Ross Valory

As mentioned in an interview with BassPlayer.com.

A 1980 advertisement showing Valory with the T-40.

Valory performing with the Stingray HH in 2008.

According to this forum, Valory recorded the Escape album and played the Escape tour with an Ovation Magnum II.

As mentioned among the players on the Steinberger website.

If you pause at 2:36 in the video, you see Ross Valory playing his iconic Steinberger L2 bass, which was mainly used on the Frontiers album (1983). If you look real closely at the pickups, you can see that it has no pickup rings, meaning it was not an XT-2, which someone else stated previously. The XT-2 wasn't introduced until way after the L2, and by the time it was introduced, Ross had switched to Jackson basses. The XT-2 also came with pickup rings, which the early Steinberger basses did not have. Ross himself did not talk about his basses very much, or mention them all that often, but from looking at the bass, it appears to be a Steinberger L2.

As mentioned in an interview with BassPlayer.com.

The bass cabinet as listed by Ampeg as part of Valory's private collection.

As mentioned on GHS Strings' website.