Low Power Guitar amp from AA5 Radio

[cloudhopper]

Here is a $5 purchase, an All American 5 (AA5) radio. Uses 5 tubes and no PT. Sound dangerous? Ok......so here's my idea, remove the 12BE6 pentagrid converter tube, substitute a 82 ohm, 2 watt resistor for the removed tube's heater filament (series filament configuration), remove the T1, T2, T3 transformers, rewire the 12BA6 to a pentode input stage like an EF86 and feed into the triode of the 12AV6 with the diodes unhooked. To avoid shock, a simple radio shack 1:1 audio input isolation transformer removes the input jack from potential line voltage. I'll also wire a jack in for an external speaker, looks like the internal speaker is 3 ohm so it should be fine for hook up to an external 4 or 8 ohm speaker. I'm guessing it will be around 2 watts of SE power from the 50C5 pentode power tube. I will probably not bother with a tone control, I'll just use the guitar tone for adjustment, and I'll play with the coupling cap values a bit to adjust initial tone. The 12BA6 is designed for RF and IF instead of AF but I'm thinking it's worth a try. What do ya think? Am I crazy? If it works, it will be a super cheap low power amp and I know there are tons more of these in the flee markets, most need the 50 and 32 uF caps replaced, but they are cheap too. If the 12BA6 doesn't work for the first stage, the good old 12AX7 has the same heater filament voltage and power requirement and could be fitted right in with a socket change.

Carl

[MichaelJ1965]

I tried it by just jumping into the audio stage. I did not get much volume out. I "think" that the audio stage needs more voltage/current than the guitar puts out. I still have the tubes and all the other parts. It would be cool if you get it to work...

I also noticed that the solder did not take well. It sort of balled up without sticking. I don't know what caused it.