EVH 5150III EL34 Ground Loop in FX Loop

FondledDuck

FondledDuck

Well-known member
Just picked up a used EVH 5150III EL34, having issues with the effects loop. Getting a bad ground loop hum when the loop is engaged. I swapped out the FX loop tube but no change. I've isolated it all the way down to merely running a 10ft cable in the loop send into return and still getting hum. Only time I don't get hum is if I use a small patch cable using the same method. All cables tested good. I replicated same tests with my other amps and they are silent. Are these amps known to have ground loop issues in their fx loops? Anybody have similar experiences? Any advice? Thanks.
 
My 6l6 version did but it was from my ABY split into to EVH front input. I don’t engage my effects loop in the amp as I’m using it as my solo boost only which sounds killer btw. Upgraded to the Lehle splitter and all was better. The end.
 
Are you 100% that it’s a ground loop, or just noise from the long cable run? When you move the cable around with your hand, can you hear it back through the amp?
 
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It wont be a ground loop, the ground is still connected with the fx loop disengaged so switching it in/out wouldnt make a difference if it was a ground loop.
 
IIRC those amps have the channel master volumes before the loop, so if you are not running the amp loud your send level out the loop will be low and your signal to noise ration will be screwed. Try it with the amp up at proper operating volume.
 
WarHed said:
It wont be a ground loop, the ground is still connected with the fx loop disengaged so switching it in/out wouldnt make a difference if it was a ground loop.
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burger said:
Are you 100% that it’s a ground loop, or just noise from the long cable run? When you move the cable around with your hand, can you hear it back through the amp?
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Not 100%, but it’s the only amp under same condition that has the noise issues. I think it’s interference with power…when I move the return cable closer to power input the noise increases…
 
FondledDuck said:
These cables are good, tested in other amps with good results. Cable run is not excessive…10ft send, 10ft return.
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When using an effects loop, I always use a good shielded cable and keep it as short as possible. 10ft is long for an effects loop.
 
I noticed my 100w 6L6 Stealth getting a ground type of hum in the loop as well. I hardly ever use my loop and I don't recall it doing it previously, but it's been there the past few months. I tried swapping the power tubes and all the preamp tubes one-by-one and it's still there. With a cable in between it doesn't hum, but when I put a pedal in-between it does. I've tried different pedals and get the same result. I've also tried the same pedals and cables with other amps and have no hum. I have all good cables - Colossal, Mogami, & Canare.

I haven't gone too crazy trying to track it down, but next I'm going to try a battery in those pedals rather than a power supply (I use a Voodoo Pedal Power Plus 2) and see if that makes a difference. I'm also going to try cranking up the volume to see if that has any impact on the voice like mentioned above.

FondledDuck, do you notice any other odd noises? I have this ever so slight hum in the background on the green and blue channels. It has a ground hum type of sound, but it's very low in volume. It's something that wasn't there before, but since I typically live on the red channel I couldn't tell you when it started. It increase is volume as the volume goes up. I've wondered if it's related to the louder hum I get when I engage the loop w/a pedal.
 
fearhk213 said:
I noticed my 100w 6L6 Stealth getting a ground type of hum in the loop as well. I hardly ever use my loop and I don't recall it doing it previously, but it's been there the past few months. I tried swapping the power tubes and all the preamp tubes one-by-one and it's still there. With a cable in between it doesn't hum, but when I put a pedal in-between it does. I've tried different pedals and get the same result. I've also tried the same pedals and cables with other amps and have no hum. I have all good cables - Colossal, Mogami, & Canare.

I haven't gone too crazy trying to track it down, but next I'm going to try a battery in those pedals rather than a power supply (I use a Voodoo Pedal Power Plus 2) and see if that makes a difference. I'm also going to try cranking up the volume to see if that has any impact on the voice like mentioned above.

FondledDuck, do you notice any other odd noises? I have this ever so slight hum in the background on the green and blue channels. It has a ground hum type of sound, but it's very low in volume. It's something that wasn't there before, but since I typically live on the red channel I couldn't tell you when it started. It increase is volume as the volume goes up. I've wondered if it's related to the louder hum I get when I engage the loop w/a pedal.
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No other noises…
 
FondledDuck said:
Does it without any pedals in the loop
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ah ok. Is the loop a separate board that attaches to the main amp board via some cables? I would also check the solder joints on the jacks of the loop it self and trace points/lines from those jacks to make sure nothing is lifted or solder joints are cracked.

its weird that it happens with long cable but not with a short patch cable. if it is a solder joint, perhaps the longer cable is putting enough pull on a solder joint to cause that noise but a short patch doesnt have the same pull. One way to check is plug in that short patch cord and just wiggle the end gently while its plugged in. see if you get any noise.

Hope that helps.
 
Bash_Man said:
ah ok. Is the loop a separate board that attaches to the main amp board via some cables? I would also check the solder joints on the jacks of the loop it self and trace points/lines from those jacks to make sure nothing is lifted or solder joints are cracked.

its weird that it happens with long cable but not with a short patch cable. if it is a solder joint, perhaps the longer cable is putting enough pull on a solder joint to cause that noise but a short patch doesnt have the same pull. One way to check is plug in that short patch cord and just wiggle the end gently while its plugged in. see if you get any noise.

Hope that helps.
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Tried the short cable (patch cable) and no noise, only when I have 10ft or more of cable will it introduce noise
 
FondledDuck said:
Tried the short cable (patch cable) and no noise, only when I have 10ft or more of cable will it introduce noise
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only thing I can suggest next is to check solder points and PCB trace points from the Loop jacks to their next point. Aside from that, your next option may be taking it to a tech.

sorry couldn't be much help.
 
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