I`m long time tube crazy, tube amplification sounds different and magic to me. Semiconductors technology advanced so much but still warm tube sound is something i always being after.My research showed me that only available options on the market is that to use Panny bottlehead, buy something crazy expensive like Ground zero reference 2T, build something yourself or pay someone to do it.All solutions have shortcomings.Panny is outdated, 2T is expensive and only can do 2ch.Build it yourself has it`s challenges but doable.Tube circuits was around for about 100 years, technology perfected almost to the point of snake oil like Mundorf caps better sounding then AuricapsPanasonic vs Nichicon.. etc etc..tube purists goes as far as not having anything semiconductors in their units.What I realised is that combined tech is the best for mobile installations.tube preamp with solid state amplification sounds great and can be practical in car installs.after investing quite a bit of my time and money into this I came up with a couple possible solutions.First cost must be affordable for average person.It should be easy to insert into sound path.and it should look good.I used a few well regarded tube units during my years in audio, Home stage and recording so I have pretty good ideas what it should sound like.So far I created couple solutions. it`s work in progress at this point but I do have commercial versions I can sell right now.First will be 4 ch version built by the same principals panny did in it bottlehead. 1 double triode tube for both channels. circuit is simple and stable. power consumption is less than 1A fused at 1.5.Here is some picturescase is extruded aluminum 5.75"x7.75"x2.75all connectors on one side.Unlike some tubes is user replaceable any 12AX7 or equivalent can be used to experiment with sound difference. By default I supply Russian military grade 12AX7 . many different tubes available on the market, US, German, tubes still in production in China, Russia and 4 european factories. That tube was used in military equipment so NOS surplus is good too.tubes in this design is good for 10000 hours . I chose military grade for vibration resistance purpose. If it was good for planes it will be Ok for car too.Each channel specs:2 gain potentiometers for each pairInput sensitivity 0.1-6VFR [email protected] +_1 dbTHD0.05%S/N95dBI tested it with 3 different amps and 4 HU.preamp inserted in sound path after HU before final amplification.Tested with Dynaudio 3 way set passive.can be used for 2way active as well, will be setting 650.6 with DSP active to try if DSP alter tube effect in any way before amplification.Questions?post it here or shoot me PM.