1. Register NOW and become part of this fantastic knowledge base forum! This message will go away once you have registered.

Reamping still very noisy! Help!

Discussion in 'Recording' started by danbronson, Feb 14, 2008.

  1. danbronson

    danbronson Guest

    I had this problem before, and thought it was because I was using unbalanced cable. But now I've gone and bought a TRS 1/4" to XLR cable and the noise problem remains.

    Feel free to download this file using the first link, or stream it with the second:

    http://uploadfile2.putfile.com/getfi...4421314213.mp3
    http://media.putfile.com/Reamp-Test

    0:00 (first third) - live performance (no noise)
    0:11 (second third) - reamped performance (tons of noise!)
    0:22 (last third) - the direct guitar signal recorded via DI (no noise)

    My chain is as follows... my guitar is going into the instrument input of the DI, DI goes out to amp (this in/out is parallel to the instrument in), also XLR out (on the other side of the transformer in the DI) to line input on my Presonus Firepod (level at 100%). The amp was recorded into the Firepod with an SM57.

    The first and last thirds of the clip were recorded at the same time. Then I switched the XLR/TRS from the line in to the 'cue mix line out' on the back of the Firepod. This meant while playing back the DI'd guitar, it would feed out to the amp. This is where a ton of noise is introduced. The noise ONLY happens when the cable is plugged into the Firepod (otherwise the amp is silent, except for the usual hiss associated with not having a guitar plugged in). The noise is also there regardless of whether I am PLAYING the DI'd guitar back or not, so the problem is not in the recording part, but in being plugged into the Firepod. I also have an XLR/TS cable and the problem exists when using that too.

    I have tried using different outputs on the Firepod, the cue mix line out works the 'best'.

    Any ideas?
     
  2. moonbaby

    moonbaby Mmmmmm Well-Known Member

    First off, why are you plugging the XLR out of the DI box into the LINE input on the Firepod? DI outs are typically NOT line level, but MIC level.
    You should be using an XLR-to-XLR cable for this, just like any other DI application, live or in the studio. Running the XLR out of the DI box to a 1/4" LINE level input will result in horrendous noise because the MIC level of the DI's XLR output doesn't have enough gain to drive the LINE level on the Firewad. The fact that you're having to crank the gain control on the Presonus to "100%" bears this out. It's also probably why that 3rd clip sounds so BAD, tone-wise.
    Secondly, when you're playing back the recording through the Firepod and using it's line-level output into your guitar amp, you have another gross mismatch in level/impedances. This time, though, it's reversed; you're attempting to run a "hot" line level signal into a very sensitive guitar amp input jack. Another very noisey situation there.
    I vaguely remember your first posting of this and wondering why the XLR-to-1/4" cable was being used (TRS or TS). DI boxes, especially passive ones that use transformers, do not boost the signal level of the input source. An electric guitar's pick-ups have a very weak output level in the first place. Pushing them through a DI box and on to a line-level input designed to "see" a much hotter signal is a sure-fire way to get a lot more noise than you want.
    You need to learn your audio signal levels and impedances and how they all interface together. Until you learn how to properly structure your gain stages, this is what will occur.
     
  3. danbronson

    danbronson Guest

    I don't have any problems with volume levels. I send the signal to a line in because the only outputs I have are line outs. I want to make sure what goes in is equal to what goes out, so that the level hitting the amp is the same whether it's the original performance or the reamped one. I 'have to crank the level to 100%' because 100% is what will come out of the Firepod.

    I'm not running a hot signal into a guitar amp's input jack, it's going back through the DI first to bring it back down to exactly the level I started with.

    I don't have any problems with noise as far as the conversion of any of the recorded audio goes. As you can tell by the third clip, there is no noise added by running the guitar through the DI and into the line input. And of course it sounds bad, that's what guitars sound like before they hit an amp.

    Now, the noise is added when the 1/4" to XLR is connected to the DI, and the DI is connected to the amp. My DAW doesn't have to be playing any guitar back at all for the noise to be there. The volume levels, however, are perfectly fine. It's just that my Firepod seems to be introducing noise, or maybe you're right at this point about the DI not converting things correctly (though converting a balanced line level signal down to an unbalanced instrument level signal doesn't seem like it should be too hard to do to me).

    In any case, it's hard to see past your scatterbrained writing and condescending attitude if you're actually on to something.

    Perhaps I should just ask this. How would you attempt to reamp guitars without getting any noise?
     
  4. Boswell

    Boswell Moderator Distinguished Member

    danbronson, you're not listening to what moonbaby is telling you. You do have level problems, despite what you think.

    When recording, the XLR out of the DI box should go to an XLR mic in on the FirePod using a standard XLR-XLR mic cable. From what you say, your DI box is a passive transformer unit. This is a step-down transformer, giving you a high-impedance input and a low-level balanced signal out. The signal at the XLR is similar to that from a dynamic microphone, so it needs to go into a mic input to get enough noise-free gain in the pre-amp.

    When playing back (re-amping), you have more of a problem. You should be using a device that takes the balanced line-level out of your FirePod and produces an isolated unbalanced signal of very much reduced amplitude to go back into your amp. Devices that do this are sometimes called "re-amp boxes". Some DI boxes are designed to be multi-purpose and can be used for re-amping, but I think yours as it stands is not in that category. It's because you are not using any sort of re-amp box that you are getting the noise problem. Although you say you are connecting back through your DI box, I don't think you have got it connected correctly.

    So what can you do to solve your problem? You could go out an purchase a proper re-amp box, or, if you are careful, you can indeed use your transformer DI box as a re-amp box, but it involves wiring special cables. The technique is to use the step-down property of the DI box to attempt to match your signal levels. For the cable between the FirePod balanced line out and the instrument input of the DI box, you need a cable that has a TRS jack on the FirePod end, but with only the tip and sleeve wired, and not the ring. On the other end, you wire a TS jack as usual. This gives you an unbalanced high-level signal. For the lead from the DI box to the amp, the connections will depend on how your DI box is wired internally. If the XLR out of the DI box is centre-tapped to ground, wire an XLR line socket with pins 2 (signal) and 1 (ground) only to a TS jack tip and sleeve respectively. Do not connect to pin 3. If the XLR out is floating, wire XLR pins 2 and 3 to TS jack tip and sleeve respectively and do not connect to pin 1. You will now have the necessary equipment to re-amp without noise.

    That may all sound a bit technical, but you have a problem that needs either a technical solution or the purchase of a re-amp box. Good luck, and come back if there's anything you're not sure about.
     
  5. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Hey, Dan.
    To answer your question, I use a real re-amp box: the Radial X-Amp, readily available at your local GC. I use it on the line out of a real mixer, either one of my Allen & Heaths, or Tascam DM24's. And when I DI a guitar, it sounds bright and clear, not muffled. That's because I know how to properly use and connect a DI box, some of which I've built myself using components Dean Jensen (RIP) suggested to me many years ago.
    My writing wasn't "scatter-brained", nor did I intend to be condescending.
    It was based on the 35+ years of experience that I've had in this field hooking $*^t up and not blowing it up. I've probably seen ten thousand talentless, scatter-brained players who haven't got a clue as to how to connect and interface their gear properly and then bitch about it. Make that ten thousand and one.
     
  6. danbronson

    danbronson Guest

    Alright, sorry to be a dick. In any case, thanks for clarifying what's going wrong here.

    I suppose I have a lot to learn about impedance and just need to be more aware of what I'm doing to my signal in the future. I had been told using a DI would work fine by a friend who records, but I guess he probably doesn't know what he's talking about.
     

Share This Page