Diving into the DIY tube preamp for the first time. Definite newbie especially with tubes.
I have the mono octal boards and two PS-4 power supplies. I have assembled a single board from each for testing purposes. I plan on running 6sn7 tubes with 12.6V in series using FW bridge from a dedicated 12.6V transformer (RadioShack 12.6V CT). On testing my wall AC I am around 126V. The transformer measures roughly 14.4V AC. When I hooked everything up I get 13.7V DC at the heaters.
Per the manual I tried lowering R2 to get better regulation but it only dropped the heater voltage to 13.5V. I rechecked all parts and they are correct. I am a bit stumped now in trying to figure out what is preventing me from getting the 12.6V I need. Line AC? Transformer? Regulator? Should I keep lowering R2 till I get the value I want.
Thanks for the help
I have the mono octal boards and two PS-4 power supplies. I have assembled a single board from each for testing purposes. I plan on running 6sn7 tubes with 12.6V in series using FW bridge from a dedicated 12.6V transformer (RadioShack 12.6V CT). On testing my wall AC I am around 126V. The transformer measures roughly 14.4V AC. When I hooked everything up I get 13.7V DC at the heaters.
Per the manual I tried lowering R2 to get better regulation but it only dropped the heater voltage to 13.5V. I rechecked all parts and they are correct. I am a bit stumped now in trying to figure out what is preventing me from getting the 12.6V I need. Line AC? Transformer? Regulator? Should I keep lowering R2 till I get the value I want.
Thanks for the help
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Here is the circuit I am using. Same populated components. I do not have the high voltage transformer wired in at the moment. Also haven't fully grounded the boards as they are just sitting on my workbench to test. Not sure if that matters
http://tubecad.com/2010/03/21/push-pull power amp example for ps-4.png
http://tubecad.com/2010/03/21/push-pull power amp example for ps-4.png
Was able to get heater voltage down to 13.1V. Adjustable regulator is seeing 14.75V. It is outputting the above. Double checked resistors and they are 1.07K and 124 ohm which should give me roughly 12V. Unless my math is wrong it should be outputting a regulated 12V. At this point should I keep adjusting the resistor till I get the voltage I need or should I re-evaluate elsewhere?
So decided to build the other power supply board and everything worked out fine. Took me a little bit to realize the difference between the two. The board that wasn't working was built on the wrong side of the PCB. Switched the regulator around and voila... 12.6v. Pesky boards look almost identical on each side.
I now have 12.6V for the heater which is supplying the two 6sn7 in series. Added the HV rectifier tube and I get a stable 270V B+. Gonna fine tnbe to get around 300V but that shouldn't be too bad.
Hopefully tomorrow I can wire some input/outputs to see if I get any sound. Then it's time to figure out how to arrange the unit into its home. This is going to be a true dual mono preamp with separate power supplies and transformers. Only common part will be the power switch/cord
I now have 12.6V for the heater which is supplying the two 6sn7 in series. Added the HV rectifier tube and I get a stable 270V B+. Gonna fine tnbe to get around 300V but that shouldn't be too bad.
Hopefully tomorrow I can wire some input/outputs to see if I get any sound. Then it's time to figure out how to arrange the unit into its home. This is going to be a true dual mono preamp with separate power supplies and transformers. Only common part will be the power switch/cord
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