Had to take a break...
Ok, I'm back, so lets get on with things.......
to answer about the troughs/conduit.... Still with out knowing what your planning here is this what I percieve...your pouring a ground level slab. With a perimeter footing, correct?
Is this an add on, or seperate bldg? Is the control room slab going to be seperate from the studio slab? Is this going to be "room in a room" type construction? Do you have a plan drawn(sorry if that was dumb)and if so has it been posted here? It would help me see exatctly what it is your doing, but I'll still try to help.
Troughs: in concrete, john has a detail showing troughs and or conduits in a slab. I only can try and interpret them. First though, your original question was in regards to electrical outlets flush with a floor. A concrete floor. In the studio, I would percieve these for amps, keyboards, rack units etc. Probably along the wall studio perimeter, correct? OK, first, there is a probably a specific code, usually, that states where, outlet height,(in wall),how many per circuit, distance between on ea. wall etc. You are placing these boxes in concrete, and your thinking about the brass cover plates, with removable screw offs, correct? Well, I would check with your local BID on this. They may not allow it in residential construction, I CAN"T say. I DON"T know for sure. Only they can tell you if it meets code there. Now, I understand why you want to do this, so you wont have wall penetrations. But running the conduit requires a complete plan prior to pouring so all electrical is in place and stubbed out. And I am NO professional at this, so as to suggesting things, I'm only trying to percieve what your doing, and have told you things I might think about, or do, or have done. As to the concrete floor, by what youve said, this IS the floor. No floating rooms, no floating floors. Correct? I was trying to describe only what I had done in regards to layout my electrical, and some of the things you can do. I DID have a floating floor, with built in troughs, that condained 4 conduits on one side, and audio cables on the other. Each trough was lined with grounded sheet metal. In concrete, your slab will only be aprx. 4". Is this correct?
A trough in concrete, as Mr. Sayer shows at his SAE site,is shallow, appears to be aprx. 1 1/4" deep by 6"wide, with 1" x 1/4"deep rabits on ea. side to support probably a 1/4" steel plate. This appears to be for audio cables. Not electrical. He also shows conduit buried in the concete. For audio, I presume. As he shows his electrical wall outlets, on the wall construction page, being in the wall, below an acoustical absorber. Are you thinking about troughs? From what to what? How are you going to terminate the troughs, under rackmounts? And to the console? What types of signals will you be running in the troughs? These are justs questions that maybe you've already answered
and maybe not. Maybe I'm just blabbing away and your laughing like mad

Let me know if you want me to continue, or buzz off, ok. This is a project that demands thourogh planning, and I'm willing to help if you need it. If not, have a great day.
fitz