Supratek options and alternative tubes!!!! For those that are considering ordering a new preamp from Mick. As many of you know, Mick will custom make the preamp with a host of options: like a mono switch for the phono stage, gain switches, input and output configuration etc. The 6sn7 dual triode is the standard tube offered for line gain in all of the supratek's with the exception of the cabernet which uses a directly heated triode px4 for gain duty. The 6sn7 is a great sounding high gain dual triode tube that has gained favour and has been vitually reincarnated in many modern amp and preamp circuit design as opposed to it's electrically equivalent 9 pin miniature cousins like the 12ax7,12au7,12at7 family of dual triode tubes that were so common in the typical commercial circuits of the 60's,70's and 80's in the likes of Marantz, macs,fisher, and ARC's etc. And like he better minature 9 pin tubes [telefunkens'siemen,amperex, mullard etc] prices for nos 6sn7's and equivalents have escalated into the stratosphere with no end in site. "Check out the market value of a nos telefunken ecc803"[an uprated 12ax7 dual triode]These are typically trading now at close to $1000 a pair!!! The tung sol round plate 6sn7's are now trading at $200+ a pair if they are new in box! Geez gang.... 10 years ago you could buy tung sol rounds NIB for $10 a tube..... makes the stock market or your average mutual fund investments look pretty silly. Concerned yet? It's great for many of us that have collected a stock of nos tubes, but what about the newbie that wants to voice his gear with something other than crappy sovteks or the chineese equivalents????? Yes gang, there are alternative tube options that one can acquire for the suprateks that are very plentiful, dirt cheap, low in demand,and sound as good as the "best" of the 6sn7 tube family and at a fraction of their cost. What are they you ask? Single triodes..... 6j5's,6c5's,6p5's,or the magnificent 7193. Yes...some of these tubes have less gain than the 6sn7 but that can also be a huge benefit to those that have too much gain and very little play with their volume control. Example: I can only use the low gain setting on the syrah in my rig as the high gain switch gives me to little play on the volume pot [9 oclock on the dial is loud] The alps pot that Mick uses has typically sounded best around 12 oclock or higher in most any preamp employing the alps pot. If you need more gain,one can order the preamp with 2 sockets/channel and use a pair of single triodes and have the same high gain as the dual triode 6sn7 without having to route the signal through the contacts of the switch. If one needs less gain and is handy with a soldering iron, simply unsolder 2 wires to the 2nd tube socket. There are a huge selection of nos 6j5 types, metal envelopes,shoulder shaped G bottles,gt glass bottles from all of the great US munufacturers like kenrad, tungsol, sylvania, national union,RCA,Marconi etc as well as the great euro equivalents from Genelex,MO valve,brimar etc. Some are of round plate construction,some flat plate and a few are mesh plates. The 40's metal based sylvania 6j5 gt sounds every bit as good as the insanely expensive metal based 6sn7 vt-231. The kenrad 6j5gt sounds very similiar to the kenrad black and typically sells for $15 a tube. The 6p5g and 6c5g [lower gain than a 6j5]is in a different leaugue altogether and will outperform all of 6sn7. For the daring,or technically inclined DYI types.... I have saved the best for last as rewiring the tube socket is in order here to accomodate the 7193! The 7193 triode is a strange looking octal tube with plate and grid caps on the the top of the glass. These are electrically equivalent to a 6j5 single triode or 1/2 of a 6sn7. They were munufactured by RCA, NU, kenrad and tungsol as far back as the early 1930's.Many were used in old Juke boxes in their day as well as some early 50's tv sets. This tube just stomps on any 6sn7! Simply said.... there is no going back once you hear it. It's like comparing a telefunken ecc803 to a ge 12ax7, or a we350b to a 6L6. Halographic like no other,dead quiet,microphonics are non existant, super liquidity with incredible clarity,a silky sweet top end that floats into your room,the bass energy and drive of the kenrad vt-231 but far crisper and 3 times as tight. I use the cortese in my main system with my very efficient Tannoy Westminster's driven by VAC pa-90 monos employing the genelex kt-77 output tube. With the 6sn7's in the preamp I have very little room for play with the volume control whereby a single 6j5 is perfect for my application. I have unsoldered the other socket whereby I use only 1 6j5/channel. If I change amps or speakers that are lower in sensitivety, I simply solder 2 wires to the second socket. This allows me the gain flexibility without routing the signal through another switch. It also allows me the abilty to compare the dual triode 6sn7's to single triode 6j5 or equivalents like the 6c5's,6p5's and 7193,s. Some food for thought for those the are considering a new supratek preamp.
