They can work as stand alone preamps and run the line out into converters, or you can run optical ADAT out into another interface to expand channel count. I used these for about 6 months and then bought a full sized 24 channel Audient Console with the same preamps, so I no longer need these. The item "Audient ASP800 8 Channel Microphone Preamp" is in sale since Monday, October 21, 2019. This item is in the category "Musical Instruments\Pro Audio Equipment\Preamps".
The seller is "gussyboy298" and is located in Glasgow. This item can be shipped to United Kingdom, Antigua and barbuda, Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Australia, United States, Bahrain, Canada, Japan, New Zealand, China, Israel, Hong Kong, Norway, Malaysia, Mexico, Singapore, South Korea, Switzerland, Thailand, Bangladesh, Belize, Bermuda, Bolivia, Barbados, Brunei darussalam, Cayman islands, Dominica, Egypt, Guernsey, Gibraltar, Guadeloupe, Grenada, French guiana, Iceland, Jersey, Jordan, Cambodia, Saint kitts and nevis, Saint lucia, Liechtenstein, Sri lanka, Macao, Monaco, Maldives, Montserrat, Martinique, Nicaragua, Oman, Pakistan, Paraguay, Reunion, Turks and caicos islands, Aruba, Saudi arabia, South africa, United arab emirates, Ukraine, Chile, Bahamas, Colombia, Costa rica, Dominican republic, Kuwait, Panama, Qatar, Trinidad and tobago, Uruguay.