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Okay so my JVM210c is ridiculously noisy! I get a constant electrical hum which is increased by the master volume but not affected by the preamp. Im aware theres a fair amount of hiss on the gain channels without a noisegate but this is a seperate issue. Its my second rig and has never been abused; just rehearsals and the occasional gig.
Source of power definitely has an impact; the noise is massively reduced when using a power conditioner but still not completely silent compared to another amp!
Same can be said for putting pedals infront of it - if i take a feed from a power conditioner for my pedal board then there is a noticable difference in background noise and interference from the JVM.
In anticipation of your responses, i've tried many times going straight in the front of the amp and ive used a tonne of different power sources, IEC's, extensions etc in many different locations.
Amp has recently (last 3 months) had a full and thorough service, and new valves in both pre and power amp. Its completely stock other than the 'Plexi Cap Mod', which has no effect on the power amp or transformer what so ever.
I'm stuck for ideas, tried allsorts to get rid of the issue! Its getting to the point where i'm considering getting rid of it which i really dont want to do; other than all the noise problems i'm happy with the tones and versatility i get from it
Hope someone can help!
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"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Is there any chance it could have anything to do with the plexi cap mod?
So, by process of elimination, the fact that the hum and noise is 'controlled' increases or decreases) with the master volume, that confirms the issue is in the preamp?
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
That mod is just a 1uf cap parallel with the 2k7(iirc) resistor on the 1st stage of the 2nd preamp valve. Subtle effect on tone, not a serious mod or anything.
So if it's a fault with the AC power supply getting to the valves, should I be looking at dodgy valves or looking deeper in to the amp? Tested the valves in another amp and had no issues and all come up okay on a tester (practically brand new)
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
I've got a few spares knocking around somewhere; I'll try mixing and matching different Chinese tubes in the v3 and v4 positions, see if that achieves anything
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
I'll get some spares from my gig case tomorrow and try them in the jvm over the weekend.
Anything else worth trying that I've missed??
Then some silly bollocks frontman decided to plug his wireless mic psu in the 2gang extension from my power conditioner that was running my pedalboard and it was noise central! Horrible digital-like electrical hum and interference ont dirt channel.
Unplug the psu. Silent again.
So confusing!!!
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Had one feed from power conditioner going to back of stage; 2 gang for amp and g major 2.
Another to front of stage for pedal board. This is the one that the wireless mic psu was put into by mistake (desk was on my side, easy done). When that was put on to a different circuit, all was silent as it should be!
Had the same problem before; if either the amp or pedalboard shares a circuit with anything else (usually regardless of what it is), then it gets fucking noisy!!
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
I'd love to know how/why there's so much interference though. You say it could be some sort of earth leak?
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein