Sorry for my reply being a few months late… I have only recently joined this forum, but as this is of interest to many people here, it's worth making a quick list.
So here goes, a list of EEG amplifiers with some of my comments. Starting from rock bottom (price-wise):
1. 100 Euros - Olimex SMT openEEG (built in Bulgaria)
2-channel bipolar amp, 256SPS, 10bit resolution, usb interface
Just launched, unbelievable good price. This is about the same (or cheaper) than some gaming devices such as OCZ NIA or Neurosky. But unlike the gaming devices, this is a real, usable amp. However, don't expect user manuals or any such thing, Olimex is actually a PCB manufacturer and not a product house...
2. less than US$300 – self build modEEG amplifiers having 2, 4 or 6 channels
The only way to go if you want a really cheap 4 or 6 channel amplifier. Ready made PCBs can be brought, but you are on your own with mounting all in a suitable enclosure and figuring out how to inter-connect everything. Well it's easy - I am a EE. But it's a daunting task for beginners, the openeeg forum attests to that.
3. US$ 300 – Emotiv EPOC
I should actually not list this device here, at least not at this price, because this $300 version does not allow for raw EEG data. I also have my misgivings about this device’s extremely low 1Mohm input impedance, making it a bit of a toy, not for serious work.
14-channel monopolar, 128SPS, 14 bit resolution, propriety wireless
4. US$600 – USB or wireless EEG pendant (Australian built)
2-channel bipolar amp, 128/256/512SPS, I think it’s 12bit resolution
Good performance but not well build (it’s build into a cheap MP3 player housing)
5. US$600 – QDS Focus USB (Argentinean built)
2-channel bipolar amp, 256SPS, 16bit resolution
Many happy users, but I have my reservations, it uses a 9V battery which dangles on the OUTSIDE of the enclosure, at one stage the battery connector that was fitted was of such bad quality/poor fit, that new devices where working intermittently…
http://www.brain-trainer.com/cgi-bin/sh ... item_id=60
6. US$710 – Neurobit Optima2
2-channel bipolar amp, up to 2000SPS, 16bit resolution, wireless bluetooth
The Neurobit name I remember from many years back when they sold a silly little one channel device. I don't know the Optima, but on paper it seems like quite a nice amp.
7. US$1040 - Neurobit Optima4
4-channel bipolar amp, up to 2000SPS, 16bit resolution, wireless bluetooth
8. US$1200 – Contec KT88-1016 (Far east)
16-channel monopolar amp, I think they use a 12-bit ADC
This is the only amp that is shipped with cables and electrodes included, especially when considering that this unit has 16 channels, this is a saving of $100s (!)
Unfortunately I can't give any further comments about this amp, as I don't know much about it. If anyone has color photos of the INSIDE of this or other Contec amps, please send them to me [firstname.lastname@example.org
9. US$1200 – Alpha200
10. US$1800 – Alpha400
2- and 4-channel bipolar amps, 501(k) FDA approved, 256SPS, 16bits, USB
11. US$1240 – Brainmaster 2EB
12. US$2695 – Brainmaster Atlantis I
2- and 4-channel bipolar amps, 256SPS, USB, Atlantis has 24bit resolution
13. US$1995 – J&J Engineering I-330-C2+ 6channel (only 2 EEG channels)
14. US$3195 - J&J Engineering I-330-C2+ 12channel (only 4 EEG channels)
2- and 4-channel bipolar amps, 1024SPS, 16bits, USB
15. US$2230 – QDS Excalibur (Argentinean built)
16. US$3580 – QDS Quantum (Argentinean built)
4-and 8-channel bipolar amp, 256SPS, 16bit resolution, RS232
I have my misgivings about this manufacturer. I have back-engineered an Excalibur (from hi-res, color photos which where sent to me). It uses a 6th order anti-aliasing LPF but with 10% tolerance capacitors. Go figure. Also, if the proprietor claims 0nV noise for his amps, my respect for him goes down the toilet. 0nV noise is a scientific impossibility, just as 0Liters/100km fuel consumption for your car would be.
This is by no means a complete list. You can google for names such as BrainQuery (PET), MindMaster, ProComp, NeuroAmp (EEG Info), Nexus, Nexstim, BioSemi, Braintronics, gTec, Cadwell, Philips etc. for more. The last five mentioned companies make these 32, 64… 256 and more channel equipment.
As you can see, most amplifiers are 2 or 4 channels only and of bipolar design. These amplifiers are actually intended for neurofeedback use. For BCI you ideally want as many channels as possible, say at least 8, preferably 16 or more. Many-channel amplifiers are always monopolar, as a bipolar design would be more expensive and clumsy to use, having to jumper many reference inputs together.
There is a real hole in the market for an entry level 8+ channel amplifier for BCI use. I am thus working on a 8/16 channel entry level amplifier. Just started, so it’s early days, but I think a price bracket of US$500-600 should be achievable.
As tempting as the Emotiv is, I would not recommend it (see my comments elsewhere on this forum). Item (1) the 100 Euro Olimex amplifier, although using these silly little “stereo” 3.5mm jack plugs, is an absolute steal. It has just been launched, but don’t expect the supplier to help you with technical queries. You buy it and are on your own. Although only 10bits, I regard this as a “real” (read usable) amplifier. Other cheap gaming devices such as OCZ NIA and the Neurosky are only single channel and should therefore not even be considered.
FORGET dry electrodes, especially on entry level (gaming) devices. For instance, the OCZ NIA, is a reasonably well engineered amplifier, with very good build quality, but it’s performance is lousy. A well respected friend did tests, and he claims that this is due to the dry, carbon bristle sensor used. There is a lot of talk about dry, and capacitive sensors. They are all problematic or, if you find something that works, will be very expensive. Getting a capacitive sensor to work in a lab is one thing, selling it in the real world, that does not want to hear about electrostatic sensitive devices – and the protection of such, is quite another. Wet saline electrodes are OK – just. But if you want proper reliable signals, you should go with proper prepping and conductive gel applied electrodes.