hey everyone
i just finished building my bloo la2a, all voltages in my unit against the bloo manual test ok and are not far off from the specs written on the bloo manual. i found an oscillating pulsing clicking thumping humming noise when i turn it on. it would change speed of oscillation and pitch as the gain knob was turned.
now the volume of the noise would always be the same volume. it would be on maximum on the meters on my protools and if i have audio feeding the la2a, the noise would stay the same level and the audio i fed would change volume as i turn the gain knob. the noise would also change bass depth when the +10 +4 gr switch were changed.
this would only occur after a few seconds once the unit is turned on, i presume that is because the tubes are warming up. sometimes it will not make the noise until i start passing audio thru it or making the audio clip using the gain knob but it always makes the noise eventually.
my bloo unit has r38 with a 22k resistor as instructed in the bloo manual. i also have the combination of r34/22k and r36/1K. ive read on numerous posts that r38 must not be a resistor and must be a straight wire if you use the 22k/r34 and 1k/r36 combo but it made no difference in solving the issue so i left r38/22k in.
i started changing the tubes and noticed i was getting different results and eventually changed the 12bh7a and the noise issue stopped. i had a low hum, but its in the boundaries of my other equipment hum. problem solved!!!.
stupid me, i didnt stop there and started fiddling with the first and the second 12bh7a tube i was using and swapping back and forth without letting the tube or unit cool. i would take the tube out and install the other tube in once i turn the unit off! :
now the oscillation has come back with the second tube i used. this time the noise is more deeper, more bass unlike the first 12bh7a where the noise was more mid and high pitch.
i am thinking to myself, maybe the tube is not faulty because of my poor handling of the tube but because i wired the unit up wrong? could leaving r38 resistor in, cause the 12bha tubes to fault or are tubes generally sensitve and because of my poor handling of the tubes, it then became faulty? the reason being is that the first 12bh7a tube i installed was new, never used, even though its 6 years old. the second tube i installed was nos and an expensive tube.
what do you guys think?
i just finished building my bloo la2a, all voltages in my unit against the bloo manual test ok and are not far off from the specs written on the bloo manual. i found an oscillating pulsing clicking thumping humming noise when i turn it on. it would change speed of oscillation and pitch as the gain knob was turned.
now the volume of the noise would always be the same volume. it would be on maximum on the meters on my protools and if i have audio feeding the la2a, the noise would stay the same level and the audio i fed would change volume as i turn the gain knob. the noise would also change bass depth when the +10 +4 gr switch were changed.
this would only occur after a few seconds once the unit is turned on, i presume that is because the tubes are warming up. sometimes it will not make the noise until i start passing audio thru it or making the audio clip using the gain knob but it always makes the noise eventually.
my bloo unit has r38 with a 22k resistor as instructed in the bloo manual. i also have the combination of r34/22k and r36/1K. ive read on numerous posts that r38 must not be a resistor and must be a straight wire if you use the 22k/r34 and 1k/r36 combo but it made no difference in solving the issue so i left r38/22k in.
i started changing the tubes and noticed i was getting different results and eventually changed the 12bh7a and the noise issue stopped. i had a low hum, but its in the boundaries of my other equipment hum. problem solved!!!.
stupid me, i didnt stop there and started fiddling with the first and the second 12bh7a tube i was using and swapping back and forth without letting the tube or unit cool. i would take the tube out and install the other tube in once i turn the unit off! :
now the oscillation has come back with the second tube i used. this time the noise is more deeper, more bass unlike the first 12bh7a where the noise was more mid and high pitch.
i am thinking to myself, maybe the tube is not faulty because of my poor handling of the tube but because i wired the unit up wrong? could leaving r38 resistor in, cause the 12bha tubes to fault or are tubes generally sensitve and because of my poor handling of the tubes, it then became faulty? the reason being is that the first 12bh7a tube i installed was new, never used, even though its 6 years old. the second tube i installed was nos and an expensive tube.
what do you guys think?