Tube spacing - blues junior chassis.

[hughesp]

I've got a blues junior chassis (& cab & speaker) from an amp that died a while back...

I've got a circuit I want to try out which will use eithe 2 x 6l6 tubes or 2xEl34 tubes and 2x 12ax7 tubes and i was thinking about using the chassis & cab from the dead amp. New transformers, etc...

The chassis holes from the previous sockets are big enough to put octal sockets in for the power tubes, but I'm wondering about the spacing of the tubes. They won't be touching, but it seems like these tubes would be quite close to each other.

I know there are people running 6v6 tubes and 5881 tubes in modified blues juniors. I'm just not sure how good this would be for heat/tube life.

My other option would be to use every other socket hole, and then drill a new hole, perhaps mounting horizontally, for the first 12ax7, while all the rest hang in the normal vertical configuration. That tube won't have great ventilation, but I wonder if it is better to have a 12ax7 mounted that way than to have 2x6l6 tubes too close together.

Thoughts?

[M Fowler]

I don't think it is a problem depends on what you mean by not much ventilation. Might have to design the back of the combo cab to be a bit more open.

This photo shows a Redplate amp and how close one can go.

Mark

[hughesp]

Seeing a picture of someone else's blues junior with 5881 tubes:

[img:800:471]http://www.duhvoodooman.com/miscimages/ ... 5881s].jpg[/img]

It just seems closer than I ever otherwise see!

[Structo]

Keep in mind when you add different transformers or a extra tube, the clearance between them and the speaker.
Many have been frustrated only to find the chassis won't fit back in the cab after modding the amp.

[hughesp]

already thought about that. So far my measurements suggest I'll be fine with the Iron I'm planning to use...

The big thing is to stick the new big OT further away from the PT side of the chassis. (a bigger PT, where the stock one it, would hit the speaker for sure).

Not a big deal - and the added distance cuts down hum anyway.

Just want to be sure about sticking two octal tubes so close together.... I might stick with El34s, as they are a good deal narrower than 6L6 tubes...

[Phil_S]

The octal tubes have more than enough clearance from each other in that picture. I'd be more concerned about distance to the speaker magnet. I can't see what it is, but it also looks OK.

You are probably limited to octal tubes in straight bottles. Coke bottle shaped glass probably won't fit.