Topic: Noisy microtrack

[dfroom]

I am new to this forum and new to the Microtrack.

I am having a problem with noise. 

I have firmware 1.3.3.  I purchased an XRL to TRS adapter set (2 in, 2 out) from "The Sound Professionals."  I was trying to make a recording, classical music, using an Audio Technica 825 (a decent stereo microphone). 

I was using the Microtrack's phantom power.  The AT-825 is not on the list of compatible microphones (M-Audio website), but "Sound Professionals" refer to it as a good microphone to use with the Microtrack, even in their description of the xrl-trs adapters.  The AT-825 book gives a wide range for needed phantom power (I think something like 5 - 45 v).  I also know that others have used the AT-825 with the Microtrack, but, I think, for non-music recordings (I googled the combination).

I was comparing the Microtrack to an M-Box going into a laptop with an external harddrive, or to a decent DAT.  I was hoping to use the Microtrack as an acceptable alternative (lots less to lug around, and probably more reliable and better sound than the DAT).

The Microtrack levels showed as VERY low.  In order to get any sound at all, we had to turn things all the way up (H setting, with input volume up full).  I tried this with and without the 27db boost.  With the boost, it got up to something acceptable.  But it was REALLY noisy!  LOTS of hiss.  And without the boost, it was still very noisy.

Based on your collective experiences, do you think the noise coming from phantom power?  from the adapters?  from this microphone/recorder combination?  or could I have a bum unit? 

The only other recording i've tried is with the supplied mini-microphone into the 1/8' jack.  I have to set the levels pretty high, but the noise isn't bad.

The AT-825 also runs off a battery.  I didn't know this when I tried it.  We've always used phantom power from the M-Box (or, previous to that, from a DAT).
I'll try this again with the battery in the AT-825 and phantom power off.

I got a Microtrack based on the recommendations of a favorite classical audio engineer.  He uses the Microtrack to take a signal from a big Soundfield stereo microphone running into the Soundfield pattern box that supplies the power to the microphone.  So, except for taking basically a line input, he is really only relying on the Microtrack's A/D converter, which he says is very fine.  But, clearly, he is not the one to give me advice on doing this with microphones that cost under $1000.

I would greatly appreciate any advice.

Thanks,

David

[SClassical]

I am new to this forum and new to the Microtrack.

I am having a problem with noise. 

I have firmware 1.3.3.  I purchased an XRL to TRS adapter set (2 in, 2 out) from "The Sound Professionals."  I was trying to make a recording, classical music, using an Audio Technica 825 (a decent stereo microphone). 

I was using the Microtrack's phantom power.  The AT-825 is not on the list of compatible microphones (M-Audio website), but "Sound Professionals" refer to it as a good microphone to use with the Microtrack, even in their description of the xrl-trs adapters.  The AT-825 book gives a wide range for needed phantom power (I think something like 5 - 45 v).  I also know that others have used the AT-825 with the Microtrack, but, I think, for non-music recordings (I googled the combination).

I was comparing the Microtrack to an M-Box going into a laptop with an external harddrive, or to a decent DAT.  I was hoping to use the Microtrack as an acceptable alternative (lots less to lug around, and probably more reliable and better sound than the DAT).

The Microtrack levels showed as VERY low.  In order to get any sound at all, we had to turn things all the way up (H setting, with input volume up full).  I tried this with and without the 27db boost.  With the boost, it got up to something acceptable.  But it was REALLY noisy!  LOTS of hiss.  And without the boost, it was still very noisy.

Based on your collective experiences, do you think the noise coming from phantom power?  from the adapters?  from this microphone/recorder combination?  or could I have a bum unit? 

The only other recording i've tried is with the supplied mini-microphone into the 1/8' jack.  I have to set the levels pretty high, but the noise isn't bad.

The AT-825 also runs off a battery.  I didn't know this when I tried it.  We've always used phantom power from the M-Box (or, previous to that, from a DAT).
I'll try this again with the battery in the AT-825 and phantom power off.

I got a Microtrack based on the recommendations of a favorite classical audio engineer.  He uses the Microtrack to take a signal from a big Soundfield stereo microphone running into the Soundfield pattern box that supplies the power to the microphone.  So, except for taking basically a line input, he is really only relying on the Microtrack's A/D converter, which he says is very fine.  But, clearly, he is not the one to give me advice on doing this with microphones that cost under $1000.

I would greatly appreciate any advice.

Thanks,

David

Hi David,
Can I hear a sample of your audio? When you say high hiss I do not know what you are relating/comparing it to. So after listening to a sample I might understand how loud your hiss is and if it is normal. Also what is the distance of your mics from the audio source? What is your setting on your MT (bits/kHz)? I'm curious.

Thanks
Simon

[dfroom]

Sorry, I should have said - I was recording first at 44.1,16 bit, to make quick and easy transfer to CD.

I didn't save a sample of the recording.  I'll try to make a recording again, and this time save something to share.  I'll try 44.1, 16 and 24 bit.  (While I think I can hear the difference between 16 and 24 bit, I really can't hear any differences between 44.1 and 48 -- and since 44.1 is CD standard, I usually go with that).

The microphone was set where we normally set it for these concerts.  It was 15 feet or so from the performing area (a moderately resonant space), and about 9 feet off the floor.  It makes a decent recording there with the MBox.

David Froom

[guysonic]

While you might have a defective Microtrack deck that's noisy, more likely the noise is from using the Microtrack's Phantom Power.  Suggest trying using the mic's internal battery supply, and turning OFF Microtrack Phantom Power.

[dfroom]

OK, I tried battery power for the AT 825 microphone.  Made two very small recordings, one with the battery, one with phantom power from the Microtrack.  No difference.  So it isn't phantom power that is making the loud hiss.

In fact, I think it is the low level from the microphone.  In order to get any signal at all, I have to put the LMH switch on H and turn the input all the way up.  I still get very low levels, but at least I get something.  To compare,  I tried making a recording from the M-Audio supplied T microphone.  Instead of the levels all the way up, I had to turn them down to about half or less. 

Even though I got a lot more signal from the T microphone, when I compared playing back at similar volume levels, the noise is the same -- though the T microphone has so much signal that I to turn it up much too loud to here the signal.

So I suspect that the problem is not noise, but noise to signal ratio.

Once again, I am plugging an AT825 microphone into XLR-TRS adapters from Sound Professionals, and then into the 1/4" inputs of the Microtrack.

I am recording at 44.1/24.

The 27db boost is off.

If it isn't phantom power, and it isn't the microphone itself (which works fine plugged into other recorders), it is

the XLR to TRS adapter that is not letting all the signal through
OR
the 1/4" input itself is bad
OR
the microphone preamps aren't any good
OR
this microphone just is a bad match for the Microtrack.

Any suggestions?

David Froom

[scoper]

I am also concerned about this - I haven't tested in all configurations, but I do record a lot of acoustic shows - both amplified (such as a club concert) and not (such as an orchestral concert). If it is the MT preamp itself that is adding the noise, that's a real problem. I have not tried using an external preamp and going line-in, which presumably should lower the noise.

One of the reasons I got the MT in the first place was to reduce the gear I have to carry - if I'm down to mics>battery box>MT or mics>phantom adapter>MT, I'm happy. The one show I've taped so far was pretty loud, and I was very pleased with the result, even during the between-songs quiet periods.

If it is the MT preamp, is this something that can be fixed with firmware?

Scott

[guysonic]

OK, I tried battery power for the AT 825 microphone.  Made two very small recordings, one with the battery, one with phantom power from the Microtrack.  No difference.  So it isn't phantom power that is making the loud hiss.

In fact, I think it is the low level from the microphone.  In order to get any signal at all, I have to put the LMH switch on H and turn the input all the way up.  I still get very low levels, but at least I get something.  To compare,  I tried making a recording from the M-Audio supplied T microphone.  Instead of the levels all the way up, I had to turn them down to about half or less. 

Even though I got a lot more signal from the T microphone, when I compared playing back at similar volume levels, the noise is the same -- though the T microphone has so much signal that I to turn it up much too loud to here the signal.

So I suspect that the problem is not noise, but noise to signal ratio.

Once again, I am plugging an AT825 microphone into XLR-TRS adapters from Sound Professionals, and then into the 1/4" inputs of the Microtrack.

I am recording at 44.1/24.

The 27db boost is off.

If it isn't phantom power, and it isn't the microphone itself (which works fine plugged into other recorders), it is

the XLR to TRS adapter that is not letting all the signal through
OR
the 1/4" input itself is bad
OR
the microphone preamps aren't any good
OR
this microphone just is a bad match for the Microtrack.

Any suggestions?

David Froom

When doing bench noise tests on the TRS inputs, I did notice that the Signal-to-Noise is way better with the +27 dB boost ON!!!

Suggest turning on the +27 dB boost and trying again, but if still very noisy, maybe your Microtrack is defective to having excessive noise not usual in most the shipped units?

[dfroom]

I did in my first tests try the 27db boost.  The signal to noise seemed worse -- certainly at least as bad.  I had the impression that the 27db boost brought up everything -- signal and noise.

David

[guysonic]

I did in my first tests try the 27db boost.  The signal to noise seemed worse -- certainly at least as bad.  I had the impression that the 27db boost brought up everything -- signal and noise.

David

I agree with your logic about the boost, but this is really not the case in practice with measurements.  The +27 dB boost actually has LOWER noise for equivalent gain as compared to when the +27 dB boost is off.   Maybe this is because the noisy (1st or 2'd?) stage operating without the boost is gain-lowered when the stage that applies the boost (which is maybe lower noise) is raised? 

Pasted is the screenshot graph I generated (input loaded with 1K ohms) showing the the gain with +10 db more gain with +27 dB boost in "L" (yellow) applied is actually LOWER than the "H" (violet) setting with boost off.  The Yellow trace is with +10 dB more gain, but is showing lower noise than the non-boosted "H" gain operating AT 10 DB LOWER INPUT GAIN.  This is what I was refering to as the +27 dB boosted gain is operating at lower noise, at least with the units I have tested so far.

[dfroom]

So are you saying that recording with the level set on "L" and the 27db boost on, you get quieter noise and higher signal than with the level set on "H" and the 27db boost off?

I'll try this.  The 27db boost recording I tried was with the level switch on H.  Even here, the signal was not very high.  To get a signal with the AT825 that approached the level of the AT825 into an MBox, I had the level on H, the input sliders all the way up, and the 27db boost on.  It still wasn't as loud as it should be, but the hiss was really and obvioulsy loud.

Something is preventing adequate signal getting from these microphones to the Microtrack.

David

[guysonic]

So are you saying that recording with the level set on "L" and the 27db boost on, you get quieter noise and higher signal than with the level set on "H" and the 27db boost off?

I'll try this.  The 27db boost recording I tried was with the level switch on H.  Even here, the signal was not very high.  To get a signal with the AT825 that approached the level of the AT825 into an MBox, I had the level on H, the input sliders all the way up, and the 27db boost on.  It still wasn't as loud as it should be, but the hiss was really and obvioulsy loud.

Something is preventing adequate signal getting from these microphones to the Microtrack.

David

Have you updated the firmware to at least ver. 1.2.3?  Sounds to me like you have the original 1.03 firmware that these are shipped with, and with the L-M-H gain switches reversed?  This is where H is really "L" position.

[dfroom]

No, I have the latest firmware.  And the LMH switch works just fine. 

In fact, with input set to 1/4",  the slider levels turned all the way up and nothing plugged in, when I hit record I can hear the background noise jump up in stages from L to M to H.  Does that happen with your Microtrack?

i am certain now that the problem is lack of signal from the microphone (AT825), even though this microphone provides more than adequate signal to other recorders.  Maybe the Microtrack pre-amps are inadequate?  In any casae, when I record myself playing a piano with the AT825 five feet away, with the signal turned all the way up and the slider on H, when I put the recording in an editing program, I see my peak volumes are between 20 and 25, with 100 at the place where clipping begins.    So with my maximum recorded level so low, no wonder I hear so much noise.

It makes no difference if I use the AT825 with a battery or with Microtrack's phantom power. 

Any ideas?  Does anyone else have this problem?  Or do you folks use external pre-amps?  Or is it possible that I have a bum unit?

I'm going to try some different microphones when I get the chance, and also some spdif recording.

Thanks,
David

[dfroom]

I tried recording with the Microtrack, using the TRS inputs and spdif inputs, taking a line level from a computer playing CD quality music.

No problems.

I still can't figure out why I get such a low level using the AT825 microphone.  I know the mike works.  I know it isn't phantom power.  I know my xlr to trs adapters are fine. 

Has anyone used this microphone with the Microtrack's microphone preamps and gotten a decent signal?  Has anyone had any trouble getting adequate signal from a microphone through the TRS inputs and the Microtrack preamps?

Thanks,
David

[guysonic]

I still can't figure out why I get such a low level using the AT825 microphone.  I know the mike works.  I know it isn't phantom power.  I know my xlr to trs adapters are fine. 

Has anyone used this microphone with the Microtrack's microphone preamps and gotten a decent signal?  Has anyone had any trouble getting adequate signal from a microphone through the TRS inputs and the Microtrack preamps?

Thanks,
David

Check the actual wiring of your XLR-to-TRS adapter, it seems the ONLY thing that could cause such a low output if + output is being shorted to ground, or - minus side of the balanced mic outputs is NOT connected. 

The mic has 200 ohms output spec, so the deck is NOT loading the mic, and the AT825 mic sensitivity is more than adequate to produce a level where +27 dB boost at "L" setting should provide acoustic piano recording to full satisfaction.

[scoper]

My testing:

AT853 > 3 Wire BB > attenuator cable > 1/8" to dual TRS > MT 24/48, Kingston Elite 4GB CF card.

Set to full attenuation (no signal)

Here are the Average RMS settings from Adobe Audition for the resulting noise on each setting:

Line in, no gain: -97.87 dB
Line In, half gain:  -93.38 dB

Mic "M", no gain:  -91.47 dB
Mic "M", half gain: -85.95 dB

Mic "H", no gain: -83.8 dB
Mic "H", half gain: -77.46 dB

I assume the higher the gain within each preset, the louder the noise level. I did not attempt the +27db settings, as my understanding is that this is digital gain which would increase both signal and noise. I also did not try the 1/8" inputs. Maybe another time.

Setting "M" looks to be ok - I'm not sure I'd want to try "H" at a quiet show.

I assume that a preamp added to the chain PRIOR to the MT would help a great deal... adding signal level but no (or little noise).

My purely non-technical, non-scientific results. I have not tried the MT at an actual quiet show - may be a week or two until I can get to one.

YMMV, of course.

Scott