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Mic - Preamp - Compressor - Audio Interface (Low Input Signal vs High Hiss Noise)

Discussion in 'Preamps / Channel Strips' started by mactreouser, Apr 1, 2014.

  1. mactreouser

    mactreouser Active Member

    All the while, I recorded my vocal & instruments like guitar directly from the Mics (condenser & dynamic) to the Audio Interface.
    And, recently, grabbed a preamp + compressor for recording. Sound is good! In fact, facing an issue ~ Low Input Signal BUT High Hiss Noise Level!!! This makes me spent a big times to tweak the Denoiser + Expander + Noise Gate to reduced the Hiss Noise. Indeed, quality/colour of the recorded audio like guitar, cello... not as sweet & pretty like the source anymore after the tweaked!

    My setting was :
    Mic to Preamp to Compressor to Interface (am I wrong?)

    Mic directly recorded from the audio interface (previously) given High Input Signal and Hiss Noise was acceptable.
    But now, thru the preamp + compressor (I though it supposed producing Higher Input Signal) Input Signal was low. When turns up the Gain Level from the interface, Hiss Noise is turning up too.

    Hope to hear from your precious suggestion and advices! Your replies are appreciated!
    Thanks in advanced! wink.gif
  2. Boswell

    Boswell Moderator Distinguished Member

    Welcome to RO!

    This sounds like a problem with what is called gain staging. Put simply, it means adjusting the input and output levels so that a signal passes through without distortion but also with minimal increase in background noise.

    Please tell us the make and model numbers of the preamp, compressor and audio interface you are using, and list exactly the inputs and outputs of each that the signal route takes. It would also help to know what the level controls were set to on the preamp and compressor.
  3. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    I see in his member information that he uses Zoom R24, Presonus Firepod, GT55, Neumann m147 But, doesn't say which preamp and compressor.
    Boswell, with a tube mic like the GT55 could it be that the fantom power of certain preamps is not strong enough ?

    I guess we'll get a better Idea when knowing what's the make and models... ;)
  4. mactreouser

    mactreouser Active Member

    Appreciate ,Boswell !!

    Behringer Ultragain Pro MIC2200
    Behringer Composer Pro MDX2200
    Presonus Firepod
    Zoom R24

    Thanks for help!
  5. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    I guess it may be a wiring or impedance matching problem. You need to match the inputs and outputs to the same nominal level. Check the switches of +4 or -12db behind the Behringer Composer Pro MDX2200.
  6. Boswell

    Boswell Moderator Distinguished Member

    Thanks for the equipment list, but how did you have them interconnected? Do you get excessive noise if you don't go via the MIC2200 and MDX2200 but plug the microphone directly into the Firepod? Both those other pieces of gear unfortunately are well-known for having high internal noise levels.

    @pcrecord: the GT55, in common with most tube mics, has its own power supply and therefore does not need phantom power.
  7. mactreouser

    mactreouser Active Member

    I was using TRS cables for the output, and seemed the switches of +4 or -12db doesn't matter to it?!

    Mic to Preamp to Compressor to Interface, this was the chain.

    Many thanks to your kind suggestion and advices!
  8. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    Ah !! Yes Boswell, I new there was something to them.. (I don't own a tube mic myself)

    Mactreouser : the problem you describ is often due to a unit that is sending a faint signal and the next on the chain need to boost it too much.
    So I read in the MIC2200 manual the outputs trs and xlr are wired in parallel together. Make sure the balance between the gain and output level is ok. A lot gain and Hi output or a hi gain and low output can result of more noises.
    Then in the manual of the mdx2200 it is said nowhere that the TRS are not affected buy the level switch


    Connectors XLR and 1/4" jack
    Type RF filtered, servo-balanced input
    Impedance 50 kOhm balanced, 25 kOhm unbalanced
    Nominal operating level +4 dBu/-10 dBV switchable
    Max. input level +21 dBu balanced and unbalanced
    CMRR typ. 40 dB, >55 dB @ 1 kHz

    So with the switch you change the input value and not the output. If it has no effect for you, you may have used the sidechain input instead of the input called (INPUTS) xlr or trs.
  9. mactreouser

    mactreouser Active Member

    Wow...Really appreciate!!! :D

    Thanks for clarified it!

    1. I'll try it over again on +4 & -10 soon.
    2. Can I have some idea about how to use the sidechain? I would love to do a test drive.
    3. C'ld you please share your own experience about how you adjust the right Input and Out level from the Preamp to get the good input level and lowest hiss noise?

    Appreciate again! ;)
  10. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    Mic2200 : First thing, make sure you adjust the mic/line switch to mic and add the 48v only if your mic needs it. deactivate the EQ to start. Sadly, this unit don't have a gain and output seperate meter so you have to guess. start with the output to 0db, put up the gain so the output level peak at -6db
    MDX2200 : start with the gate to off and peak limiter to off. Put the output to 0db and put the attack/release to auto. Start with the ratio of 2:1 and the thresold to 0db and while making the source play, lower the thresold until you have a gain reduction of 2-4db. Check the results. Now that your gain stage is nearly standard.. play with the other options to meet your taste !!
  11. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    Side chain is used to input a second signal into the compressor that will be use to influence the compressor behavior independently of the source who's been compress. Exemple : you could send a guitar to the compressor and a vocal to the sidechain. When the thresold is reached by the vocal, the guitar will be compressed. Hope it is clear enough. More info about sidechain in the manual ;)

    Edit : if you send the vocal to the side chain it won't be heard in the output of the compressor, it only serve as a reference for how the compressor will behave on the guitar signal.
  12. mactreouser

    mactreouser Active Member

    I'm sorry for my Big + Huge Mistake during the previous recording ~ DID NOT Switch to the MIC (mic/line)!!! :cry: Why I met this big mistake? That's because the indicator diagram showed as "Mic to Release the button", that was what I think of during sound check! So, It supposed Button In for Mic!!!
    Today, I check sort this out and pretty nice result I got, finally! Thank you for your precious efforts.

    This is interesting...but i'm not so sure how this works?!! Btw, do we need this setup?
  13. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    You don't need it. It's an extra feature. What happen is that a compressor monitors the level of the signal you send in the input and if that level is higher than the thresold, the compressor will lower the output level accordingly to the ratio, attack and release. So if we keep our exemple of a guitar in the input of the compressor without side chain ; if you play the guitar at a level that pass the thresold, the output level will be lowered. Now if you add a vocal as a side chain signal. The compresor won't analyse the guitar input anymore, it will react to the level of the vocal. if you sing louder and pass the thresold, the guitar will be lowered. This technic is use for many purpose; if you want to make sure a certain signal will always be louder than an other for exemple...

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