Hi
My name is Pedro
I´m portuguese
I´ve just finished building one of "all about circuits" projects: The Vacuum tube audio amplifier.
It uses a single 12ax7 valve to produce some 2 to 3 W power output throught a 8ohm speaker.
I´d just like to say that it works great! I´ve build it mainly out of scrap components ( the only "expensive" thing was the impedance matching coil which cost me 20).
The mods I needed to make to the circuit were:
1-I´ve used a much larger filter capacitor in order to reduce the 50hz "hum",
2-I decided to use a 12v to 220v transformer to the plate voltage, since it is hard to find 110v transformers here in portugal. The result was that about 270V are arriving at the tube and still it works as expected.
3-I´ve reduced the input resistor to 50k
TWO QUESTIONS:
1-Where do I fit a volume control to the amp?
2-Is it possible to associate more 12ax7 tubes in order to obtain more volume?
3-I was recently able to obtain a large stock of PCL-80 and PCL-82 tubes. Are these usefull for audio amp projects?
I´m now using my new valve amp for guitar recording and I´me very pleased with the final result.
Thank´s for the DIY
Regards
Pedro
My name is Pedro
I´m portuguese
I´ve just finished building one of "all about circuits" projects: The Vacuum tube audio amplifier.
It uses a single 12ax7 valve to produce some 2 to 3 W power output throught a 8ohm speaker.
I´d just like to say that it works great! I´ve build it mainly out of scrap components ( the only "expensive" thing was the impedance matching coil which cost me 20).
The mods I needed to make to the circuit were:
1-I´ve used a much larger filter capacitor in order to reduce the 50hz "hum",
2-I decided to use a 12v to 220v transformer to the plate voltage, since it is hard to find 110v transformers here in portugal. The result was that about 270V are arriving at the tube and still it works as expected.
3-I´ve reduced the input resistor to 50k
TWO QUESTIONS:
1-Where do I fit a volume control to the amp?
2-Is it possible to associate more 12ax7 tubes in order to obtain more volume?
3-I was recently able to obtain a large stock of PCL-80 and PCL-82 tubes. Are these usefull for audio amp projects?
I´m now using my new valve amp for guitar recording and I´me very pleased with the final result.
Thank´s for the DIY
Regards
Pedro