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Synth to DI or Ebtech to Mic preamp on mixer
Old 19th January 2020
  #1
Gear Nut
 

Synth to DI or Ebtech to Mic preamp on mixer

I need to boost the line level outs of my synth (Roland D-50) to get it to a usable level for recording on the 1/4" Line In jacks on my Juno-Gi (just plugging directly and cranking all the gains and levels remains incredibly weak).

So, I'm going to connect the D-50 to either a couple DI boxes or an Ebtech Line Level shifter and from there to the XLR mic preamps on my mixer. My understanding is that is this scenario both the DI box and the Ebtech will do exactly the same thing. I just want to confirm that both are producing the correct impedance and signal expected by the preamp.

If I use the Ebtech then I would plug the D-50 into the +4dB IN on the Ebtech, then run the -10dB OUT to the mixer with a 1/4"-to-XLR cable. I'm assuming that it doesn't matter whether anything is balanced or unbalanced because this is just short runs for home recording. So if I use a TS 1/4"-to-XLR this should be fine I suppose.

The advantage of the Ebtech is that you only need one of them, because it has 1/4" stereo ins and outs.
Old 20th January 2020
  #2
Gear Nut
 

Sorry, I guess I didn't make it clear in my post: I'd like to know if what I described makes sense?
Old 20th January 2020
  #3
Lives for gear
 

What you're suggesting for the level shifter makes little sense. Better (assuming it shifts levels in both directions, as many do) would be to connect the synth to the -10 inputs and the +4 outputs to the mixer line ins. Dual DI boxes should be fine as you describe.

Two quick thoughts to try first, though. One, are you currently using balanced (TRS) cables? If so, try unbalanced TS cables instead. Connecting an unbalanced output to a balanced input with TRS cables very often does not work well as the ring is merely floating, leading to interference, noise, low levels, etc.

Two, failing that, have you tried connecting the synth directly to the mic inputs on the mixer (with the input trim turned down)? You may find that works out just fine. Avoid having phantom power enabled on the mixer for those channels.
Old 22nd January 2020
  #4
Gear Nut
 

I have tried plugging both TS and TRS cables directly from the D-50 to the Juno-Gi, but it made no difference as far as levels were concenred. Same with the Line Level shifter if I stick it in between it makes no difference to levels, regardless of whether I plug the D-50 into the -10db or into the +4dB.

lf I go straight from the D-50 into the XLR MIC preamp on my mixer, as you mentioned, then the levels are strong, but actually seem too strong because I have to turn down the volume on my monitor. Although oddly the meter on the mixer doesn't seem to register it as being strong. I don't know what's up with that.

Well, anyway... the reason I wanted to use the Line Level Shifter or the DI boxes to condition this supposedly strong level down to what the preamp expects. I haven't actually tried this yet.
Old 22nd January 2020
  #5
Gear Nut
 

So doing a little more reading and a little more experimenting. Apparently the most important thing when connecting devices is to make sure the receiving end has a much higher impedance than the sender. Crucial thing: if the receiving end has a lower impedance you will get a weak, thin sound.
But synth manufacturers don't seem to publish impedances of their 1/4" input and output jacks, because I couldn't find any for the D-50 and Juno-Gi.
My little Behringer 502 mixer has what looks to be 2.6kOhm on the mic input.
My little Behringer DI100 DI box has a "Load impedance" of 600Ohm which I guess is the impedance on its XLR balanced out. (???)
The manual for the DI recommends plugging a keyboard into the DI, attenuating this down by pressing the -20dB button, and connecting from the DI into the MIC XLR input on the mixer.
Old 23rd January 2020
  #6
Lives for gear
 

Output impedance of a line level output is probably around a couple hundred ohms, maybe less. Input impedance on line level inputs tends to be several kiloohms or more. Impedance pecs are often not given because they're largely irrelevant for line level connections; the output is pretty much guaranteed to be much lower impedance than the input, making things easy.

For microphones, the impedance of both ends was traditionally 600 ohms. Having the same impedance maximizes the power transfer, which for a dynamic microphone is or at least was a good thing to aim for. Many modern microphone preamps do have a somewhat higher input impedance, but plenty of clean gain for it to work out fine in practice.

For a DI box, things pretty much just work. Plug the synth or whatever into the box, and the box to a mic input. If the signal is too hot, you can turn on the pad in the DI box, but very often even with synths that's not needed. If you have a ground loop and the DI box has a ground lift switch, engage that to get rid of the ground loop. The theory behind it is interesting, but unnecessary to make them work well.
Old 23rd January 2020
  #7
Gear Nut
 

Makes sense. D-50 to DI to Mixer board to Juno-Gi seems to work, so I'll just stick with that.

I don't know why the line out on the D-50 is so weak but I guess we'll never know.
Old 27th January 2020
  #8
Gear Nut
 

So as a follow up, I've got my D-50 plugged into two DI boxes with attenuation button pressed to attenuate them down, and from there into the XLR MIC preamps on my mixer, and from there the Main Line out from the mixer to the Line INs on the Juno-Gi, and it's working fine.
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