• 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.

6V6 line preamp

Buzz

Preamp is up and running. Q1 is IXTP08N100D2. Thanks.

When I play music on tpa3118 amplifier with 20 db gain there is an unpleasant buzzing, when music is over Folsom tda7297 amplifier with 32 db gain buzz is even more pronounced. There is buzzing recording "11 Apr 21.53.mp3.txt" (rename to mp3). I do not have oscilloscope and my knowledge of electronics is 0. Any suggestions about what the problem is?
 

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diyAudio Chief Moderator
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Foobar shows main activity around 2.2kHz and it sounds like an oscillation. Try with only passively filtered PSU and if it goes then it should be something with the B+ regulator build or its application. Try it in two wire output mode then by shorting F+ to S+ and F0 to S0 locally at its output connector. Put a 0.1uF across the reg's input connector too. That rectification valve is being asked for too much constant current or it sees a bigger than allowed smoothing capacitor is another suspicion. If on the other hand its a wiring or build style issue see about shorter wires and bad loops or the grid stopper resistors physical distance to the grid pins and their values.
 

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diyAudio Chief Moderator
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That's a 5U4G equivalent, see not to overload it with a bigger than 40uF capacitor on its output. As you don't have an oscilloscope the only debugging method is to remove and change or substitute things and see what happens. You will not easily know what to look for by guessing.
 
That's a 5U4G equivalent, see not to overload it with a bigger than 40uF capacitor on its output. As you don't have an oscilloscope the only debugging method is to remove and change or substitute things and see what happens. You will not easily know what to look for by guessing.
It's max 20uF and i know it is mission impossible. When I put it in a box I'll ask some one locally for help
 
Extra temp protection with dual fan pcb with microcontoller here in Greece the summer its too HOT
This micro controller uc consumes very little energy with this programming because it goes to sleep after 60 seconds of inactivity. It wakes up after two minutes and controls the temperature. If needed (42degrees up limit) will activate the fans and adjust their speed according to the measured temperature. It goes back to sleep when the measured temperature stays below the threshold I have set 38 degrees down limit for as long as it takes. (60 seconds)
I'm currently using a single fan for the DAC that I have 4X4 cm with a starting voltage of 4.68V very sillent having a margin of up to 10.50V but I do not think it will ever overcome 7V in the summer. Before i have 52 degrees on heatsink
now 42-43 steady.
 

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