Author Topic: RF Interference (Read 347 times)

ajdover · « **on:** August 05, 2009, 04:52:54 PM »

I just purchased a '95 Epic off of eBay. It's in very good shape, a few dings here and there, but nothing major. Got it a few days ago, oiled the fingerboard, cleaned it up, polished the brass, put new strings on, made some truss rod adjustments. So far so good.

Today I noticed that when I have the pan pot turned all the way forward (neck pickup only) or all the way backwards (bridge pickup only) I pick up (no pun intended) a radio station (Q98 here in Fayetteville, NC). If I back it off a little bit, it goes away/gets quieter.

Puzzled, I took it to my guitar tech. We plugged it in at his shop, did the same thing with the pan pot, and low and behold, no RF interference. He suggested I take it to another location to see if maybe it was a location thing, so I did. Did the same drill, no RF interference.

Took it home, tried new cables, switching the ground on my F1-X, etc. No difference. At home, I pick up the radio. I don't have this problem with any other bass I own (I own 26) to include my '06 SC Sig Standard, my '04 Dragon's Wing, or my '91 Essence.

Before I did any of this I called Tony at Alembic. He told me to look at the connectors going to the pan pot, to see if any were frayed. They're not. He also suggested checking to see if the circuit boards are touching the shielding paint. They're not. Finally, he told me to check the jack for problems. As far as I can tell, it's OK. Tony, God bless 'im, told me I could always send the harness back to be rewired. Don't want to do that if I don't have to, but it's there if I need it (man, Alembic is a great company!).

Has anyone else had this problem? I don't want to take out the electronics if I don't have to and create only more work for Tony. If anyone has anything else I can try I'd appreciate it.

Thanks in advance,

Alan

dannobasso · « **Reply #1 on:** August 05, 2009, 05:53:31 PM »

Alan maybe da gubment is listenin' in!

ajdover · « **Reply #2 on:** August 05, 2009, 06:45:36 PM »

God help me if they are! ;-)

bob · « **Reply #3 on:** August 06, 2009, 01:04:05 AM »

I had a strange radio problem, though I thought it was with my SF-2 rather than a bass, and since yours seems related to control settings, it probably isn't relevant, but anyway...

Whenever I played through the SF-2, I picked up some AM sports station (I figured out the frequency, but forget). If I played the same instrument through a different amp, no problem. Since I use the SF-2 as my preamp, it was difficult to truly isolate it, but as I recall I figured out how to use the preamp-out from another amp and narrow it down.

I was stumped for ages, discussed it with Alembic, and so forth. Eventually, I accidentally discovered that the problem only occurred when the wall-wart (power supply) from my headphone amp was plugged in. Could have even been on a different circuit, didn't need to be otherwise patched into the system - as long as that little box was in the wall, my SF-2 was going to put out baseball scores, or whatever.

I sort of think the SF-2 was jointly responsible, or at least overly sensitive, but I've never had the problem with anything but that one particular wall-wart.

Probably won't help, but might be worth thinking about.

mario_farufyno · « **Reply #4 on:** August 06, 2009, 06:19:50 AM »

I had this exact problem with my Rogue here in Brazil. I was completely frustrated because Alembic's PUs are shielded and shouldn't have this problem at all. Everything seemed right at harness, but - you know - when you live in a country that doesn't take a real attitude against illegal gospel radios, you can't expect much. But sending the harness to mother ship was tottaly off my reallity, either. Brazilian laws would made me pay (high) taxes just to send it and get it back. It could cost me something as 200% over its declared value!

So I was left by my own (only solution seemed to be moving away).

I first tried to avoid this problem instaling one ferrite bead per PU, but I don't think it did much about it (Rogue got just one for both PUs). Anyway, you should check it to verify if you have one and if PU's cables are properly wraped around it. I also cleaned the conections. I know you've tried this before, but I finally solved most of my RF issues just when changed all cables in the chain (all cables at pedalboard and the conection to the cabinet, too). I confess still having some problematic places where I prefer not to use it, though. But now they are fewer and signal/noise ratio improved a lot (isn't a thing you could notice when entire band is playing).

I don't know how bad your problem is, but since cables change it doesn't bothers me anymore. Have to say I've also changed the way I adjust the Bass, though (never full pan the PUs and don't use the filter wide open, anymore). I know this looks somekind of limiting, but still got all tones I need from it. So, it is working fine now.

Hope this brings you ideas...

mario_farufyno · « **Reply #5 on:** August 06, 2009, 07:14:18 AM »

sorry, doubled post

(Message edited by Mario Farufyno on August 06, 2009)

mario_farufyno · « **Reply #6 on:** August 06, 2009, 07:26:20 AM »

I forgot that also reduced gain at trim pots a bit...

Check these old threads:
http://club.alembic.com/Images/393/17271.html?1111351599

http://club.alembic.com/Images/393/23914.html?1136555070#post52108

http://club.alembic.com/Images/394/25558.html?1141081839#post56057

It seems the beads should be the answer...

(Message edited by Mario Farufyno on August 06, 2009)

jack · « **Reply #7 on:** August 06, 2009, 07:57:15 AM »

I've never had a problem on my 95 Epic, I'm no help at all, but you have my sympathy- just going by the website, that seems like a real nightmare: http://www.q98fm.com/

ajdover · « **Reply #8 on:** August 12, 2009, 07:04:32 PM »

I've taken my Epic to a couple of other locations, and there is no problem at all with RF interference. So now I'm a bit confused - is it my location, the preamp, or what? As I said, I can always send it back, but nothing I'm doing is working (I've tried different cables, too). Any suggestions?

Alan

David Houck · « **Reply #9 on:** August 12, 2009, 07:15:00 PM »

Alan; I may be way off base here as I can't remember what control cavities look like for the different models, but is it possible to switch pan pots with another one of your Alembics?

ajdover · « **Reply #10 on:** August 12, 2009, 07:22:02 PM »

Dave,

I have no idea. I'd have to defer to Tony Stouffer on this one.

Al

keith_h · « **Reply #11 on:** August 13, 2009, 04:56:23 AM »

Al,
As I said in a note I had the same situation when I first received my Orion. I would pick up a station in Fuquay-Varina but only when I faced that direction and only when I was upstairs in my bonus room. If I'd move downstairs or was at someone elses house it went away. While I am not close to the transmitter all I can figure is the direction of the hills and valleys concentrate the signal and my bonus room happens to be in the beams path. Once I received a new preamp from Alembic I no longer had the problem.

Keith

mario_farufyno · « **Reply #12 on:** August 13, 2009, 08:35:03 AM »

RF interference always has to do with your placement. As said Keith, you can control it by changing your position in the room. In some degree, at least.

The question is to learn where the RF is finding its way into your signal path. People at Alembic claims their PUs are shielded by their own faraday cage. Alongside the use of the ferrite bead we shouldn't expect it could pick up any eletromagnetic noise. So, if its PUs and Harness are properly shielded we couldn't solely blame the Bass for it. But this also only happend to me with the Rogue, so if it is not the source, it certainly make things worst.

I believe this got more to do with capacitance issues on Cable, Pedals or Amp that turns them into a big antena when connected to Alembic Eltronics (or indutance, I'm not eletronic expertise). Remember that a Capacitor (or Condenser, if in a Mic) can charge one plate just being near it. So you don't really need to have the circuit touching something, just near enough. It seems it can happen even if the wiring inside a cable isn't uniform (if too stepped or bended during use) or if the plug conectors are hurted.

After doing the Bead thing I've tried it at a problematic spot I knew. It was then I noticed the problem was still there (although considerably lower in volume). I took everything off my signal chain (Effects, Eqs and PreAmp), just Bass+Cable+Amp, but it persisted.* That Cable was fairly new and looked okay, but I couldn't say if it wasn't stepped in the stage some other night.

Then I took the Bass off and noticed the RF still was interfering. It was almost nothing, but you could hear it at background (and it changed its character if I bent the Cable). So, the Bass seemed to be just amplifying something that was already there due to the Cable. That night I've had to play standing still in a position where it wasn't too anoying and also took the pedalboard off, since all that conections seemed to get things worst.

My suggestion is pass both PU cables trough the Bead with one turn if possible - thats why I got a second bead, it was difficult to pass both cables twice around it - and test your Bass again with just one (good) Cable and a Combo (skip the F1 or any rig with lots of conections).

mario_farufyno · « **Reply #13 on:** August 14, 2009, 04:59:38 PM »

I forgot one thing: You must always be aware to not let Cable rolled up, this turns it into a coil. You can control these RF interference at some point changing the direction it is laying.

slawie · « **Reply #14 on:** August 15, 2009, 09:03:10 PM »

The human body is a wonderful thing. Try this.

Do it again while holding the strings with your left hand.

Slowly turn around with your right hand in the air.

If the signal gets louder in any particular direction. Viola you are an antenna!

It might not get rid of the problem but it does cause some slight amusement to those who walk in on the scene.

Check your grounding.

slawie