Converting 8Ohm Cab to 2Ohm

[Downunderwonder]

I would put the switch in the YBA300. That takes the amp to 4/8. The 2ohm option with the external switch is then 8ohms.

On the offchance you need to run the amp at 2ohms you can open it and flip. Putting the switch outside would leave you open to accidentally running 2ohms into 8ohm cab, which would be quite bad for the tubes.

 

[bassmeknik]

I would put the switch in the YBA300. That takes the amp to 4/8. The 2ohm option with the external switch is then 8ohms.

On the offchance you need to run the amp at 2ohms you can open it and flip. Putting the switch outside would leave you open to accidentally running 2ohms into 8ohm cab, which would be quite bad for the tubes.

This is much more complicated than putting the switch in the cab as the switch in the head would require isolated output jacks to be added... not near as easy as mounting it inside a wood cab on your existing jack plate.

 

[bassmeknik]

I would put the switch in the YBA300. That takes the amp to 4/8. The 2ohm option with the external switch is then 8ohms.

On the offchance you need to run the amp at 2ohms you can open it and flip. Putting the switch outside would leave you open to accidentally running 2ohms into 8ohm cab, which would be quite bad for the tubes.

We are talking tube amps with output transformers with limited taps? What I think you are suggesting here is to mount 2 series wired jacks to the output and switch between those and the stock jacks, difficult but feasible. The 2 series wired jacks will have to be isolated from the amp chassis... it really is MUCH easier to mount the switch inside the cab.

 

[Downunderwonder]

We are talking tube amps with output transformers with limited taps? What I think you are suggesting here is to mount 2 series wired jacks to the output and switch between those and the stock jacks, difficult but feasible. The 2 series wired jacks will have to be isolated from the amp chassis...

No, the YBA300 comes with a simple mod prepared on the OT circuitboard to reroute the transformer, the 2ohm tap becomes an 8ohm tap.

 

[bassmeknik]

cool, then that is a viable option

 

[walterw]

so the transformer has an 8Ω tap to use? yeah, that would be the easiest way, wouldn't it? just wire the amp to switch between 4 and 8 instead of 2 and 4.

otherwise, with the cab you could avoid the extra moving part of the switch and wire it with two switching jacks marshall-style, one series/parallel for 8Ω and the other straight parallel for 2Ω.

 

[awilkie84]

I would put the switch in the YBA300. That takes the amp to 4/8. The 2ohm option with the external switch is then 8ohms.

On the offchance you need to run the amp at 2ohms you can open it and flip. Putting the switch outside would leave you open to accidentally running 2ohms into 8ohm cab, which would be quite bad for the tubes.

The YBA already has a 4/2 switch and, while it does have an internal mod that can be done to convert it to 4/8, I don't want to be messing with the circuitry in there. Besides, taking the amp apart is like an hour's work in itself.

 

[bassmeknik]

I have been searching the web all day trying to find a cut-away view of a toggle switch to clarify how the toggle position relates to which contacts are in use. Here is a link to this view:https://www.google.com/search?q=internal view of a spst toggle switch&espv=2&tbm=isch&tbo=u&source=univ&sa=X&ei=BFjZU7zgA8ObyATD4ILIDg&ved=0CBwQsAQ&biw=1600&bih=775#facrc=_&imgdii=_&imgrc=5QBRhcNbPgVI2M%3A;9VUAwkJD8m5EuM;http%3A%2F%2Fi01.i.aliimg.com%2Fimg%2Fpb%2F703%2F076%2F302%2F302076703_780.jpg;http%3A%2F%2Fwww.alibaba.com%2Fproduct-detail%2Foff-on-off-toggle-switch_241742656.html;404;273 (this is a side view of a switch)

You will see that the toggle lever is rocks back and forth on a pivot, the other end of the lever makes and breaks the connection. This is what I meant when I said the lever faces the set of contacts not in use...