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Note the following. Do these not have a built in synth engine?
"This Proteus 2500 does not have a sound ROM installed. You will need to supply your own in order to use this unit. This Mo'Phatt takes standard E-mu 16 and 32 MB sound ROMs. You can use your ROMs from Command Stations and also from Proteus 2000 series rack synths and keyboards. This is a great way to add sound ROM capacity to your studio or replace a broken Emu synth.

The following ROMs will work with this unit:
9061: Siedlaczek Orchestra 32 MB ROM.
9062: Pure Phatt 32 MB ROM - standard in Mo'Phatt, MP-7 and MK-6.
9063: Beat Garden 32 MB ROM - standard in Orbit 3.
9064: Ensoniq Project 32MB ROM - Containing sounds from EXP-1 Real World and EXP-3 Urban Dance expansion boards
9082: Protozoa 16 MB ROM - standard in Proteus 1, 2, 3.
9065: Vintage Collection 32MB ROM - Standard in Vintage Pro
9083: Definitive B-3 32 MB ROM - standard in B-3.
9066: Protean Drums 32 MB ROM - Standard in PX-7
9084: Techno Synth Construction Yard 32 MB ROM - standard in Orbit 3.
9081: Holy Grail Piano 16MB ROM - From Q-Up Arts, utilizes a new sample processing and preset programming technology called VMS, for Virtual Modeling Synthesis, developed exclusively for E-mu products
9085: Orchestral Session Vol. 1 32 MB ROM - standard in Virtuoso 2000.
9086: Orchestral Session Vol. 2 32 MB ROM - standard in Virtuoso 2000.
9087: World Expedition 32 MB ROM - standard in Planet Earth.
9088: Sounds of the ZR featuring the Perfect Piano 32 MB ROM - standard in Ensoniq Halo.
9089: X-Lead 32 MB ROM - standard in Xtreme Lead-1, XL-7 and XK-6.
9140: Proteus Pop Collection - Standard in Proteus 2500, contains same 32 MEG sample set a"
SN 110204182 9180