Members BillyCorgan Posted March 3, 2006 Members Share Posted March 3, 2006 It seems that my JMP-1 is causing hum in my rack. Here is the chain. Any ideas? I'm pulling the JMP-1 out of the rack to see if there's any solution other than just not using it. I want to run them both at the same time. Link to comment Share on other sites More sharing options...
Members WKG Posted March 3, 2006 Members Share Posted March 3, 2006 I get a hum from my JMP-1 also. Others who have them have posted that the transformer hum is being amplified by the housing. I can confirm that as it went away when I had the top off when I was tinkering with the tubes. When I put it back on it picked up the transformer hum, took it back off, hum was gone. The way the transformer is mounted causes it as it rests against the lid of the unit. It doesn't translate into the signal path as it's a mechanical issue. If you've got a hum in the signal path then I'd think it was either a ground problem or a bad cord somewhere. BTW, I see you replaced the Strategy PA. I went with the Mesa 20/20 to use with mine. Great little amp. Very portable and still really, really loud when I need it. Link to comment Share on other sites More sharing options...
Members BillyCorgan Posted March 3, 2006 Author Members Share Posted March 3, 2006 Originally posted by WKG I get a hum from my JMP-1 also. Others who have them have posted that the transformer hum is being amplified by the housing. I can confirm that as it went away when I had the top off when I was tinkering with the tubes. When I put it back on it picked up the transformer hum, took it back off, hum was gone. The way the transformer is mounted causes it as it rests against the lid of the unit. It doesn't translate into the signal path as it's a mechanical issue. If you've got a hum in the signal path then I'd think it was either a ground problem or a bad cord somewhere. BTW, I see you replaced the Strategy PA. I went with the Mesa 20/20 to use with mine. Great little amp. Very portable and still really, really loud when I need it. Someone on Hugeracksinc told me to remove one of the shields on a cable. I'm gonna try that tonight. I still love my Strategy 500. It sounds so much better than the 2:90 but it's just so heavy in this case that i have. (+ i'd only be able to take the Triaxis or JMP-1.) When i get a 6 space SKB and a retube for the 500 i'm gonna start using it again. Link to comment Share on other sites More sharing options...
Members gargamelesp Posted March 3, 2006 Members Share Posted March 3, 2006 i have a jmp1 and it had bad hum as well. Then i got a decimator ProrackG. total silence. without playing, you wont know if the amp is turned on. this might be the solution for u Link to comment Share on other sites More sharing options...
Members BillyCorgan Posted March 3, 2006 Author Members Share Posted March 3, 2006 Originally posted by gargamelesp i have a jmp1 and it had bad hum as well. Then i got a decimator ProrackG. total silence. without playing, you wont know if the amp is turned on. this might be the solution for u If this cable thing doesn't work i'll be sure to check one out. Link to comment Share on other sites More sharing options...
Members WKG Posted March 3, 2006 Members Share Posted March 3, 2006 Originally posted by BillyCorgan Someone on Hugeracksinc told me to remove one of the shields on a cable. I'm gonna try that tonight. I still love my Strategy 500. It sounds so much better than the 2:90 but it's just so heavy in this case that i have. (+ i'd only be able to take the Triaxis or JMP-1.) When i get a 6 space SKB and a retube for the 500 i'm gonna start using it again. Is the hum in the signal path? Did you try isolating it using a ground lift? That may help narrow it down. I needed easy portability and earthquake volume isn't a current requirement, although I am somewhat amazed at what the little Mesa puts out. The EL84's help with the cleans to. After changing the clean side preamp tube to a RI Tung-Sol it livened up and gain some dimensionality. I settled on the recommended JJ ecc83s high gain in the distortion side. Works fine for me. I need to try the JMP-1 into my old non-master Superlead with 6550's. Link to comment Share on other sites More sharing options...
Members millertime Posted March 4, 2006 Members Share Posted March 4, 2006 when i had a jmp 1 i had the same thing ..the only thing that will fix it is a ebtech hum eliminator. it doesn't change your tone either. Link to comment Share on other sites More sharing options...
Members Karloff Posted March 4, 2006 Members Share Posted March 4, 2006 The jmp-1 transformer really had a loud hummmmm... Few mths back,theres a guy in Marshall amp forum with the same hum problem... and he did something to the top lid cover i think..not quite remember though... Link to comment Share on other sites More sharing options...
Members Cowinacape Posted March 4, 2006 Members Share Posted March 4, 2006 I just got a JMP-1 the other day and had it open to try swapping tubes, but I never noticed which side is which? which side is the gain, and which side is the clean (meaning the tubes)? Link to comment Share on other sites More sharing options...
Members WKG Posted March 4, 2006 Members Share Posted March 4, 2006 Originally posted by Cowinacape I just got a JMP-1 the other day and had it open to try swapping tubes, but I never noticed which side is which? which side is the gain, and which side is the clean (meaning the tubes)? VB1 is the clean side, VB2 is for the distortion channels. Link to comment Share on other sites More sharing options...
Members Cowinacape Posted March 4, 2006 Members Share Posted March 4, 2006 Thank you WKG! Link to comment Share on other sites More sharing options...
Members dmk Posted March 4, 2006 Members Share Posted March 4, 2006 get one of thesehttp://www.ebtechaudio.com/he-2des.htmli didnt think it would work, but it does!i'm running a jmp1, pod xt pro and 6100 preamp all together now with no ground loop problems at all.absolutely the best thing i've bought for my rack ever. Link to comment Share on other sites More sharing options...
Members WKG Posted March 5, 2006 Members Share Posted March 5, 2006 Originally posted by Cowinacape Thank you WKG! You're welcome! Link to comment Share on other sites More sharing options...
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