• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Aikido 12Vac

I build a PA150 amplifier and decided to use an tube preamp in front of it. Since i am literally virgin with tubes and after doing some research i decided to go with Mr. Broskie's Aikido 12Vac. I received the PCB and i was impressed with the quality of the board, this thing is twice as thick as my PA150 boards!!

[IMGHTTPDEAD]http://img404.imageshack.us/img404/5537/img0649q.jpg[/IMGHTTPDEAD]

[IMGHTTPDEAD]http://img507.imageshack.us/img507/3443/img0807u.jpg[/IMGHTTPDEAD]

[IMGHTTPDEAD]http://img854.imageshack.us/img854/7758/img0808fg.jpg[/IMGHTTPDEAD]
 
Nice board layout and quality, i'm interested in the caps values from the voltage sextupler

Voltage%20Sextupler%20Circuit.png


Best Regards
 
I finish Assembling the preamp and went directly to test it before i did some measuring...bad idea. It did not smock or smell but the sound was horrible, it was clipping at very low volume. i contact Mr Broskie who email the same day and gave some advise. after doing some measurements my B+ was at 23V. after a while of starring the pcb i notice i had one diode and a capacitor in reverse...Rookie!!! after correcting this the B+ went to 73V. test the preamp and the sound was a lot better but now i have a hum on both speakers. if you see the pic on post #4 you'll see o ground the chassis to the house ground, i remove this but the hum remains, i will try adding a 0.1uf capacitor fix this or grounding from -C11 or chassis. any advise about getting rid off the hum will be greatly appreciated.
 
Tell us about the chassis too, I'm always curious about those, since my mechanical skills are sub-par.
I don't have much skill either, i work with simple tools in my laundry room. i get all my aluminum from the local metal market or the recycling place. i get the 1/4 angle bar 1/16 thick from Home Depot for the joints. i built my amplifier chassis and i spent like $60 and its like a tank. i could have build cheaper but i did a few trial and error. at the end is very gratifying.
 

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Maybe output running close to ac coming from transformer? Is the volume pot grounded? For signal ground you could daisy chain all the RCA grounds together and bring one wire to one ground point on the board. It looks like you are only using one winding of the mains transformer. Are the other two wires attached together a center tap?
 
I just received the "Aikido 12vac" board. Nice board and layout, very compact. There is an option to make it a "Aikido 18vac" using a higher voltage power source and 12AU7 tubes.

I am planning on using a 24vac transformer and 5814A tubes (12AU7 similar). A few component changes and I should have a B+ of about 180vdc.

I attached the sextupler with the values for the Aikido 18vac capacitors. The Aikido 12vac uses larger uf capacitors. I am planning on using the 18vac capacitors called for but higher voltage ratings as shown, the limitations being how large of caps can be fitted to the board.

I will report back soon.
 

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I'm still working mine, it's taken me more time then I expected it. when I power it up there is no smoke but i feel and smell like and iron is on. I left it for a few minutes and it did not go away. still there is no smoke. i touched some components to check the temperature but none where hot. i get more time to check it on the weekend.
 
As shown is the B+ I expect with a 24vac transformer as well as the cathode resistors I have chosen. DC operating points as calculated by LTSpice. The 12vac aikido circuit is identical to the topology of the "regular" aikido circuit.
 

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Schematic for power supply?

As shown is the B+ I expect with a 24vac transformer as well as the cathode resistors I have chosen. DC operating points as calculated by LTSpice. The 12vac aikido circuit is identical to the topology of the "regular" aikido circuit.
Hi tomlang!
How do you get the V3 =+180V?:confused:
Please give a schematic for power supply.
thank you!