Will a dbx 1046 compressor pass phantom power?
dbx 1046 passing phantom power
- Thread starterAman121
- Start date
yetanotherx
Member
You shouldn't be passing +48V in to your compressor to begin with. How are you wiring the compressor in? If you're doing it between the microphone and the mixer, that's a bad idea. It should (preferably) be wired in as an insert on your mixer console, which would solve your +48V problem.
No inserts on the console. Just wondering if it is possible to run things this way. The compressors in question were originally wired in line with wireless receivers, and that seemed to work fine. Since we had to get rid of all the installed wireless systems with the band shift a few years ago, the compressors have sat unused. I'm just exploring options to put them to use. If this won't work I'll just get a few stand alone phantom power supplies.
No, phantom power can not be "passed" through active devices or transformers. The differential signaling that phantom power takes advantage of stops at the input receiver , and a new signal is generated at the output by the driver chip or transformer.
The only devices I can think of that can pass phantom are mic splitters and then only on a hard passive split.
Hope this helps
Dover
The only devices I can think of that can pass phantom are mic splitters and then only on a hard passive split.
Hope this helps
Dover
An insert configuration is the normal deployment for compressors, using a cable like this:
Pro Co IPBQ2Q10 (10') | Sweetwater.com
soundlight
Well-Known Member
Another problem here is that the DBX 1046 does not have a microphone preamp in it - the signal coming from the wireless mic receivers was probably more line level than mic level, so it worked fine. The gain reduction in the 1046 probably expects a line level signal to compress - I don't know how it would fare with a weak, un-preamp'd mic signal.
+1. Many wireless microphone receivers provide a line level output, either only line level or in addition to mic level, and that is probably what was run to the comp/limiter. So unless you have channel inserts or can come up with some other approach then what you need is likely not four channels of phantom power but rather four mic preamp channels that also provide phantom power. Then the outputs of the preamps run to the dbx 1046 and the outputs of the comp/limiter into mixer line inputs.
Given the above issues and the potentially related cost, it may be important to distinguish between seeing some benefit to having the comp/limiters available and wanting to use them simply because you have them.
Perhaps I should have reworded. I dont plan on using them just because I can, I just wanted to make them available if a need arises. Also, I did some expirementing with a dynamic mic and one of the comps. They worked just fine with the mic running straight through. There did seem to be a reduction in compression as compared to running a balanced line level signal, but nothign terribly noticable and certainly within useable parameters. Also, all of the old receivers were set to mic level output. So while it may not be intended or ideal, runnng a mic level signal through these guys certainly will work. So I porbably could just use phantom power suplies if I wanted to.
If it works for you that's great, but in general it would be a definite misapplication and the dbx 1046 manual even specifically states "The 1046 is designed for nominal -10 dBV or +4 dBu levels."
Looking at the related specifics in greater detail, the dbx 1046 manual states that the compressor threshold is adjustable from -40 dBu to +20 dBu and the limiter threshold is adjustable from +4 dBu to +22 dBu (off). There is no standard level for microphone outputs as it is dependent on the sensitivity of the microphone and the SPL at the microphone, but let's use an SM58 as an example and it has a sensitivity of -54.5dBV/Pa with 1Pa=94dBSPL. That's -52.3dBu/Pa or 12.3dB below the minimum threshold for the compressor with a 94dBSPL input at the microphone. To get to the minimum -40dBu of the compressor threshold would apparently require 106dBSPL at the mic while just 3dB of compression at a 3 to 4:1 ratio would require 115-118dBSPL at the microphone. I don't know the venues or music styles involved, but in many cases if you are getting that kind of level at the microphone then it may not require much reinforcement in the first place. Realistically, many microphones have a higher sensitivity but this does reflect that with a direct microphone input the limiter will almost certainly be useless and the effectiveness of the compressor will likely be limited.
There may also be other factors to consider and the input impedance may be one of those. Just for some comparison, the input impedance of an XLR input for an A&H GL2400 is 2k Ohms, for a Yamaha LS9 it's 3k Ohms, a Mackie 1604-VLZ3 is 2.5k Ohms, dbx's own preamps run between 330 Ohms and 4.2k Ohms, a Behringer X32 mic input is 5k Ohms, a Midas XL8 is also 5k Ohms and an Avid SC48 is 5.5k Ohms. The dbx 1046 input impedance is specified as >50k Ohms, so about 10 to 20 times that of a typical microphone input. While you want the destination (mixer or in this case comp/limiter input) impedance to be greater than the source (mic output) impedance, you want maybe 10:1 rather than 100-200:1 and that much higher input impedance could further reduce the level into the comp/limiter.
You may also want to consider what happens to the dbx comp/limiter when it sees phantom power on the input. Unless your phantom power supply has an output that blocks the DC power then the phantom power will be going to the dbx and unlike most mixer inputs, since it is not expecting to see phantom it may not be designed to block it.
But if you feel it works acceptably for you then that's all that matters. I just wanted others to understand some of the potential issues involved.
Looking at the related specifics in greater detail, the dbx 1046 manual states that the compressor threshold is adjustable from -40 dBu to +20 dBu and the limiter threshold is adjustable from +4 dBu to +22 dBu (off). There is no standard level for microphone outputs as it is dependent on the sensitivity of the microphone and the SPL at the microphone, but let's use an SM58 as an example and it has a sensitivity of -54.5dBV/Pa with 1Pa=94dBSPL. That's -52.3dBu/Pa or 12.3dB below the minimum threshold for the compressor with a 94dBSPL input at the microphone. To get to the minimum -40dBu of the compressor threshold would apparently require 106dBSPL at the mic while just 3dB of compression at a 3 to 4:1 ratio would require 115-118dBSPL at the microphone. I don't know the venues or music styles involved, but in many cases if you are getting that kind of level at the microphone then it may not require much reinforcement in the first place. Realistically, many microphones have a higher sensitivity but this does reflect that with a direct microphone input the limiter will almost certainly be useless and the effectiveness of the compressor will likely be limited.
There may also be other factors to consider and the input impedance may be one of those. Just for some comparison, the input impedance of an XLR input for an A&H GL2400 is 2k Ohms, for a Yamaha LS9 it's 3k Ohms, a Mackie 1604-VLZ3 is 2.5k Ohms, dbx's own preamps run between 330 Ohms and 4.2k Ohms, a Behringer X32 mic input is 5k Ohms, a Midas XL8 is also 5k Ohms and an Avid SC48 is 5.5k Ohms. The dbx 1046 input impedance is specified as >50k Ohms, so about 10 to 20 times that of a typical microphone input. While you want the destination (mixer or in this case comp/limiter input) impedance to be greater than the source (mic output) impedance, you want maybe 10:1 rather than 100-200:1 and that much higher input impedance could further reduce the level into the comp/limiter.
You may also want to consider what happens to the dbx comp/limiter when it sees phantom power on the input. Unless your phantom power supply has an output that blocks the DC power then the phantom power will be going to the dbx and unlike most mixer inputs, since it is not expecting to see phantom it may not be designed to block it.
But if you feel it works acceptably for you then that's all that matters. I just wanted others to understand some of the potential issues involved.
