PG Music Home Forums General Discussion Off-Topic Another "What's your opinion" question

My interface has phantom power on it. Is it good, bad, or indifferent to leave it switched on? I only need it when I plug the condenser mic in, and when I use a dynamic (Shure 58) it plugs in through the preamp and then the patch bay and then the interface, all by 1/4" plugs so it doesn't hit the XLR where the 48v is.

Opinions?

You have your Shure SM58 using 1/4" connection?

I'd turn it off when not in use.

I agree, turn it off, but I was taught it does no harm to a dynamic mic.

The preamp has XLR 'In' though right?
It sounded like your 58 might be using a 1/4" connection. That's what threw me.
I pictured one of those big old XLR/1/4" adapters hanging from the preamp .. and shivered.

No, the preamp is XLR in (or 1/4 - it has both) and 1/4" out. When I have used the new mic I went right to the M-Audio so I don't have preamp feeding preamp.

Phantom Power does not flow thru the properly wired dynamic mic, by design.

That said, I usually turn mine off when using a dynamic, but in fact it does not matter. The way the dynamic mic is wired and the way the phantom power works precludes any DC flow in the dynamic mic.


--Mac

And again, remember that I only plug THAT condenser mic into the M-Audio. The dynamic goes into the preamp, though only because I have it. I could probably have lived without it, but it was a good buy, and I would buy a zircon encrusted toilet seat if it was a good buy. The M-Audio apparently has a preamp in it (I should probably find out, huh?) and that preamp is routed through the patch bay so the M58s and the vocoder run through the patch bay to the M-Audio (loves me some patch bay!) like the keyboards, the drum machines....

Eddie try pluggung the sm 58 directly into the interface. Its almost guaranteed to be less noise in the signal chain than the way you are doing it now. No need to have the phantom power on but my guess is that you'll have a cleaner signal going direct into the audio interface. To answer your question, since youhave phantom power in your interface you already have a mic preamp. No reason for phantom without use as a mic preamp.

Okay so I have the M-Audio Fast Track Pro interface. I don't know if it has a preamp or not. When I plug the mic directly into it, the clip light flashes WAY before I can record a vocal track anywhere near close to hot enough. Immediately after recording vocals, I am sitting there doing gain change 3db at a time until it't loud enough to be usable. No matter what I have tried in the past, my choices were clipped or WAY too low. One of the other folks here suggested a preamp, which I bought. The vocals are warmer, more present.

But bottom line, am I sending a preamped signal into another preamp (the interface)?

Absolutely the Fast-Track Pro has 2 mic pre-amps in it. If you are using one of the line-ins, then you aren't doing what you worry about.

You shouldn't be clipping with normal vox, into an SM-58. If the light is just lighting, it's quite possible it's just a 'signal present' LED and not a clipping LED.

Just checking here, but you are following these instructions from the manual, correct?:
"Using the Mic/Inst Inputs
Connect your microphone, instrument or line level source to the Fast Track Pro’s front panel Mic/Inst inputs. Make sure the associated channel’s Inst/Line button is set to the out (Inst) position for microphone or instrument input, or to the in (Line) position for line level sources. If you are using a condenser microphone, be certain to slide the 48V PH Power switch to the On position (after connecting the microphone to the XLR input). If your microphone input signal is too hot (Clip LED lights steadily), press the Pad button to lower the input level.
Adjust each channel’s input GAIN knob to achieve a fairly steady green Signal LED without triggering the red Clip LED, while audibly testing your input levels (i.e., strumming the guitar, or speaking into the mic)."

That is, you need a steady green light, without steady lighting of the red clipping indicator. Note the comment about the pad switch if you are tripping the clipping indicator too much.

This should give you a reasonably hot signal without having to do the gain changes you refer to.

That's a decent interface and the mic preamps should be pretty clean in it. If you have a more clean mic preamp, then use it's line-out into the fast track pro, with the switch set to line-in. Take note also about the comment on this switch in the manual (front panel controls section) that if you are connecting via XLR (which you are not) then that switch has no effect.

-Scott

What I have been doing, with pretty good result, is plugging the M58 into my little Audio Buddy preamp via XLR, then the out of that preamp goes to my patch bay, and the patch bay to the M-Audio interface. Everything in the room passes through that patch bay. Much more efficient to use 12 inch 1/4" cables to make patch bay connections then be running 20 ft cables to route signal. I have my little patch bay map and 11 and 12 out go to the M-Audio. So, for example, the drum machine is 4 in. I patch that to 11 out and the drum machine is routed to the M-Audio. But you know how a patch bay works.....

This has been in place for like a year (minus the preamp) and works just fine for what I need.

Eddie,
You are totally missing what Scott is saying.
The Fast Track Pro has enough available gain to get you all the signal, and then some, that you need WITHOUT the use of another pre-amp. You're just not setting stuff up correctly.
Your patching scheme is irrelevant.

What is there to set up incorrectly? You plug in a cable and turn the knob until the clip light comes on. When I do that my vocal track is extremely weak and I have to gain change it. I can't record with the clip light on are it is distorted. Even when the attenuation light rides solid green with an occasional red flash on the clip light, the vocals are WAY too low, like they look like almost a flat line in the track. Instruments recorded through the same interface are fine. Adding the preamp made a big difference.

All I want to know is whether leaving the phantom power on all the time hurts anything because the switch to turn it on and off is buried and a hassle to get to. As long as I use my SM58 this is moot. When I want to use that new condenser mic I need it on. I am not happy with that mic at this point anyway....

Technically there is nothing at all wrong with choosing to use an outboard mic preamp with the external audio device in question as long as the Line Input to that device is selected as the input from the external mic preamp.

There can be good reason to use a different Mic Preamp than the one built into your sound device, because different Mic Preamp designs can bring their own sonic coloration to the project. For example, I will use one of my "tube" Mic Pres for certain tasks like vocals, where I think that the sound they create is "warmer" than the sound that the Mic Pre built into my audio device can deliver with its all-solid-state design.

As far as leaving the Phantom Power turned on all the time, there is a caveat to doing that and it is all about what happens when a Condenser Mic that requires Phantom Power is plugged into a "hot" Phantom Power mic jack. This may damage sensitive components inside the Condenser Mic due to voltage transients. The recommended method for hookup then is to connect the Mic cable to the mic and preamp *BEFORE* turning Phantom Power on via the included switch. This is one of those things that you can indeed violate and it would seem to be okay as the Mic likely will not become instantly damaged if you forget and plug it in while the Phantom Power is turned on. But it is not good practice to do so for there can and likely will be damage at some time or other and your expensive Condenser Mic may be rendered functionally useless for the task at hand.

Quote:

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What is there to set up incorrectly? You plug in a cable and turn the knob until the clip light comes on. When I do that my vocal track is extremely weak and I have to gain change it. I can't record with the clip light on are it is distorted. Even when the attenuation light rides solid green with an occasional red flash on the clip light, the vocals are WAY too low, like they look like almost a flat line in the track. Instruments recorded through the same interface are fine. Adding the preamp made a big difference.

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Something is wrong with the Gain Staging of your hookup.

Most likely suspect is that you are plugging the Mic into the jack but leaving the Switch that corresponds to that jack on the "LINE" input setting instead of the MIC setting, which would indeed ac exactly as you have described. Switch it to the Mic input setting and try again. If the level is still low like that, it *might* be something damaged in that unit's mic preamp, but that is rather doubtful at this point.


--Mac

"What is there to set up incorrectly? You plug in a cable and turn the knob until the clip light comes on. When I do that my vocal track is extremely weak and I have to gain change it. I can't record with the clip light on are it is distorted. Even when the attenuation light rides solid green with an occasional red flash on the clip light, the vocals are WAY too low, like they look like almost a flat line in the track. Instruments recorded through the same interface are fine. Adding the preamp made a big difference."

Something seriously wrong here. Without being there, it is hard to say what is wrong, assuming you've already taken care of the mic/line level switch Mac referred to.

Also, I don't know how your controls are setup for the software for the Fast Track Pro, but it's possible that you don't have the input 'digital' fader on the Fast Track set to take advantage of all of the analog signal at the inputs, which would allow clipping to show on the front panel, but not send all of that signal to the DAW track. I don't see an M-Audio specific control for this, which is unexpected, but it might be associated with your Windows volume control mixer.

Lastly, how about mic technique? SM58 are reasonably 'hot', no need to be eating the mic; particularly as you will get unusable proximity effect (load up on low frequency).

I also suspect bad cabling/grounding with a 60 Hz or DC offset present which can make 'solid red' happen; You shouldn't really see solid red while recording vox, even with gains dialed up.

Eddie, without having the data at hand, I would guess that the SM58 is probably one of the most used and readily available mics in home studios. The mic pre-amp in the Fast Track Pro has more than 40 dB of gain available according to their specs; full specs here:

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Mic Inputs (A/D)
Input Impedance
2.7k Ohms unbalanced, 5.4k Ohms balanced
Maximum Input Level
from +24dBu @ min gain, pad on to -40dBu @ max gain, no pad
Channel-to-Channel Crosstalk
< -110dB
SNR
-101dB, A-weighted
Dynamic Range
101dB, A-weighted
THD+N
0.005% (-86dB) @ -1dBFS, 1kHz
Frequency Response
20Hz to 20kHz, +/- 0.1dB
Preamp Gain
>40dB
Pad
-20dB pad

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The SM 58 should work ideally with this set of specs.

Also, your definition of 'hot' is of interest. In one of your threads you mention the clipping that shows up in some of your tracks, but had no indication of this happening whilst recording.

There is something really odd going on. The only way to troubleshoot it, in my opinion, is to remove elements from your signal chain and fully understand the system at it's simplest possible configuration.

Here's my suggestion:

1. Get a mic cord; one that you've proven is without shorts or shielding issues.
2. Use the cord to plug the SM58 directly into one of the XLR inputs on the Fast Track Pro.
3. You should be dialing in about 1/2 gain, (my estimation) on the input trim control on the front of the Fast Track Pro, for most normal vocals. Don't eat the mic, back away 6" or so - should be fine in your new 'booth. I would find some fluffier comforters to hang out in front of the moving blankets - separate them by some distance of a few inches by nailing a 1"x6" wide side facing down across the tops of the doors and simply draping the comforter over those - they'll space the comforter out away from the moving blankets. BTW, the moving blankets would do well to be out away from the door surface a bit of distance as well.
4. Look in PG's device selection/input gain control section - this may or may not exist. In my DAW, I have control over how hot to record the incoming digitized audio stream, independent from the analog trim/gain control on the front of the device, and independent from the software gain control for the interface. This has been true on my PreSonus Firebox as well as my TASCAM US-800. I'm guessing PG software has a similar control, though I can't remember it from my PTPA days. I strongly suspect something awry here. It could be in the Windows mixer applet as well, if you have selected the Fast Track as the primary device (make sure this is the case - I raise my hand as more than once not doing this, and the onboard mic in the lappy was selected and clean enough to fool me that I thought I was going through the external mic chain, but was actually picking up the lappy microphone). Ensure that if you have a software 'trim' on the mic in some control panel, set it to unity gain. Could be an M-audio specific mixer applet, could be something that looks like Windows' own setup, etc. This is critical and where I'm guessing your system is jacked up.

5. If you've confirmed the above, you should be able to record vocals without steady clipping - steady clipping implies a steady sound going into the channel and vocals, unless you are humming constantly, don't provide that. Your room should be quiet enough that even on very high gain, when you are not singing, no green nor red clipping light should light.

The resultant waveforms should be un-clipped and should not be low level, that is, visual study of the waveform should show nice usage of the track lane height for the track, relatively speaking compared to other tracks.

Use of an outboard pre-amp is, as Mac pointed out, often useful and desirable, but with 40+ dB of gain on the Fast Track, you should have sufficient gain there to do this experiment and it should be nice and clean, with a claimed 101 dB of SNR and 101 dB of dynamic range.

Here's what I can tell you fromt he office. The mic and cable are the same mic and cable that we just finished using for 6 weeks of rehearsal. The issue is that the level when I record into RB is extremely weak. Allow me to diagram.

____________________


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____________________


That is how wide my band of signal is. I would expect it should be more like

____________________
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____________________


At any rate, what I need to know how to do is to make that band of signal be wider. Also know that the first example is when the clip light on the interface is just just starting to light up when I belt a hotter note out for dynamics. I know I can't push the input side of it any more or I will clip. I just want to know why RB is recording my vocals so low when the input signal is strong.

Let see if I have an idea.First I'll post my asumptions and you correct me if I have this wrong.
1.Without the other pre amp you turn up the control on the FTP until the clip light blinks?
2. The vocals are recorded week?
Questions.
1. what do the RB meters look like when you sing into the mic the the program idle?
2. Have you gone into the Windows mixer, not the FT mixer, and turned up the record slider for the FTP?
I bet you find the Windows mixer record slider is down.

The record side of the Fast Track in Windows sound hardware properties is grayed out and can't be adjusted. I could change the playback volume of that device, but that recording tab is grayed out. Has always been that way for now the 3rd computer. Being that it is a USB device, does it or doesn't it bypass the Windows sound bus?

I have not payed attention to the VU meters on RB, but if I recall from just seeing (rather than actaully watching them) when speaking into the mic in an idle state they do nothing.

Now, let me also add that when I speak into the mic in an idle state, the sound coming out of my monitors (or headphones) is plenty loud. If I just play the track back and sing along with it as I do for 2-3 "learning" takes, the mix is fine. Then I hit RECORD AUDIO, do the same thing having touched no knobs or settings, and the recorded take is about 1/3 the level of the dry take.

So let me now ask this about the volume slider of the track's display. It would be logical to me that the slider on the track is not relevant while recording, only when playing back. Do I need to make sure that the slider is full hot when I record? Again, it seems illogical that the volme slider would matter when recording. If I am wrong about that, great news.