FantomPwr Posted March 12 Report Posted March 12 Hi Everyone - I'm a new member here, and I'm hoping that one of you can help me solve a problem I'm experiencing with my first boompole. I do volunteer audio capture work for a local acting group in Ashland, MA that has recently begun creating short films. Here is what I'm currently using for gear: a Zoom F8N Field Recorder, a pair of Sennheiser MKE 600 shotgun mics with Auray DUSM-1 shockmounts, an Auray BP-59A 9.5-ft boompole with internal coiled cable and side-exit XLR-M, Bose QC-25 noise-cancelling headphones, and several Kopul Series 5000 mic cables of various lengths. Here's the problem. When I have one of the mics atop the boompole (internal cable plugged in), a good mic cable connecting the boompole's side-exit XLR to a mic input of the recorder, and the recorder powered by its AC adapter, I get a nasty 120-hz hum about 30db below the dialog I'm trying to capture. Other info: (1) If I touch the boompole, the hum increases; if I also touch the recorder, the hum decreases. (2) If I unplug the AC adapter (i.e., run on the AA cells), the hum disappears. Nice workaround, but the best lithium AA cells won't get me thru an 8-hour shoot. (3) If I reconnect the adapter and bypass the boompole's internal cable, the hum disappears. (4) I ordered and replaced the internal cable, but that had NO effect on the problem. (5) Using the phantom power of the recorder or the AA cell inside the mic also has no effect. So, I realize that Auray isn't considered a premium brand, but I am disappointed to discover that these coiled cables aren't properly shielded. Are K-Tek's coiled cables likely to have this problem too? Might the problem be solved if I just jumper pin 1 of the XLR to the body of the boompole? Quote
Derek H Posted March 12 Report Posted March 12 I would try a different AC adapter first. I think that's most likely the problem is you have a cheap and noisy one. Unless you can solder trying to troubleshoot the cabling will be challenging. The only thing with the XLR (including inside the pole) cable you could check is if pin1 and the shell of the XLR are connected. Sometimes having it connected or not connected can make a difference for certain combinations of gear. Another option.. get a big rechargeable battery to run the Zoom so you can avoid the AC adapter entirely. Professional sound mixers would choose rechargeable NP1 type batteries or Smart batteries like from Inspired Energy but you could probably come up with something cheaper from Anker or another quality battery brand. Like a big power block that has USB and 12V outputs. Just make sure it has a connector with the correct voltage for your Zoom. The pitfall there is some of those things are designed for phones and other smart tech and might put itself to "sleep" in certain scenarios. Quote
Rick Reineke Posted March 12 Report Posted March 12 You can check if the AC power supply is the problem by temporarily running the F8n on it's internal AA back-up batteries. Does the inference occur in all locations? Quote
Paul F Posted March 12 Report Posted March 12 " If I touch the boompole, the hum increases;" That suggests that the shield on the cable is not properly terminated or non-existent. 120Hz - that will be the bridge rectifier in the AC adapter. Nothing you can do about that. Going with batteries may solve the problem today, but there is an underlying problem that may turn up again since this suggests that the setup is vulnerable to interference of another kind. I suggest an inspection of the cable and it's terminations. Does the cable have a shield? I think you should consider a battery solution regardless as you plan to do short films. So AC power does not seem practical in that case. Many of us with F8s use Sony NPF batteries and a battery plate. Quote
OB1 Posted March 12 Report Posted March 12 I agree on the AC versus battery. Try both and see if the noise is still there. If not, I'm betting it's the cable for sure. 120hz is generally in the bridge area but other anomalies can also cause noise in this range. Quote
Tim Norris Posted March 12 Report Posted March 12 12 hours ago, FantomPwr said: Are K-Tek's coiled cables likely to have this problem too? Not all boom poles are created equal. I recall experiencing intermittent electrical interference with my first internal coiled cable Vdb pole, and always at one particular spot on The Magnificent Mile in Chicago, above an electrical vault. In January 2000, covering the Iowa Caucus, I bought my first internal coiled cable K-Tek pole to replace the Vdb pole, mostly because it was much longer and candidate Bush didn't like to get close to the press. I first noticed a reduction in all handling noise as well as a reduction in wind noise, which I had attributed to the wind protection on my Schoeps mic. You will likely be pleased with a top of the line K-tek pole. Cheers, Tim Quote
Patrick Farrell Posted March 12 Report Posted March 12 The fact that you can bypass the boom cable with an external XLR and the noise goes away is pretty telling. I'd get a multimeter and check the wiring of the internal cable, all pins in relation to the others as well as to the XLR shell. Then compare that to the wiring of your known good working cable and you should have your answer. (Definitely wouldn't advise jumping pin 1 to the boom pole as you suggest. The pole and consequently your hands should stay isolated from the audio path.) Quote
The Documentary Sound Guy Posted March 13 Report Posted March 13 Only thing that hasn't been mentioned is you could try plugging the AC adapter into a ground lift and wear rubber soled shoes while you are booming. But a better boom cable and better battery system is what you really need. The F8N should accept up to 15V in via the hirose plug, so power it via a proper external battery pack. Ditch that AC connection ASAP, it's a hazard in more ways than one. Quote
FantomPwr Posted March 19 Author Report Posted March 19 Well, after a couple of weeks, I'd like to thank all of the people who responded to my query. Here's what I've gleaned from your many suggestions. (1) I shouldn't depend at all on the AC adapter that came with my F8n (part # AD-19). In my view, any AC adapter that doesn't have a 3-prong AC plug sticking out of it, with the ground lug connected to a metal case that shields the entire adapter, shouldn't be used on a filming set at all. Consider mine "ditched". On 3/12/2025 at 12:35 PM, Paul F said: Going with batteries may solve the problem today, but there is an underlying problem that may turn up again since this suggests that the setup is vulnerable to interference of another kind. I suggest an inspection of the cable and it's terminations. Does the cable have a shield? (2) Evidently, Auray is shipping their cabled boompoles with coiled cables that are not properly shielded. At least, that's what I was told by a CSR at Gradus Group recently. (Gradus Group is the parent company of Auray Audio). I didn't mention in my first post, but I tested the internal cable with a CT-100 cable-tester. It revealed no continuity issues (Pin 1 in --> Pin 1 out, Pin 2 in -- Pin 2 out, etc). But that test doesn't reveal if pin 1 is actually the shield for the other two wires, as it should be. Comments? On 3/12/2025 at 11:22 AM, Derek H said: Professional sound mixers would choose rechargeable NP1 type batteries or Smart batteries like from Inspired Energy but you could probably come up with something cheaper from Anker or another quality battery brand. Like a big power block that has USB and 12V outputs. (3) I'm ready to purchase a decent pair of battery packs, a compatible charger for them, and the battery adapter that allows it to power the recorder (via the Hirose 4-pin female socket). B&H sent me two quotes, one for a Deity solution ($765) and another from a lesser brand for about $600. My recorder only cost me $900 plus tax. Can anyone give me specific brands & model no's that come in a bit less pricey? Also, the recorder accepts input values of 9 thru 18 volts. Would I be smart to shoot for 15V batteries, so that I could get longer runtimes out of them? If some of these questions I'm asking are too off-topic, I'd be happy to start a new thread.... Quote
Paul F Posted March 19 Report Posted March 19 23 minutes ago, FantomPwr said: It revealed no continuity issues (Pin 1 in --> Pin 1 out, Pin 2 in -- Pin 2 out, etc). But that test doesn't reveal if pin 1 is actually the shield for the other two wires, as it should be. Comments? Open up the connector and see if there is a shield. Quote
Derek H Posted March 19 Report Posted March 19 Yeah you won’t hurt an XLR cable by unscrewing the boot and taking a look inside the connector to see how it was wired and what the shielding situation is. Just be gentle with the wires while you have it open and put it back together carefully. I’d recommend 2x IDX brand NP1 type batteries with JL-2+ charger. They’re very high quality and won’t let you down. You could get a cup (battery adapter cable) that terminates in a Hirose pin and plug it straight into your Zoom. There’s no need for a DC distro like the diety if all you want to do is power the recorder. There’s also a brand called cable techniques that makes rugged, simple and affordable DC distro boxes that use all Hirose ports for power in and out of you wanted to add that capability down the road. Quote
The Documentary Sound Guy Posted March 19 Report Posted March 19 1 hour ago, FantomPwr said: (3) I'm ready to purchase a decent pair of battery packs, a compatible charger for them, and the battery adapter that allows it to power the recorder (via the Hirose 4-pin female socket). B&H sent me two quotes, one for a Deity solution ($765) and another from a lesser brand for about $600. My recorder only cost me $900 plus tax. Can anyone give me specific brands & model no's that come in a bit less pricey? Also, the recorder accepts input values of 9 thru 18 volts. Would I be smart to shoot for 15V batteries, so that I could get longer runtimes out of them? You could try operating off camera batteries (eg Sony L-Series) with an appropriate hirose cable adapter. These are cheaper (both charger and batteries), but lower capacity. Capacity isn't a function of voltage; there's no advantage to using a greater or lesser voltage ... just pick a battery that supplies the voltage you need (and be aware that the point at which the battery can be considered "dead" will be higher with a higher nominal voltage). Capacity is measured as (m)Ah or sometimes (m)Wh. I'm guessing the quote you got were for so-called HiQ batteries ... in which case a single battery costs ~$300 or so, but should last more than a day powering just your F8n. You could buy one less battery if you are concerned about saving money. You should really figure out your power draw and size your battery purchase on that basis. I doubt you'll find a system that is significantly cheaper on a per-capacity basis. In general, you get what you pay for with batteries. Quote
FantomPwr Posted March 30 Author Report Posted March 30 On 3/19/2025 at 3:17 PM, Paul F said: Open up the connector and see if there is a shield. So, I did exactly that to the XLR-F connector at the pole top. It revealed the 3 wires, and the neatest shrink-wrapping job I've ever seen. So tidy in fact that I was not able to see any of the solder-points, the wire colors, or whether or not there was a shield. I didn't want to start stripping back the cable's insulation, so I reassembled the connector. Yes, I chickened out. You can all laugh now.... Quote
Paul F Posted March 30 Report Posted March 30 Chicken out? No, you were smart to leave a good job alone. A nice job like that tends to indicate they know what they are doing and did it properly. Quote
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