Iron

Iron

Eimac - Scaling Up

"TL" or low mu tubes are much easier to drive than "TH" or high mu tubes.  Driving a TH tube takes a power amplifier circuit.  This is where MOSFETs shine.  The advantage of TH tubes like the 100TH below is that by the ver design, they have to be run in A2.  This makes them capable of producing a lot of power.  And because they are very difficult to work with, they are usually a lot cheaper.

Where do you go from there?  The 304TL of course.  Here we were able to find some 304TL tubes at a moderate price which allowed for good old fashioned A1 driven through a interstage transformer.

These are currently being built with 4 chassis.

2A3 Push Pull

A 2A3 Push Pull amp is as perfect of a 10 watt amp as you can get.

This amp was designed to be a throwback to the start of higher power audio reproduction.

Inside there are no electrolytic caps, only film used with a MOSFET capacitance multiplier circuit.  It employs 6SL7 to 6SN7 to 2A3 with fixed bias.  Latest version uses high capacity chokes. 

This amp is built like a tank.  We had it temporarily on a shelf for storage and the shelf gave way.  The amp landed on the floor and gouged the wall.  The only damage was a slightly bent tube pin on one of the 2A3s

Building with Eimac tubes - 35T

Eimac tubes make great amplifiers as they can produce a lot of power from a relatively small size, employ the hight of 1940's military technology and are relatively affordable.

The downside is that they require very high voltage, most need A2 drive and they are very mildly radioactive.  ☢  👀

 The power requirements can be extensive.

Buttoned up, what is not shown is the 20 pound power transformer sitting below.
(Yes that is Elvis and hard to see but a St. Christopher medal)

They also make great nightlights and space heaters

Fender 300-PS Transformers - Bass Amp

What to do with a Fender 300-PS output transformer and Power Transformer. Build a 200 watt amp.

This amp uses the original Interstage Phase Inverting transformer driven by a 6V6GT to a quartet of KT88 tubes.  The tubes shown are test mules.  This was made for a working Bass player and apparently it delivers the power he was looking for.  I really could not test it anywhere near full power.

It is kinda heavy