I would like suggestions on high quality zero to near zero noise phantom power for my condenser mic's. I run four and want the option of using a single PAS or Two depending on venue. Currently I'm using a Mackie DFX-12 and it is muddy (compared to by-passing the mixer & Mic direct to PAS, although the 24v doesn't give optimum performance). If I set the gain on the bose PAS channel 1 & 2 from the mixer past 2 I get a lot of HISSSSSS.
Do I need a Microphone preamp with 48v phantom power? Maybe even a limiter / compessor combo?
Suggestions?
Original Post
Hi Kyle,
I have been working with Wess on this. He is using the Rode S-1 Condenser and Rode is telling him he needs the full 48 volt phantom power for optimal performance of the mic. Wes is using the Mackie board mainly for the power supply and is getting some hiss from the board. I have the same board and it is doing the same for me. Our stage volume is considerably higher so it's not as much of a factor but Wess is doing more acoustic and solo type music where you can hear the hiss. Wess is looking for a suggestion for an outboard unit that has 48 volt phantom power and won't inject the noise he is getting from the Mackie board. I think the Mackie board is just a little noisy. We have played around with optimizing the trim settings and it reduces the noise but it never completely goes away. We are using balanced XLR's out of the Mackie board into the PAS with decent cables and it still is noisy. Wess, I'll do a little looking into a stand alone phantom power supply if that exists as that may solve your problem. Any ideas Kyle?
Hi Wess - My band uses a couple of condenser mics (Crown CM-310's) in our set up. We run all the mics through a Soundcraft mixer, and use the 48 volt phantom from the mixer, not the 24 volt from the PAS. We tried a Mackie DFX-12 for one practice, and went right back to the good old Soundcraft - much better sound quality and much quieter.

We have found that when running balanced XLR lines into the PAS that the best signal to noise ratio is when the trims are completely turned down at the PAS. We run into preset #4 (presets v2) and it sounds very good, with very little extraneous noise. We set the individual channel trims and output volume at the mixer as high as we can, turn the trims at the PAS all the way down, and set the PAS channel volumes and the masters to around 2 o'clock.

You could also try the -20 pad / direct box route that has been discussed quite a bit on this forum, but I haven't tried that yet myself, so I can't speak for it.
Hey guys,i am using the mackie DFX-6.I did find it to give Hiss with the Pas turned up.I use a neuman KMS 105 mic into the Mackie dfx6,using the phantom power on the mackie,then i go L side out unbalanced into a BBE max then into a direct box (whirlwind imp 2) then into channel 1 of the Pas.I even use the R side out unbalanced into a IMP2 into channel 3 of the Pas.For some reason this seems ( for me anyway) to enhance the 32 bit effects on the mackie.ON the mackie everything is set to unity gain.Otherwise set flat.I use the controls on the Pas remote to fine tune the sound.The remote controls are very sensitive & its very important to make sure all your gain staging is at its optimal.The difference is good sound verus excellent unbelievable sound.The IMP2 is a little expensive & i think the whirlwind Imp pad xformer(impad 20) ($14) will do the same job.Any way i think your problem is with the Mackie mixer.Now you just need to find a solution.Fear not the Bose boys will be on the case for you.....
Well I've stayed out of this one because when I was "testing" the Rhode S-1, I didn't think there was any degradation running direct into the Bose when compared to 48v with a Yamaha OV-1. Actually I preferred the sound when running direct into the Bose system.

Anyway, I did a search on google for phantom power supply and came up with these, and a plethora of others.

Audio Technica

$60 Single channel
AT8801

$139 4 channel
CP8506

Mac Midi Music page with several brands (click the picture)



Wess, I don't have any experience with any of these except for a couple of the AKG battery operated ones. But I haven't tried these with the Rhode S-1.
Last edited by ST
Wess - I guess the point I was trying to make is that before you go spending more money on more stuff that will probably NOT fix your problem, take another look at your set up. The phantom power is most likely NOT be the cause of your noise problem. Or the Mackie. Or the Rode. I think that any mixer output running a balanced line into the XLR preamp input of the PAS is going to cause some noise, unless the signal is padded, or you keep the trim on the PAS turned all the way down. Regardless of whether or not you're using phantom power, a cardoid or condenser mic, and regardless of the brand of mixer (although some ARE noisier than others) - you're going to get noise the minute you turn that PAS trim up without a padded signal.

You originally said "If I set the gain on the bose PAS channel 1 & 2 from the mixer past 2 I get a lot of HISSSSSS". There may be no need to set it past 0, if you've got the front end adjusted properly. The Mackie isn't a bad board, don't give up on it yet - you have your phantom power, your effects, and decent preamps all there, with very versatile routing options.

Try it with the PAS trim turned completely down, and see if you can get the volume and tone you need like that, before you go buying more stuff that you may not need.

I did a "blind" A-B test with two identical mics (the Crown CM-310's). One was run through our standard mixer set up into channel one of the PAS, and the other was plugged directly into channel two the PAS using the 24 volt phantom. Most of the band could not tell the difference, and the ones that could, preferred the mixer channel.
Let me add some technical ramblings to the 48/24 discussion. Condenser microphones require phantom for a couple of reasons

a) power an internal pre-amp
b) supply polarization voltage to the capsule
c) run an internal DC-DC converter that in turn fuels either preamp, capsule or both

Most condenser mics fall in category a). In this case, reducing the phantom from 48V to 24V has virtually no effect. In theory you can get higher voltages out of a 48V supply, but at this point you would clip the input of you mic preamp anyway.

In category b), the effect of dropping the phantom is that the overall sensitivity of the mic goes down by 6 dB. On the other hand, the max SPL goes up by 6dB. In general, you will simply have to turn up the trim a little more, but there shouldn't be any other effects.

Case c) is basically hit or miss. Either it works just fine or it doesn't work at all. I don't think there is any in-between.

Again, most mics these days fall in category a) and that's one of the reason why the the International Engineering Consortium (IEC) in it's standard 61938 (1996) in section 7.4.5. explicitly recommends
quote:
Although 12V and 48V systems are still in use, 24V systems are preferred for new developments

and that's why we've chosen 24V.
Guys,
If you're getting HISS from your mixers running XLR into the PS1s, then use the 20dB imp pads. I've used them in both configurations (with and without) and the imp pad makes all the differnece in terms of low noise and seemingly clearer signal (not to mention less feedback when using mics due to better gain stanging).

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