Line Outputs

[Manfred]

Hello,

i have two questions regarding the six line outputs of the 2Box module:

1. Which level do the outputs have. Is it the "professional" +4dbu or consumer standard with -10dbV?

2. What kind of Jacks should be used, mono (unbalanced) or stereo (balanced)? At the manual one can read:

The OUT1-6 outputs have the ring contact to ground. So if a balanced TRS to XLR cable would be used, the XLR negative signal is
correctly grounded.

So i guess it doesn't matter if it is a stereo or mono jack?

Manfred

[edtc]

Hi Manfred

I made some tests with the outputs , using a RME soundcard ...

I used out1 , the loudest snare trigged with the panel button , all internal volumes at max , "physical "volume knob at max too...

At +4db input , i even had to reduce the trig level at -6db (UNIT-PREFERENCES/TRIG) to have a 0db signal ...
So , it s definitively not a -10db...
You ll have to chose +4db inputs , and even reduce the gain setting

As you saw in the manual , connections are unbalanced , that means a mono  jack is ok ... and as ring is grounded , you can also use a stereo jack ...

have a nice day

[Manfred]

Hello,

got my Cakewalk UA-101 today which has switches at the line inputs where you can choose between +4dBu or -10dBV. This was actually the reason why i asked.

I did a similar test too but with totally different result. For me it is clear that the line outputs have the -10dBV level. This was my test:

- created following test sound with certain frequencies at certain levels
 http://www.4shared.com/file/k68awEPE/TestSounds.html
- set KIT-ENV-LAYER to FIX
- set internal volumes to high levels (close to max)
- triggered the sound by setting the level at UNIT-PREF-TRIG and the buttons at the brain
- recorded the output

Setting the UA-101 inputs to -10dBV results in recordings very close to the original test sound. Deviation between original test sound and recorded sound is less than 1dB. Maybe by adjusting the internal volumes accordingly this can even be reduced.

TestSound (dsnd-file):



Recorded File:



Setting the UA-101 inputs to +4dBu results in recorded levels that are way too low.

Does your RME interface have Preamps which amplified the signal? I'm asking because you mentioned that you set a "physical" knob to max.

Manfred

[edtc]

I was speaking about the volime knob of the drumit5 ... i ran a TRS to XLR directly in my RME (HDSP 9632) . It has no preamp it s just a balanced line in ... you can chose in control panel if it handles -10 or +4 db...

i will retry this week , to see if i made any mistake while testing ... But , when i did them, it was with all levels at maximum value , from the sample volume to the mixer level , and also with drumit knob all the way up ....

i monitored results using totalmix , it s the RME sound cards control pannel , and it has accurate meters ...

[edtc]

Finally , i re-did the tests just now ... and i think you are right...

My mistake was that i ran tests with out1+2 in remix mode without the "!" mark , so the main volume knob was active and boosted the volume a lot...

Then i retried selecting "1+2!" and it showed a lower level of -10 db ...

Danke schoen Manfred , i learned some more again tonight

[rcprod]

I have a few question regarding the outputs.

I tried using unbalanced 1/4" cables going to the inputs of my RME Fireface and was getting a noticeable humming sound (ground?). When I tried balanced 1/4" cables the humming sound was gone. The manual says that the outputs are 1/4" TS. Will there be any phase issues caused from using the balanced cables (TRS) with the 1/4" TS outputs? Why are the balanced cables helping when the outputs are designed for unbalanced cables?

Thanks.   

[edtc]

it s strange ...

did you try to plug another unbal gear with the same cables and did you have the same hum ?

did you try other unbal cables with the 2 box ?

If you use a laptop , sometimes it helps to remove the ground fromthe DC adapter...

On the fireface , did you chose UNBAL for the inputs ?

[rcprod]

I'll try another keyboard tonight that uses unbalanced cables.

I was using 4 quality 1/4" unblanced cables. As each cable was plugged into the RME Fireface 800 the hum became louder. I am not using a laptop.

I was not aware that one could select "UNBAL" for the inputs on the RME Fireface. I will take a closer look at the manual.   

[edtc]

I was not aware that one could select "UNBAL" for the inputs on the RME Fireface. I will take a closer look at the manual.   

... you  cant select UNBAL for the inputs , but maybe -10 us unbal and +4 is balanced ... not sure ...

[spoenk]

Will there be any phase issues caused from using the balanced cables (TRS) with the 1/4" TS outputs? Why are the balanced cables helping when the outputs are designed for unbalanced cables?

"when an unbalanced output drives a balanced input, the differential inputs are fed by the signal and common respectively. this allows for the common-mode rejection to suppress any interference that is injected into the line. ..."
Bob mcCarthy

why should there be phase issues?

[rcprod]

why should there be phase issues?

I was reading a thread at Gearslutz and they were discussing the possibilities of phase issues related to using a balanced cord with an unbalanced output. I just found it a bit confusing.

Manfred had the following quote in his post, "So if a balanced TRS to XLR cable would be used, the XLR negative signal is correctly grounded."

So I guess it would be best to use a balanced 1/4" to xlr when plugging into a PA to avoid humming sounds? Does this info posted by Manfred mean that a balanced 1/4"  to balanced 1/4" cable would also work better when going into a balanced input?

[spoenk]

So I guess it would be best to use a balanced 1/4" to xlr when plugging into a PA to avoid humming sounds? Does this info posted by Manfred mean that a balanced 1/4"  to balanced 1/4" cable would also work better when going into a balanced input?

IMO yes + yes

[crackettt]

So I guess it would be best to use a balanced 1/4" to xlr when plugging into a PA to avoid humming sounds? Does this info posted by Manfred mean that a balanced 1/4"  to balanced 1/4" cable would also work better when going into a balanced input?

IMO yes + yes

I was looking into this stuff for the first time today (going from the kit to a mixer), and ran into an article that confirms that you should use balanced TRS leads to hook up an unbalanced output to a balanced input.

here's the interesting bit:

Connecting Unbalanced Outputs to Balanced Inputs

Unbalanced sources are very common, especially in consumer electronics (phono pre-amps, cassette decks, etc). Also, many keyboards, samplers, and other electronic sound sources have unbalanced outputs. When these devices need to be connected to a balanced input (such as the ADC1 USB), it is important to understand the proper method of cabling.

An unbalanced-to-balanced connection should use a 3-conductor (balanced) wire. The explanation behind this technique is somewhat complicated, and it is beyond the scope of this article. For an in-depth look at the technical explanation for this solution, read section 5.4, "Shield Wires", of The Clean Audio Installation Guide. ( http://www.benchmarkmedia.com/caig/ )

The connecting cable should have the cold signal conductor of the cable tied to ground at the source-side only (the unbalanced end of the cable). The load-side of the cable will be connected in a typical balanced configuration.

A more sophisticated connection may be needed for aggressive common-mode rejection, which may require modifying the equipment. For information about this type of setup, refer to the "Shield Wires" section (5.4) of The Clean Audio Installation Guide.