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Strange echo from amp head with headphones

K

KoRnKloWn420

Dec 7, 2019
6
1
#1
I hope this is the right forum to post this in, I didn't see any threads directly related to technical issues with amp heads.

I searched all over the interwebs and couldn't find any issues similar to mine. I have a Peavey MiniMega bass amp head, I have used headphones with it in a house I lived in previously with roomates, but in my new apartment I've noticed something strange. When I plug headphones into it at my new apartment there is a strange echo. If I don't play anything there isn't really a buzz or hum, but when there is sound it has a slight echo, and here's the strangest part, the echo is out of tune. At first I thought my bass was out of tune, but then I realized I could play a single note and it is out of tune with itself.

Also it is not just my bass, so it's not the pickups, I practice by plugging my computer into into my amp head and I play along to music, and if I unplug my bass and only have my computer plugged in the music has the same issue, it has a slight echo and is out of tune with itself.

Something else to note is that in my new apartment I haven't actually connected my amp head to my cabinet, I keep my cabinet in a practice room and I take my amp head there to practice (the cabinet is too small for my little room). In the practice room connected to my cabinet it doesn't have the same issue, and in the previous house I lived in it didn't have the issue with my cabinet or headphones. I also have a smaller practice amp in my apartment that I use, and it doesn't have the issue (although I haven't been able to test my little practice amp with headphones, it requires a 1/4 inch to 1/8 inch adapter, which I don't currently have).

I've suspected that it could be a ground loop, but everything I can find on ground loops doesn't sound like this, from what I can find online ground loops are a humming or buzzing sound, not a strange out of tune echo.
 
#2
It's not a ground loop.

I'm not sure what it could be though.

Actually, I just thought of something... is the mic on your computer live by any chance?
 
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#3
agedhorse said:
It's not a ground loop.

I'm not sure what it could be though.

Actually, I just thought of something... is the mic on your computer live by any chance?
Click to expand...
He has the problem through his headphones. I don't have any theories either, but would be amazed if the computer mike picks up the sound from his headphones. Is the computer plugged in exactly the same way as you used to use it? Do you have the echo without the computer plugged in?
 
#5
SteveIII said:
He has the problem through his headphones. I don't have any theories either, but would be amazed if the computer mike picks up the sound from his headphones. Is the computer plugged in exactly the same way as you used to use it? Do you have the echo without the computer plugged in?
Click to expand...
I was thinking if he was playing his bass near the keyboard of his laptop and the onboard mic was on and the headphones were being driven by the laptop, it is a possibility.

I have this problem with a laptop based measurement system where the laptop mic sometimes gets configured on by the software at boot up. I always need to verify that the onboard mic is actually off, or I get a latency artifact in the measurement.
 
#6
agedhorse said:
I was thinking if he was playing his bass near the keyboard of his laptop and the onboard mic was on and the headphones were being driven by the laptop, it is a possibility.

I have this problem with a laptop based measurement system where the laptop mic sometimes gets configured on by the software at boot up. I always need to verify that the onboard mic is actually off, or I get a latency artifact in the measurement.
Click to expand...
I think we need more infor on the setup. I understood his setup to be both bass and computer running into bass amp and headphones plugged into headphone jack on amplifier.
 
#7
That's a real puzzler.

I initially thought that it might be the strings between the nut and the tuners resonating (I have one bass that is so bad I have foam stuffed in to damp them) but not if it happens with a laptop as well.
 
#8
It certainly sounds like some sort of feedback or loop through the computer. Whether its external feedback through the air or some kind of internal weirdness I have no idea. I think I'd try playing along to music on a mobile phone or something, not the computer, to try and isolate it a bit more. And, naturellement, do what AH suggests and check the mike.
 
#10
My WAG is still with KOSMOS(R) :)

The OP plugs his/her computer output into the 1/8" Aux input on the MiniMega. He/she is not going through their computer.

The Aux input on the MiniMega must be also going through the KOSMOS. I could see people may want this to listen to pumped up bass from the aux input.

"KOSMOS C" calculates harmonics and adds them in. It may be a clocked circuit and has some delay.

Here is a harmonic sequence
Open A:
55hz (A)
110hz (A)
165hz (E)
220hz (A)
275hz (C#)
330hz (E)

Up one octave:
110hz (A)
220hz (A)
330hz (E)
440hz (A)
550hz (C#)
660hz (E)

To make the higher A sound once octave lower
"KOSMOS A" will add in 55hz
"KOSMOS C" will add in 165Hz, 275Hz, ..

It must be delaying the adding of harmonics. Note too these are not 100% in tune, harmonics work like that.
The OP may be an actual Golden ear that can hear slight pitch deviations and small amounts of latency. There are people with excellent hearing but it's more rare that this board would make one believe.

Or the amp could be broken. Turn off KOSMOS and see?

If anybody has a recording of one sustained note on this head it could be apparent.
 
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#13
  1. Thanks for all the replies guys. Kosmos is always off, don't really use it. I was thinking the same thing maybe it's a strange loop in the sound card of the computer. My computer doesn't have a mic plugged in, but could be the circuitry maybe. I thought I tested it without my computer plugged in, but I don't remember now. It's been a while since I took my amp head home, I'll have to test it again and let you guys know.
 

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