The Dude Posted August 18, 2009 Share Posted August 18, 2009 If I am in the wrong area let me know were to go, but I have been fighting some noise issues with my pre amp. This mainly is only on the phono stage, now on the phono stage there is a diode or cap that has 4 parts one is connected to ground and the other three go to the 3 different inputs. Now let me back up for a moment when you have ground issues noises etc. is it do to lack of ground or to much ground. I get this hum even if the record player isn't hooked up. I found if I touch the chassie it goes away, or if I touch the postive wire it gets worse(positive I mean not ground wire on the input jack). Now to let you know for some reason I felt it necesary to replace the electrical cord and connected the ground to the chassie. Anybody got any ideas, could this capicator be bad or do I maybe have some bad ground connections. Any info should be helpfull. At one point I was planning on just using the chassie for a pre-amp kit, but like I posted in another post I am holding back for a purchases on a new house thanks duder Quote Link to comment Share on other sites More sharing options...
Cut-Throat Posted August 18, 2009 Share Posted August 18, 2009 Let me ask you a few questions. Does your pre-amp have a 3 prong plug? When you say you replaced the electrical cord and connected the ground to the Chassis; what kind of cord was there in the first place? And why did you "find it necessary to replace it"? How did you connect the ground to the Chassis? What kind of amplifer are you using? Does the Amplifier have a 3 prong plug? Why would you suspect a capacitor? (Not likely) We need some more info to diagnose what is wrong here. Quote Link to comment Share on other sites More sharing options...
philipbarrett Posted August 18, 2009 Share Posted August 18, 2009 Ground noise can be caused by both "not enough" (equipment is floating & hunting for a ground) or "too many"(equipment is connected to ground in 2 or more places and their is a voltage potential between them) paths. I'm trying here to dissect your rather cryptic post. 1) you say "mainly on the phono" if that means there is also hum on other inputs I would suspect that the reason it's louder on the phono is the much higher gain from this input relative to the others - CLUE : if hum is present on all inputs then it's unlikely that the phono section is at fault or the caps or whatever you see back there 2) "if I touch the chassis it goes away" - CLUE : chassis is looking for a ground, you are providing one 3) "if I touch the postive wire it gets worse" - as it should, you're a great antenna & you've just connected yourself to a highly sensitive input 4)"I felt it necesary to replace the electrical cord and connected the ground to the chassie" if I presume this didn't fix anything then it totally contradicts statement #2 As mentioned above, without more information (the makes & models of your equipment would be a start) we can't go much further. Right now, basically all you've told us is that your car of undertermined age, model & make won't start! Quote Link to comment Share on other sites More sharing options...
The Dude Posted August 19, 2009 Author Share Posted August 19, 2009 Let me ask you a few questions. Does your pre-amp have a 3 prong plug? When you say you replaced the electrical cord and connected the ground to the Chassis; what kind of cord was there in the first place? And why did you "find it necessary to replace it"? How did you connect the ground to the Chassis? What kind of amplifer are you using? Does the Amplifier have a 3 prong plug? Why would you suspect a capacitor? (Not likely) We need some more info to diagnose what is wrong here. first to all I am using a dynaco pat-4 and a kenwood basic m2a. I dont reacall why I replaced the cord the old one might have been cut or split, I put in a iec connector so I can use any power cords if I needed one. After switching to other sources the um is just as bad. So I dont believe it is the capacitor. Quote Link to comment Share on other sites More sharing options...
The Dude Posted August 19, 2009 Author Share Posted August 19, 2009 Ground noise can be caused by both "not enough" (equipment is floating & hunting for a ground) or "too many"(equipment is connected to ground in 2 or more places and their is a voltage potential between them) paths. I'm trying here to dissect your rather cryptic post. 1) you say "mainly on the phono" if that means there is also hum on other inputs I would suspect that the reason it's louder on the phono is the much higher gain from this input relative to the others - CLUE : if hum is present on all inputs then it's unlikely that the phono section is at fault or the caps or whatever you see back there 2) "if I touch the chassis it goes away" - CLUE : chassis is looking for a ground, you are providing one 3) "if I touch the postive wire it gets worse" - as it should, you're a great antenna & you've just connected yourself to a highly sensitive input 4)"I felt it necesary to replace the electrical cord and connected the ground to the chassie" if I presume this didn't fix anything then it totally contradicts statement #2 As mentioned above, without more information (the makes & models of your equipment would be a start) we can't go much further. Right now, basically all you've told us is that your car of undertermined age, model & make won't start! the hum is on all sources now that I went back and check and when I touch the positive side like you said I get a great radio station coming in. You guys have all ready made some since of this, thanks for your help so far. If you need any more info let me know. Sorry for sounding so confuseing I seem to do that alot. So since it goes away when I touch it that means its looking for ground right, then why did grounding my new cord to the chassie not take that away is it possible to have a bad ground in the house. If so why doesnt my other recievers hum. duder Quote Link to comment Share on other sites More sharing options...
philipbarrett Posted August 19, 2009 Share Posted August 19, 2009 Take a regular (cheap) power cable and cut off the female (equipment) end. Strip back the insulation about 4" to expose the 3 wires inside & then cut back the black & white ones, leaving only the green. For safety, tape over the black/white ends. Now, strip back about 1" of insulation on the green wire & using a clip, physically connect the copper strands to the chassis of your preamp, a place without thick paint would be best. Plug your modified cable into an electrical oulet. Less hum? No hum? PB Quote Link to comment Share on other sites More sharing options...
jacksonbart Posted August 19, 2009 Share Posted August 19, 2009 Don't let that stop you for reaching for the stars. Quote Link to comment Share on other sites More sharing options...
Cut-Throat Posted August 19, 2009 Share Posted August 19, 2009 first to all I am using a dynaco pat-4 and a kenwood basic m2a. I dont reacall why I replaced the cord the old one might have been cut or split, I put in a iec connector so I can use any power cords if I needed one. After switching to other sources the um is just as bad. So I dont believe it is the capacitor. I am guessing that the dynaco pat-4 or kenwood had a 2 prong power cord and you replaced it with a 3 prong - IEC - Correct ??? If so, what I would do is disconnect the ground from the IEC to whatever you connected it to in the amp or pre-amp. - These units were designed for a 2 prong plug and you have probably made a ground loop by connecting the ground of the IEC to something in the amp or pre-amp. I'd stick with the original design! Quote Link to comment Share on other sites More sharing options...
philipbarrett Posted August 19, 2009 Share Posted August 19, 2009 I am guessing that the dynaco pat-4 or kenwood had a 2 prong power cord and you replaced it with a 3 prong - IEC - Correct ??? If so, what I would do is disconnect the ground from the IEC to whatever you connected it to in the amp or pre-amp. - These units were designed for a 2 prong plug and you have probably made a ground loop by connecting the ground of the IEC to something in the amp or pre-amp. Unless you physically added a ground wire on the IEC to the chassis of the Pat-4 then both should be floating which is what I believe the problem to be from the symptoms described (touching makes it better). The "ground wire" test mentioned in my last post should confirm or deny this. Quote Link to comment Share on other sites More sharing options...
Cut-Throat Posted August 19, 2009 Share Posted August 19, 2009 I am guessing that the dynaco pat-4 or kenwood had a 2 prong power cord and you replaced it with a 3 prong - IEC - Correct ??? If so, what I would do is disconnect the ground from the IEC to whatever you connected it to in the amp or pre-amp. - These units were designed for a 2 prong plug and you have probably made a ground loop by connecting the ground of the IEC to something in the amp or pre-amp. Unless you physically added a ground wire on the IEC to the chassis of the Pat-4 then both should be floating which is what I believe the problem to be from the symptoms described (touching makes it better). The "ground wire" test mentioned in my last post should confirm or deny this. Well, I dunno - But I believe in putting the unit back to it's original state first. Then start trouble shooting from there. Mods are great - If you know what you're doing! Quote Link to comment Share on other sites More sharing options...
The Dude Posted August 19, 2009 Author Share Posted August 19, 2009 Ok so I tried what phil said to do with the ground wire clamped to the pre amp then pluged into the socket, I actually tried this on the power amp to(which it seemed to make some difference but the hum was still there). I tried what cut-throat said and disconnect the ground that I installed with the iec plug, that made no difference. So to answer any question about physically adding a ground when installing the iec I did just that. But like I said I removed the wire to put it back to original 2 wire. I couln't agree more with cut-throat about how Mods are great if you know what your doing. But this is the way I learn by experimenting sometimes I just cant see things like the pros do. Last but not least the only way the hum goes away is by me actually touching the pre amp or power amp(doesn't matter which one just need to be touched) then it goes away completely. duder Quote Link to comment Share on other sites More sharing options...
Cut-Throat Posted August 19, 2009 Share Posted August 19, 2009 OK, was the hum always there? - Or did it just happen recently? If so, what new thing did you do to your syst Ground loops and Hum can be a ***** and are not easy to solve in the least. Quote Link to comment Share on other sites More sharing options...
LarryC Posted August 19, 2009 Share Posted August 19, 2009 I can ask this question since I am so sub-elementary ignorant: can & should the A/C wires be reversed, essentially reversing the plug like in the old days? Quote Link to comment Share on other sites More sharing options...
The Dude Posted August 19, 2009 Author Share Posted August 19, 2009 OK, was the hum always there? - Or did it just happen recently? If so, what new thing did you do to your syst Ground loops and Hum can be a *** and are not easy to solve in the least. yes it was always there, the pre-amp and amp both were bought around the same time from different people. I replaced the cord right off the bat which again was do to a cut cord. Hooked them up together and been fighting/playing with ever since.just thought it was normal until I tried other integrated systems. Quote Link to comment Share on other sites More sharing options...
The Dude Posted August 19, 2009 Author Share Posted August 19, 2009 I can ask this question since I am so sub-elementary ignorant: can & should the A/C wires be reversed, essentially reversing the plug like in the old days? I guess you could you would end with a hot/neutral reversal which could end up being the right way. But like you I am so sub-elementary ignorant. Quote Link to comment Share on other sites More sharing options...
Cut-Throat Posted August 19, 2009 Share Posted August 19, 2009 I can ask this question since I am so sub-elementary ignorant: can & should the A/C wires be reversed, essentially reversing the plug like in the old days? Bingo !! - I think you may have nailed it ! - I never thought of that, but it certainly was true of most old amplifers. Quote Link to comment Share on other sites More sharing options...
philipbarrett Posted August 20, 2009 Share Posted August 20, 2009 I can ask this question since I am so sub-elementary ignorant: can & should the A/C wires be reversed, essentially reversing the plug like in the old days? Bingo !! - I think you may have nailed it ! - I never thought of that, but it certainly was true of most old amplifers. No, I looked at the schematic, the 1st thing the Pat-4 power line hits is a transformer which has no opinion on the hot/neutral issue. Quote Link to comment Share on other sites More sharing options...
The Dude Posted August 21, 2009 Author Share Posted August 21, 2009 Thanks for all your help folks I will give a few things a try this weekend and see what I come up with, but at least I am on the right path. duder Quote Link to comment Share on other sites More sharing options...
Guest David H Posted August 22, 2009 Share Posted August 22, 2009 Duder, take it slow. Go get some 2-3 prong adapter from the hardware store so you can lift grounds and flip the plugs without issues. Then take your system down to the bare minimum, ie. preamp, amp and speakers with nothing else around (especially cable boxes, TV's and monitors, or computers. then re-run all of your tests. Also make sure no high current draw appliances are running, and be mindful of halogen lamps as well. Make sure all of your RCA cables are in good condition and shielded. If the noise remains cycle the power on the preamp, if the noise level drops, the preamp may be the source of the noise. I spent 4 hours yesterday isolating a ground loop. Turns out I had to lift the ground on all 3 of my amplifiers, and relocate my active EQ. now the system is dead quiet. Good Luck Dave Harris Quote Link to comment Share on other sites More sharing options...
The Dude Posted June 5, 2010 Author Share Posted June 5, 2010 Just to give you guys a update. After using my Rotel-402 for the last 8 or 9 months, and digging around for parts for this pat 4 or trying to decide to give that sp 8 tube preamp kit a try. I decided to put my soldering skills to a test on the pat 4 and get the replacement power caps and lots of other caps in the pc board. Alls I can say is wow what a difference what some fresh caps can do. Theres is no more hum, and the bass is nice and tight. I am quite please with this 40.00 worth of upgrades made. Plus I feel safe with my soldering skills to get that Tube preamp kit(once I sell some other stuff and save the money maybe after the wedding this month). But thanks for all your guys help. Nick Quote Link to comment Share on other sites More sharing options...
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