Now that you have chosen your configuration and method, you'll need hardware to suit. You're only as good as your tools, and getting it right the first time saves expense down the line.
Several components are needed - sensors to detect the brainwave signals, an amplifier to convert it into digital data, and a computer to process it.
Your training is only as good as your detection equipment, so sensors matter.
There are several different types of sensors available.
The most common electrodes (sensors) are either sintered Silver-Silver Chloride (Ag/AgCl) or Gold. Individual sensors attach to the scalp using a conductive paste (EEG paste), or a full sensor cap connects to the scalp using a conductive gel (Electrogel).
They make an excellent contact with the scalp, have low environmental interference, and give a strong, reliable signal. That is why they are the clinical standard. The downside is the 'goo-factor' - the residual gel or paste left in the client's hair.
Silver Chloride sensors generally sell for $10 each, or a full 19 sensor cap sells for about for $350.
Wet sensors use a pressure-pad soaked in a saline solution to make a contact against the scalp.
They are cheap as chips and leave no mess, but are highly sensitive to interference, making it difficult (usually impossible) to get a reading that is good enough to use.
Dry sensor technology is developing quickly, but it's not there yet.
Comfort is a concern, but practically there are two main barriers; interference, and price. Their sensitivity to interference makes them rather 'jumpy' compared to gel sensors, but most of all the prices run between $20,000 and $40,000. It's new technology, so nobody knows their life expectancy.
Given the impact on the session price, I would suggest waiting until prices drop.
Now that you have an idea as to what configuration you'd like, it's time t look for an amplifier to fit your need (and your budget).
A single sensor system with a wet sensor (above) could go for as little as $120. A two sensor amp sells for between $600 and $2000, while a 19ch amplifier will run between $5500 and $10,000.
What do you need to look for?
You want an EEG amplifier with good shielding against environmental noise (to keep your signal clean), one that is durable, and most of all has good customer service in case of a problem. The latter can be the hardest to find.
Also, it's really nice if it has standard sensor ports, and doesn't need a special type.
A choice of bitrates (bps, or bits per second) is handy. The minimum clinical spec is 250bps, though some can reach up to 8000bps. Counter-intuitively, the faster your bitrate, the better resolution you have on slow wave signals. The only reason to have bitrates above 2048bps is for infra-low training.
Another thing to check is whether it uses sequential or simultaneous sampling; whether it takes its samples one sensor at a time, or all together in one stream. For example, it might take a bit of data from sensor 1, then sensor 2, and so on, or it may collect all at once. Most therapists in-the=know prefer simultaneous sampling, though it does cost a little more.
A good precaution is to get an amplifier that is compatible with many software platforms. Some amplifiers only work with the software provided with it, so if it doesn't fit you need or you need to upgrade, you will need to buy another amp. It's an expensive error.
Once you decide on your software, you will know the required specs for your computer.
It is always a good idea to get a computer that's a bit faster than the minimum requirement. If you are spending thousands on your hardware, don't skimp on the last bit.
A computer with an i7 quad core processor, 8GB of ram and at least 2GB of video memory will be fine for just about any software platform. These run between $1000 and $1500.
If you use a mac, then it's time to buy a PC.
Now that you have chosen your methods, software, and hardware, it's time to get some training.