Indication that if you have a "one-person" DB not covered by PBGC, your DC contribution is limited to 6 percent of compensation.
Indications that if you have a Schedule C, your deductible DB contribution is limited to your Sched C earnings. Also, if you have a DB and DC, DC contribution is limited to 6 percent of compensation.
Further indication that if you have a "owners" DB not covered by PBGC, your DC contribution is limited to 6 percent of compensation :
Further indication that if you contribute to a DB, you can contribute up to 6 percent of comp to a DC. Further, if you limit contributions to a DC to 6 percent, you can fund your DB to 150 percent of the liability.
More evidence that in a combined DB / DC situation, if the DC contribution is less than 6 percent, the DB contribution is not limited.
Passage of the Pension Protection Technical Corrections Act of 2007
Adding a 401k to a DB means you can add $16,500 (plus $5,000 if age 50+) plus 6 percent of compensation (not to exceed $14,700) :
Front-loading of a new defined benefit plan. Probably wrong in saying that you can have both a DB and a fully-funded profit component of a 401k of more than 6 percent :