Threshold on a compressor that goes in +dbu values

[Mataya]

Hi,
I hope someone could explain this a bit more.

I have a dbx 160a hardware compressor and it works fine. I just don't understand why and when would I use a threshold that's in a + value and that's 20dbu in + that this unit has.

I always see threshold values going from 0 to - some db. Is this because it's an analogue hardware and I only see negative values on digital plugin's... or wtf is going on here.

Thanks
this is the unit if you wanna check it out

https://dbxpro.com/en/products/160a#specifications

[TheDragonborg]

I dunno my Alesis 3630 compressor goes up to +20 dB on the threshold...

[Loque]

I speculate its the analog headroom above (digital) 0db, which is useful for hard driving the compressor.

[orthodox]

Unlike digital 0 dB, which usually means 0 dBFS ie relative to Full Scale or digital clipping level, in analog world, 0 dB is calibrated to some Standard Operating Level measured by a VU meter. Analog devices like that compressor have a substantial headroom above that level.

[Mataya]

Unlike digital 0 dB, which usually means 0 dBFS ie relative to Full Scale or digital clipping level, in analog world, 0 dB is calibrated to some Standard Operating Level measured by a VU meter. Analog devices like that compressor have a substantial headroom above that level.

Thanks, I think I got it.

I only used this device for recording dialogue into computer. But I guess if I would plug this unit into live system somewhere, I could expect levels that are in analogue domain meaning going over 0db, so I would adjust the threshold for this higher signal levels and probably stayed on a + side.

tx
M

[orthodox]

I only used this device for recording dialogue into computer. But I guess if I would plug this unit into live system somewhere, I could expect levels that are in analogue domain meaning going over 0db, so I would adjust the threshold for this higher signal levels and probably stayed on a + side.

Yes, that's totally OK, provided all the devices in the FX chain are capable to handle such levels. Reducing the analog level is easy, it's done with passive components.

[selig]

Unlike digital 0 dB, which usually means 0 dBFS ie relative to Full Scale or digital clipping level, in analog world, 0 dB is calibrated to some Standard Operating Level measured by a VU meter. Analog devices like that compressor have a substantial headroom above that level.

Indeed - this device has 24 dB headroom over it's "0 dB" mark.
Digital dB is "dBFS", analog is typically "0dBVU", and the "zero" isn't the same in both systems since analog systems have headroom and digital do not (not counting floating point digital in this case).
Typically, an A/D and D/A has a relationship of -18 dBFS being equal to 0dBVU, but in higher end convertors you can calibrate this to different levels.