| T O P I C R E V I E W |
| les_maverick |
Posted - 07/09/2011 : 12:21:06 PM
Aloha
I bought a Live Wire Solutions ADI Active DI Direct Box
Can someone explain what this means:
The Live Wire ADI Active DI Direct Box offers you 1/4" high impedance input and throughput, balanced XLR output.
I wanted a 1/4" output so that I could go to a line level jack on the
mixer.
I wanted to use this for my acoustic elect guitar and passive ukulele.
Thanks,
Les |
| 15 L A T E S T R E P L I E S (Newest First) |
| les_maverick |
Posted - 08/16/2011 : 5:15:08 PM
Yes Aunty. Paul and Lawrence have been a big help !! |
| wcerto |
Posted - 07/20/2011 : 10:40:44 AM
See you guys, I told you Lawrence is the "Sound Man Extraordinaire"!!!!! Don't you just love how he talks? |
| Lawrence |
Posted - 07/20/2011 : 06:56:13 AM
quote:
This braid defeats the efforts of magnetic fields to create interference in the signals.
Yes- except that the word "reduces" rather than "defeats" would be more accurate. The "shield tube" is not nearly 100% effective at eliminating magnetic interference but is very effective at eliminating electrostatic interference. And of course this also depends upon the quality of construction of the shield. There are cables available that have one braided shield inside another forming a dual shield and these are even more effective at reducing interference but still do not eliminate it entirely.
This is the reason balanced signal connections were developed. You have a device at the receiving end of the wire (either a differential amplifier or a transformer) that can take two opposite polarity signals, effectively invert one of them, and then add them. Any interfering signal that gets through the shield of the cable will cause the SAME signal (not an opposite signal) to be introduced onto the two wires inside the shield. These interfering signals will then get CANCELLED when one of them is inverted and then added to the other.
So with some increased expense, (three wires instead of two and either a transformer or a special "inverting and subtracting" a.k.a: differential amplifier), interfering signals can be very greatly reduced.
Sorry for the somewhat technical talk, but this is the reason for using balanced cables and devices in professional audio applications, especially for very low level signals (such as microphones).
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| rendesvous1840 |
Posted - 07/20/2011 : 06:23:18 AM
The sleeve portions of the TRS cables, and one terminal of the XLR plugs in those cables, goes to a braided wire tube that completely encloses the two shielded wires from the other connectors. This braid defeats the efforts of magnetic fields to create interference in the signals. This is the source of the hum you were getting, and why it went away when you changed cables. It's not that your other cables had a defect, just that they are susceptible to picking up a hum from electronic stuff. It could be as simple as fluorescent lights in the area. Motors and generators can also cause hum. Sometimes just relocating equipment can help, but it isn't always possible to move everything on a stage. Plus you have to figure out which piece is the culprit. So much easier to change cables.
Unko Paul |
| les_maverick |
Posted - 07/18/2011 : 10:16:50 AM
Lawarence:
We have been experiencing a hum in the speakers. This was with the cables that came with the speakers and mixer from Guitar Center.
But I had to use a 1/4 inch to dual rca jack to go to line in on the speakers.
Last night I took those cables out and used a cable with XLR into the line in on the speaker.
On the other end, I had to use a XLR to 1/4 adapter to plug into the mixer Main out jacks.
Guess what...... Hummmmm gone !!
Now I have to go buy some XLR to 1/4 cables for the speakers.
I also need a similar one for my DI to mixer.
Thanks for all the help. |
| rendesvous1840 |
Posted - 07/18/2011 : 06:07:03 AM
The TRS cable is often used as an extension cord for headphones. Usually in the smaller 1/8" size now, but in the "olden days" headphones used 1/4" plugs.
Unko Paul |
| Lawrence |
Posted - 07/18/2011 : 05:48:05 AM
Les,
The balanced TRS plug has a metal "Tip" with a bump on it, then an insulated spacer (usually plastic), then a metal "Ring" (the second conductor connection, then another spacer, then the whole back end of the shaft is called the "sleeve" and is the third conductor which is usually the shield (outer conductor).
There are two kinds of signals that are sent over such a connection:
1) A BALANCED MONO signal which uses the two conductors inside the shield to carry OPPOSITE polarity versions of the same signal (a.k.a. - balanced - like a see-saw). The reason for this is that interfering signals (such as hum and motor hash and RF, etc) which are coupled into the cable from outside (magnetically), can be cancelled out at the receiving end because they will not be opposite polarity like the desired signal.
2) The same cable can also carry an unbalanced STEREO signal where the two inside conductors carry the LEFT and RIGHT channel signals. However, stereo signals as almost never connected thru a single XLR connector (the microphone style connector). These XLR connectors are almost always reserved for BALANCED signals. But you could easily have a TRS to TRS cable that connects between two stereo devices, or connects two balanced mono devices.
For more detailed information you should consult one of the many Recording Websites that also have introductions to Recording Engineering, such as HomeRecording.com.
Maybe Salman Khan should post some videos on this subject, yah?!
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| les_maverick |
Posted - 07/17/2011 : 5:54:55 PM
Unko Paul
I see the balanced plug has two rings ?
Does it mean stereo ?
I think Guitar Center sold me junk speaker cables too.
I got 1/4 to 1/4 but I need XLR to TRS ?
Les |
| rendesvous1840 |
Posted - 07/16/2011 : 08:13:56 AM
If you looked at the pix I posted yesterday, it's no wonder you're confused. I managed to put the same picture for the balanced and unbalanced 1/4" plugs. Sorry for the confusion. I corrected it today, so you don't have to open your plugs. Recheck the pix in my other post.
UnkoPaul |
| Lawrence |
Posted - 07/15/2011 : 1:12:23 PM
Les,
In my lexicon, an instrument cable is specifically an unbalanced cable with 1/4 inch TS plugs at either end. This cable goes from the Guitar, Uke, or whatnot into the INST input on the DI box, and is typically made to have very low capacitance because of the very high impedance of some instrument pickups. The XLR to TRS (balanced) cable mentioned above goes from the DI box to the mixer and typically handles a medium or low impedance balanced signal. This second cable is not normally called an instrument cable, but is sometimes called a XLR to TRS Microphone cable, or an XLR to TRS line cable.
Even if you use an XLR to TS (unbalanced) cable, it should still work, but you will get a little less signal into the mixer from the DI box AND you will be more likely to have Hum and Noise problems.
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| les_maverick |
Posted - 07/15/2011 : 10:51:51 AM
Lawrence
Hmmm, now I have to make sure my instrument cables are balanced.
I hope they are marked or I guess I can unscrew the cap and check inside.
Thanks,
Les |
| Lawrence |
Posted - 07/15/2011 : 07:08:06 AM
Sounds OK Les...
The Alesis manual also says to use MONO TRS cables on all 1/4 inch inputs. TRS means balanced (three wires, Tip, Ring and Sleeve). 1/4 unbalanced is properly referred to as a TS cable (just Tip and Sleeve). The schematic in the manual shows TRS (balanced) jacks even on the stereo inputs 5&6 and 7&8, so Alesis did the right thing for these channels, and you still should use XLR to TRS balanced cables from your DI boxes to the 5 (Left) and 7 (left) inputs (for two instruments) as you are planning.
Good luck with your show!
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| les_maverick |
Posted - 07/14/2011 : 11:05:01 AM
Lawrence
I am using channels 1-4 for mics and wanted to use channels 5/6 and 7/8 for a guitar and ukulele ?
Unko Paul
Thanks for the info. I do not know what this all means !!
Les |
| rendesvous1840 |
Posted - 07/14/2011 : 08:07:12 AM
Most of us who have used mics know what all this means, but just in case someone is wondering what connectors balanced/unbalanced/XLR/1/4" refers to,here's pix.
http://www.google.com/products/catalog?q=TRS+connector&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&tbm=shop&cid=18309321361795445186&sa=X&ei=ly0fTvnmAeHq0gGmsKmnAw&ved=0CDoQ8wIwAQ This is the TRS or balanced ¼ “ connector. Similar to the standard ¼” guitar plug, but with a third wire and connection.
http://www.guitarcenter.com/Monster-Cable-S-100-1-4--Straight---Angled-Instrument-Cable-102469707-i1128536.gc This is the standard unbalanced ¼” guitar connector. It has two wires and connectors in it.
http://www.switchcraft.com/Category.aspx?Parent=684 This is the XLR connectors.
Unko Paul
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| Lawrence |
Posted - 07/13/2011 : 09:42:48 AM
Page 9 of the Alesis Multimix 8 manual states the following...
Line Inputs (Channels 1 – 4)
The line inputs, marked LINE IN, are balanced 1/4” jacks that
offer the same 50dB of preamp gain and the high-pass filter
provided by the mic inputs (however, phantom power does not
apply to line inputs). These inputs accept line-level instruments
such as keyboards and drum machines. If you find that your
instrument has a weak line signal, just plug it into channels 1 – 4
and crank it up with the Gain knob.
A useful rule to follow is always RTFM! 
Another Rule is to buy (or bring) more than you think you will need (as in more channels, mics, etc), as it usually works out that you really will need more than you think.
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