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6AR6/Triode Input Board/MIT-RTX/max build

Posted by Chris Spafford on February 11, 2003 at 17:28:35:
Hello, all. I'm currently listening to a just-completed pair of Dyna MKIIIs that belong to a friend; I agreed to do an "ultimate" build for some cash. I obtained all ceramic/gold tube sockets, Cardas RCA jacks, and MIT-RTX caps for the fabulous input board Ned at Triode Electronics sells. The C-L-C power supply is as follows; 5U4G Tung Sol, 20 uf Solen, upsized Hammond 3 hy 250 ma choke, and a series/parallel pair of top-'o-the-line Nichicon Gold 68Ouf/400VDC to make a 340 uf/800VDC cap... bypassed by another 20uf Solen. This feeds the A431 Primary. It was quite difficult to stuff those huge MIT coupling caps on the board, but the improvement is worth it 10 times over compared to orange drops. From extensive trials on my Triode boards, the best setup is to jumper both tube heaters for 6.3 V and use a 6DJ8 as the Cascode V1, and a 6FQ7/6CG7-- great!!! The kicker is that I convinced him to go with the 6098/6AR6 TungSol built, Bell Labs/Western Electric designed sweep radar tube in place of 6550s. I hardwired the sockets for them, so there is no going back easily... not that anyone would! I simply cannot believe this tube!!! I know I've raved extensively, but I finally have a platform with enough capacitor storage, a great circuit, and fantastic parts to REALLY hear the tube. I literally cannot get the amps to hard-clip; they just progressively limit bandwidth. (I'm sure, of course, I could clip them-- I like my speakers, though) The 6098 sound is the true "iron fist in a velvet glove" sound that tubes like the KT77, 350B, and KT88 approach... for about 20-50 times the per tube cost of the 6098! I have bought my last output tube costing more than $20, NIB. I have paid an average of around $5 for these tubes. Next up is the BIG ONE; the 3D21!!! BTW we A/B'd the TungSol and the Bendix 6384; the TungSols absolutely SMOKE the Bendix. The Bendix may look tough, but the Tung Sol has the sound. I'd like to repeat my offer to lend a quad of these 6098s to anyone who wants take 'em for a spin; I will include pinout details and easy conversion instructions. If you can solder, you can do it! Email me and if you pay the $3.50 shipping, I'll send 'em out! Say NO MORE to $100=$300 insanity prices for output tubes. When I go through Ham Radio links and see 6098s, 3D21s, 5933/807Ws, 6146s and others for $5-$30 I retroactively kick myself for my 15 years of manic collecting of overpriced popular tubes.(Oh well, at least I didn't lose money on most of them when I sold them) Even the humble 807 can adapt in to many circuits (I've got them in my ARC D76) and at about $4 per, they come so close to GEC KT88 performance... well, don't take my word for it. One final note-- Robert H. Sector 7-G et al, I need the tube number for a variation of the 6550... a la TT21. Email if you have it or know where I can get some. Thanks!