dbx Expnders - 3bx, 5bx

This is a new thread which continues from a somewhat unrelated thread that I was pulling off topic.

Hi Sean - re: DBX expanders, three points:

1. The maximum Harmonic and Intermodulation distortion specs for the 5bx are .15%. Which is not small, but it's inaudible compared to the fact that the average vinyl record has had about 30db of compression in the recording and mastering. 30db!!! Now THAT is distortion. If I can remediate that, at a very small sonic cost - for myself, I prefer to. I have tried to hear a substantive enough "negative" difference in a PROPERLY adjusted 3bx or 5bx to know that it's not imaginry, and I can't. But maybe that's me.

2. Expansion/Compression is really a very simple process which in and of itself produces very little in the way of "artifacts". Re-expanding a compressed signal is not a big deal. The only parameters are Transition Level (the db level at which soft is made softer, and loud is made louder etc. and Ratio (the % change to boost or lower volume as a function of deviation from the transition level). As you stated - it's better if you can match the expansion parameters to exactly reverse the compression - but if you can't it's not that big a deal. All you're changing is the relative volumes (amplitudes) of possible related harmonics. You're not introducing phase or time distortion. So you may not be hearing exactly what was recorded, but you're a lot closer than you were listening to the vinyl straight.

In addition - and this is no small advantage - the expansion process by it's nature REDUCES any vinyl noise (which I also consider SERIOUS distortion) very significantly, because it sees it as in the "soft" zone.

3. There is a common misperception that the 1bx expands the entire range, the 3bx expands over 3 freq. ranges and the 5bx expands over 5 bands. This is not true - they all expand the entire spectrum as a whole. The only criteria for expansion are the db levels of the material above or below the transition level. Since the "Transition" level and expansion ratio are user defined, you can get a pretty darn good result. The 5bx makes this very easy, since it has a remote and 5 memory presets. If in doubt - underexpand.

4. They do split the freq. spectrum into bands for the purpose of "Impact Restoration", which seeks to undo the inherently very slow Transient Response of the vinyl media itself and the damage that lazy recording engineers did with Peak Limiters. Now this comes under what you mention as a personal preference - there HAS to inherently be some phase distortion going on here (but again I haven't been able to hear it distinctly.) However they designed these circuits - they did a darn good job. That's the cost. The benefit is the restoration of what a stick hitting a drum actually sounds like. Pop! I'd rather hear that than a phase correct Phoof....

But again - as you said - these are my personal preferences. It's impossible to listen to a vinyl record and hear the "truth". So it is just a tradeoff that I prefer to make. Fix a large amount (about 30%) of one type of distortion while introducing a small amount (maybe 2 or 3%) of another type.