Hi, N00B here... I live in the City, and ive started picking up this noise on my preamps, Redhead, and my audio interface pres. WTH is that? Its erratic, but constant. Maybe we can have a laugh and pretend its aliens, but id like to eliminate it from my studio, because all that extra noise gets recorded! Any ideas?
wtfisthisnoise.mp3 is just the sound of a poreamp from an audient id44 interface, nothing plugged in...then i turn on a mic, then turn it off...
redhead.mp3 is a bass amp with nothing polugged in, thats the noise it picks up. HELP!
wtfisthisnoise.mp3 is just the sound of a poreamp from an audient id44 interface, nothing plugged in...then i turn on a mic, then turn it off...
redhead.mp3 is a bass amp with nothing polugged in, thats the noise it picks up. HELP!
It may be an external source. See if it varies with the time of day, or the day of the week. Try an AC line filter.
Try shorting plugs in the inputs, to verify whether the noise is gone with the plugs.
Try shorting plugs in the inputs, to verify whether the noise is gone with the plugs.
HELP! Electrical noise interference | TalkBass.com
Here is a copy of the thread which has audio samples...
Here is a copy of the thread which has audio samples...
I got the interference out of a cheapo RA-88a mixer with attention to detail. When a yellow truck drove by I would get dogs barking "dixie" on my signal. Also police & fire radios, and if the RCA cable to power amp was over 6' long, I would get AM sports talk radio on it.
First off, the gain circuits need to be in a steel case. Ferrous. This could be connected to safety ground.
Power inputs (preferably DC from wall transformers) need to be filtered internally with an 11 turn choke on a toroid. Salvage ones from flat screen TV or ATX supplies will work. Has to have short wire from inlet jack to coil, 2" of wire makes an RF transmitting antenna. The IEC AC input filter tends to have a much less aggressive inductor.
Then DC supply needs a parallel cap (could be type X). Also a 250 vac (Western hemisphere) or 330 Vac (eastern hemisphere) metal oxide supressor parallel across the line to prevent pops from lightning or motor shutoff. As I was making a virtual gound with zeners for op amps, I used 220 uf filter caps parallel .1 uf caps for each. For hum reduction I used a double pi arrangement of capacitors with 2 ohm resistors between first & second section. Actual resistor value depends on your current load.
Each RCA jack input needs a 33 pf disk cap center to analog ground. Located right at the jack back. I found the analog grounds were quieter by isolating the rings from case with o-rings, and connecting rings to analog ground instead. Single input theory says this is incorrect, but I didn't have a single input.
Twisted pair inputs can go to a differential receiver such as an op amp. Or a transformer. Short wire from jack to common mode suppressor is important. 33 pf disk cap on jack back shouldn't hurt anything.
Outputs need a 8 to 14 microH coil mounted near the jack, to prevent RF coming in that way. Wire wound around a AA cell or china marker will do.
Make sure you don't have internal oscillation of fast slew rate parts, which can cause funny howls on their own.
Also internal switcher supplies require their steel own case with extensive filtering at outputs to the analog parts. Disassemble a dead Peavey product (as CS800s) for instruction. (I did).
First off, the gain circuits need to be in a steel case. Ferrous. This could be connected to safety ground.
Power inputs (preferably DC from wall transformers) need to be filtered internally with an 11 turn choke on a toroid. Salvage ones from flat screen TV or ATX supplies will work. Has to have short wire from inlet jack to coil, 2" of wire makes an RF transmitting antenna. The IEC AC input filter tends to have a much less aggressive inductor.
Then DC supply needs a parallel cap (could be type X). Also a 250 vac (Western hemisphere) or 330 Vac (eastern hemisphere) metal oxide supressor parallel across the line to prevent pops from lightning or motor shutoff. As I was making a virtual gound with zeners for op amps, I used 220 uf filter caps parallel .1 uf caps for each. For hum reduction I used a double pi arrangement of capacitors with 2 ohm resistors between first & second section. Actual resistor value depends on your current load.
Each RCA jack input needs a 33 pf disk cap center to analog ground. Located right at the jack back. I found the analog grounds were quieter by isolating the rings from case with o-rings, and connecting rings to analog ground instead. Single input theory says this is incorrect, but I didn't have a single input.
Twisted pair inputs can go to a differential receiver such as an op amp. Or a transformer. Short wire from jack to common mode suppressor is important. 33 pf disk cap on jack back shouldn't hurt anything.
Outputs need a 8 to 14 microH coil mounted near the jack, to prevent RF coming in that way. Wire wound around a AA cell or china marker will do.
Make sure you don't have internal oscillation of fast slew rate parts, which can cause funny howls on their own.
Also internal switcher supplies require their steel own case with extensive filtering at outputs to the analog parts. Disassemble a dead Peavey product (as CS800s) for instruction. (I did).
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The interference experts: Neil Muncy (RIP), Jim Brown, Bill Whitlock, Henry Ott, would say that all RCA connector shells should be attached directly to the chassis (no insulator rings).