• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

The 33 Amplifier

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Describes an audio amplifier using a pair of 33 tubes in Class AB2 PP. For those unfamiliar the 33 is a 2V filament type.

In triode operation max power is 2.5W while UL connected max power is about 4.5 W. Not for everyone but an interesting look at what is possible while power requirements are small.
 

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An interesting article, pitty it seems to be a dead thread.

p.s. that was a great calculator you had on the bench!


That calc is an HP71B, got it while working at HP in 1984.
More powerful than a locomotive, it runs HP BASIC. I bought a 3rd party extra memory module for it, fits into the magnetic card reader slot. It has a data IO to the outside world, the HP Interface Loop. Has most of the same commands as the HPIB (IEEE488) Interface. Also have the matching disc drive, tape drive & a buss card to communicate with a desk top running on MS DOS.
And an extra 71B. The HP 71B can run as a Controller or Slave.:)


Looks like not many interested in 2V Toobes. I did it as a Proof of Concept.
Why do something like a Williamson or Mullard, everyone else has done that!:D
 

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I love the HP's, I find the RPN a natural way to use a calculator. I had a summer job once at JET (Joint European Torus) project and they asked me to write some software where you could define a formula using matrices as variables and then do the calculation. I was a teenager at the time but was familiar with an HP calculator so I set up the software to run the calculations using RPN. It was a Norsk Data mini computer.

Anyhow, I have half a dozen 3A5 tubes, I guess you can call them "2V tubes" more or less.
 
Soon after, my mother allowed me to connect to the power line & I never again had reason to use or experiment with tubes intended for battery operation.

I remember those "discussions."

A few old battery tubes wired together made for a real crummy guitar amp. It wouldn't get loud no matter how many 67.5 volt batteries were wired together. I got better sound from those big round germanium TO-36 transistors removed from the back of a car radio. Three 6 volt lantern batteries would make them crank.....4 would blow them up.

Once wall outlet privileges were granted, there were a couple of "suspensions" usually provoked by fireballs, selenium rectifier stink, or exploding capacitors. Those old wax and paper covered multi section electrolytics salvaged from old radios had zero tolerance for abuse, and the guts could find their way out from any possible angle or direction with great ferocity. No, the 1N60 diode removed from a dead transistor radio will NOT replace a 35W4.

I have half a dozen 3A5 tubes, I guess you can call them "2V tubes" more or less.

The "2 volt" tubes were designed to be powered by a single lead acid cell, or 3 wired in series from a typical car battery (6 volts in the day).

The 3A5 and newer "battery tubes" were designed to be powered from a single carbon zinc cell. The hot ticket filament source in my childhood was one of the monster batteries used for starting the 0.049 Cubic Inch glow plug (Diesel) engines from the model aircraft that were popular in the early 60's.
 
The hot ticket filament source in my childhood was one of the monster batteries used for starting the 0.049 Cubic Inch glow plug (Diesel) engines from the model aircraft that were popular in the early 60's.
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The #6 cell used by phone companies?? Especially in the 30s. Still out there. Seems to me I found a Ni-Cd vers a while ago.:)


The 3A5 is a toob looking for something to do. Tiny Class B Amp? Clandestine transmitter?:D Maybe
 

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The #6 cell used by phone companies??

Googling "#6 battery cell" then selecting "images" brings up pictures of the " igniter" batteries that I used to light my tubes and start my airplanes, so yes same cell.

The 3A5 is a toob looking for something to do.

It was designed for radio transmitters. I tried them when I had the idea of putting a small tube amp INSIDE the guitar body since total filament power was .3 watts. I also experimented with several different "battery tubes" but they were too microphonic and lacked the ability to produce a "cranked" guitar sound.

I wound up using a 6AK5 driving a 6AK6 for a "micro Champ" 5C1 type amp. The early Champ is a two stage SE amp, and the "micro" version made more power than the push pull amp made with battery tubes. The whole thing would run for a few hours from a 7.2 volt RC car NiCad.

About 15 years ago I made a custom headphone amp for a neighbor of my brother. It was a modified version of one of my TSE amps. We tried several tubes with the 31 and the 33 being the best choices. I don't know which the customer wound up using. He really liked the amps I made for him, but the whole family and all the fancy cars vanished one day during the 2007 economic mess.
 
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