Biaeothanata-Bassist Posted April 4, 2014 Share Posted April 4, 2014 Hey guys I've recently put my Sony E100 SRP equaliser back in my bass rig and when I was changing the plug to an IEC to work with my power conditioner, I noticed it didn't have a ground/earth wire, just the brown and blue wires. Obviously, i didn't think anything of it. anyway, put it in to the rig and it caused some really nasty humming noises to come through the chain. I isolated each unit in the chain and determined it was the equaliser. I checked all the other unit's plugs to see if they all had grounding wires and yeah, they all have the green/yellow banded earth wire. The humming coming from the equaliser was so bad that I've actually removed it completely from the chain again. So, is it possible to wire in a ground wire to a unit or what can i do to stop it? I'd like to use the unit in my chain but can't go having that much excessive noise coming through the rig. I even tried putting a noise gate after the unit but as soon as you hit a bass note, you can hear the buzz coming through with it. Oh just as a side not, the EQ was set totally flat at the time too so i eliminated that it was frequency buzz too. I've also read the "humming noises" sticky thread in the repairs section but couldn't really find an answer in there. Thanks! Steve Quote Link to comment Share on other sites More sharing options...
Thunderbird Posted April 4, 2014 Share Posted April 4, 2014 I would think that if the unit is metal you could drill it and put some little screws in and then use a bit of earth wire with eyes crimped to the ends and put it on say the top and bottom of the unit in the kind of way that they put an earth loop on a sink unit or radiator I should imagine something like that may work but hopefully some one a bit more clued up than me could tell you for sure Quote Link to comment Share on other sites More sharing options...
HowieBass Posted April 4, 2014 Share Posted April 4, 2014 The Sony equaliser will be a double insulated appliance (look for a symbol on the back of a square within a square) and shouldn't need to have an earth connection. There's some discussion (though old) on the addition of earths to double insulated units here http://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=3854 where basically the advice seems to be don't do it. As for what's causing the hum, have you got all electrical power coming from the same wall socket? Quote Link to comment Share on other sites More sharing options...
Biaeothanata-Bassist Posted April 6, 2014 Author Share Posted April 6, 2014 Hey Thunderbird and Howiebass, thanks for your replies. Thunderbird - I would go doing that but I don't want to go mutilating the unit just yet in case there's something else I can do with just the wiring, thanks for the tip though and I will bare it in mind for if all else fails Howiebass - I've looked on the back of the unit and can't see a symbol like that anywhere? There's certainly nothing around the wiring suggesting it's double insulated either. Also, all the units in my rack are being run off a Samson Pb-10 pro power conditioner which is being run off one wall socket plug. Is there anything else it could be? Thanks Quote Link to comment Share on other sites More sharing options...
BigRedX Posted April 6, 2014 Share Posted April 6, 2014 This is a rack mounting unit? I would suspect that the problem lies with the casing touching one of the other devices in the rack. If you take it completely out to the rack and connect it up so that the only the signal cables and the mains lead physically connect it to the other devices in your rack does the problem go away? Quote Link to comment Share on other sites More sharing options...
Biaeothanata-Bassist Posted April 6, 2014 Author Share Posted April 6, 2014 Hi BigRedX, yeah the unit is a proper purpose built rack EQ, it's a 31 band graphic equaliser. Really good piece of kit. I'll go and take it out now and see if it still buzzes when out of the rack. If it doesn't, what can I do to prevent it from buzzing in the rack? Thanks again Quote Link to comment Share on other sites More sharing options...
HowieBass Posted April 6, 2014 Share Posted April 6, 2014 (edited) If it's a metal cased unit in a rack with other metal cased units (which are earthed) and there are metal to metal connections where bolts secure the units to the frame then surely the Sony casing will already be earthed? Be interesting to see what happens when you do isolate it though. Edited April 6, 2014 by HowieBass Quote Link to comment Share on other sites More sharing options...
BigRedX Posted April 7, 2014 Share Posted April 7, 2014 I'm thinking that the problem will be one of the other units in the the rack where the case earth and the signal earth aren't connected. However having the Sony unit in the the rack is connecting them causing an earth loop. Quote Link to comment Share on other sites More sharing options...
HowieBass Posted April 7, 2014 Share Posted April 7, 2014 So he needs something like these? http://www.sweetwater.com/store/detail/IsoTabs/ Quote Link to comment Share on other sites More sharing options...
BigRedX Posted April 7, 2014 Share Posted April 7, 2014 [quote name='HowieBass' timestamp='1396856946' post='2417887'] So he needs something like these? [url="http://www.sweetwater.com/store/detail/IsoTabs/"]http://www.sweetwate...detail/IsoTabs/[/url] [/quote] Maybe. But he'll also need to stop the case of Sony unit touching the cases above and below it in the rack, which is why I suggested physically isolating it from the rack as a starting point. The trick with these problems is to only change one thing at a time, otherwise you're unlikely to be able to track down what is causing it Quote Link to comment Share on other sites More sharing options...
Biaeothanata-Bassist Posted April 7, 2014 Author Share Posted April 7, 2014 Hey guys, it's still buzzing when out of the case I don't know if there's a problem with the unit it's self? It still works fine but there's just that horrible buzzing noise. Problem is, because i use a compressor, it amplifies the hum a bit more when i play. Quote Link to comment Share on other sites More sharing options...
HowieBass Posted April 7, 2014 Share Posted April 7, 2014 I don't know the Sony unit so I can't comment on what faults have been known to develop with them but if it were me I'd have the compressor first in the chain and the EQ at the end. Quote Link to comment Share on other sites More sharing options...
BigRedX Posted April 7, 2014 Share Posted April 7, 2014 As I said previously, in cases like this you need to proceed slowly and logically to try and track down the problem. I'm assuming that everything was working fine before you added the Sony EQ? Can you list all the other equipment in the rack and how it is wired up both with and without the Sony. Quote Link to comment Share on other sites More sharing options...
Biaeothanata-Bassist Posted April 7, 2014 Author Share Posted April 7, 2014 Yeah everything was working fine before hand. As it currently is (and was before I added the EQ in to the rack) the signal chain is: Bass -> Planet waves 20 foot custom series gold tipped cable -> DBX 1066 compressor -> Aphex Aural Exciter 103C (harmonic boost) -> Hartke LH500 amp -> Ampeg SVT 410 HE cabinet. All items being powered off of a Samson PB-10 Pro rack power conditioner, all units connected up with normal pedal cables (admittedly they're cheap cables until I can afford to go all XLR but they're what I've always used and they never cause any issues). I use a different cable to connect to my cabinet though, I had it made at a local guitar shop out of really thick cable. All of the units apart from the Sony EQ have 3 cables in the power lead: blue, brown and yellow/green striped. All these units have been working together for a year without causing any hum or buzzing. As it is now, there isn't any external noise from all of these units unless i stick Sony EQ in to the chain. Quote Link to comment Share on other sites More sharing options...
BOD2 Posted April 7, 2014 Share Posted April 7, 2014 Do you get the humming noise with ONLY the Sony unit in the chain ? (i.e. Bass -> Sony -> Hartke) Quote Link to comment Share on other sites More sharing options...
Biaeothanata-Bassist Posted April 7, 2014 Author Share Posted April 7, 2014 Hi BOD2, yeah I did get it that way as well. I tried each unit on it's own to the hartke amp (left them all in the case powered up too whilst doing this) and it was only the Sony EQ that had the buzzing. No other units did it, even with all the units still switched on in the rack case, the only one to buzz was the Sony EQ. Quote Link to comment Share on other sites More sharing options...
BOD2 Posted April 7, 2014 Share Posted April 7, 2014 If you take the Sony out of the rack, connect it between the bass and amp and it is buzzing on its own then that suggests a fault with the Sony rather than a problem with it "interacting" with the other items in your rack. Quote Link to comment Share on other sites More sharing options...
BOD2 Posted April 7, 2014 Share Posted April 7, 2014 Can't find any user manuals or other info on the Sony but I did find one on eBay with a few good photos. The unit is "double insulated" - one of the photos on eBay shows the "square within a square" symbol just next to the serial number. So that confirms there is not meant to be an earth wire in the mains cable. Looking at the other photos - there seems to be a "UNBAL/BAL" switch at the input at the rear. Does this switch make any difference to the buzz ? There's also an "BALANCED IN-OUT LEVEL" switch at the rear. Does this make any difference ? Quote Link to comment Share on other sites More sharing options...
HowieBass Posted April 7, 2014 Share Posted April 7, 2014 Some background information here on ground loop hum in audio systems which might be of help http://www.soundonsound.com/sos/1994_articles/aug94/groundloops.html Quote Link to comment Share on other sites More sharing options...
Biaeothanata-Bassist Posted April 7, 2014 Author Share Posted April 7, 2014 (edited) BOD2 - I haven't tried using them both together out of the rig as it's a pain removing everything haha. But i might do that. On mine i didn't see the symbol you mean about the double insulation but i don't doubt it's there. It does have the unbal/balanced switch but that basically just switches between the jack / xlr plugs and i don't have any xlr cables to try it with. The -10/+4dB switch (in out level that you mentioned) just changes the boost, still buzzes in both positions. I've tried it both ways. In the +4dB position, it just amplifies it a bit Howie - thanks pal, i'll give that a read in a minute Edited April 7, 2014 by Biaeothanata-Bassist Quote Link to comment Share on other sites More sharing options...
BigRedX Posted April 7, 2014 Share Posted April 7, 2014 (edited) AFAICS most of the devices you are using are designed to be run at line level rather than instrument level. Have you tried wiring them into the effects send and return on the amp rather than in front of the amp input as you appear to be doing at the moment. I think at some point you are going to have to take everything out of the rack and wire it up without any of the units physically touching each other to find what is causing the earth loop. Edited April 7, 2014 by BigRedX Quote Link to comment Share on other sites More sharing options...
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