Gents, now that we are approaching delivery of some of the LGs and some of you are buying tubes, here are some guidelines. This info will all be in the user manual.
Don't forget that the tubes must have either 6sn7 or 12au7 pinouts or an adapter that conforms to this.
The total draw from the heater supply is limited to 1A. This covers A LOT of tube types.
Be aware, however, that tube heaters are run in series when they are 6V and parallel when they are 12V.
So, the maximum heater current for 6V tubes per tube is 1A. But, the maximum current per tube for 12V tubes is 500mA because they are in parallel.
The LG has two plate voltages, 300V and 200V.
The triode pair in each bottle is in what is called a totem pole configuration. This means that each triode section see half the plate voltage. Thus, with 300V each triode sees 150V and, obviously, with 200V each triode sees 100V. The totem pole is what allows the front end to self-adjust to many different kinds of tubes.
Also, the gain of the amp is 1/2 the mu of whatever triode is used.
Most of the tubes that you will use will be at the 300V setting (certainly 6SN7s and 12AU7s and equivalents). But some, like 6922 can only handle a max of about 130V on their plates. Thus, for these tube types I've provided the 200V setting (100V per triode).
Then there are weird beasts like 6H30. 6H30s pushes the amp to its limits in every possible way. Their heater current is 800mA. Definitely within the amp's abilities because they are 6V tubes, but still high.
However, 6H30s can run at 150V. But if they do they suck huge amounts of plate current when biased the way they would be in the LG. Hence, even though 6H30s can be run at 300V the MUST be run at 200V in order to control their plate current. This may be true of other tubes that we are not yet familiar with.
It would have been possible to provide adjustments for this, but then the amp would have literally become a tube tester and you would have lost the fairly simple plug and play operation that it has now.
Don and I will try to provide lists of tubes that should work (see website) and you'll need to exercise some care in choosing and running tubes, but for the most part things should be fairly simple.
Also, the LG HV supply has a shutdown feature if the plate current is too high. The amp will simply shut off.
And, the one heater mistake that you can make is to put 6V tubes in with the 12V heater setting. If you're paying attention you will see this immediately since the tubes will start to glow like a light bulb. Normally if you turn them off quickly they won't be damaged.
If you exceed the max heater current the amp will, eventually, fail. Maybe not right away, but the heater supply will just get too hot.
But, if you are thoughtful and careful you should be able to roll a lot of tubes through this amp.
like these http://www.head-fi.org/t/624548/woo-audio-6sn7-to-6f8g-tube-adapters
