some new shielded RCA cables from RadioShack or whatever (don’t waste money on overpriced Monster cables) and see if that solves the problem. If not, try swapping out the adaptor for a new one.
If that fails, surround your house with a Farraday cage.
NAD does make great amplifiers. It’s a shame that they never took my suggestion of building a portable music player called the GoNAD.
This only occurs when you plug in the new computer? What if you replace the computer with some other component located at the exact same spot on your desk?
You can probably mitigate this to some extent by turning the volume on your computer way up, and then adjusting your amplifier as desired. This will increase the SNR of your audio signal.
In any case, you can likely get rid of the interference with a Ferrite choke. Go to Radioshack and buy a few, then snap one onto the cable from your computer to the amplifier. If it helps, attach the others (unless the noise is gone at that point). It doesn’t really matter where you put them on the cable.
If you live in a flat area this won’t work, but if you live in one of those rugged areas where moving the radio changes which stations you receive, try moving the computer/amps. Also make sure you don’t have looped cable: it’s not because “the electrons will get dizzy”, it’s because loops of cable form a magnetic field which is highly susceptible to induction. The loops form a magnetic field, if this magnetic field gets poked by another magnetic field the electricity in the cables changes, thus the signal being carried by the cables changes; what gets to the amps is the mixture of the original signal plus the bothersome magnetic field (in this case, a radio signal).
I had similar problems with a record player (I could not play LPs on Sunday afternoon, because if it was at 33rpm it ‘caught’ the ham-operator neighbor) and a radio/tape player (if I was listening to tapes and the dial was set to 105fm, it would ‘catch’ the police dispatcher from the station down the block… but only when the tape was in the middle! - making sure to move the dial out of 105 when I was going to play tapes solved it). Electromagnetism can be a bitch sometimes.
For the sake of review: the problem did not exist with the previous computer, a G4 PowerBook. Exact same wires: unplug from old computer, plug into new computer, now have the problem.
I live in Manhattan; a hillier section than most but moving the amp is not a possibility, it’s a rather small room with limited options for what goes where. And if it were the position of the amp or loops in the wires, wouldn’t it have caused the same problem with the old computer?
I wonder if it has to do with the Macbook Pro’s metal casing vs the Powerbook’s plastic. My gut tells me this shouldn’t matter since the output jack should be sufficiently insulated from the case but… it seems plausible to my extremely layman brain.
Edit: Sorry, I swore powerbooks were plastic. Maybe they have different type of metal, or the Pro just plain has worse insulation for the sake of making it smaller?
This thread on MacRumors says that inside the Macbook Pro the audio system itself is improperly shielded, and that unless you want to take apart the Macbook and fix the shielding yourself, there’s not much you can do other than get an audio system that filters the noise. Though I think putting a faraday cage around it might work if you don’t care about Wi-Fi.
No, because it’s the whole circuit that resonates. You’ve changed a part of the circuit (the computer); the old circuit didn’t resonate, the new one does. Mind you, if what’s picking up the signal is (as Jragon’s information points out) a circuit within the computer itself… maybe you can move the computer, but other than that you seem to be SOL.
Radio pickup is a strange beast, and the exact cause can be difficult to pin down. Typically the system needs to pick up the signal, and also needs a component that will detect the audio component from the RF. Most amplifiers can oblige with the latter, although in this case it is possible that the output circuits of the Macbook are doing the detecting. I assume you tried the ferrite rings at both ends of the cable. Does the pickup occur when working with both external power and when running from battery alone? One also wonders if the amp itself is grounded. That is probably the biggest issue in annoying RF pickup.
Anyway, curing RF pickup is often effected by adding small bypass capacitors to the various cables in use. This will be a pain here, because you probably are not in the market for building or modifying cables. But a small ceramic capacitor between the centre wire and shield at each end of each signal cable is a good bet to bypass the RF, and get rid of the interference. (Doing the same across the speaker terminals is sometime needed when the amp picks up RF itself.)
Another totally different solution is to simply purchase an Apple Airport Express. No more wires from computer to audio system. Very nice. I have three, one on each story. Listening via one right now streaming from a Macbook Pro. If you get really enthusiastic you can put a dedicated DAC on it, and the sound quality goes up rather significantly versus the really very basic audio quality you get from the internal audio circuits in any laptop.
You may have a ground loop - your new Macbook Pro may be earthed in a different way to your old Powerbook, and this has created the loop. Try running the Macbook on battery for a bit, to see if the problem goes away. If it does, then you need a hum eliminator - this could be a stereo DI unit with ground lift, or a specific device (google ground loop eliminator/isolator) - they don’t cost much.
Good luck. I spent several hours last night assuming that my newly reorganised (and portable) laptop/audio interface combo was a bust due to the digital hash on the output, until I remembered my cool ground loop isolator, and was back on track.
I had this problem for a long time and I finally realized it was the signal from my cell phone causing induction/interference. If you have your phone in you/in your room, try moving it outside the room and see what happens.
This actually appears not to be the case; the TRRS plug with 3 stripes are for devices that have one port for both audio input and audio output; neither the new nor the old computer is set up like that (they have separate audio in and audio out).
Radio Shack doesn’t have any TRRS minijack to RCA adapters anyhow.
I have five ferrite chokes from Radio Shack as recommended by Absolute above. Does that have any effect on the recommendation to put a ferrite BEAD on the cable? Basically the same thing, or something different?
A friend recommends I sheathe the cable in aluminum foil (sounds time-consuming but I’m willing to try) or wrap its entire length in wire and ground each end. Comments?
Will this work with my NAD amplifier and the Yamaha speakers attached to it? I have no interest in any solution that involves pitching my audio system and starting over from scratch. My music is on my computer (and not in iTunes, btw, don’t use it, can’t stand it). If I got one, would I attach to it essentially the same minijack-to-RCA adapter and a much shorter set of RCA cables, plugging it in a foot or so away from the amp? And then I reference it as my SOUND OUT device?
Yay! That’s what I was hoping for!