Connecting External Amp to Macbook

Question

Hi, sorry if this is one of those "dumb" questions, but I know Macs well but not electronic equipment...
I have a multi-media show that needs some BIG sound to it. In the past, I've hooked up my office speakers to my Mac, but that just doesn't cut it. I have a pretty nice Roland piano amp, is there a way to hook that up to the Macbook, and what would I need? Or if I could score a nice PA amp like a JBL, could I hook that in somehow? What would I need to do on that?
Thanks for any help.
Mark

Answer 1

FWIW, I am a live performance sound mixer by trade & I have had very good results using the 1/8" stereo jack audio output on my new Macbook to connect it to a large, professional audio system of about 20,000 watts. However, keep these tips in mind for best results:
1. Garbage in = garbage out. IOW, use high quality audio sources wherever possible. A highly compressed MP3 audio file will never sound as crisp & detailed as a 24 bit, 96KHz AIFF file, & the differences will be much more noticeable on a high quality, high power playback system. If you use iTunes to import CD tracks, make sure you set the import preference to "Apple Lossless." Better still, use an app like Audacity to import the tracks or other source material directly into a high quality AIFF format. Do any necessary mixing in that uncompressed format & only compress the final mix if necessary to make it compatible with your presentation playback format.
2. Do not directly combine the left & right signals in the stereo mini-jack to get a mono signal. For instance, don't use a stereo-to-mono adaptor plug (which really is suitable only for splitting a mono signal into two outputs, regardless of what the guy at Radio Shack or wherever tells you). Instead, use a specially designed adaptor with resistors in it that isolate the two outputs, or (much!) better still, use a mixer with separate inputs for each channel.
3. You can also use just one channel of the stereo signal, as described in another post, but keep in mind that hearing only one channel of a stereo signal may not sound right. Avoid using a mono 1/8" plug in the stereo jack if you do this. This will short out one of the channels. It won't damage the Macbook, but it may introduce a noticeable amount of distortion in the channel you use. Instead, get an adaptor with a stereo 1/8" plug that splits the channels into separate outputs & use just one of them. (If you are using a musical instrument amp, you can use a 1/8" stereo plug to two 1/4" jacks adaptor & a standard 1/4" to 1/4" patch cable.)
4. Set the Macbook's audio output level to near maximum & leave it there. Never try to reduce its output to adjust the volume of the attached system -- you will just increase the hum, noise, & residual distortion of the output relative to the signal. If you are using a mixer, it will have an input gain control or "pad" switch that can be used to match the output of the MacBook to its input requirements. If you are using a musical instrument amp, use an input designed for synthesizers or other similar devices if available. If you must use a guitar input, you should obtain a "pad" adaptor that reduces the signal strength by about 20 dB. Basically, the MacBook outputs a "line level" signal, so your playback equipment should be capable of handling that without having to turn down its primary or channel volume controls to nearly off to keep from overdriving anything.
5. To avoid stress & strain on the MacBook's jack, use an adaptor cable rather than a one-piece adaptor that results in a long, inflexible plug & adaptor combination hanging off the side of the MacBook. If you need to use a security lock & cable in the MacBook's security slot, you will have to avoid the fat, solid adaptors anyway, since the slot & jack are closely spaced. (If you use a typical security cable with a rotating locking head, also be careful not to allow it to rotate around & apply side pressure to the plug.)
6. Use good quality cables & adaptors. You don't have to spend a fortune on over-priced "audiophile" cables because the MacBook's audio outputs are low impedance, relatively high current ones quite capable of driving normal, run-of-the-mill cables, but you do have to have good connections to insure a clean signal. Mostly, this is a matter of using mechanically well-made plugs & jacks with good contact materials, not the construction of the cables themselves.