DI with line level output?
Old 28th January 2013
  #1
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Thread Starter
DI with line level output?

Can anyone recommend some affordable DI boxes that have balanced line level output? I just need to balance line level, I don't need to change the level and definitely don't want mic level output. Input will be line level also. +4 on both sides.

I'm trying to send the output from a Vox Tonelab LE through a snake to a backline rack. The snake is only about 30 feet and maybe I will just send unbalanced, but I would prefer balanced. The problem is all the DI's in the $100 range that I can find output mic level and I need line level.

I also need to make sure the ground will not be lifted cause the Tonelab seems to need it for some reason to work properly.
Old 28th January 2013
  #2
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I can't think of one. I've done the experiment, and unless the stage is very noisy, just using a good buffer before the snake will successfully push the signal thru a 30' cable with no loss. If you're exposed to noisy (electrically) stages in badly built bars, then the cheapest solution is two cheap DI boxes-one changes signal to mic level/balanced and at the other end of the snake you have another reversed to change it back to line level. Both have to be passive. Of course, there's a fancy powered version of this from Radial engineering but it's a LOT more than two used DIs.
Old 28th January 2013
  #3
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Thread Starter
Ah so that's what they mean when they talk about using passive DI's "backwards". Got it.

Yea the Radial J+4 looks super nice, but too expensive for my blood, especially since I don't need stereo.

I did find one last night from Whirlwind, the "ISO1" which might do the trick.

You are probably right I should just try a long cable first and see if its ok. I can drive plenty of level through it from the Vox Tonelab, I guess that's what you mean by a "buffer". Seems like all of these DI boxes will take away from the signal too, so one has to ask themselves, what is worse, little noise from 30 feet of cable or signal loss from an extra transformer.
Old 28th January 2013
  #4
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Old 28th January 2013
  #5
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That little device is so close to what I need except for one problem, it's ground lifted
Old 28th January 2013
  #6
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Quote:
Originally Posted by Dewdman42 View Post
That little device is so close to what I need except for one problem, it's ground lifted
Why?
Old 28th January 2013
  #7
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Thread Starter
well my vox tonelab is EXTREMELY sensitive to grounding issues. The Whirlwind ISO1 at least has a switch to enable/disable the ground lift. Ok, but you're right its double the price and size.
Old 28th January 2013
  #8
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Quote:
Originally Posted by Dewdman42 View Post
well my vox tonelab is EXTREMELY sensitive to grounding issues. The Whirlwind ISO1 at least has a switch to enable/disable the ground lift. Ok, but you're right its double the price and size.
If the audio ground is isolated (via the transformer) on the XLR end, ground noise from your tonelab will not pass to the mixer input.
Old 28th January 2013
  #9
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Old 28th January 2013
  #10
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Old 28th January 2013
  #11
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Thread Starter
Quote:
Originally Posted by drbob1 View Post
You'd still need two of the adapters. If you have to go that way, I'd just get:

Rolls DB25B Passive Direct Box with Ground Lift Switch DB25B
They're decent quality and will work for what you want...
Thanks Bob, That's a great reference i will keep that one in mind!

Quote:
Originally Posted by zoff View Post
If the audio ground is isolated (via the transformer) on the XLR end, ground noise from your tonelab will not pass to the mixer input.
isolation transformers only isolate the ground circuits, they don't stop noise from passing through if it has been picked up already into the audio due to either a ground loop or RF interference. Ground lifts can cut ground loops. Putting ground lifts in the wrong place can also cause more RF interference because it turns a dangling ground line into an antenae, more or less. That's why they have ground lift switches so that you can decide in the situation whether to lift the ground or not.

The Vox tonelab is very sensitive to picking up interferences and noise related to grounding, even when its all alone not plugged into any other amps and no ground loops. I actually prefer to have ground connected, not disconnected, so that the tonelab and my guitar will be properly grounded, not having to touch my strings to ground it.


Quote:
Originally Posted by zoff View Post
You really don't need a second (transformer) adaptor on the rack end to unbalance the signal, a simple xlr to 1/4 cable will do.

Check here for wiring info:

Sound System Interconnection
Yes that is handy, but are there any downsides to that method?
Old 28th January 2013
  #12
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Quote:
Originally Posted by Dewdman42 View Post
Yes that is handy, but are there any downsides to that method?
No. I think you are confusing audio ground with chassis/earth ground. Its very unlikely that you will pick up RFI from the xlr cable, so a second ground lift on the rack end is unnecessary YMMV.
Old 29th January 2013
  #13
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Thread Starter
my tonelab does not have any earth ground other than what might come through the audio ground. they are not all connected?
Old 29th January 2013
  #14
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Quote:
Originally Posted by Dewdman42 View Post
my tonelab does not have any earth ground other than what might come through the audio ground. they are not all connected?
They can explain better than I can:
Sound System Interconnection

The point I'm trying to make is that there is very little chance that your are going to pick up RFI on a +4 line level signal via a balanced xlr cable. I really don't see a need for a second ground lift on the rack end of the xlr cable, the signal ground is already lifted at the transformer.
Old 29th January 2013
  #15
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Thread Starter
Yea actually I don't want ground lifts at all.
Old 29th January 2013
  #16
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If you will only be ever going 30 ft and not longer, I'd try just taping a guitar cable to your snake and be done with it. Many of us have 30' of cable between guitar and pedalboard or pedalboard and amp with no ill effects. Would be a lot cheaper as well...
Old 29th January 2013
  #17
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The Vox Tonelab is an electronic device so it's output impedance is inherently (relatively) low, we'll assume 600 ohms and unbalanced at +4 level.

That signal should have NO PROBLEM going 30 feet unbalanced without degradation, transformers and other stuff inline with your snake will cause signal degradation and noise as you pointed out.

I don't know what your snake is but it's just a matter of making adaptors and getting the signal into and out of the snake without polluting your grounds.

Try it unbalanced, it should work fine. Keep your wiring away from the AC power cords that feed other signal devices, induced noise is the worst enemy of longer unbalanced lines.

Good luck and good music to all!
Old 29th January 2013
  #18
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Quote:
Originally Posted by Dewdman42 View Post
Can anyone recommend some affordable DI boxes that have balanced line level output? I just need to balance line level, I don't need to change the level and definitely don't want mic level output. Input will be line level also. +4 on both sides.

I'm trying to send the output from a Vox Tonelab LE through a snake to a backline rack. The snake is only about 30 feet and maybe I will just send unbalanced, but I would prefer balanced. The problem is all the DI's in the $100 range that I can find output mic level and I need line level.

I also need to make sure the ground will not be lifted cause the Tonelab seems to need it for some reason to work properly.
you need a bridging or matching transformer, not a DI! a bridging transformer will change the impedence by around 10:1, so the 200ohm output becomes a 2kOhm output, so probably not ideal. you CAN locate matching transformers and build one into a small box, and this will probably be the most economical option.

Some of the nicer DI's (NOT cheap tho) like my Demeter Tube Direct (VTDB) have a "boost" option that takes the signal pretty much back up to line level... If you want help with schematics and trafo choice, PM me and I'll do what I can to help you out within your budget.
Old 29th January 2013
  #19
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Thread Starter
Thanks foldback, that is what I think I going to try at this point. I also found out last night the receiving device at the other end of the snake is unbalanced inputs (even though its manual states balanced, incorrectly).

Quote:
Originally Posted by foldback View Post
The Vox Tonelab is an electronic device so it's output impedance is inherently (relatively) low, we'll assume 600 ohms and unbalanced at +4 level.

That signal should have NO PROBLEM going 30 feet unbalanced without degradation, transformers and other stuff inline with your snake will cause signal degradation and noise as you pointed out.


Quote:
I don't know what your snake is but it's just a matter of making adaptors and getting the signal into and out of the snake without polluting your grounds.
I'm actually using a planet waves snake to send my mics and guitar stuff back from front of stage to the backline rack. So there is a DB25 connection on each end and then any configuration of connectors that I feel like soldering.





Quote:
Try it unbalanced, it should work fine. Keep your wiring away from the AC power cords that feed other signal devices, induced noise is the worst enemy of longer unbalanced lines.
I have to run also a long extension chord from the back of stage to front of stage to power the tonelab and a few pedals. How far away from the snake do you think I need to keep that cable? everything else in the snake will either be balanced, plus there is one midi.
Old 29th January 2013
  #20
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I routinely have an IEC power cable and my 1/4" cable going from pedalboard to amp/power source right next to each other with no ill effects -- usually taped down with the same strip of gaff tape. As long as the power cord and cable are sufficient quality, you should be fine.
Old 29th January 2013
  #21
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Quote:
Originally Posted by nedorama View Post
I routinely have an IEC power cable and my 1/4" cable going from pedalboard to amp/power source right next to each other with no ill effects -- usually taped down with the same strip of gaff tape. As long as the power cord and cable are sufficient quality, you should be fine.
What he said.
Old 30th January 2013
  #22
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http://www.zzounds.com/item--EBTLLS2PKG

TRS to XLR out +4 balanced
And will take -10 unbalanced in.

It's the only thing I've found that is not noisy when plugging digital keyboards into a snake. DI boxes always make noise even with grd lifted. The LCD screens on some electronics cause noise issues.
Old 30th January 2013
  #23
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Quote:
Originally Posted by Manfrensengensen View Post
EBTech LLS2 Line Level Shifter at zZounds

TRS to XLR out +4 balanced
And will take -10 unbalanced in.

It's the only thing I've found that is not noisy when plugging digital keyboards into a snake. DI boxes always make noise even with grd lifted. The LCD screens on some electronics cause noise issues.
I'm not sure what kinds/brands of DI boxes you've been using that have this problem, but quality DI's don't exhibit this issue. I'm speaking from experience with regards to Radial (PRo or JDI) and Countryman across numerous vintage synths and even a '65 Farfisa Compact Duo. If there's an issue with noise, there may be a larger ground issue than a ground lift can solve.
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