You really don't want to put, for lack of a better term, 'lower quality' pedal type units in the effects loop. The effects loop outputs a much hotter signal from the effects send output than a bass guitar puts into an effect pedal. If you have a high quality, rack mount type effects unit, the effects loop works great. For the Zoom type pedal units, put the unit between your bass and amp input and it will work fine.
This is not specific to Ampeg at all.
Thanks. What about standalone pedals in the loop? The goal is to switch on and off multiple effects at once, and to be able to use the compressor on the amp itself.
FWIW, I had crappier multi-pedals than this in the effects loop of some other amps I owned and they all worked fine...