I have a Crack with Speedball. I have also added resistors between RCA & volume pot + a switch to force headphone jack ground even if phone plug is connected + a selector switches to change R1 resistor values on Speedball boards.
This all worked well for some time. Then my 12BH7 started to slowly fade away and channels were not in balance anymore. I changed the tube and sound was OK again. However, after a while I started to hear some background noise.
At first I didn´t care about it too much because I thought it was just new tube breaking in. Then I noticed another weird behavior. While forcing the phone jack ground earlier logically muted the phones, now it only drops the volume level and sound becomes monophonic. The background noise is also strictly mono, it is exactly the same on both channels. Noise comes and goes, it is not constant.
I have changed the both tubes to known good tubes (12AU7 + 6080). It didn´t change anything.
Here is a soundclip of the noise. It is recorded with a mic from the headphones (HD-650).
soundcloud.com/transuranicheavyelements/crack/s-ZBQ0w (add https:// on front of the link. I am not able to post links here)
Any ideas? I´m puzzled because noise is the same on both channels and it is not tube. Noise on one channel only would lead us to, for example, broken LED contact like I had earlier this year after rolling the tubes too eagerly. Also, grounded phono connector still gives signal to phones…I don´t understand (That doesn´t prove anything though
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