We would have to know some particulars about the two items you wished to compare. The DBX against what? Passive line stages are one thing while active line pre amps are another. Both have their advantages and disadvantages. To compare either of these types of component devices against the DBX unit would require a decision regarding how you will set up and use the system. If long cable lengths are required between the line stage and the power amplifier, a passive unit might not be acceptable as the changing impedance of the potentiometer as it adjusts volume levels will determine output/input impedances. There are no buffer stages nor any DC filtering in a truly passive device until you begin looking at transformer/autoformer coupled passive devices. Otherwise, the quality of the volume control will largely determine the quality of sound you hear from a passive unit. Spend a substantial amount for the volume control (say, with stepped ladder type dual mono controls) and other passive parts and you might get the best performance available at a "reasonable" price. That is, if your system configuration meets the set up requirements.

Typically a passive unit will affect the dynamics and possibly the frequency response of the system in all but a narrow range of settings on the volume control. However, with no active electronic circuits in the signal path, most passive controls sound "better" than many active components. Active line stages, however, almost always offer more flexibility in system set up, component matching and listening levels.

The problem is you are asking a hypothetical question which has no definite answer without having definite products and situations to compare. Additionally, we don't have much of an idea what you consider to be an "improvement" in sound quality. I would expect most Stereophile readers to assume the Onkyo will almost always come out on the short end of any comparison between it and a reasonable line stage, but you will have to be the judge in this case unless you can provide more information.

I was using an Creek OBH 10 between my ADC and my TT rig to keep computer recording levels below 0db. I compared it to the lp transfers I have made without it and the OBH soften the sound slightly. I have taken it out and lowered the output of my Phono Stage to keep levels lower.

ST went through this a few months back with passive line stages and how they are less transparent than we believe they should be. I know JA likes the NHT unit for $99 and it may be worth a try at some point. I have used a Niles rotary control line level input switch box when I have run out of inputs. It is transparent and cost about $50 from www.jr.com .

NHT PVC