Tube testing on TLaudio FAT1 compressor

One of my favorite things is to fix and optimize my equipment.

This time it was the TLAudio Fatman FAT1 compressor that I had bought second hand. I remember the seller saying "It's analog equipment! It has some noise!!" (...I responded...ok...)

Last time I used it in my OpenMic participation and yes...it made some strange noise that you can hear at the start of the video.

So there was something I was doing wrong!

I tested some cables and found out that I had to use a balanced cable to connect the FAT1 to my audio interface in order to eliminate this noise. It seems that the unbalanced cable received electromagnetic interference from my PC which was responsible for that noise.

Then again, since I just started, perhaps I should clean the dust...or take some pics too:

From this picture you can see why this baby is a piece of art as opposed to cheap tube preamps!

And now the fun starts. After some cleaning, before closing it again I should test my tubes and see if I can get a better sound.

Here are two videos I did to finally check and decide which tube should be in it:

This first video is the recorded noise that each tube makes while and after it warms up. The 12AU7 tubes have less noise and something strange seems to happen as they warm up... I understood the low noise though when I did the 2nd video:

Here a piano sequence was recorded on my loop pedal and kept playing as I was changing the tubes. We can see that the 12AU7 tubes have significantly lower signal levels overall...not just lower noise. Then I think the choice was a matter of taste. I went towards the Ruby tubes 12AX7AC5 which seems to have a sweeter and more round sound, as my 2nd choice was the Matsushita 12AX7 that I removed from and old Teisco guitar amp.