Ilford Multi-Grade Equal To 30 Yellow...?

I use an Omega diffuse color enlarger head dialed at 30 yellow for my B&W printing much of the time for the kind of results I desire, but I'd like to give the condenser head a try.
The pack of Ilford Multi-Grade Filters sits beside it and I'm guessing that the "0", which is a lite orange might be a good place to start, but not sure.
Also, do I place these filters on top of the glass which slides into those "levels" according to what size lens I'm printing with ?

I would suggest you are over developing your negatives.

According to Ilford's Contrast Control data sheet, 30Y (single-color) on an Omega Color head is the equivalent of a 1.5 Multigrade filter. Depending on how you like your prints to look, that's just a bit below "normal" contrast. Get it here and look on page 3: http://www.ilfordphoto.com/Webfiles/2006130201152306.pdf

A Multigrade filter of 0 would equal a 90Y on your color head, so that would result in very low-contrast prints.

Which condenser head are you using? Usually there's a filter drawer below the condenser lenses.

'Much appreciated JimJim - and I was considering the 00 filter!
I'll have to be back in the lab to see what "condenser head" it is. I do know it's one of the Omega's.

I switched from condenser head to diffusion head a few years ago, and I realized the condenser had a little bit more contrast overall. One upside to the diffusion head was that dust on the negatives didn't seem to be as big of a problem.

I've always used Omegas, started with a B-600, used a B-22XL for a long time, and now have a D2V for 4x5 negs. Using a Saunders/LPL for most other work, which I think is the latest incarnation of the Omega brand. Solidly built and easy to find spare parts for all of them. If you haven't seen it, KHB Photografix has a site with everything you need to know: http://www.khbphotografix.com/omega/index.htm .

Jim