Rivera Rockcrusher Question (Z Input)

[bbaug14]

If I'm running a 100W head at 50W by pulling two tubes and I'm running into an 8ohm cab, I should plug into the 4ohm speaker output of the amp for the impedence mismatch. My question is if I'm using the Rockcrusher as well, set to the 8ohm setting to match the load, does this present any problems to the amp?

 

[chumbucket]

Yeah, plug into the 4 ohm setting on your amp.
Did you try measuring the Rockcrusher with a meter while it was plugged into a cab and switch through the settings? It will probably be a little more than 8 ohms. Better too large than too small of a load.
If you've got the Rockcrusher though, why are you pulling two tubes?

 

[bbaug14]

I was just messing around and wanted to hear the amp at 50W through the Rockcrusher vs 100W. I started to think about it and I wanted to be sure I wasn't going to damage my amp doing this. As for taking a measurement, I'm not sure I follow. The load, regardless of what input I put the amp at, isn't changing. What would I be measuring exactly?

In the manual it says when using 2 - 16ohm cabs to use the 8 ohm setting because they are in parallel. This makes sense as the load to the amp would affective my be 8ohms. In my case the load is 8ohms but the amp is creating an impedence mismatch to 4ohm. I'm not sure if I shouldn't be using the Rockcrusher or not in this way. Hopefully someone around here knows.

 

[bbaug14]

I contacted Rivera on this and they basically said don't do it. Now, I believe it was a sales person who gave me this info, and he didn't provide any technical reason, so take it with a grain of salt.

 

[bbaug14]

Also, I did some research on this subject and attenuators in general and from what I've been able to find, it should be okay to run an amp minus 2 tubes as long as the cab and the attenuator match. This makes sense to me as the affective load is not changing, nor should the attenuation value.