Pablo, I own the SFL-2 and use Amperex PQ tubes and you'll find the best position for your best tubes are in LVS2 and V2 and LVS1 and V1 are the next best position. I have two sets of red labled Herleen Holand tubes that I tried and installed the first pair in LVS1 and V1 then the next pair into LVS2 and V2 positions and got noise when tapped on tubes as you described so I swithed the LVS1 & V1 pair with LVS2 & V2 pair and no more noise. I now use Amperex PQ in LVS1, V1, LVS2, V2 positions and the red lable Herleen Holand Amperexes in the remainig positions and all is quiet, also as mentioned above the Herbies tube dampers work great.
Tubes and microphonics
I want to know when microphonics affect the sound.
I have a Sonic Frontiers Line 2SE Preamplifier. I tried many tubes like Valvo, Siemens, Reflector 6H23NEB.
Recently I bought two matched pair of Amperex 6922PQ White Label Made in USA. I think that the Amperex are better than the others, but I could see that they are less silent.
When I knock the cover of the preamplifier I can hear the knock clearly in the speakers. That not happen with the others tubes. The 6H23NEB are the most silents.
I think that Amperex have more gain than the others. But I don´t know when that is critical to the sound.
Please let me know your experience with your tubes and preamplifiers.
Thanks,
Pablo
I have a Sonic Frontiers Line 2SE Preamplifier. I tried many tubes like Valvo, Siemens, Reflector 6H23NEB.
Recently I bought two matched pair of Amperex 6922PQ White Label Made in USA. I think that the Amperex are better than the others, but I could see that they are less silent.
When I knock the cover of the preamplifier I can hear the knock clearly in the speakers. That not happen with the others tubes. The 6H23NEB are the most silents.
I think that Amperex have more gain than the others. But I don´t know when that is critical to the sound.
Please let me know your experience with your tubes and preamplifiers.
Thanks,
Pablo