Back on Tuesday 27 May 2008, Simon Williams was like: > Hello. > > I often run the PA system for my CU at uni. So far we've been using > jack-jack leads to connect guitars to the desk. However, my Dad has > recently started using jack-XLR leads at my home church and says that > it's much better. > > After a very long conversation and lots of googling (which incidentally > provides no info at all on the subject), I'm now completely confused. > > Are guitars mic or line or what? Hi-Z Line level. (The output level can vary quite drastically depending on the type of pickup though) > > The rationale for using jack-XLR leads and connecting to the mic input > on the desk is that guitars have mics in them so they are mic level. > Apparently the battery unit in the guitar doesn't make it line level, > but I'm not convinced. A battery is for active pickups. Pickups that don't need batteries are passive. > > The other thing I don't understand is that if that is the case, why do > people use DI boxes? A DI box takes a high impedance (line level - I > think) input and converts it to low impedance output (mic level). If the > guitar is mic level already then what's the point? The DI converts a line level (regardless of impedance level) signal to Low-Z mic level. The reason for this is that line level signals can't travel long distances without degrading, but Low-Z mic level signals can go much much further. I wouldn't run a -10 dBu signal much futher than 20 feet. (A +4 dBu line level signal can go quite a long distance though) Most sources like keyboards are -10 dBu though, and levels on guitars can be all over the place. A DI is used because it can take a wide range of signal levels and change them all to a uniform Low-Z mic level signal that can travel a long distance. They also usually have a ground lift switch for when your FOH and Stage power are sourced to different grounds to prevent ground loops. (The hum you sometimes get when plugging in a guitar or keyboard) Some can be placed in between a head-amp and cabnet. Some have pad switches. Some are active, some are passive. Some are crap. (I'm talking about you, Behringer) > > Please, could someone shed some light on this because I'm now very > confused. > I wouldn't recommend plugging into a line jack, or a mic preamp. Both can be made to work, and both can be a mess. I would recommend getting DI boxes. The cheap ones that still work good, are the passive IMP DI boxes made by Whirlwind. (~ $40) I prefer active DI boxes because they have a better frequency response, but they cost quite a bit more. I recommend: BSS AR-133 - Great for keyboards because of the pad switch Countryman Type-85 - Great for guitars because they can also go in between the amp and cabnet. They're also indestructible. Anything made by Radial. -Reuben > Thanks in advance. > Simon > _______________________________________________ > Linux-audio-user mailing list > Linux-audio-user@xxxxxxxxxxxxxxxxxxxx > http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
