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Please dont beat me for this question

Discussion in 'Recording' started by EricWatkins, Feb 24, 2009.

  1. EricWatkins

    EricWatkins Active Member

    Ok, I'm just going to show my stupidity here. I have an AT-4047, an SM7B, and an LA-610. I have been trying to get a good recording of my buddy that is doing a straightup acoustic guitar and vocal thing. The guitars come out pretty good with two AT-2020s in stereo and a direct line into the console also.

    The first time I tried to record him, I used the AT-4047 into the LA-610 and then that goes line out into a mic/line transormer and then into the board (Tascam DM-4800). Everytime he got good and loud on the mic, the signal sounded kind of brittle and a little fuzzy. I just realized today that the LA-610 was set to mic/500 ohms as opposed to mic/2000 ohms. Could this be what was making this happen. The SM7B is rated at 150 ohms and the AT-4047 at 250 ohms. I feel like such a bonehead because I shouldnt be able to miss with these mics but I am shamefully having a hard time getting a good vocal. They all sound a bit overdriven. Opinion? Rotten tomatoes? Remy helped me understand a LOT about the LA but I am pretty thick skulled and I didnt realize I had this set like that at the time. Thanks in advance for any help.

    Eric
     
  2. Davedog

    Davedog Distinguished Member

    It sounds more like your gain-staging is incorrect. I personally love the sound differentiations when I use the variable input impedances on a device. It does not sound like the impedance is the problem in that you do not have to match them necessarily to get a clean sound.
     
  3. EricWatkins

    EricWatkins Active Member

    Man, this is just kicking my butt then. I go mic - LA-610 - DM-4800 line input through one of those mic to line plug type transformers. I watch the input meters on the screen of the DM and I'm letting it peak somewhere between -6 and -12. The funny thing about the LA's meter is that it goes from nothing to pegged really easy, depending on the performance. I had the "Gain" at +5 and the level at about 7, no eq boost and then the compressor at like 5 and set to limit with a decent amount of makeup gain. Of course the numbers on the compressor are arbitrary. Maybe I need to back up the preamp output some more. However, when I do, even though the DM is showing signal and I can hear it, the LA isnt showing anything on the output of the pre when it's low. I feel like a serous idiot about this by the way.
     
  4. EricWatkins

    EricWatkins Active Member

    Dave, I'd love to send you an example if I can email one to you. SIncew it's not my material, I dont want to post it publicly.
     
  5. EricWatkins

    EricWatkins Active Member

    Well, I've got a friend coming over tonight to out the LA-610 through some more paces. I am going to try to set the input to 2k impedance. The manual says that the impedance of the pre should be 10 times that of the mic. I'm also going to try to engage the 15db pad on the input. Hopefully some combination thereof will render better results. I'll follow up.
     
  6. Link555

    Link555 Well-Known Member

    sound like your input signal is too large?

    A pad might be a good idea.
     
  7. moonbaby

    moonbaby Mmmmmm Well-Known Member

    When you say"mic-to-line transformers", is this a simple cable adapter or is there an impedance transformer involved in this? This shouldn't be in the circuit, and will cause mismatching of levels and distortion. You do NOT take the line level output of a mic pre and feed it through a transformer designed to switch a mic from Lo-Z to Hi-Z. Unless you want mass-distortion artifacts...
    I used to have a couple of Tascam DM24's. Doesn't your DM4800 have insert points on the channels? That is where I'd return the LA to the Tascam, through the insert return (if possible). This will prevent you from running the preamplified mic through yet another preamp (in the DM). Running a preamp into what is typically labeled as a line input can be iffy, because many mixers simply attenuate the signal and route it through the mic pre circuitry. Try the insert point as a line input. Capiche?
     
  8. TheJackAttack

    TheJackAttack Distinguished Member

    Why aren't you going XLR all the way into the Tascam? It seems pretty silly to me to use some conversion adapter that's unnecessary. Turn down the line level of the LA610 and/or the gain on the compressor. In fact I would start without the compressor all together and see if that isn't a contributing factor. At some stage you are too hot so start at the beginning and work your way through.
     
  9. Davedog

    Davedog Distinguished Member

    Dont the XLR's on the DM-4800 switch between mic/line? If so you shouldnt be anywhere except into this with just a cable and the channel switched to LINE.

    Then adjust accordingly.

    If there is a separate line input then you dont need a transformer of any kind. Like Moon said. This presents a lot of mismatching impedance-wise and will create exactly what you are describing.
     
  10. EricWatkins

    EricWatkins Active Member

    There is a mic input and a line input on each channel. The mic inputs are balanced XLR and the line inputs are Balanced 1/4". They are selectable via a switch per channel. So no, there arent any XLR line inputs. There are unbalanced inserts though. You know, I dont see anything on that XLR to 1/4" that says it's a transformer. I'm sure that's what I asked for when I bought it but now I'm not sure because it has been so long. Any suggestions on what I could try tonight to make some headway. I have a radial passive DI. Couldnt I run through that backwards to get the 1/4" to the right level? It does seem like I'm jumping through hoops a bit here. Thanks for all the help thus far.
     
  11. TheJackAttack

    TheJackAttack Distinguished Member

    If you need to diagnose then run it right into the XLR input, engage the 10db pad and start getting your gain structure set up. I'm pretty sure the TRS Line In of the DM4800 runs through the same preamp anyway-also padded. That's how the Tascam I used back in the 90's worked.

    You will be doing lots of monkeying if you try to jack rig an adapter to get into the ring of the Insert. It can be done but should be thought out.
     
  12. EricWatkins

    EricWatkins Active Member

    Thanks Jack. To show my stupidity even further, I know that one wouldnt usually go preamp to another preamp but that is what you are saying now. But I'm wondering, if I go line level from the LA to the mic pre input on the Tascam, is it really just a matter of taming the signal down with the pad and trim pot so as to not overdrive the pres on the Tascam?
     
  13. TheJackAttack

    TheJackAttack Distinguished Member

    This is essentially it. If your converter is a simple XLR male to TRS converter you could just go straight into the <Line In> after you verify the signal path is ok via pure XLR routing. Ideal is for a perfect world.

    Remember that the best trouble shooters start at the beginning and make the chain as simple as possible. Verify. Change 1 thing and verify again. It is all just wire regardless of the labels and boils down to gozintas and gozoutas.

    The problems arise when you mismatch connections or gain stages. To prevent problems, I used to make my own cables in pairs and had all kinds of conversions-xlr to trs; xlr to ts; xlr to rca; trs to ts; tt to whatever. You get the idea.

    If you want maddening I'll relate a story of a live gig at San Diego bay where some kid stuck a pin in the snake going out to FOH (a beautiful Crest board pre-Peavey). During the gig. We found the problem but I was sweating pretty good.
     
  14. Davedog

    Davedog Distinguished Member

    The line ins will not be part of the mic pres. Use that. If you already are and there is nothing else in the path.....(where did you say something about a transformer???) then its all about your gain-staging.
     
  15. Cucco

    Cucco Distinguished Member

    Just FYI -
    I just looked over the block diagram for the DM4800. The line inputs do indeed go through the same preamplifier stage as the mic pre, regardless of the switch setting. Therefore, it shouldn't make any difference whether you're coming in via XLR or TRS.

    That being said, the only way to bypass this is to come in unbalanced through the insert. John's right - dorking around with this can be a pain (but it's done all the time).

    The problem definitely sounds like a gain staging issue to me. Is there any chance you have a spare headphone amp lying around? If so, take the output directly from the pre into the HP amp and listen for that distortion. If you don't have the HP amp, but have a cheap ol' mackie or similar mixer, feed it into one of the line (only line, not mic/line) inputs and listen there too.

    If you're not hearing the distortion, then there's your answer.

    The other thing - your settings on the 610 sound a little odd.

    It sounds like you're driving the input of the compressor pretty hard then squashing it and then trying to make the gain back up again. For both voice and guitar, gentle compression should be all that's needed.

    Try backing the compression off, get rid of the limiter switch (I would very rarely consider using a opto limiter for guitar and only a little more commonly for voice). In fact, try bypassing it all together and then bringing it back in gently. If it works while bypassed but occassionally clips, work the gain until there's no more clipping. Then, and only then, re-engage the compressor at more moderate settings.

    With my limited experience with the 610, I've found that vocals work fine with the pre gain at 0 and the level knob in the upper portion of the range (or gain at +5 with the level further down) and compression (Peak reduction) between 2 and 4 and the gain to where the signal sits right in the mix.

    For guitar (acoustic) - for an average, larger body instrument, the settings aren't too off from the voice with maybe a hint more compression.

    Keep us posted...but for now...after a 3 hour rehearsal of the Planets...I'm tired and going to bed.

    Cheers-
    J.
     
  16. Davedog

    Davedog Distinguished Member

    Now why the hell would they do that? What part of the difference between MIC and LINE do they not get?????

    So as I understand it, theres no way around the mic pres except the inserts???

    That would suck in my world.
     
  17. EricWatkins

    EricWatkins Active Member

    Ok guys. Thanks so much for all your help thus far. I brought in another singer ( a friend) just to try to help me with this problem. I set the impedance to 2k and removed the line out of the LA to the insert and also trimmed back my levels a bit. It sounded really detailed and sweet. I think I got it. My only problem is that this singer is not as hot as the other but I still think I have it now. Maybe it was overdriving the mic pre even through the line input. Cant wait to try it with the singer I was having problems with. Thanks again.

    Eric
     
  18. TheJackAttack

    TheJackAttack Distinguished Member

    I used to have to use a couple of Tascam "studio" boards back in the day and they were all like that.

    Lots of times if I had something critical to record I would rent a board or use my Crest monitor board. I sort of developed a distaste for Tascam that lingers. I was quite pleased when the studio went digital and went PT.....three months before I got out of the Corps.
     
  19. BobRogers

    BobRogers Well-Known Member

    Good. sounds like you are on the right track.

    On the question of your "transformer" (I'm thinking the better word is "adapter.") If it is just XLRF to TRSM my guess is that it is simply an adapter. If it's in good working order, plugging and XLR cord into it simple converts the type of balanced connector. This should not have contributed to to the problem.

    There are some plugs that are designed to match impedance - basically a DI box. These are typically XLRF (balanced) to TS(M) (unbalanced). And the ones I've seen have the input/output impedance marked on the side. If this is what you have it could have been a problem. Again, go into the XLR input.

    I have tons of adapters of all kinds from years of running live sound, but in the studio I try to buy or make the correct cables and keep them out of the signal path. Just one more thing to go wrong.
     
  20. Cucco

    Cucco Distinguished Member

    Don't get hung up on the impedance - 500 ohms will work fine -actually it should work quite well.
     

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