Members Mjf222 Posted January 17, 2018 Members Share Posted January 17, 2018 Attached is a video of my DRRI plugged into a 2015 Les Paul with no effects. The hum becomes overwhelming at volume 5. I took the same guitar to a local guitar store and did not experience this hum on the DRRI at the store. I have played this amp at several venues and multiple guitars with the same result so i do not think it is anything at my home. I replaced all tubes twice and still have the issue... Also tried it with multiple cords....Any help would be greatly appreciated. Thanks!!! Link to comment Share on other sites More sharing options...
Members Mjf222 Posted January 18, 2018 Author Members Share Posted January 18, 2018 Any input would be appreciated Link to comment Share on other sites More sharing options...
Members WRGKMC Posted January 18, 2018 Members Share Posted January 18, 2018 Problem is totally obvious to me.First off, its not the amp itself. Amplifies amplify what they are fed by the input jack and that includes hum. Because the hum occurs when you turn the volume up - its a perfect indication that what connected to it has a major shielding problem.First off would be a total crap cord. Sounds like its got a busted ground connection to me. Guitar cords are shielded. They have a hot wire that carries the signal in the center and a braded shielding around that hot wire that grounds out the hum. When the connection to the grounded shield go bad, all you get is hum when you turn up and possibly a very weak signal. If hum was getting into the amp by some other avenue it wouldn't be affected by the volume control like yours is.I'll also note cheap plugs on cords are riveted together. It only takes a few tugs and the end of the plug comes loose. Grip the tips of the cables and see if you can spin the tip or the sleeve (not the cover that unscrews) If the metal spins you know that jack is toast and needs replacement. Cheap cords come with cheap connectors that simply fall apart. Some are so bad you're lucky to get through onw gig with them. If the tip and sleeve seem firm, unscrew the cap where the wires are soldered and check and see if a wire is ripped loose. In that video its likely the connector that was plugged into the amp, but hum can come from either end when ground is lost. If you buy NEW CORD, be sure it has 95% shielding or better. Your cheap cords are only 70% because they skimp on copper braiding. you want that braiding so it blocks all hum from getting in and high quality jacks. Its not like you have to spend allot either. You just have to know where to get the good deals. Monoprice has high quality cords with excellent shielding and they are excellent in cost. I been using one for over a year and its as good as any of my other high quality cords. The issues can also come from a foot pedal left on, specifically a high gain pedal. If you turn the pedal off and the hum goes away that's pretty normal. Theres always a low level of hum coming from pickups and cables. Gain pedals simply magnify it like a microscope. Best way to battle it, is first, don't use so much gain, 2 turn the pedal off when not in use, 3 add a noise gate/hush pedal that will silence the noise when you stop playing. 4 get a better gain pedal which doesn't hum so badly. Lastly the issue could be a broken ground wire in the guitar. The nuts on guitar jacks can loosen up and the wires break off. Gibson's are usually soldered very well to tough cables so re-soldering is rarely needed after tightening. If its a generic, the soldering jobs are all over the place, you have to remove the jack and look. There's also a ground wire that goes to the bridge to ground the strings. If you messed with the electronics in any way, the ground problem can be any place in there. Single coil can hum like a bastard too, especially if you're in a room that had dimmers or older CRT TV's or computer monitors. These kinds of high radiation devices create magnetic radio waves the hot wire between the pickup and amp are picking up the AC waves like a radio antenna. You have to make sure there are no weak spots in the shielding when hum changes in volume as its turned. Lastly there's a super rare possibility the jack on the guitar amp is damaged. If you get that hum with nothing plugged in then the jack which has a built in switch isn't grounding the input making the amp silent. Again, a loose jack can cause this. If this is a newer amp that uses plastic input jacks that mount to a PC board, its possible the solder connections got cracked by the cord being yanked. If the jacks are metal then they are chassis mount, they connect to wires that are unlikely to break. Again, if you unplug the input and the hum disappears, the amp isn't the cause if the hum. Its the cable guitar or whatever you have plugged in between. Link to comment Share on other sites More sharing options...
Members Mjf222 Posted January 19, 2018 Author Members Share Posted January 19, 2018 Thank you!!!! I appreciate the detailed response. I will try your suggestions and leave feedback. Thanks again! Link to comment Share on other sites More sharing options...
Members onelife Posted January 30, 2018 Members Share Posted January 30, 2018 Problem is totally obvious to me. First off, its not the amp itself. Amplifies amplify what they are fed by the input jack and that includes hum. Because the hum occurs when you turn the volume up - its a perfect indication that what connected to it has a major shielding problem... That is not always the case. If there is ripple in the B+ then it will be amplified by the gain stages. The Volume control on the DRRI is after the first gain stage so it will have an effect on the amount of hum being heard through the speaker. If the Volume control has no effect on the hum whatsoever then that would indicate ripple in the negatve bias supply for the power tubes. The ultimate test, however, is to try the amplifier with nothing plugged into it. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted January 30, 2018 Members Share Posted January 30, 2018 I skipped that because it didn't seem to apply yet. I wanted him to unplug and turn up which he seems to have done because he didn't return and post anything back. What clued me in was he said - "The hum becomes overwhelming at volume 5" and the volume gets louder in the video when he demonstrates it being turned up. Hum would only increase unless the hum was occurring before the channel volume. As you know fenders use a dual triode and the chances of 1/2 a triode humming are pretty slim. It may have been the preamp tube but I wasn't going to try and advise him to try that before ruling out the simple stuff first. Another clue is when you look carefully at the video, you also hear the dip in the hum due to phase cancellation when he changes angles to the amp. He seems to be wearing the guitar and the dip in hum when changing angles is another indication of poor shielding and the hum is coming before the amp. If I were to guess I wouldn't be surprised if he was plugged into a speaker cord by accident. I was hoping he's post back and let us know the results but I suspect he found his cord was bad and simply moved on. Link to comment Share on other sites More sharing options...
Members onelife Posted January 30, 2018 Members Share Posted January 30, 2018 My suggestion would be to adjust the Volume control on the guitar and listen to what effect that has on the noise. If the guitar's volume control does not eliminate the noise then I would repeat the test on all four of the amplifier's inputs. Link to comment Share on other sites More sharing options...
Members AJ6stringsting Posted August 13, 2018 Members Share Posted August 13, 2018 Put a noise gate in the effects loop of your amp too, set it be be as sensitive to opening up easily . Link to comment Share on other sites More sharing options...
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