Author Topic: Confusion about guitar level signals to Line inputs  (Read 444 times)

Esppse

Confusion about guitar level signals to Line inputs
« on: May 24, 2022, 01:37:50 AM »
Hi,

I have a hexaphonic guitar pickup (Roland), I am trying to break out the 6 separate signals to go into Dante AVIO Inputs (XLR Line Inputs). I was researching for a DI box, a 12:1 transformer is used to bring a guitar signal to Mic level for a preamp, but what if there is no mic preamp, and I need to go straight to line level(anything my daw can see and use with Line 6 HX Native).

Do i use a 1:1 for a higher signal? Or would reversing the transformer to 1:12 work when not using a mic preamp?

GibsonGM

Re: Confusion about guitar level signals to Line inputs
« Reply #1 on: May 24, 2022, 04:43:59 AM »
I think you need a multi-channel unbalanced to balanced converter.  I did a quick check; depending on where you are, you could find one for < $100US as a DIY, or pay more for a built unit.   There are any number of DIY solutions (DI box > DIY preamp...) if you want to be creative.

What is your interface? It has no mic preamp??


Something like this, but if you need SIX in/out, it will be pricier...  https://www.sweetwater.com/store/detail/CleanBoxPro--art-cleanboxpro-2-channel-balanced-unbalanced-level-converter

HTH!
MXR Dist +, TS9/808, Easyvibe, Big Muff Pi, Blues Breaker, Guv'nor.  MOSFace, MOS Boost,  BJT boosts - LPB-2, buffers, Phuncgnosis, FF, Orange Sunshine & others, Bazz Fuss, Tonemender, Little Gem, Orange Squeezer, Ruby Tuby, filters, octaves, trems...

Esppse

Re: Confusion about guitar level signals to Line inputs
« Reply #2 on: May 24, 2022, 05:02:19 AM »
I think you need a multi-channel unbalanced to balanced converter.  I did a quick check; depending on where you are, you could find one for < $100US as a DIY, or pay more for a built unit.   There are any number of DIY solutions (DI box > DIY preamp...) if you want to be creative.

What is your interface? It has no mic preamp??


Something like this, but if you need SIX in/out, it will be pricier...  https://www.sweetwater.com/store/detail/CleanBoxPro--art-cleanboxpro-2-channel-balanced-unbalanced-level-converter

HTH!

My interface is 3 of these:
https://www.audinate.com/products/dante-enabled/audinate/audinate-dante-avio-2-channel-analog-input

I require Dante connectivity, which is why it has been a little challenging finding an affordable solution. Is there a way to do this passively? I was hoping to just convert unbalanced to balanced using a transformer on each string.

Esppse

Re: Confusion about guitar level signals to Line inputs
« Reply #3 on: May 24, 2022, 10:13:07 PM »
Would a passive DI transformer somehow step up the signal?

GibsonGM

Re: Confusion about guitar level signals to Line inputs
« Reply #4 on: May 25, 2022, 06:50:49 AM »
That's a little bit out of my expertise, but since there are no active devices with a simple transformer you're going to have a loss, there is resistance etc. involved.
This says as much  https://www.soundonsound.com/sound-advice/q-does-di-box-raise-signal-level

When I looked around yesterday about this, a couple of sites suggested if one is doing this, that they'd also need some kind of preamp after the impedance transformation...I'm thinking, "why can't this be done entirely with a preamp?".    Another search finds this:  https://www.radioworld.com/tech-and-gear/tech-tips/build-an-unbalanced-to-balanced-adaptor
So the orig. question, raising inst. level to line level, isn't too bad.

In this day & age, there HAS to be something you can buy to do the job quick & easy, but if you like to build, I'm SURE this can be done.  I'm not familiar with the Dante tech, so I can't give you a "yes" or "no" on whether a 6-channel preamp is the best way to go, or if there's an inexpensive ready made solution, sorry...
MXR Dist +, TS9/808, Easyvibe, Big Muff Pi, Blues Breaker, Guv'nor.  MOSFace, MOS Boost,  BJT boosts - LPB-2, buffers, Phuncgnosis, FF, Orange Sunshine & others, Bazz Fuss, Tonemender, Little Gem, Orange Squeezer, Ruby Tuby, filters, octaves, trems...

PRR

Re: Confusion about guitar level signals to Line inputs
« Reply #5 on: May 25, 2022, 12:10:39 PM »
For each input: a unity-gain buffer. Turn the AVIO all the way up.
  • SUPPORTER

Processaurus

Re: Confusion about guitar level signals to Line inputs
« Reply #6 on: May 26, 2022, 01:20:04 PM »
For each input: a unity-gain buffer. Turn the AVIO all the way up.

Agree, use a 6 channel high impedance (1M+) buffer for the 6 pickup coils. Suggest a FET input opamp such as TL07x series. Or if you want a little character I like the sound of the discrete GGG JFET buffer, I built a 6 channel thing for a friend to interface a divided (piezo based) pickup with a mixer.

The reason you want a buffer is the 6 magnetic pickup coils need a higher input impedance than a regular mixer/audio interface (~10K). Pedal land and guitar amps are in the 1M input impedance range. If the impedance is too low, the sound gets dark and muffled. The same problem will happen feeding a passive guitar or bass directly into a regular di box, or transformer- the impedance is too low and the tone gets worse.

If you’re in the same room as the interface, you don’t need to balance the signal with transformers etc. The magic of DI’s is for isolating ground loops and going through 100’ snakes without adding noise. When you’re close to all of the stuff you can keep it all unbalanced.

Go in the 1/4” line inputs on your interface and use the gain there. If you don’t have 1/4” inputs you could get a little hosa 8 channel TRS to XLR snake to be the adapter.

It is easy to make a pseudo balanced TRS or XLR output to the hex pickup buffer/preamp, you could do the very economical “pseudo balanced” or “impedance balanced” output, like here:
https://www.epanorama.net/blog/2010/02/23/unbalanced-to-impedance-balanced/
You try to match the output impedance of the opamp driving the “hot” (Tip/xlr pin 2) with a resistor to ground on the “cold” (sleeve/ xlr pin 3). If using TL07x opamp PRR pointed out they have an internal resistor in series w the output, so no series resistor needed on the opamp out, and the RS on the “cold” side to ground would be  150-200 ohm. Note there is no output cap shown on the schematic, which you need if running off our single supply 9v.

If you forego the pseudo balanced out (6 resistors) but may use a trs to xlr converter, you must use stereo/trs jacks and connect the sleeve to ground, otherwise it will float and add noise on the interface end. Might as well add the RS resistors, and get correct noise rejection.

Processaurus

Re: Confusion about guitar level signals to Line inputs
« Reply #7 on: May 26, 2022, 01:26:26 PM »
Realized all of this assumes there is no preamp for the Roland hex pickup in the guitar. If there is, you just need a box to breakout the individual hex signals and get them into your interface, you don’t have to preamp them twice.