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Author Topic: Trade offs of using active cables?  (Read 1518 times)

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Offline checht

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Trade offs of using active cables?
« on: April 03, 2018, 07:12:20 PM »
I'm saving to get a set of active cables with PFA's for use with Schoeps mk4's and wonder if anyone has info on what, if any, downsides there are to going this route?

I imagine there might be more susceptibility to rf and other interference, as I think the actives are unbalanced.

Would this be more or less of an issue when recording loud rock shows?

Anything else to consider when deciding whether to use actives or not?

Many thanks,
Chris
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Offline bobby bourbon

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Re: Trade offs of using active cables?
« Reply #1 on: April 04, 2018, 02:18:19 AM »
When I got mine, Jerry Bruck told me (and I talked to that man for more hours than I care to admit and he would care to remember) the only problem I may encounter was if they were placed too close to lighting. This was right when the balanced CCM was made available. He said if I was going to record in close proximity to lighting, I *may* experience problems with noise He didnt suggest in any way I should count on it. I guess now there are more radio waves than there were. If you think that may be a problem, you can put a join in your cable. That can help in carrying too. The majority of times Ive used the schoeps was with a length of roughly 6'.  I clip the remaining 10' on only when necessary. If the cable is put together with no compromise in quality at the join it should not make a difference and will add good benefit. This pictures nice.  I was looking for something from the white house and found this. This was the last bug found. Cant see it in preview but hopefully it shows up.

Offline goodcooker

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Re: Trade offs of using active cables?
« Reply #2 on: April 04, 2018, 08:10:20 AM »

I've never had any problems with interference when using active cables for Schoeps, Neumann or AKG.

Only problem I had was dealing with the cables themselves - they like to kink up and I like to keep the capsules attached - so every so often I take the capsules off and unwind and rewrap them to straighten them out.

Not long ago I was recording stage lip and a musician moved one of the monitors on top of  my cables running along the edge of the stage. It cut right through it. Most active cables - especially the nBob cables I use for Schoeps are far more delicate than most cables. The remote cables I have for the MBHOs are much more robust and they are techflexed.

Always remember to run your cables perpendicular to lighting and power cables - meaning if you have to get any where near them to cross them at 90 degree angles - never run your cables parallel to lighting or power runs!
Schoeps MK41 > nBob > PFA || MBHO KA300 > PFA
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Offline DSatz

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Re: Trade offs of using active cables?
« Reply #3 on: April 05, 2018, 08:30:24 AM »
The original Schoeps active cables were designed to be supple. Maybe 20 years ago Schoeps changed over to Kevlar-reinforced insulation, which put a real damper on the cables being cut through accidentally. I cycle through my Schoeps equipment every 15 years or so and send it to the factory for checkout, so over time my older active cables have been updated, and I'm glad about that.

--There definitely are more RF sources in the picture than there were in 1973-74 when the Colette series was introduced. The transmitters (a/k/a cell phones) typically operate at higher frequencies than were common in those days, and use signalling systems that produce "edgier" sounds if those signals are picked up and converted to audio (= "detected"). But the main controlling variable (other than transmitter power, of course) is the proximity of the transmitting device to the point(s) of entry and detection in the circuitry. If someone puts a cell phone or pager directly onto your mike cable while you're recording, even a completely balanced system can be subject to audible interference.

It's a "relative" situation with numerous variables. Jerry's right that CCMs are preferable to the modular Colette series if you know that RFI is likely to be a particular problem. But that has to be weighed against the Colette system's interchangeable capsules and active accessories, which the CCM series doesn't have. To me the modular approach still seems essential for most applications, while the CCMs still feel to me like they're for more certain specific applications (e.g. fixed/installed systems). I'm biased, though, because I bought in (literally!) to the modular system early on, and took advantage of its wide range of options. If Schoeps put the CCM amplifier circuitry into a tiny modular package that allowed interchangeable capsules (even without the extra connection needed for active accessories), I'd buy four of them in a flash.

I live in New York City, have used Schoeps microphones to record perhaps 2,500 live concerts and other events (fairly often with active accessories--I use active cables but also active extension tubes sometimes), have heard RF in my recordings only once ever that I can recall, and that was with microphones of the older CMT series (discontinued in the 1970s/80s). That was before cell phones existed, but in the heyday of "citizen's band" (CB) radio. A taxi driver drove by, presumably with an illegal booster amplifier in the trunk. Those could go up to 1000 Watts, and being illegal, they weren't tested and type-approved by the FCC, nor professionally installed for the most part; "dirty" (spurious out-of-band) signals were common. Still, the interference lasted only a few seconds.

In more recent years I've recorded many opera productions with capsules suspended from the balcony of a downtown church on 10-meter active cables instead of the usual 5. By then nearly everyone in the audience had cell phones, and there was never any problem with RF pickup. But those capsules and cables were 10+ feet above the audience's heads--and as I said, that distance matters greatly. Put a transmitter close enough to almost any circuit and you'll get interference.
« Last Edit: April 18, 2018, 12:13:13 AM by DSatz »
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Offline ArchivalAudio

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Re: Trade offs of using active cables?
« Reply #4 on: April 05, 2018, 11:50:01 AM »
Thanks to DSatz for that explanation.
I'd also go back to note about the lighting cables:  To say that anytime you run a mic cable balanced, shielded or otherwise if it is going to cross, and touch or be in close proximity be sure it crosses at the intersection at 90° this will halp to eliminate the possibility of 60hz (or 60 cycle per second) hum or buzz that can occur when a mic cable crosses a power cable. Though this has nothing to do with RF interference, but introducing hum , buzz or noise.

If you get PFA's get the longer "extended" barrel, which can supply up to 60 v, and also help to eliminate any RF interference because of the shielding in the units.
http://naiant.com/studio-electronics-products/inline-devices/pfa-phantom-power-adaptor/
Quote
The PFA is available in both standard and extended XLR barrel connectors. The extended version fully shields the circuit, with a total length including boot of 100mm. The standard version length including boot is 70mm. The extended version may be preferred in difficult EMI environments. Both barrels will directly connect to any phantom-powered XLR input.

The extended length barrel may also contain a circuit to generate up to +60V polarization voltage required for certain "active" remote capsule microphones. The polarization voltage will be regulated to the voltage specified by the microphone's manufacturer. With this option, the PFA will generate the required voltages for the "active" microphone system with a phantom power supply of at least +16V.
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Offline checht

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Re: Trade offs of using active cables?
« Reply #5 on: April 05, 2018, 12:54:16 PM »
Many thanks all for the great information. Now I'll move forward with no worries, and be sure to cross at 90 degrees.  ;)
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Offline Gordon

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Re: Trade offs of using active cables?
« Reply #6 on: April 07, 2018, 12:36:53 PM »
I've been running neumann actives for 11 years with zero issues.  the last year has been with nick modded lc3's with pfa. 
Neumann ak40 > Nick mod lc3 > Naiant PFA or km140 > Sound Devices MixPre-6

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Offline fanofjam

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Re: Trade offs of using active cables?
« Reply #7 on: April 08, 2018, 08:01:43 AM »
If you get PFA's get the longer "extended" barrel, which can supply up to 60 v, and also help to eliminate any RF interference because of the shielding in the units.

FWIW, this isn't a universally accepted recommendation without considering WHY you'd select this option since the longer barrel PFA are more expensive and draw more power (and of course, have a longer barrel).  As already mentioned above, RF isn't much of a concern, especially if the rest of the equipment in your rig isn't also RF protected, and powering at 60v versus the original PFA voltage (I think something like 40 or 42 volts) results in only a couple of db in mic sensitivity but zero change in frequency response.  I've long maintained that both of these are differences without much distinction, but that's me and I recognize others may not feel the same.  That said, if you're into spending extra money for RF protection and getting 2 more db out of your capsules at a 'cost' of a larger barrel and some amount of power drain, then yes i agree to go with the long barrel version of the PFA.

Offline fanofjam

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Re: Trade offs of using active cables?
« Reply #8 on: April 08, 2018, 08:15:06 AM »
You asked about tradeoffs of using active cables...to me one of the biggest tradeoffs is the decrease in the overall reliability of your rig.  Cables and reliable power have always been the weak points in my rig.  Someone already mentioned that their cable got cut when a monitor sliced it in two. 

With actives when you lose a cable you also lose your mics.  With the full body option, you're usually not dead in the water if a cable goes wonky on you since there are always spare XLR cables to borrow (or carry your own spares).

Online jbell

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Re: Trade offs of using active cables?
« Reply #9 on: April 08, 2018, 09:33:59 AM »
I have run schoeps actives for several years without any issues!!  I also use a KCY PFA with the extended barrel that is 60v and has the low noise option.  The added RF protection, powering the caps to spec, and low noise chip seems like a great idea for an extra $20(that is cheap for this hobby).  The 60v PFA are longer than the standard version, but in comparison to a set of schoeps or Microtech Gefell bodies they are way smaller.  I haven't had any issue with the extra power required.  I can't say that I even consider that a problem or noticeable.  I recently switched to Microtech Gefell M20 caps with actives and had the cables built as KCY so I can use my existing PFA and extension cables.   I like the single cable setup.  As for cables getting cut I have a 2 foot active set and use extensions so if one was cut I always have a backup extension or can use them in combination for a longer cable run.  I also have a 5 foot extension in case I ever need to run stealth.  There really are great options for actives in today's taping world.  Plan wisely and you can be set for most situations
« Last Edit: April 08, 2018, 09:44:05 AM by jbell »
Microtech Gefell M20's> Nbob KCY> Naiant PFA(60V)> Sound Devices Mixpre-6

Offline DSatz

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Re: Trade offs of using active cables?
« Reply #10 on: April 08, 2018, 09:37:53 AM »
fanofjam, I agree strongly with your main point, which really applies to any specialized interface. I hate proprietary connectors of all kinds. For exactly the reasons you say, manufacturers shouldn't make up their own special versions of connectors for standard functions. But Schoeps invented this whole approach, and there was no standard for this type of connector at the time; there still isn't.

Over the years I've probably used Schoeps active accessories for live recording as much as anyone else here, and I don't think I've ever had an operational failure with any of them.*

____________
* The fine print: My active cables are all factory originals, and I maintain my Schoeps gear in part by tracking each serially numbered piece (capsules, amplifiers and active accessories) and sending them each back to the factory for checkout every 10 - 15 years or so. I also store my active accessories with those gray plastic caps on both ends--if you've lost any of yours, you can order replacements from Redding Audio, and I recommend that.
« Last Edit: April 08, 2018, 09:40:25 AM by DSatz »
music > microphones > a recorder of some sort

Offline illconditioned

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Re: Trade offs of using active cables?
« Reply #11 on: April 08, 2018, 02:11:48 PM »
If you get PFA's get the longer "extended" barrel, which can supply up to 60 v, and also help to eliminate any RF interference because of the shielding in the units.

FWIW, this isn't a universally accepted recommendation without considering WHY you'd select this option since the longer barrel PFA are more expensive and draw more power (and of course, have a longer barrel).  As already mentioned above, RF isn't much of a concern, especially if the rest of the equipment in your rig isn't also RF protected, and powering at 60v versus the original PFA voltage (I think something like 40 or 42 volts) results in only a couple of db in mic sensitivity but zero change in frequency response.  I've long maintained that both of these are differences without much distinction, but that's me and I recognize others may not feel the same.  That said, if you're into spending extra money for RF protection and getting 2 more db out of your capsules at a 'cost' of a larger barrel and some amount of power drain, then yes i agree to go with the long barrel version of the PFA.

The "long barrel" version likely has a separate oscillator to generate the polarization voltage.
The regular version drops the P48.
Perhaps that isolated oscillator may help with HF rejection.
Or perhaps it is the added filtering (L,C) at the connectors.

Clearly experiments need to be done, with an RF source and scope.
« Last Edit: April 08, 2018, 02:17:30 PM by illconditioned »
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Offline drewloo

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Re: Trade offs of using active cables?
« Reply #12 on: April 08, 2018, 02:30:47 PM »
Also the 60V version can be ran with a lower phantom power voltage (down to 16V) instead of the standard 48V, so that could save some battery life.
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Online jbell

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Re: Trade offs of using active cables?
« Reply #13 on: April 08, 2018, 04:40:13 PM »
I think the longer barrel covers the entire circuit for RF protection.  The standard XLR leaves part of the circuit exposed. 

If you get PFA's get the longer "extended" barrel, which can supply up to 60 v, and also help to eliminate any RF interference because of the shielding in the units.

FWIW, this isn't a universally accepted recommendation without considering WHY you'd select this option since the longer barrel PFA are more expensive and draw more power (and of course, have a longer barrel).  As already mentioned above, RF isn't much of a concern, especially if the rest of the equipment in your rig isn't also RF protected, and powering at 60v versus the original PFA voltage (I think something like 40 or 42 volts) results in only a couple of db in mic sensitivity but zero change in frequency response.  I've long maintained that both of these are differences without much distinction, but that's me and I recognize others may not feel the same.  That said, if you're into spending extra money for RF protection and getting 2 more db out of your capsules at a 'cost' of a larger barrel and some amount of power drain, then yes i agree to go with the long barrel version of the PFA.

The "long barrel" version likely has a separate oscillator to generate the polarization voltage.
The regular version drops the P48.
Perhaps that isolated oscillator may help with HF rejection.
Or perhaps it is the added filtering (L,C) at the connectors.

Clearly experiments need to be done, with an RF source and scope.
Microtech Gefell M20's> Nbob KCY> Naiant PFA(60V)> Sound Devices Mixpre-6

Offline fanofjam

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Re: Trade offs of using active cables?
« Reply #14 on: April 08, 2018, 08:18:40 PM »
Also the 60V version can be ran with a lower phantom power voltage (down to 16V) instead of the standard 48V, so that could save some battery life.

So can the other one.  I dId it all the time with my psp2 at the 12v setting since batteries last alot longer.  Note that this difference is bc of powering the mics at 12v phantom vs 48v phantom, not bc of the lower power draw of the 48v pfa.
« Last Edit: April 08, 2018, 08:47:14 PM by fanofjam »

 

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