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Author Topic: A little help in finding type 5693 tubes Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 04-07-2004 08:24 PM                     Luciano, Never had any problem with the 6AS7's and blowing out speakers. each tube was fused with a fast blow fuse if things went shorted internally. The sound of an OTL is quite good but nothing comes close to the Pass Labs single ended MOSFET Class A stuff I've been building. The Pass is far better sounding than any tube amplifier I've listened to or owned and as one would expect they run as hot or hotter than a tube amp of comparable size. Jeff S. The reason your Sovteks last so long is because all McIntosh amps output stages are biased for Class B operation... including the solid state stuff. Take them to high bias class AB or Class A and you'd get a few months life span at best. Here is a typical OTL power amp that could use 6AS7's or the 6C33CB. Both are actually voltage regulator tubes. Mark  |  IP: Logged Luciano Brigite Master Film Handler Posts: 277 From: Sao Paulo, SP, Brazil Registered: Jan 2002 posted 04-07-2004 11:38 PM                     Aaron beat me by 4 minutes with his post about the Sovtek and Svetlana tubes . Now that I think about it,who's the manufacturer for those "National" branded tubes? about 2 years ago I bought 6 of their 6L6GC's and they're worth they do work but it takes nothing for them to glow red even with a bias cranked up to full (nearly 58V) and 380V+/- on the plates running on class AB-UL. If it's true what Mark said ,that those tubes won't put out more htan a few months in a or AB class then I'll get kinda displeased with them because among the amps I plan to build someday are a few class A PP ones..hte others are class A SE/SE-UL class AB PP/PP-UL and A/AB PPP . I'm starting to think I'm a kind of diehard DIY dude because I wanna do most of the stuff including the xformers. right now I'm at 51% of the primary winding for a 5000 ohm SE OPT. it's being wound by hand with an average of 181 turns per hour, the total turns acording to my math is 2557 for primary and 102 for secondary,1"x1"GNO iron stack with gap. The OTL circuit Mark posted resembles (??) a transistor amp schematic It also seems kinda easy to build,the PSU however may be not because of all the voltages needed . Something in that circuit that left me thinking is why two phase inverters? unless I'm making a mistake here, the arrangemet with the V2 and the other with the 1/2 V3 are phase inverters ( damm my head that keeps forgetting names of those arrangements) Since the tubes mentioned are voltage regulators,maybe the 6336A's will have some use in such circuits? I saw a few of those tossed around,NIB, inna junk/surplus depot. if they're not costing a few bodyparts maybe I'll get them for a try  |  IP: Logged Aaron Sisemore Flaming Ribs beat Reeses Peanut Butter Cups any day! Posts: 3061 From: Rockwall TX USA Registered: Sep 1999 posted 04-08-2004 11:35 AM                     quote: Now that I think about it,who's the manufacturer for those "National" branded tubes? the 'National' brand (red and white box) along with the 'Amperex', 'Bugle Boy', 'Mullard', and 'Cetron' brands are trademarks owned by Richardson Electronics . It's ironic that Richardson is one of the last US companies that still manufactures tubes here in the US, yet almost all of its receiving and low-power transmitting tubes are rebranded Russian and Chinese garbage (I would assume that your glowing 6L6's were probably Chinese)... They have the tooling (most likely the Philips/Amperex equipment) to manufacture 'common' audio types, but I guess the market isnt out there for mass-produced quality tubes anymore. -Aaron  |  IP: Logged Luciano Brigite Master Film Handler Posts: 277 From: Sao Paulo, SP, Brazil Registered: Jan 2002 posted 04-08-2004 03:32 PM                     The National 6L6CG's I got are russian. tried to take a pic. of it but the webcam is being crappy lately, anyway here it is.. Sovtek as 2 kinds of 6L6's, the ones I bought two weeks ago ate the WXT+ and doesn't looks any close to the National. I couldn't find a pic of their other 6L6. the National still has the lightbulb stem in it. and for the 5693, I'll go for it's equivalent, the 6SJ7,it's a lot cheaper and can be found easy for a while.  |  IP: Logged

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