So, below my early impressions regarding CV3986 tubes after a few listening sessions. First session was very short, just about 3-4 songs only. There were no any magic sound even after 10 min of heating while listening the music. The sound was not typical for CDM, sounds some like jammed. Sound stage was narrow, vocals have been laid back. But low ends goes more deep and have more detailed layering comparing with stock tubes and even with Sonotones 5719 while not so tight and fast. But with my previous experience, tubes probably need about 1-2 hours burning time after first installed. Next listening session was more than 45 mins and finally tubes become sounding better! Lows becomes more tighter, not as dry and fast as stock tubes, but more organic and beefy. Mids not as forwarded as Sonotones. Treble not extended and sounds smoother, while having decent details in this region. I have some songs with fatiguing trebles, so using CDM with such tubes I can listening this tracks without any discomfort. IMHO CV3986 suits for genres like EDM, modern pop music, blues and some jazz track and other music with rich lower ends. I think this tubes fairly universal type, particularly if you are listening not very quality mastered hi res tracks. But for classic music, good recorded jazz, vocals and for more examining listening I would definitely prefer Sonotones 5719 because of their focusing on mids and treble, more air and crisp sound, wider soundstage. But CV 3986 also very nice tubes, driving rock concert records will force you dancing and jumping with hordes of people! I have been listening this tubes mostly with Legend X and Centrance Cerene dB. IMHO they are good for HF and iems having dry and monitor sound like Cerene dB, it will add some juice for them, or demanding in lower frequencies region, like Legends. Unfortunately I do not like this tubes with my current ciem Ambient Accoustics AM10c. That’s why this journey to be continued...