Power tube spacing question

[gtrrich]

Hi everyone,

Just wondering, are there any hard fast rules on Power tube spacing, (or pre-amp for that matter) for a push-pull amp? I'm building a Princeton based amp, with 2 6v6's. I measured the distance between the tubes on my Deluxe Reverb RI and they are about 2 1/2" apart. Can I run them a little closer together to save some space, or will this cause trouble down the road? Thanks in advance!

[loudthud]

You could go a little closer. A lot depends on how much ventilation there is. Heat is the enemy of most things electronic.

[black_labb]

there is usually specs in datasheets, but keep in mind they are optimal situations. better ventilation means you can get away with closer tubes as loudthud said.

[pontiacpete]

I just measured the distance betw the 6v6s of my princeton and they are about 1.25" apart.

[RudeBoy]

With ventilation you should be in good shape. Some tubes even had two power sections in one envelope. For example 6DZ7 contains (contained?) two 6BQ5 sections in one octal base envelope.

[CharlieP]

It all depends on if you ever want to use large bottle tubes like the KT66's. 2½ inch spacing is a must for the large bottles.

[gtrrich]

Thanks for the input everyone. A couple more quick questions:

I'm assuming ventilation means an open back cabinet? I'm not planning on putting a fan in there. Is having an open back all that is needed?

Pontiacpete -what model Princeton do you have? Princeton Reverb?

Thanks

[pontiacpete]

I have a silver face early 70's princeton reverb.

you probably would want to do an open back cabinet.

pete

[CharlieP]

Ventilation also means, area around the tubes to dissapate the heat from each tube. Closer spacing, heat has more interference from other tubes and more heat build up. Heat is not tube friendly.

[PeteG45]

I just measured my build (5F2A) and the tube sockets are 2 1/2" on center so they are about 1 1/2" apart. I based the spacing off of my Peavey ValveKing which are about 1 1/4" apart and I have a pair of KT66s in there. I'm only going to run a pair of 6V6s or a single 6L6 or single KT66 so spacing should be OK.

No problem with heat in my Peavey but it is an open back cabinet with lots of room inside. The KT66s sound gooooood.

[txstrat]

Have been running the amp in the pic for more than three years now (regular rehearsals once a week). Two JJ 6V6s (25W OT) with no more space than a thumb in between them.
Never had an issue. Just my 2C.