Blutz Wave Amplifier
From Dragon Ball Wiki, the ''Dragon Ball'' encyclopedia
The Blutz Wave Amplifier is a machine that amplifies natural Blutz Waves by 1,000%. It was built by Bulma while she was under Baby's control. Saiyans may transform into Great Apes even without a tail if the energy given by Blutz Waves is correctly amplified, and therefore this machine may be used on tail-less Saiyans.
This machine was used to turn Baby into a Golden Great Ape. Later, during the fight with Omega Shenron, Vegeta uses the same machine to advance to Super Saiyan 4, since he lacked a tail.
It appears that an artifically high concentration of Blutz Waves can also be used to re-energize a Great Ape. Using the Amplifier, Bulma was also able to bring Golden Great Ape Baby back to full power, after being knocked out by Goku.