• 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.

Buzzing Aikido pre-amp

I've built a couple of the 12Vac but never had a buzzing problem. Does it buzz in both channels?

Try removing the wires from the volume pot (or input jacks) and solder short jumpers across input connections on the board.

Try connecting the negative side of C11 to the chassis ground. The chassis ground should also be connected to the frame of the volume pot and the ground connection on the AC inlet.

Check to make sure all of the diodes and filter caps have been installed the right way round.

See if your build resembles the one in the link below. There are other parts to this build. Look around the WoS.ca site.

https://wallofsound.ca/wp-content/uploads/2016/12/Line-Stages-Part-4-board-assembly.pdf

Steve
 

qguy2000

Member
2018-09-24 2:50 pm
Buzzing at both channels

No chassis at this point

I removed all pots and input wires, there is only wires to Female RCA connected to the outputs

The pre-amp worked ok in the past, so diodes and caps are correct. I just changed coupling caps and input wires and the problem started. I placed it back to original config, but the buzzing remained

I've built a couple of the 12Vac but never had a buzzing problem. Does it buzz in both channels?

Try removing the wires from the volume pot (or input jacks) and solder short jumpers across input connections on the board.

Try connecting the negative side of C11 to the chassis ground. The chassis ground should also be connected to the frame of the volume pot and the ground connection on the AC inlet.

Check to make sure all of the diodes and filter caps have been installed the right way round.

See if your build resembles the one in the link below. There are other parts to this build. Look around the WoS.ca site.

https://wallofsound.ca/wp-content/uploads/2016/12/Line-Stages-Part-4-board-assembly.pdf

Steve
 
Last edited:

qguy2000

Member
2018-09-24 2:50 pm
Not sure what this means, I might need to call a friend on this one

dc elevating the filaments cures the buzz, worked for me all the time..




Will reflow the solder joints, this is what my skills is capable as of this moment

B+ and filament voltages are the same right now, as it was when it worked

How do I check for ground connections, there is no chassis and the only wires installed is the AC input and Audio output

Reflow all the solder joints. Check your ground connections. Measure voltages.

S.
 
As per your C10 image the 12Vac power supply elevates the filaments. Make sure the ground terminal, NOT the neutral on the AC inlet is connected to circuit ground. See attached picture of how I connected circuit ground to chassis and AC inlet ground (it's one of the green wires on the left side) on a 12Vac using a 10 ohm resistor and a small film cap.

Wherever possible solder component leads, tube socket pins, etc. on BOTH sides of the circuit board.

Inspect the circuit board carefully to see if any traces have been damaged or pulled away from the board especially close to component solder pads.
 

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TonyTecson

diyAudio Moderator Emeritus
2003-05-29 2:57 am
Maybunga, Pasig City
there is the PE or protective earth ground, then there is the psu ground or 0 vdc reference, then there is the signal grounds, these are treated differently....

obviously if you don't use a metal chassis, this PE ground can not happen..
more so if your house wiring did not include grounding wires...

these are issues that were discussed to death in this forum...