This is my project for low cost, low voltage, simple, 2+2W Class A stereo tube audio amplifier.
Characteristics:
- Safe:
60 Vcc max (12+12Vac 35 VA line transformer + diode voltage doubler)
- Cheap:
less than 100 €
- Active Components:
V2 = PL504 (preferred) or PL500,
V1= ECC82 or 12FQ7 or 12BH7 (preferred)
- Easy:
it uses 220 Vac (110+110) / 24 Vac (12+12) 35VA line transformer as audio transformer, the low anode voltage (about 58Vcc) reduces the core saturation risk.
Note: for the best audio performances you may use a real audio transformer 600-800 ohm 5W (military surplus)
- Indestructible:
it withstands permanent output short circuit.
- Low distortion:
it uses negative feedback to reduce distortion.
Schematic (one channel audio + power supply for both channes and filaments):
ampli511 - Servimg.com - Free image hosting service
V2 pinout (anode = CAP):
V1 pinout:
Characteristics:
- Safe:
60 Vcc max (12+12Vac 35 VA line transformer + diode voltage doubler)
- Cheap:
less than 100 €
- Active Components:
V2 = PL504 (preferred) or PL500,
V1= ECC82 or 12FQ7 or 12BH7 (preferred)
- Easy:
it uses 220 Vac (110+110) / 24 Vac (12+12) 35VA line transformer as audio transformer, the low anode voltage (about 58Vcc) reduces the core saturation risk.
Note: for the best audio performances you may use a real audio transformer 600-800 ohm 5W (military surplus)
- Indestructible:
it withstands permanent output short circuit.
- Low distortion:
it uses negative feedback to reduce distortion.
Schematic (one channel audio + power supply for both channes and filaments):
ampli511 - Servimg.com - Free image hosting service
V2 pinout (anode = CAP):
An externally hosted image should be here but it was not working when we last tested it.
V1 pinout:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
My first hybrid amp had a 12ax7 front end into a mosfet power amplifier.
The mosfet part had +/-45 volts supply so this 90 volts was also the supply (decoupled) for the 12ax7.
My first fully valve amp was a pair of el84's on the output with 12au7 as phase splitter and 12ax7 as amplifier front end.
This worked a treat.
My next was el34 based and was a bit more trouble to get working. I had hum and noise problems but eventually sorted them out. The PCB could have been better but I learned a lot from that project.
The mosfet part had +/-45 volts supply so this 90 volts was also the supply (decoupled) for the 12ax7.
My first fully valve amp was a pair of el84's on the output with 12au7 as phase splitter and 12ax7 as amplifier front end.
This worked a treat.
My next was el34 based and was a bit more trouble to get working. I had hum and noise problems but eventually sorted them out. The PCB could have been better but I learned a lot from that project.
Last edited:
This is my project for low cost, low voltage, simple, 2+2W Class A stereo tube audio amplifier.
Characteristics:
- Safe:
60 Vcc max (12+12Vac 35 VA line transformer + diode voltage doubler)
- Cheap:
less than 100 €
- Active Components:
V2 = PL504 (preferred) or PL500,
V1= ECC82 or 12FQ7 or 12BH7 (preferred)
- Easy:
it uses 220 Vac (110+110) / 24 Vac (12+12) 35VA line transformer as audio transformer, the low anode voltage (about 58Vcc) reduces the core saturation risk.
Note: for the best audio performances you may use a real audio transformer 600-800 ohm 5W (military surplus)
- Indestructible:
it withstands permanent output short circuit.
- Low distortion:
it uses negative feedback to reduce distortion.
Schematic (one channel audio + power supply for both channes and filaments):
ampli511 - Servimg.com - Free image hosting service
V2 pinout (anode = CAP):
An externally hosted image should be here but it was not working when we last tested it.
V1 pinout:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
hello ,
very good build , possible up voltage for up power out in audio , 100 V= si very good , me proto is based to your schéma
and very up in good choice to OPT at 250 V= 😉
many thank Pilovis
Hi, really good project, i already try it on an breadboard, and works great 🙂
But on my project i want to add 2 things:
1º Bass, treble adjusts, not anything too much elaborated, just basic adjusts
2º A magic eye indicator with EM80 or EM84 tubes
But i dont know much about tubes operation, so wanted to ask if its possible to include this 2 things, and if there is a schematic with this two changes
Thanks in advance
But on my project i want to add 2 things:
1º Bass, treble adjusts, not anything too much elaborated, just basic adjusts
2º A magic eye indicator with EM80 or EM84 tubes
But i dont know much about tubes operation, so wanted to ask if its possible to include this 2 things, and if there is a schematic with this two changes
Thanks in advance
Your OT is without air gap, probably, and it easy will saturate. You can make gap EI plasing with paper 0.2 mm between E and I.
Going by his use of 220v/24v transformer this would translate to 672 ohms primary with 8 ohms on the secondary.
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