Dual rect. running in 50W mode + Hot Plate + 8ohm cab?

Jacko123 · Mar 13, 2009

Hi guys. I need to make sure I'm not going to break anything.

I will retubing my amp with only 2 power tubes tonight to get 50W (as per parge 14 of the manual) ... I'm a basement/bedroom player for now, plus I want to experiement with different power tubes, both 6L6 and 34's.

I have an 8ohm Hot Plate attenuator. I remember seeing someone mention that I should run my 8ohm cab from the 4ohm output jack. Can I still use my 8ohm attenuator? I'm afraid I don't quite get all these ohms business yet.

Any help would be greatly appreciated.

Areola · Mar 13, 2009

So your 4ohm output is now actually putting out 8ohms due to the alteration of the power tubes.

So by pulling 2 tubes from the amp, using the 4ohm output into an 8ohm Hotplate and an 8ohm cab your rig rating is merely this:
50watt @ 8ohms

My advice would be to put those other 2 tubes back in, because I've done exactly the same thing, and the Hotplate really isnt needed when you pull those extra tubes. It just makes your tone buzzier. I had a jam on the weekend using my DR at 50watts with no attenuator and it was having trouble being heard over the drums and the bass when my output was at 10.

Mind you, you might like the buzziness. I do, so I'm not too worried. If i want clean/crisp sounds, I've got my Orange AD30.

Areola · Mar 13, 2009

Also, you can safely mismatch by 2x

Forget the change of ohms for a second... you can safely run an 8Ohm cab from either a 4 or 16ohm output. You cannot run a 2 ohm cab from an 8 ohm out, or a 16 ohm cab from a 4ohm out. that's overloading it. when you mismatch by 2x you are simply reducing the power and slightly altering the tone. I believe if you put a 8 ohm cab in a 16 ohm output you're getting a lower volume and a slightly higher ended signal, but if you put the 8ohm cab into the 4ohm out, you are getting a slightly bassier signal and less volume. Its a very handy trick to bring down the volume of such a loud amplifier.

What i used to do was pull 2 tubes, AND run my 8Ohm hotplate and cab from the 8ohm output (which was actually putting out 16ohms now).

Jacko123 · Mar 13, 2009

That's awesome! Thanks for the information.

coppa · Mar 14, 2009

when 2 tubes are pulled your 8ohm cab plugs into the 4ohm output. A 16ohm cab would plug into the 8 ohm output. you cannot run a 4 ohm cab safely with 2 tubes pulled out.

if your hotplate is 8ohm then it plugs into the 4 ohm output. if the ouput on the hotplate is 8 ohm then you must plug in an 8 ohm cab into your hotplate.