M Audio Fast Track Pro mic gain issue

[Alex Richards]

To get a usable signal I need to turn up the gain almost to max, which leaves very little headroom. I have searched the M Audio forums and others who have the same issue have been given the response 'it's normal, preamps are only 40dB'. I also saw a post on another forum where someone said they were having the same problem with multiple interfaces.

It is the same on both an XP desktop and Win7 laptop, with either a dynamic or condenser mic.
Any ideas?

[Billum]

Hi Alex,

I agree that 40dB of gain on a mic preamp seems rather low - I would normally expect at least 50, and 60dB or more of clean gain is not at all unusual, especially if you're expecting to use ribbon mics.

I'm a little confused as to your terminology though - when you say that turning the gain up to max leaves you very little headroom, do you mean that it leaves you very little margin for turning the gain up further if the source is too quiet? That is not normally referred to as headroom, but something like 'gain in hand'.

In fact you probably have quite a lot of headroom, which is the margin between your loudest audio input and the onset of clipping, so the lower your input gain, the greater your headroom.

The FT Pro has quite good analog-to-digital converters, and a fairly low noise floor, so even if you have around 20dB of headroom under these circumstances (i.e. your input is peaking at -20 on the input scale), you could make perfectly good recordings and never have to worry about the possibility of clipping in your life! Many experts (the venerable Mr Robjohns among them) recommend keeping input levels down around the -15dB level as a matter of course, as the hardware & power supply is much less stressed at these levels, especially on less than professional equipment, and the sound can be significantly purer.

Recording at 24bit resolution will still give you plenty of signal-to-noise ratio, so for an inveterate optimist perhaps the lack of input gain could even be seen as a blessing in disguise....?

[Alex Richards]

Thanks for the detailed response Billum, appreciate the help.

With the gain turned up it is very easy to cause clipping and there is very little gain-in-hand, or none at all.

It will be used to record voice-overs only(hence the need for lots of gain), so I decided to get a cheap preamp to give more control over the signal. Any recommendations below £50?

[zenguitar]

And what level are you achieving in your DAW? -6dB, -10dB, -12dB, -18dB?... Or, to put it another way, how are you defining a 'usable' signal?

Andy

[Alex Richards]

And what level are you achieving in your DAW? -6dB, -10dB, -12dB, -18dB?... Or, to put it another way, how are you defining a 'usable' signal?

Andy

One that isn't noisy (or at least noise that isn't noticable). Either I turn the gain up which introduces noise, or I normalize in software which brings the noise up.

[zenguitar]

And what level are you achieving in your DAW? -6dB, -10dB, -12dB, -18dB?... Or, to put it another way, how are you defining a 'usable' signal?

Andy

One that isn't noisy (or at least noise that isn't noticable). Either I turn the gain up which introduces noise, or I normalize in software which brings the noise up.

So, the noise level is essentially the same regardless of the gain level. In that case I think we should be looking for the source of the noise rather than looking at the gain in the Fast Track Pro.

Andy

[ef37a]

Alex, do NOT buy a cheap mic pre amp!
I have a Fast Track Pro and yes the amps are gain shy but they are quiet. Any cheap "tack on" is going to be noisier*
Spend your nifty on a small D capacitor mic, I run the AKG Perception 150s (now 170, ess'same mic) and don't have a sensitivity problem. These run about 60quid but there are cheaper Chinese caps that should serve.
*The Pro has inserts post mic/line/instru' amps. I had considered at one point building a wee line booster around an NE5532 or sim' to give a controlled 0-30dBish boost. Not done it yet tho!

PM me if you want some level set examples and noise figures.

Dave.

[Alex Richards]

So, the noise level is essentially the same regardless of the gain level. In that case I think we should be looking for the source of the noise rather than looking at the gain in the Fast Track Pro.

Andy

No it's not the same, sorry for not explaining it properly. It seems that the majority of the gain is applied during the last quarter turn of the gain knob. When I turn it the last, say 5%, a gentle hiss is introduced (thermal noise?). I am monitoring on headphones, nothing else connected. If I do not turn it up full the resulting waveform is very small, and when normalised it also brings up the backround noise that is not usually noticeable.

[Alex Richards]

Alex, do NOT buy a cheap mic pre amp!
I have a Fast Track Pro and yes the amps are gain shy but they are quiet. Any cheap "tack on" is going to be noisier*
Spend your nifty on a small D capacitor mic, I run the AKG Perception 150s (now 170, ess'same mic) and don't have a sensitivity problem. These run about 60quid but there are cheaper Chinese caps that should serve.
*The Pro has inserts post mic/line/instru' amps. I had considered at one point building a wee line booster around an NE5532 or sim' to give a controlled 0-30dBish boost. Not done it yet tho!

PM me if you want some level set examples and noise figures.

Dave.

Thanks for the advice.
The mic will be used only for voice-overs, will a small D be sufficient?

Do you think a beginner could make a line booster? I have done a little soldering before.

[zenguitar]

So, the noise level is essentially the same regardless of the gain level. In that case I think we should be looking for the source of the noise rather than looking at the gain in the Fast Track Pro.

Andy

No it's not the same, sorry for not explaining it properly. It seems that the majority of the gain is applied during the last quarter turn of the gain knob. When I turn it the last, say 5%, a gentle hiss is introduced (thermal noise?). I am monitoring on headphones, nothing else connected. If I do not turn it up full the resulting waveform is very small, and when normalised it also brings up the backround noise that is not usually noticeable.

I'm sorry Alex, I didn't make the point as clearly as I should. When I asked previously you said that when you recorded with lower gain and then normalised, the noise was the same as it was if you recorded with higher gain. As I understand it now, you either have the hiss from the pre-amp if you turn up the gain, or have a problem with the noise floor (a different noise) if you record with lower gain.

I know it might seem pedantic, but the reason for the questions is to help establish whether the problem is with your working methods, the FT Pro, something else in your system, or a combination of things.

You need to be careful using the size of the waveform in your DAW as a guide to the level of your recording, it is only there to give a visual indication of the track as a whole and it isn't an accurate meter. The part of your DAW that you need to look at is the meter on the input. That is the right tool to establish whether or not you are getting a suitable output from your FT Pro.

If you are recording at 24bit, you want to be aiming for your track input meter to be peaking at around -12dB. Adjust the gain of the FT Pro until you are getting that sort of level.

Do not normalise the recording. Not only is it completely unnecessary, it removes all of your headroom and (as you have discovered) it brings up the noise floor. Normalisation isn't generally used in music recording, we use more sophisticated tools at the mix and mastering stages to make things as loud as needed.

So, give that a try and see if you actually need to push the FT Pro gain into that last 5% travel. If it sounds quiet on playback, make sure you have your DAW output settings right, and you have the channel output fader at unity gain, and if it's still too quiet, turn up the volume on your headphones.

Andy

[Alex Richards]

As I understand it now, you either have the hiss from the pre-amp if you turn up the gain, or have a problem with the noise floor (a different noise) if you record with lower gain.

Correct.

I know it might seem pedantic, but the reason for the questions is to help establish whether the problem is with your working methods, the FT Pro, something else in your system, or a combination of things.

No worries, I appreciate you trying to help. I should have specified noise floor instead of assuming you knew what I meant.

You need to be careful using the size of the waveform in your DAW as a guide to the level of your recording, it is only there to give a visual indication of the track as a whole and it isn't an accurate meter. The part of your DAW that you need to look at is the meter on the input. That is the right tool to establish whether or not you are getting a suitable output from your FT Pro.

Really? Isn't it just an amplitude/time graph? Why would the amplitude of the waveform differ from the input level on the meter? When I say small I mean barely there at all. Obviously I use the meters to check levels before recording, but aren't there more pitfalls with all the different scales (dBFS etc, which I still haven't fully got my head around)?

If you are recording at 24bit, you want to be aiming for your track input meter to be peaking at around -12dB. Adjust the gain of the FT Pro until you are getting that sort of level.

Can't get that high without clipping.

Do not normalise the recording. Not only is it completely unnecessary, it removes all of your headroom and (as you have discovered) it brings up the noise floor. Normalisation isn't generally used in music recording, we use more sophisticated tools at the mix and mastering stages to make things as loud as needed.

That was an example of the extreme lengths I had to go to. Also, for clarification, I am not recording music with this set up.

So, give that a try and see if you actually need to push the FT Pro gain into that last 5% travel. If it sounds quiet on playback, make sure you have your DAW output settings right, and you have the channel output fader at unity gain, and if it's still too quiet, turn up the volume on your headphones .

Andy

I don't think a client would appreciate that response if I gave it to them, haha.

[zenguitar]

So, give that a try and see if you actually need to push the FT Pro gain into that last 5% travel. If it sounds quiet on playback, make sure you have your DAW output settings right, and you have the channel output fader at unity gain, and if it's still too quiet, turn up the volume on your headphones .

Andy

I don't think a client would appreciate that response if I gave it to them, haha.

LOL

I wasn't suggesting telling that to the client !!! I was looking at the distinction between your input levels and your output levels for monitoring.

But, essentially, it seems that your FT Pro is distorting before you are able to reach even -12db in your DAW. I presume you are recording speech? What microphone are you using? It could be that you have very low output from your mic, possibly a fault, or possibly a fault with the FT Pro. Have you tried other microphones? Or are you recording an exceptionally quiet source that needs far more gain than normal?

Andy

[Alex Richards]

But, essentially, it seems that your FT Pro is distorting before you are able to reach even -12db in your DAW.

I think it is the mic that is distorting, with having to be so close to it

I presume you are recording speech?

Yes, and maybe foley in the future

What microphone are you using?

Roxdon EM 1

It could be that you have very low output from your mic, possibly a fault, or possibly a fault with the FT Pro.

Indeed. There is a problem (discussed here: http://www.soundonsound.com/forum/showf ... t=1#926392 ).

Have you tried other microphones?

AKG C1000S which I think is not well suited to this task. I read that it is a back electret mic that is more suited for drums, amps etc. I have also tried a cheap dynamic mic(£2.20!) that is only used for talkback, obviously I won't be recording with this though, haha.

Or are you recording an exceptionally quiet source that needs far more gain than normal?

Andy

Not yet, but I would like to be able to.

Also, sorry to be a pain but could you clarify your statement about not relying on the waveform to judge levels?

[zenguitar]

Also, sorry to be a pain but could you clarify your statement about not relying on the waveform to judge levels?

Sure, it's no problem Alex...

The purpose of the waveform you see in audio tracks on your DAW is to give you a guide to what the audio is doing when you are editing it, it is there to help you spot the beginning of words or phrases, or help spot drum beats. A tool to help get you to the right area, but once you are working on it you use the DAW's audio tools to home in on the parts you want, or call up a dedicated audio editor.

It isn't calibrated accurately as an audio meter. For example, I've recently recorded some samples using Reaper and while the waveform in the Reaper track shows the initial attack clearly, the sustain barely registers even though it is clearly audible above the noise floor. I really have to zoom in and expand the track massively to see that there is anything there.

The DAW track waveform really is just there to help you navigate your tracks.

And when I suggested using other microphones, I wasn't talking about your final product. When you are trouble shooting a problem, you HAVE to break it down into smaller parts. Using another microphone isn't the solution to your problem, it is a tool to help you identify whether your problem is your mic or something else. You work through your recording chain step by step and eliminate things one by one until you are finally left with the cause of the problem. And once you have the cause of the problem, you then have an idea how to solve it.

You mentioned an AKG C1000S, and while it may not be an ideal mic for the purpose, it is still a good and well respected mic. But the purpose of trying it is to see whether or not you get distortion/sufficient gain with a different mic. And that is the test you need to do, with the C1000S, with the cheapy, with any other decent mic you can borrow.

As it stands, you have a problem, but instead of working through it methodically you are thinking rather than doing, and then using the thinking to take shortcuts. There are no shortcuts when it comes to trouble shooting, you really DO have to work things through step by step. And that is why previously I was trying to pin you down to hard numbers with your input gain rather than relying on the DAW waveform.

I have also tried a cheap dynamic mic(£2.20!) that is only used for talkback, obviously I won't be recording with this though, haha.

This sums up your problem... your HAHA at the end. Of course we aren't expecting you to record with a £2.20 mic (although you might be surprised, sometimes cheap gear can give great results), but you have a mic that works for talkback, and that means you have a known working mic. That means you can use it for trouble shooting.

I think it is the mic that is distorting, with having to be so close to it

Don't think, TEST.

Andy

[ef37a]

Another simple way to see that "waveforms" do not give accurate amplitude information is to think of 8 of them on screen?

They all could be neg 6 but have to be squeezed down to fit.

Dave.

[Alex Richards]

The trouble I have is that there are many problems, so whilst I have tried my best to be methodical (before I started this thread I tried using different mics, cables, computers), I am trying to fix 3 things at once as you read in my other thread.

I didn't just try one mic and then come on here with my problem, I have tried many different sources so I decided to come here to ask if anyone had similar problems, and possibly for some advice on the best ways to raise the gain. As ef37a said, the interface is a little gain shy, which was the clarification I was looking for.

[zenguitar]

Of course Alex, and we understand. But the problem we have is that you know what you have done and tried, but we don't. Hence the questions.

And as you say, you are struggling with 3 problems. So that it is all the more important that you break things down and work through step by step.

What I would suggest is that you stop work on your projects and strip down your recording system. Then start with just a mic and the FT Pro and use the hardware monitoring on the FT Pro to see whether the distortion appears at source.. and then connect to your PC by USB and test and check everything again. If the noise appears, you might have a ground loop problem...

if all is OK, make some test recordings to see what levels you can record before distortion working at 24 bit. Your DAW meters are scaled for digital, if you are used to analogue recording (or using a mixing desk live)zero dB on your analogue system is roughly equivalent to -18dB on your DAW meters. And that is more than satisfactory to achieve decent recordings.

If you can achieve that, then you have no problem with recording. So it is possible that your problems lie with what you are doing once you have the recording in your DAW.

You really do need to be methodical about this. Don't skip steps, and don't make assumptions. And don't keep switching from one problem to another. Get a basic system working first, and then add the next thing.

Andy

[Alex Richards]

Update: tested with an sE Electronics mic, much better results. Will hopefully post figures tomorrow.

Andy - I appreciate the help very much, I will try the hardware monitoring tomorrow. Also, the computer is the only thing plugged in so I assume it cannot be a ground loop, as there is only one connection to the ground.

[zenguitar]

Glad it's starting to work out Alex

Andy

[ef37a]

I have been fooking about with my pro recently and can give a bit of signal level information.

Roughly, when the green LED blinks I get -20dBFS on my DAW, Samplitude se8. I will dig out my trusty Levell osc' later and give a more precise figure.

Dave.

[ef37a]

Ok, as promised.

Osc' into L line F= 998.7Hz. Green LED just lit. Vin 0.0775volts (-20dBu) pro gain at min'. Sam 8 reads -25dBFS.
Pro gain max. grn LED just lit Vin 0.006mV* sam -25dBFS.

Pro gain min. red LED just blinking Vin 1.05V sam8 0dBFS
Pro gain min. grn led on Vin 0.708 sam 8 -6dBfs.

The right line in was substantially the same.

G'Gook Alex? Well the bottom line is that if the green LED is giving it some but the red LED NEVER blinks you are getting a good level but never overloading. But you should always monitor levels by the meters in your software.

*~ -40dBu but the DMM I was using gets a bit porkified at such low levels.

Dave.

[zenguitar]

Thanks for that Dave, very helpful of you.

Andy

[ef37a]

You are very welcome Alex.

Others here know me to be agin dBu!The numbers just came out that way for the Pro and I could not be arsed to convert them to dBV!

1.05V is of course 0dBV near as d.i.t.s.
Dave.(and I would like DIY back please)

[Alex Richards]

Thanks again guys!

I am now quite happily comparing different mic placements. Any advice for recording voice-overs? From what I've read so far it's quite different to recording music.

I have been forced to use Garageband though, which has no scale on it's input meters, or anything else for that matter. Would about halfway (on garageband) be a good reference?

[ef37a]

Thanks again guys!

I am now quite happily comparing different mic placements. Any advice for recording voice-overs? From what I've read so far it's quite different to recording music.

I have been forced to use Garageband though, which has no scale on it's input meters, or anything else for that matter. Would about halfway (on garageband) be a good reference?

Voice overs! Another order of quietitude needed here! I do not jest, you will need to setup in the dead of night and even then you will hear every b'std clock in every b'std room (and next doors'!) You will be editing out passing cars, Hcopters, loo flushes....

Meters? Audacity has good enough ones and will run on most (but not all) macs (www.sourceforge.net).
I know nothing of macs or Garageband. What else can he dld chaps with 1/2 decent meters? Is Reaper mac tolerant?

Dave.