I purchased a soundtec DMX Merge.
I have a number of heads which I have programmed to use higher DMX channels that I control via PC and combine with a manual 24 channel DMX desk running 2 * 12 way packs and it works fine providing use ensure you don't split the line and you correctly...
I'm in the UK and purchased through via a UK distributer but it originated at http://www.soundlight.de/
There are also others similar www.nicolaudie.com (French Company)
There must be similar products available in the US.
I decided to used 4 soundlab G017S DMX Colourscan's for a village hall amateur production production as well as fixed lamps - wanting to take advantage of DMX heads (even though using the cheap end).
These have been used a little for mobile disco since I got them :twisted: and is OK as there...