compressors and the Aguilar DB751

malcolm.mcintyr · #1 08-02-2010, 09:08 AM

On stage, I have always used a dbx 160A compressor with my Ampeg SVT3 Pro with no problems.
Recently changed amp to an Aguilar DB751, but find that the compressor in the effects loop kills the sound, even in bypass mode. The volume drops by about half even with the DB751 return level on full (in series mode).
As a result I've stopped using the compressor, but don't understand why it has this effect in the Aguilar loop, but was fine in the Ampeg loop?

mccartneyman · #2 08-02-2010, 09:20 AM

What happens if you don't use the effects loop? Is it possible to plug your bass straight in to the dbx and then go out of the dbx to the amp input? If you can and the signal still drops, I'd suspect a problem with the compressor. But perhaps the signal of the Aquilar FX Out isn't high enough to drive the compressor efficiently.

bongomania · #3 08-02-2010, 10:40 AM

Quote:

Originally Posted by mccartneyman

perhaps the signal of the Aquilar FX Out isn't high enough to drive the compressor efficiently.

That's more or less my suspicion. One loop is designed for much higher or lower-level signals than the other, resulting in a need to totally change the gain and threshold settings on the compressor. Possibly even taking the dbx out of the running, if it is not able to adjust to e.g. a low-enough instrument-level range. But before ditching the dbx or thinking there's something wrong with it or the amp, try changing your input and output levels on the comp until its meters show a normal range of levels, and everything sounds "as it should" through the amp.

malcolm.mcintyr · #4 08-04-2010, 01:32 AM

The dbx compressor is a rack-mount studio unit, meant to run at line level, so I put it in the effects loop. It isn't meant to be driven by the instrument.
I adjusted the levels for input and output, but it just kills the sound. Maybe it always did, but the Ampeg wasn't good enough to show how much the tone was being affected, even in bypass mode.
The compressor has let me get careless with my playing technique. I think the Aguilar is telling me to forget compression and play a bit better.

gastric · #5 08-05-2010, 06:39 AM

The DB751 Fx loop can be switched from instrument to line level. Make sure you have it set properly.

Related, the Fx loop can be switched to instrument level for all you pedal junkies who wish they could run their pedals in the Fx loop.

JimmyM · #6 08-05-2010, 12:20 PM

people actually wish they could run their pedals in the loop?