Power Selection - Help Needed

zeppelinofled69 · 25th October 2010, 12:56 AM

Hello All,

I am attempting my first tube amp project, and have settled into an idea for it. The project is the Blues Preamp, located here:
http://www.ax84.com/static/corepream..._Schematic.pdf

The problem i have, is that i have no idea where to start with power. I dont know what kind of transformers, or chokes i may need,if any.

I understand that this is a novice question, so to prevent the need to ask for anything like this again, im also requesting any information on how to see what power needs the amp/preamp may need. I have been doing a lot of reading, but still cant figure this out.

Any and all help is greatly appreciated.

bob91343 · 25th October 2010, 05:27 AM

You need to compute the current draw for each tube. Add them up and you have the current rating of the power supply, which has to supply 310 Volts at that current.

No chokes will be required because the currents will be small. A few milliamperes per tube. You need to decide what kind of rectifier, silicon or tube, and if the latter, find a filament supply for the tube.

You need a transformer with a few hundred volts output. If I were doing this I would look for transformers and pick one of those available that is closest to my needs, add the rectifier, and filter capacitors. You will have a pi section filter with the 310 Volts right off the rectifier and the lower voltage after a dropping resistor. Capacitance of around 20 microfarads are probably satisfactory; you need two. Don't forget the heater supply for the amplifier tubes, 6.3 Volts at whatever current they add to.

My comments apply for a single channel; if you are making a stereo unit you double everything of course but still can run from a single power supply.

25th October 2010, 12:56 AM	#1
zeppelinofled69 diyAudio Member Join Date: Oct 2010	Power Selection - Help Needed Hello All, I am attempting my first tube amp project, and have settled into an idea for it. The project is the Blues Preamp, located here: http://www.ax84.com/static/corepream..._Schematic.pdf The problem i have, is that i have no idea where to start with power. I dont know what kind of transformers, or chokes i may need,if any. I understand that this is a novice question, so to prevent the need to ask for anything like this again, im also requesting any information on how to see what power needs the amp/preamp may need. I have been doing a lot of reading, but still cant figure this out. Any and all help is greatly appreciated.

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25th October 2010, 05:27 AM	#2
bob91343 diyAudio Member Join Date: Mar 2010	You need to compute the current draw for each tube. Add them up and you have the current rating of the power supply, which has to supply 310 Volts at that current. No chokes will be required because the currents will be small. A few milliamperes per tube. You need to decide what kind of rectifier, silicon or tube, and if the latter, find a filament supply for the tube. You need a transformer with a few hundred volts output. If I were doing this I would look for transformers and pick one of those available that is closest to my needs, add the rectifier, and filter capacitors. You will have a pi section filter with the 310 Volts right off the rectifier and the lower voltage after a dropping resistor. Capacitance of around 20 microfarads are probably satisfactory; you need two. Don't forget the heater supply for the amplifier tubes, 6.3 Volts at whatever current they add to. My comments apply for a single channel; if you are making a stereo unit you double everything of course but still can run from a single power supply.