Hello, I would like to build an amplifier (stereo SE with EL84) but the problem is that around my area it is almost impossible to buy transformers. The only shop selling them has only two types (with desired power).
One has an output of 2x200V (and 6.3V etc...) and the other one only 1x235V. Is there any schematic that can utilize such power transformer?
I have a good acces to tubes so I don't mind if the rectifier is solid state or tube. Also I don't care about the preamp section, I have ECC81,82,83 EF86 and more.
One has an output of 2x200V (and 6.3V etc...) and the other one only 1x235V. Is there any schematic that can utilize such power transformer?
I have a good acces to tubes so I don't mind if the rectifier is solid state or tube. Also I don't care about the preamp section, I have ECC81,82,83 EF86 and more.
2x200 volt gives the required voltage when full wave rectified. and 235 volts will also when bridge rectified.
Your going to have to utilize CRC filtering as this shop likely won't have a power choke.
You might want to ask the shopkeeper to measure the resistance of the transformer secondariness, as this also determines the output voltage.
Try this program to design your power supply, PSUD2
If you encounter any problems, or questions, feel free to ask.
The EL84 has a very complete data sheet, I suggest you read it, it has everything you need to build a SE amplifier.
The same goes for the preamp, all those tubes you listed have lists of operating parameters, like supply voltage anode resistance. They will also give you the amplification of the stage.
V4lve.
Your going to have to utilize CRC filtering as this shop likely won't have a power choke.
You might want to ask the shopkeeper to measure the resistance of the transformer secondariness, as this also determines the output voltage.
Try this program to design your power supply, PSUD2
If you encounter any problems, or questions, feel free to ask.
The EL84 has a very complete data sheet, I suggest you read it, it has everything you need to build a SE amplifier.
The same goes for the preamp, all those tubes you listed have lists of operating parameters, like supply voltage anode resistance. They will also give you the amplification of the stage.
V4lve.
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Apart from getting a B+ of around 300Vdc the power transformer will also need to supply about 90mA of current. ( about 35mA for each EL84 and maybe up to about 10mA for each preamp valve whichever one you go for)
I just built one based on the RH EL84 from this thread http://www.diyaudio.com/forums/tubes-valves/64604-el84-se-advicenschematics-needed.html
See Post #2 I like it. I used a 125 v transformer (pulled from a console) with a voltage doubler
See Post #2 I like it. I used a 125 v transformer (pulled from a console) with a voltage doubler
Well with 235V one I would get around 330VDC output, isn't that a bit high to power that amp? 🙂
Or with 200VAC one I would get 280VDC output, isn't that too low? :-/
Depending on what rectifier and filters you go with I think you could get the 235v to something closer to 300. Also I've read that the EL84 can handle more than the specs usually say. I've seen on guitar amp formus where they are putting 400v on the plate, but I don't have any real experience with that. I'm also a novice at this amp building stuff myself so maybe some others with more experience will offer some advice.
For class A, 275V is probably a better choice than 330V. But what's your output transformer impedance? That's a factor for the optimum operating point.
Sorry but I have no idea. The only description given is this:
Power: 40VA
Primary voltage: 230V
Secondary voltages: 200V@0,06A; 200V@0,06A; 9V@0,4A; 6,3V@2,15A;
EI78/27,5
This schematic looks also OK, as with a solid state rectifier I would get exactly 280V output.
http://gustomo.files.wordpress.com/2010/05/schaltung1.gif
The only problem is that author says the power consumption is 90Watt. I don't see how this amp consumes 90Watt of power.
Original article: http://gustomo.wordpress.com/2010/04/18/tube-power-amplifier-el84-single-ended/
2xEL84=2*(280V*0,048A)+(6,3V*0,76A)=31,67W
1xECC83=2*(250V*0,0012A)+2*(6,3V*0,3A)=4,38W
Why would I need a 90W PT when the total calculated power consumption is just 36W?
Power: 40VA
Primary voltage: 230V
Secondary voltages: 200V@0,06A; 200V@0,06A; 9V@0,4A; 6,3V@2,15A;
EI78/27,5
This schematic looks also OK, as with a solid state rectifier I would get exactly 280V output.
http://gustomo.files.wordpress.com/2010/05/schaltung1.gif
The only problem is that author says the power consumption is 90Watt. I don't see how this amp consumes 90Watt of power.
Original article: http://gustomo.wordpress.com/2010/04/18/tube-power-amplifier-el84-single-ended/
2xEL84=2*(280V*0,048A)+(6,3V*0,76A)=31,67W
1xECC83=2*(250V*0,0012A)+2*(6,3V*0,3A)=4,38W
Why would I need a 90W PT when the total calculated power consumption is just 36W?
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Because a transformer's voltage "sags" as more current is drawn (the transformer wires have a resistance, as more current flows, the voltage drop is higher, V=I*R). Small transformers will sag more than big ones with the same load, so to prevent voltage reductions, and hence distortion, transformers are usually twice the size of the calculated load.
The "sag" is what gives guitar amplifiers their distortion sound, but isn't wanted in musical reproduction. That 40 VA transformer might be good for a monoblock though.
The "sag" is what gives guitar amplifiers their distortion sound, but isn't wanted in musical reproduction. That 40 VA transformer might be good for a monoblock though.
hello ,
so possible use other build ...
the transformator to out voltage = = )
Transformateur torique 235-2x6volts - ampliatubes.fr
and me build actually
😉
so possible use other build ...
the transformator to out voltage = = )
Transformateur torique 235-2x6volts - ampliatubes.fr
and me build actually
😉
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