Jam Studio Quality Guitar Input For Ipad, Iphone And Mac Musiciansfriend
Apogee has announced Jam+, a new a portable, studio-grade USB instrument input and output. Jam+ connects your electric guitar, bass, keyboard or any acoustic instrument with a pickup, directly to your iOS device, Mac, or Windows PC. With an adapter (sold separately) you can also connect a dynamic microphone. Jam+ makes it easy to practice, and capture your best take with studio quality anywhere you go. 
What’s New About Jam+ ● Stereo output connects to headphones or powered speakers ● Low latency monitoring with Blend feature ● Overdrive mode makes virtual amplifiers and effects pedals sound more realistic ● Rugged metal body with soft touch base and three multicolor LED indicators Includes Positive Grid BIAS FX Jam software Jam+ comes with the BIAS FX Jam software bundle from Positive Grid which includes a premium selection of three amplifiers and six essential pedal effects.
Apogee has announced the new MiC 96k microphone and the JAM 96k guitar interface for iPhone, iPad, and Mac. The full press releases can be found below.
With Jam+ and BIAS FX Jam, you have realistic guitar tone for practicing, performing and recording.
As others have mentioned. An audio interface is what you need. There are tons of options at prices ranging from.
The USB cable that comes along with Rocksmith is supposed to have some kind of whiz-bang circuitry in it that allows it to work very well as a computer interface. Probably one of the best 'cheap' options. 'Most Helpful' review of the cable: [COLOR='red']This review is actually for the USB Rocksmith Real Tone cable, not the game. I recently purchased this game and decided to try the cable directly into Garageband on a Mac, since I had tried the 'Alesis Guitarlink' USB cable and found it unworkable in Garageband because of a low volume but persistent high-pitched pulsing/beeping coming from what I assume is the USB circuitry in the Alesis cable. Maybe my Alesis cable is defective - either way it was unusable. I am happy to comment that this Rocksmith Real Tone cable works perfectly with Garageband for me and is absolutely free of any unwanted noises. The cable is quite sturdy and seems almost indestructible in normal use.
There is even a strain release mechanism in the USB tail where an inline plug will disconnect without yanking any of your computer (or game console if you are using it with the Rocksmith game) onto the floor. Highly recommended. I ordered a spare before everyone figures this out and the cables end up on backorder!