The Burpster Posted June 2, 2007 Share Posted June 2, 2007 Well folks a new one to ponder over---- I have already tried this out on POD who as is as bemused as I am---- I have been through the above check list (in stickies) and its none of those. Its [b][u]not[/u][/b] an internal earth issue before you come back to me the obvious replies....... so here's the original note I sent to BOD...... to see if anyone out there has a remedy before I contact Mesa....... ________________________________________________________________________________________________________________ I have just got myself a new amp. Mesa Walkabout scout combo (awesome)...! When I play either of my PRS IVs though it, its incredible....... However when I use my Fender ('91 Custom shop 40th ann. Active/passive P+J P bass) I have a quiet but noticeable 50hz hum. This stops whenever I touch any metallic part of the bass. I have checked all the wiring, its AOK. Its already sheilded inside (by Fender) and is nicely wired with no dry joints...... Now the interesting bit..... While I had the back off the bass, I tried experimenting by earthing (by touch) various components whilst pluged in...... I discovered that if I touched ANY part the hum stopped including the metalised paint..... Oh I thought! so I tried the earth on the jack socket ,that stopped it.... Aaaah I tought LEADS---- so I tried all 3 leads that have and it still did it. So I left one of the Neutrik (metal cased plugs) lead in and the humming also stopped if I touch the metal casing of the plug at the bass..... It also stops if I touch the plug at the amp end...... Now heres the weird bit to me, if I touch the metal case face of the amp the hum stops again..... Its got me perplexed...... I have no hum at all with the PRSs which are both also active/passive..... Plug them in, back to back on the same lead and amp settings Fender = hum / PRS= silence.... Checked for noisey appliances and nothing. Any ideas? Bob. _______________________________________________________________________________________________________________ Quote Link to comment Share on other sites More sharing options...
Hamster Posted June 3, 2007 Share Posted June 3, 2007 Bob I ran this past a friend who repairs amps, and these are his thoughts without seeing the guitar & amp on his bench:> [quote]It is likely that the not-v-well-screened guitar is picking up hum induced in his body. Bodies are good at picking up hum and transmitting it. Put your hand near the tip of a jack with the other end in the input and you'll hear it. Earth yourself on the sleeve with the other hand & it goes away. He's earthing himself & his body's hum when he touches the various earths he mentions. Try walking away from the guitar and see if it stops. Not an awful lot you can do if it does, unless earthed pickup covers are a possibility. Conductive paint inside the cavities with a screw and earth wire might help, you can often get the paint from guitar parts suppliers.[/quote] Quote Link to comment Share on other sites More sharing options...
Oxblood Posted June 3, 2007 Share Posted June 3, 2007 (edited) Hamster's post says it. What you're describing is very common in any electric instrument with single coil/non-humbucking pickups, regardless of whether the instrument is internally shielded. Your body is acting as a big antenna, picking up the hum field from all the electrical appliances and mains wiring around you. It's YOU that is humming, not the bass! The bass pickups...er...pick this up. When you touch something that is earthed, like the metalwork of the bass or the amp, you're earthed, so you're no longer a source of hum. That's why bass/guitar bridges are earthed: the idea is that as long as you're touching/playing the strings (unless they're coated ones), you'll be earthed and the hum will be gone. Here's a brilliant, foolproof solution: wear a grounding bracelet, attached to the metalwork of the bass! Not inconvenient/messy at all, honest. In no way will it cramp your playing style, get in the way or lead to accidental strangulation when you take the bass off. Oh no. Edited June 3, 2007 by Oxblood Quote Link to comment Share on other sites More sharing options...
The Burpster Posted June 3, 2007 Author Share Posted June 3, 2007 Urrrm, Brilliant I think....! I can hum a perfect 50hz...... now if I can just realate that to my tuner........! I have learnt a valuable lesson, thank you both I had no idea (although having thought about it, it makes perfect sense) that we can and do act as aerials..... I will try that out to see if it indeed its I, that can rent myself out to Orange or Vodaphone...... Heerrrrrm earthing strap? I dont think so...... although......... By the way fellas, the Fender is fitted "Fender Lace Sensors" are they a rare breed of "hot" pup? I cant seem to find a lot out about them???? B. Quote Link to comment Share on other sites More sharing options...
The Burpster Posted June 4, 2007 Author Share Posted June 4, 2007 OK.... Great idea but it doesnt work.....switched off all (suspect) noisey appliances and set up so it was humming then put it down and walked away..... It still does it...... Lace sensors (still used and available for Strats) are a very acurate pup based on a humbucking design of single coil, with very special (Fender alledge secret) structure and material that should eliminate hum.... It doesn't on my set up....... That having been said, I have found a settting using the passive side of the amp and the bass switched to passive that has no hum and sounds lovely...... so maybe thats where it'll stay...... I think I'll email Fender and see what they can shed on it! Quote Link to comment Share on other sites More sharing options...
Oxblood Posted June 4, 2007 Share Posted June 4, 2007 (edited) Hmmmmm.... (if you'll pardon the pun). The fact that the bass is hum-free when in passive mode shows that these Lace Sensor pickups are indeed doing a good job of hum rejection. Therefore the hum pickup/amplification problem must lie somewhere in the active circuitry of the bass. Are you able to actually get inside the active ciruitry to examine it, or is it all encapsulated? Edited June 4, 2007 by Oxblood Quote Link to comment Share on other sites More sharing options...
The Burpster Posted June 4, 2007 Author Share Posted June 4, 2007 OB, Its not exactly hum free in passive, however I have found a setting that is..... Looks like I need to be way more specific----- In Passive mode if I have the volume on max and (then the 2 tone pots are passive linear pots) and the two tone pots at max it will have the same humm. It still does this without the battery installed ( I has one suggestion that it may be the internal resistance of the battery, which it isnt!). With the selector (4 position switch) in either of the active modes (1. straight active= 2 tones, are active ie cut and boost the signal---2. as setting one but with seperate tunable mid range boost) the hum is noticable but bearable, If the treble is at the central (0) setting or below. As soon as any treble is added the hum is proportionately louder ie more boost more hum to the point where at max it would make it unplayable in the live scenario. In either mode (pass or act.) if I back the vol pot off its max setting the hum is vastly reduced, however any more than 1/4 turn from max and the vol stops. Has this givne you any more evidence or just confused you more? Yep can get into the circuitry if neccasary but to check the circuit board wil require removal of the swirtchgear as it is soldered direct to the PCB which forms teh connections between them ..... do you want a pic? Quote Link to comment Share on other sites More sharing options...
BOD2 Posted June 4, 2007 Share Posted June 4, 2007 What you describe above is normal (when you have a hum in the first place). The hum will be at it's loudest when everything is up full and will be reduced by backing off the volume and/or the treble control. In passive mode doing either will reduce the output signal level and the hum with it. In active mode, adding treble will boost the more audible harmonics of the hum. It is still possible that there isn't actually a fault - and that "they all do that, sir". One earth connection you probably haven't been able to check is the one that should go to the underside of the bridge. It's probably ok and requires removal of the bridge to check it. You could try temporarily fitting an external earth wire to the bridge. If it makes no difference to the hum then it's a fair guess that the bridge wire is ok. Get a piece of wire and wrap one end around the metal case of the jack plug where it enters the bass, then wrap the other end around part of the bridge assembly. Some tape might help hold the wire in place at the jack plug end. Make sure you have good metal-to-metal contacts at both ends, remove your hands from the bass and then see if this reduces the hum. Quote Link to comment Share on other sites More sharing options...
The Burpster Posted June 5, 2007 Author Share Posted June 5, 2007 B, The bridge was one of the first things I did, as it was loose! It has a lovely big fat connection to earth....... I am more and more resigning myself to the fact that its a [u]"they all do that, sir"[/u] and that Fenders are just not in the same league as PRS...... In its defence it does sound wonderful in passive mode so it may just have to stay there...... Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted June 10, 2007 Share Posted June 10, 2007 [quote name='The Burpster' post='12539' date='Jun 5 2007, 10:01 AM']B, The bridge was one of the first things I did, as it was loose! It has a lovely big fat connection to earth....... I am more and more resigning myself to the fact that its a [u]"they all do that, sir"[/u] and that Fenders are just not in the same league as PRS...... In its defence it does sound wonderful in passive mode so it may just have to stay there......[/quote] Single coils do all do that, always have, but if your bridge is grounded the hum should disappear when you touch your strings. As that's generally a prerequisite to playing the hum should only occur when you're at rest not touching the strings, and a noise gate will stop even that if it bothers. Quote Link to comment Share on other sites More sharing options...
The Burpster Posted June 10, 2007 Author Share Posted June 10, 2007 BF, Thanks for that..... My quandry was why does the Fender do it when both PRSs dont? (they both are single coil pups) However I now believe that Paul Reed Smith, is not a luthier, he is in a fact GOD....... and every guitar that comes out of the American shop is touched by him before it leaves...... Much the same with Randall Smith at Mesa..... Fenders, (in my experience) conversly are unfortunatley wonderful instruments put together by primates in a factory, and require stripping and putting together properly before you play them..... and then require a great deal of head scratching and tweaking to get them "just so!" It appears I spoilt myself by buying PRSs so early in my paying career, I now expect everything else to live up to them! Quote Link to comment Share on other sites More sharing options...
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