QUESTION:  I've read the threads for along time now, but never posted anything. BUT I NEED SOME HELP. I have been using EmceePro for about a year and a half now. i'm very pleased with it, I just hate that I have to use my laptop on stage. I have some other things I want to use my lap top for and I don't feel secure in running my tracks and other programs at the same time. I've been thinking about getting a 360 instant replay. What is your opinion? I need the pro's and conn's!
 
COMMENT: I heartily agree...the only drawback is the hefty price tag. BUT! The 360 is incredibly worth it. Not only do you not have to worry about a fragile computer anymore, you have all those hot buttons that make your program so smooth and easily accessible. I've never personally used EmceePro but I've heard plenty of good things. So, not having any experience with it directly I can't make any comments on exactly "how" the 360 is better...I just know not having to take a laptop is great. I will say, we've run into that the 360 is such a powerful little bugger, it puts out a huge amount of signal, that some church boards weren't able to handle it very well. We had to manually change the output strength (dbi) of each track so we wouldn't overpower church's systems. The tracks lost some of their "depth" because the signal was so compressed. But, we have recently got new equipment with a new sound board that has a built in "pad" so that took care of the strong output signal without the track losing its depth and intricacy. When you shop for a 360, if you go the used route, make sure you get a machine that has the 24 hours of recording time! The one we got doesn't (even though the person said it did) and so we're going to have to upgrade the hard drive sometime soon. Oh, and if you fly on an airplane, make sure you tell the security people your 360 is like a computer with a hard drive so they don't run it through the normal x-ray!
 
COMMENT: Actually there are two line level standards. The one for consumer grade equipment (CD, mini-disc, cassette recorders, laptops, etc) is said to be 0 dbv when the signal level is about 0.3 volts. The professional standard for 0 dbv is about 14 db higher, or +4 dbv at approx 1.23 volts. A microphone signal can be virtually anything from about -60 db on up to -20 db or so.
The 360 Instant Replay has a nominal output of Professional grade +4 = 0.0 dbv, or about 14 db hotter than a consumer grade line level device (ie laptop). Most modern sound reinforcement consoles can handle all of these choices by the proper setting on the mic preamplifier trim. However, that said, if you are using a device such as the 360 Systems unit, you should be connecting to the mixer via the line input and not the mic-pre input. Some get away with doing the former by running thru a direct box first which will typically lose about 20 db in level. This is not a good idea, since +4 will most certainly saturate the windings of a direct box transformer causing distortion and dynamic compression, along with loss in high frequency detail. A line to line isolation transformer would be a better choice, regardless of which input you decide to use, mic or line.
 
COMMENT: The 360 Systems is a computer guys...running a stripped down version of DOS. If you think you're getting by the concept of running a computer with 360 Instant Replay, you a sadly mistaken. Besides, the EmceePro has far more features, is easier to use, and a whole lot easier to load songs into. Instant Replay was designed to do radio spots.....Emcee Pro was designed for gospel artists playing tracks. Purpose built unit or one that was built for some other purpose in mind? Gee this is so easy I cannot imagine why Instant Replay is still being used by some groups. If EmceePro had been first...which would be the dominate force today?


EmceePro and laptop noise can be fixed. First off, it is not a problem with the software of EmceePro, but has to do with one of two things:

1. Ground loops between the laptop and the sound system

2. Digital clocking noise of the laptop itself.

In any sound system there should only be one path for ground. For example, a microphone connected to a mixer input has only the one ground and the balanced plus and minus signals of the audio itself, running between microphone and the sound system. In this example no ground loop can exist. However, if you were to run a wire from the case of the microphone to the ground lug of a wall AC outlet, you would then have two independent ground paths back to the mixer. The short path between down the mic cable. from the microphone and onto the mixer input, and the long path from microphone to wall socket, to breaker box, to the wall outlet the mixer is connected to, and eventually back to the mixer. The voltage potential between these two ground paths (and there will always be a voltage potential between various ground paths) becomes amplified by the mic-pre amplifier gain. The result is the 60 cycle line frequency is now quite audible in the sound system, and multiplies of that line frequency as well, such as 120 cycles, 180 cycles, 240 cycles. You might say, "I would never connect a ground from the mic case to a wall outlet". True enough. But when you connect a laptop computer, a mini-disc or whatever to a different wall outlet than that which is used for the mixer and amplifiers in your system, you have essentially done the exact same thing. For you now have two ground paths of unequal length and resistance. Thus a voltage potential between the two paths.

The proper method for connecting AC power is to use only one AC outlet for EVERYTHING you intend to connect to the Mixer. Everything connected to your sound system should derive its power from ONE source only. This includes laptops, mini-discs, guitar amplifiers, in-ear monitors, etc. Even then, you may have a ground loop condition on laptops, for virtually all laptops use a switching power supply in order to conserve battery drain. This type power supply turns off and on many hundreds of times per second. This switching power supply scheme can, and many times does produce a phantom ground that rides (in impedance) somewhat above true ground. In other words, it has an inherent manufactured ground that is at some voltage potential above true ground. This is why a transformered direct box tends to help this situation considerably. The secondary of the direct box transformer is automatically made an extension of the mixer ground. The audio portion of the signal from the laptop is tied to the ground of the laptop, but is not necessarily connected through the direct box and on to the mixer. Instead it is fed to the mixer via the transformer windings so that any AC or DC potential is lost in the windings of the first stage of the direct box. (This also blocks phantom power from reaching the laptop as transformers will not pass DC voltage.)

Now, it is best not to use a true direct box but instead a line to line isolation box. A true direct box is intended for a source impedance of 100k ohm or so, such as found on the output of a guitar pickup. The direct box transformer has a loss of about 50:1 or greater, so that the mixer "sees" the guitar as having a very low impedance of about 150 ohms or so......about the same as a typical microphone.

The output impedance of a laptop sound card is far lower than a guitar, many times less than 40 ohms. When this is ran through a typical direct box, the source impedance the mixer sees maybe almost a dead short, or less than 1 ohm. A better method is to buy a stereo line to line isolation box. These look and feel just like a normal direct box, but they have a winding that is typically 1:1. In other words, the impedance of the output of the laptop is mirrored across the transformer and onto the mixer. It still has all the wonderful attributes of isolating the grounds one from another, but it does so without shunting the impedance down to nearly nothing. The result is a cleaner sounding signal with far more detail.

The ground lift switch on these devices should almost always be turned off, or in lift mode. This keeps the switching power supply ground noise from being transferred to the house sound system.

The other source of noise might just be the switching noise of the laptop getting into the audio and sent out as an audible signal. This is called crosstalk. If this is the case, it will not matter if you use a direct box or not as the noise will still be there. If this is your problem an external sound card, like the Turtle Beach USB device, will go a long way in cleaning up the audio.

Have fun,


Ben Harris
Southern Sound Quartet
6340 Spera Pointe Crossing
Nashville, TN 37076