Added Cloudlifter - Now picking up radio frequency?

Basilosauridae

Basilosauridae

Member
Hi friends :)

I bought a cloudlifter to use with my EV RE20 and focusrite 3rd gen solo and now I'm hearing what seem to be very faint radio signals. Some basic googling says this might be an issue with my XLR cables? I currently use this kind of cable (Tourtek Pro TPM), do you think that is the issue? and if so what should I get?

Thanks!
 
It’s not the type of cable, it’s a fault in how one is made. RF interference is a pretty nasty subject, and you need some specialist knowledge to work it out, but you need to determine what type of radio you are hearing as this sets the cure. If you live in an area that has an active AM radio station locally, then this can be demodulated by the components in many studio kit, but a preamp, taking tiny signals and processing them is a likely culprit. However, as a cloudlifter is a phantom powered device, if the ground was missing, it wouldn’t work. It is possible the cable is miswired and the shield is not connected to pin 1. Oddly as long as the wiring is 1 to 1, 2 to 2 and 3 to 3, it will work, but be lacking shielding. Obvious things to check are substituting cables. See if this makes the interference go away. If you do not have an AM station nearby, the source of the interference is less easy to determine. Can you identify the station. If it is not a local one, then it could be much harder. I had one once where I could hear a BBC local radio station through a PA system, but this ‘local’ station was from another part of the country. It was tracked down to a loop system in a bar next door, that was fed from a long forgotten about computer fed from the net. Somebody had cut through the cable and this was spreading via the mains wiring.

start with removing and swapping cables methodicall, one by one and report back.
 
rob aylestone said:
It’s not the type of cable, it’s a fault in how one is made. RF interference is a pretty nasty subject, and you need some specialist knowledge to work it out, but you need to determine what type of radio you are hearing as this sets the cure. If you live in an area that has an active AM radio station locally, then this can be demodulated by the components in many studio kit, but a preamp, taking tiny signals and processing them is a likely culprit. However, as a cloudlifter is a phantom powered device, if the ground was missing, it wouldn’t work. It is possible the cable is miswired and the shield is not connected to pin 1. Oddly as long as the wiring is 1 to 1, 2 to 2 and 3 to 3, it will work, but be lacking shielding. Obvious things to check are substituting cables. See if this makes the interference go away. If you do not have an AM station nearby, the source of the interference is less easy to determine. Can you identify the station. If it is not a local one, then it could be much harder. I had one once where I could hear a BBC local radio station through a PA system, but this ‘local’ station was from another part of the country. It was tracked down to a loop system in a bar next door, that was fed from a long forgotten about computer fed from the net. Somebody had cut through the cable and this was spreading via the mains wiring.

start with removing and swapping cables methodicall, one by one and report back.
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I very much appreciate your thoughtful response, though 98% of it went over my head. 🙃 So you are saying the cable type should be fine, but one might be faulty/broken? I live in the San Diego area, I'm not sure how close you mean by "nearby" but a quick google search is showing that there are prob at least a dozen AM radio stations within the 2-20 mile range.

Ok... so if I swap out the XLR cables and still have the issue, what would the next step be?

Thanks again!
 
A powerful AM station within 2 miles is a likely problem. But start with substitution. Short cables are better than long, braided screens better than lapped, and making certain you ground really is grounded with a meter is useful. If it’s still a problem you then start to enter the magical territory. The interference on an AM station is caused by a component, usually a junction in a solid state device, operating as a demodulator. Think back to WW2 where enthusiasts built their own radios. AM reception was quite simple. Once you track down where and how it enters your system, you can try adding filters. A simpler solution is to look for a local ham radio club. They usually have some older guys who are skilled at this sort of problem and might be able to help.
 
rob aylestone said:
A powerful AM station within 2 miles is a likely problem. But start with substitution. Short cables are better than long, braided screens better than lapped, and making certain you ground really is grounded with a meter is useful. If it’s still a problem you then start to enter the magical territory. The interference on an AM station is caused by a component, usually a junction in a solid state device, operating as a demodulator. Think back to WW2 where enthusiasts built their own radios. AM reception was quite simple. Once you track down where and how it enters your system, you can try adding filters. A simpler solution is to look for a local ham radio club. They usually have some older guys who are skilled at this sort of problem and might be able to help.
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Hmm what do you mean about the ground being grounded? I don't really know anything about electrical stuff but a few months ago I had an issue where turning off a light was causing interference in my cables and I think someone mentioned something similar.
 
Living between Rugby and Daventry (both had powerful AM transmitters) here in UK I was kept very busy 'proofing' all sorts of gear against RF. However they were internal mods and must be made by the maker or a good tech.

First thing to establish is if the Cloudlifter is the actual culprit. Max out the gain on the Solo with the mic wrapped in a duvet. Then boost the signal digitally and see if you can hear radio. If not then get onto the CL's retailer and ask for help. Likely they can do FA but it is usually the first step to getting kit repaired.

So, cables: Better than both lapped and braided screens is a foil screen. Not as flexible as the others but I doubt you want to twirl about like Jagger? You can get two core, foil screened mic cable with an OD of about 3mm. This can then have several turns looped through a ferite ring but you will need to solder new XLR on each end.

It might be worth checking that the Cloudlifter's body IS indeed connected to cable screen! Also that the whole system is grounded. mic cable,Solo, laptop di da although from an RF point of view their lumped capacitance to the earth means they probably are anyway.

Now! If anything Rob or I have said is baffling you...BLOODY ASK! I am here all day and can walk you through any technicalities.

Dave.
 
Mexico used to be known for its high power AM stations that didn't necessarily follow the normal US rules. I don't know if that's still the case, but San Diego is pretty close to the border.
 
bouldersoundguy said:
Mexico used to be known for its high power AM stations that didn't necessarily follow the normal US rules. I don't know if that's still the case, but San Diego is pretty close to the border.
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I suspected that as well. UK used to have an excellent Radio Interference Investigation Dept, branch of the state owned GPO and the whole system, together with the BBC was the envy of the world for its technical ability and efficiency. Sadly the system has been privatized and fragmented and now help is next to non-existent.
I would expect San Diego to be even more "Wild West" than we are now!

Dave.
 
It's a little bit like those topics where people can 'hear' their computer monitor or mouse as a feint background buzzy sound. It gets in at one place, travels along the screens of the cables and cause havoc somewhere totally different - you need to kill it at the point it gets in.

Grounding - (or earthing as us Brits term it)

The bit about picking up clicks from light switches also points that way.

In the US and other coutries where not every outlet has three pins, grounding can be quite odd. The basic idea is that grounding is all about safety, not hum and interference reduction, but grounding helps that so many times. The basic concept is that AC current needs to flow. It looks for ways to do that, and most modern systems of power in houses and businesses relies on spotting unusual current flow to keep you alive, so something, maybe due to a fault or damage is live. Often it carries on working fine until you touch it - then it takes a short cut, through you to the real ground outside. This can be via water pipes, radiators, exposed metalwork, or even a wet floor. If you are wearing footwear that insulates you from the current flow, you will live, but even a small amount of leakage, if the current flow goes across your heart will kill you. We measure current in Amps, or even milliamps (thousandths of an Amp) and the old electricians rule hold good - Volts Jolts, but Mils Kills. Milliamps is enough to do the damage. Your house probably has a gizmo that detects current leaking to ground, and it kills the power. If your equipment is connected to the power source with a 2 pin connector - there is no ground connection. In modern installs, it's likely that at the point where electricity comes into the building the neutral conductor will be connected to the local ground - perhaps even a copper stake banged into the real ground. A good electrical ground is needed for safety, but also provides a framework for making sure all the screening in your studio is connected together and to the ground outside.

For your interference problem, the AM signal (FM stations work differently and rarely interfere in a way you can hear music) needs to get to the device you have that is poorly designed or faulty, and is generating the audio you can hear. It's likely that your ground is not as solid as it should be, and that is supported by the lightswitch problem - the click from the tiny arc in the switch is getting into the system.

Dave mentioned ferrite rings - you'll have seen tiny ones in the DC cable of wall-wart type power supplies, a little black lump. The idea is that a piece of ferrite has a few turns of the DC cable wound through it and DC travels through untouched, but the AC - as in the rubbish cheap power supplies produce - struggle to get through the filter. If you have an old disco loudspeaker, you can dismantle the back of the speaker and remove the huge ring of magnetic ferrite. Wrap an audio cable through it half a dozen times and gaffer tape it, and you have a home made block to AC (as in the interfering radio station). What tends to happen is that the cabling you have is acting like an antenna, collecting the RF energy, and the screens on the cables are distributing it to everything connected - which is where you need to find the culprit. It probably is the Cloudlifter, but not necessarily so - Disconnecting it and plugging the two XLRs together is a pretty good indication.

It does not mean it is faulty, its just the unlocked door, letting interference in.

If you have a test meter with a continuity setting - where touching the probes together beeps - you can go around your system and check that every ground actually is a ground - but remember some things are NOT meant to be grounded. Double insulated equipment should not have their metalwork grounded, but sometimes us audio folk do this to cure hums, but this can even open the door to more interference. Adding grounds to test if the interference get less can be a good move, but don't remove any - they are there to save your life.
 
Shure has an article on radio interference with some troubleshooting details.

RADIO INTERFERENCE ON A MICROPHONE CABLE

I'll add that for short run cables, I like to use Star Quad cable as it helps reject noise in addition to some of the ideas in the article. Lots of arguments about using Star Quad cables in the studio due to higher self capacitance but when you do the math the high end loss is well out of human hearing range. Markertek sells them premade using Canare cable. Very high quality. Still you'll have to figure out if its the cable or device first.
 
I used to use Canford Audio's starquad for stage stuff, where the dimmers used to kick out all sorts of crud - but I've not needed them for quite a while now. I never found any audible difference with them at all - as you say, well above my top end. I didn't know Shure still sold those - handy to remember!
 
rob aylestone said:
I used to use Canford Audio's starquad for stage stuff, where the dimmers used to kick out all sorts of crud - but I've not needed them for quite a while now. I never found any audible difference with them at all - as you say, well above my top end. I didn't know Shure still sold those - handy to remember!
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When ever I get into an argument about this on some of the studio building forums, I simply suggest they calculate the XC using the self-capacitance spec of the cable over any length they wish to use. Even then, I still get the, "well, cat cable has lower self-capacitance and it is all cumulative". I try not to argue anymore but it is simple math.
 
Rob, I have never heard of anyone using the ferrite magnet off a speaker for an RFI stopper. I might be wrong but I think the ferrites used as RF 'absorbers' are a different grade to that used for magnets? I think the RFI rings are designed to be 'lossy'. In any case, putting a coil in the cable in any way will help as it makes the shield more inductive and puts an impedance in the way of the RF. If OP does get some ferrites it often matters which end of the cable they go...Can't advise because RFI troubles are always 'cut and try' and usually counter-intuitive! What works one time, one place don't in another.

It is a shame the chap is so far away otherwise I would be happy to make him a selection of RF stop cables and filters. Not that external measures work most of the time. I would hope the Cloudlifter has been properly tested for RF susceptibility because if not the only way to stop it is to fit the internal filters they should have fitted in production.

Just a thought. Baz, check that all the shells of your XLRs are connected to pin One. This is not usually a problem but might be in this case.

Dave.
Folkcafe said:
When ever I get into an argument about this on some of the studio building forums, I simply suggest they calculate the XC using the self-capacitance spec of the cable over any length they wish to use. Even then, I still get the, "well, cat cable has lower self-capacitance and it is all cumulative". I try not to argue anymore but it is simple math.
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Well if we are getting into math? Star Quad cable will help with RF problems but not by the mechanism it uses to reject audio interference. That depends upon the fact that it more efficiently 'picks up' the common mode noise and delivers it to the balanced input amplifier. However, said amplifier will have long since run out of gain at RF and no gain means no CMRR capability.
It is the higher capacitance per mtr that shunts away RF a bit better but you could get the same effect by tacking 500puff or so across pins 2 and 3 of the XLR (pre amp end) I also agree, in normal studio distances and with suitably low Zout sources, the extra capacitance of SQ is going to matter diddley.

I repeat "Does the mic/Solo combination on its own product the interference, however slightly?" If so the CL is probably not to blame but if it can be PROVED to be the culprit, 'ave ago at 'em! No modern electronic audio equipment should be open to RFI these days. OK there will be rare cases where there is a very high field strength but if it is the ONLY thing affected that is not the case here.
An example of a very high RF field is the humble smart phone. Left on top of almost any audio kit it will blitter-blatter. and chirrup.

Dave.
 
I usually smile when people start this kind of stuff on forums - on the lines of you must not do this or must do that. My early years were with some really great, real engineers at the BBC, and they actually had their specific cables made to their own design - who on earth would want 7 pair multis! Handy to be able to re-use their existing connectors, and the early camera cables were often repurposed as audio cables. The people who do the doom and gloom stuff really should get out more, because on 100m of Starquad all that extra capacitance is still quite small, and is what? I small tweak of EQ to restore 'flatness'. They turn facts into scare mongering.

Dave - none of my shells are connected to pin 1. Caused more issues than ever solved them, and it does make for some issues with Class II devices where you don;t want the chassis to be connected to audio ground. The speaker derived stopper works pretty well - and great for unshielded RF isolation with things like telephone cable and close RF sources. The disadvantage is the damn magnetism - An old friend would insist on wrapping them with layer on layer of gaffer tape to make a grapefruit sized ball, so they'd not stick to everything solidly! I was introduced to the speaker magnet bodge by the man from the DTI when he called to fix interference from a short term radio licence station. He used the magnetism to stick it to a metal filing cabinet.
 
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There is certainly enough iron oxide in a ceramic magnet to work as a choke filter, albeit with a bit less effectiveness. As to my statement about math, I am talking only about capacitive reactance.

Odd how some are so concerned about losses at 25-30k. It is like I'm suggesting they create modal intermodulation disturbances in the universe or something. All fealty must be adhered to fidelity, so those listening with $5 ear buds won't be subject to my crimes against audio.

We are already discussing matters above the OP's comfort level. I chose instead to offer an easier option and added enough commentary to satisfy the tech discussion here. Hopefully I satisfied both audiences.
 
bouldersoundguy said:
Mexico used to be known for its high power AM stations that didn't necessarily follow the normal US rules. I don't know if that's still the case, but San Diego is pretty close to the border.
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We get a strong signal from XTRA in Mexico up here in Los Angeles, 120 miles north of San Diego.
 
Folkcafe said:
There is certainly enough iron oxide in a ceramic magnet to work as a choke filter, albeit with a bit less effectiveness. As to my statement about math, I am talking only about capacitive reactance.

Odd how some are so concerned about losses at 25-30k. It is like I'm suggesting they create modal intermodulation disturbances in the universe or something. All fealty must be adhered to fidelity, so those listening with $5 ear buds won't be subject to my crimes against audio.

We are already discussing matters above the OP's comfort level. I chose instead to offer an easier option and added enough commentary to satisfy the tech discussion here. Hopefully I satisfied both audiences.
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Yes, the thread has become technical (M.C. mostly!) and I apologize to the OP for that a bit, BUT! RFI issues demand technical solutions very often and it is usually the case that external measures have little effect and obviously diving in and modifying circuitry is a job for an expert.

But, we must try external ideas first. Short as possible foil cables. Ferrite absorbers. That inline XLR filter looks interesting (built a few same in my time!) but at 60 bucks ppaid a bit expensive if it does not work. Ask if is can be returned!

And, as I said, I am ALWAYS prepared to break down and try to explain anything over peeps heads. Sound recording IS a technical exercise (MUCH worse 50 years ago!) and so as problems crop up, and they will, best IMHO to try to build knowledge as you go?

Dave.
 
ecc83 said:
That inline XLR filter looks interesting (built a few same in my time!) but at 60 bucks ppaid a bit expensive if it does not work. Ask if is can be returned!
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Which is why I posted the Amzon image and price. While probably not the cheapest price, pretty easy to do a return.
 
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