Double Bass output ohms vs. speaker ohms

[chuck3]

A question for one of you who might know - getting ready for a gig using the DB through the PA. I will either use a Radial PZ-Pre as a preamp and the house monitor, or an Acoustic Image Coda as both preamp and monitor. The PZ-Pre's XLR out and the Coda's DI out both are 600 ohms output. The "instrument out" of the PZ-Pre is 1k ohms.

My question is this - I'm familiar with ohms for bass cab speakers - basically, in my world, you're talking either 8 ohms or 4 ohms, and I know how to match that up with an amp head. But are those ohms the same ohms as the ratings for the preamps? It just seems odd to me (in that case) you are talking such a low number of ohms for the cabs and high number of ohms for the preamps.

Obviously I am unencumbered by a lot of expertise about this, just got to wondering about it.

 

[drurb]

They are indeed the same ohms. If they are following convention, then the impedance ratings for the amp outputs you cited are the load that would be "seen" by the next piece of equipment in the chain.

 

[ArtechnikA]

I believe 600 Ohms is a typical impedance for DI's; something in the 50 Ohm range for microphones.
This is the "Lo-Z" (Low Impedance) phrase you see sometimes...
Lo-impedance devices are 'relatively' noise immune (and the DI's differential ('balanced') transmission method more so...
This is good for 60-cycle hum rejection.

In broad strokes, you want the "receiver" part to have a higher input impedance than your sender.
This is why DB preamps typically have very high (megohm-range) impedance.

It's all about the power.
An amp makes a lot of power and can drive a low-impedance load.

A DB Piezo pickup makes only a tiny amount of power and needs a high impedance load (if you look at the Inpit spec on those pre's I expect you'll find them in the megohm range). A 1000-Ohm output impedance from the pre is fine since it's going into an input that will be as high or higher.