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Post by Johnkenn on Oct 27, 2016 20:30:39 GMT -6
So, I've noticed that when using my Upton, I'm getting some faint radio frequency coming through. I'm pretty positive it's the Upton, but I need to double check. Could it be an unshielded cable? Possibly the cable from the mic to the PS being cheap?
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Post by mulmany on Oct 27, 2016 21:03:06 GMT -6
If you just have the psu on with no mic cable do you still hear it? With the mic lead plugged into the psu but no mic? With mic plugged in?
Be careful while doing the middle step since you will have live voltage on the mic cable pins. Always remember to turn off the psu before disconnecting or connecting the cables or mic.
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Post by popmann on Oct 27, 2016 21:38:06 GMT -6
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Post by jimwilliams on Oct 28, 2016 8:53:24 GMT -6
UM70's used high Q ceramic .022 uf caps on the output pins to ground. The lead inductance causes the rectification of rf. The easy fix is to remove them and carefully solder .022 uf mono ceramic surface mount caps across the pcb pads on the foil side of the pcb.
I had the same problem using WIMA MKP-2 film caps in the original Rode NT-2 mic design. The surface mount ceramics fixed that.
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Post by Johnkenn on Oct 28, 2016 10:52:02 GMT -6
UM70's used high Q ceramic .022 uf caps on the output pins to ground. The lead inductance causes the rectification of rf. The easy fix is to remove them and carefully solder .022 uf mono ceramic surface mount caps across the pcb pads on the foil side of the pcb. I had the same problem using WIMA MKP-2 film caps in the original Rode NT-2 mic design. The surface mount ceramics fixed that. I was told there would be no math... |
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ericn
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Balance Engineer
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Post by ericn on Oct 28, 2016 11:20:06 GMT -6
First switch out mic cable between psu and interface.
Second see if somebody you know has a mic to psu cable you can try
To Swap.
If neither of those works time to talk to Dallas or Shannon!
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Post by wiz on Oct 28, 2016 16:18:47 GMT -6
its ghosts.. .its possessed .... send it here
cheers
Wiz
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Post by jimwilliams on Oct 29, 2016 11:31:13 GMT -6
If math challenged, try some clamp on ferrite bead cores from Mouser or Digi-key. They are in plastic boxes that snap over the mic cable. Place one at the mic end and one at the preamp input end, experiment with the distance from the plug. Get some bigger versions for your power IEC cables too. Damping rf at every possible entrance point can clean up the background noise and grit. Also use them on the digital processor power and audio interconnects to damp out unwanted clock noise.
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ericn
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Post by ericn on Oct 29, 2016 14:56:06 GMT -6
RF interference is the reason I hate HOSA!
When I started at Full Compass we were located in an old shopping center, on the hill behind us was the State mental institution where behind us ( where the guy who set me on fire lives pumped full of Haldol) and Behind it maybe 250 yards from our building was a radio station and tower!
this and years on the road are what made Canare Starquad my go to cable for many years, I prefer the sound of Mogami, but if I'm going into the Unknown Starquad and Ferrit Beads all the way because I know RF won't be an issue.
In fact after Full Co moved I moved and all the local TV and Radio moved to a brand new candelabra tower 1/2 a mile from my new apartment! The stereo had to be all balanced and Canare Starquad with ferrit beads. The Engineer for the station that was behind us at work lived in the complex ( he married my receptionist after I set them up) was amazed that I could play a CD without hearing any of the local stations!
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Post by keymod on Oct 29, 2016 16:30:19 GMT -6
I used to own a Hammond M3 and it always picked up a French Canadian radio station from ten o'clock in the evening on. Funny, never any earlier.
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Post by Martin John Butler on Oct 29, 2016 19:22:36 GMT -6
I had this issue with my THD amp. Sold it.
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Post by Deleted on Oct 29, 2016 19:49:59 GMT -6
+1 for clamp on ferrite beads
The clamp on ferrite beads are really cheap. We bought a box full of them in different sizes from an electronics surplus shop. Really good investment. Exactly for such situations.
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