Not sure if I’m in the right forum section for this, but I’m sure the moderators will move me along if need be.
So I’ve just updated my set up, and I’m rocking the following:
pair of Technics SL1210 MK2
Pioneer DJM-600 mixer
Crown XLS1000 power amp
pair of Cerwin Vega E-310 speakers
I am getting feedback coming thru the speakers, and I have narrowed it down to the mixer. When I switch the amp on, its fine. You get that very low level hiss from the tweeters (which is normal). However, when I then switch on my mixer this is when the feedback starts. I can also hear it coming thru the headphones.
When I’m playing a record you don’t notice it too much. But as soon as the music stops you get the feedback.
Unplugged the turntables from the mixer, feedback noise has gone.
Plugged in a CD player to the mixer, no feedback.
Turntables are internally grounded, but I connected the external ground wire as well. Still got the feedback.
The feedback noise is a humming noise that seems to come out of the bass cone more than the mids and highs.
Also, I have noticed on my amp that the inputs are labelled ‘channel 1’ and ‘channel 2’. Whereas on the mixer they are labelled ‘L’ and ‘R’. Can you advise which channel corresponds to which?
Does the noise happen with the mixer on and the turntables disconnected? The DJM is double insulated so does not require a ground, and I know that on more recent DJMs with removable power cord there is not even a ground pin present.
right, second time writing this. Posted a response earlier, but it went nowhere…(??)
Here is what I’ve done so far:
Unplugged the decks from the mixer, kept the mixer and amp powered on. No feedback.
Plugged in mixer to the amp via RCA (instead of XLR). Kept turntables plugged in to the mixer. Still got feedback.
Plugged in a CD player to the amp via RCA. No feedback.
Everything seems to be pointing to the decks. However I have just had them serviced (replaced RCA leads, internally grounded them, and replaced pitch controls), so it doesn’t make any sense…
When the music is playing the sound is really good. However, once the music stops you get that annoying feedback.
Could a ground lift adaptor fix this? I can’t see a switch on the back of your mixer. Make sure your decks are grounded on the screws between channels 2 and 3 on the back.
if your using DVS unplug your laptop from the power supply and let it run on battery. If the hum has gone then Patch was right, To fix it get a ‘ground loop isolator’ they are about $10 - $15 on eBay. I don’t think you use DVS from your description..
I had an issue with my old DJM-600 it would lose it’s ground every now and then.. To fix it I needed to remove the turntable grounds and reattach. That got annoying so I got a simple push button switch that would open the circuit on press and close on release.
I don’t know what a ground lift adapter is buddy. Both my decks are internally grounded, and I connected their external ground cable to the back of the mixer. Still getting feedback.
it was just a temporary spring loaded switch that opened the circuit when you pressed it ‘the same as if you disconnected the ground wire’. Then when you release it closes the circuit again like reconnecting it. It was a very crude solution but it worked and I was able to fix the problem as soon as it occurred without having to fiddle with the back of the mixer.
To test if you have a similar problem just disconnect and reconnect your ground wire while a record is playing. if the feedback disappears then that’s your problem.
I dont have access to unmodded decks at present. However I had to take one of my decks back to where it was serviced, so I will get them to remove the internal ground and test it that way.
Thanks mate. The feedback isn’t that bad that you can hear it when music is blasting. Only when it stops do you hear it, at low levels the feedback isn’t too loud, but turn the gain up and it gets louder (obviously!).
It also confirms my problem for me. Just went out and bought an SL1200 that is not internally grounded (couldn’t believe the price I got it for slight_smile:. Tested it on my set up, and no feedback. Gonna get them to undo both decks next week.
The whole reason I wanted to do this was because I found the ground wire so annoying, should have known better.
having said all of the above. I just read all the other posts on that link makar1 sent me. It seems there are differing opinions on the subject, with some commenting they have been internally grounding for years without any trouble.
Either way, my experience hasn’t been so good (or maybe the technician who did it is just a muppet). So personally, I will stay clear in future.
slight_smile:. Tested it on my set up, and no feedback. Gonna get them to undo both decks next week.