jt1stcav Posted August 29, 2004 Share Posted August 29, 2004 Just curious...I'm using a Mullard GZ30 that replaces the Chinese 5Z4GT on my preamp, and thought it'd be nice to find a Mullard equivalent for the venerable 1951 Sylvania 5U4G rectifier that's used on my 300B amp. After a Google search I first spotted a Mullard GZ32 that stated it was a 5U4G equivalent. Then on another site there was a Mullard GZ37, and on yet another site a GZ31! Not all of these Mullard rectifiers can be an equivalent for the 5U4G, can they? I can't seem to find a straight answer anywhere I look...maybe someone here would know. Being a tube-noob, I'd hate to use the wrong rectifier and possibly muck things up! Any and all comments would be greatly appreciated...thanks. Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted August 29, 2004 Author Share Posted August 29, 2004 Here's the schematic for the BEZ Model T3B 300B SE stereo amp if it helps: EDIT: It's 120V obviously. Wonder why only one 300B is shown in the circuit? Quote Link to comment Share on other sites More sharing options...
3dzapper Posted August 29, 2004 Share Posted August 29, 2004 Jim, According to my database,TDSL Personal Edition availiable free at Duncansamps.com, there are no GZ substitutes for the 5U4 rectifier. Rick Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted August 29, 2004 Author Share Posted August 29, 2004 See, that's what's confusing to me, Rick. If you go to http://www.valve-museum.org/ and click on "Index to Pages of Valve Equivalents" and then select "Initial letter G" and scroll down to GZ31, you'll find the 5U4G as an equivalent. WTF? I've also been on the Duncan Amp website, and it's not listed there either, of course. So who's right? Quote Link to comment Share on other sites More sharing options...
lynnm Posted August 29, 2004 Share Posted August 29, 2004 It is a common practice. The power supply is common to both channels and is therefore shown. The amplifier sections for both right and left channels are identical and therefore the schematic for only one channel is shown. Quote Link to comment Share on other sites More sharing options...
Dflip Posted August 29, 2004 Share Posted August 29, 2004 Jim, you already have what is viewed as a great rectifier tube, especially if you are talking about the blackplate version. I have tried three different versions of the 5U4G and GB and the Sylvania early version blackplates are the best yet. Don Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted August 29, 2004 Author Share Posted August 29, 2004 No argument there, Don. Don't get me wrong; I'm not dissatisfied with the Sylvania blackplate in the slightest. Just thought that it'd be nice to have another Mullard rectifier like my pre's GZ30. It's definately not needed, just something nice to have. Quote Link to comment Share on other sites More sharing options...
Allan Songer Posted August 29, 2004 Share Posted August 29, 2004 NO Mullard 5U4G. However, there ARE two great British 5U4G and I have several of each on hand and they are NOT for sale! First is the much-revered GEC U52: The other great one is the 1940's/50's Brimar 5U4G: And if you REALLY wanna spend some SERIOUS cash on a pair of 5U4G types, then you have to get yourself a pair of Western Elecric 274B. Early (engraved base) matched pairs will set you back about $1000 or maybe even a bit more. Later examples (these were in production into the late 1970's) will go for about $250-$350 each: Quote Link to comment Share on other sites More sharing options...
3dzapper Posted August 29, 2004 Share Posted August 29, 2004 Jim, I read somewhere that the difference is direct v indirect heated cathodes and I can't remember which is which or where I found that. I seem to be having a senior moment here. Rick Edit: Allan you show off!! Quote Link to comment Share on other sites More sharing options...
MSklipsch Posted August 29, 2004 Share Posted August 29, 2004 A little less noise? Quote Link to comment Share on other sites More sharing options...
3dzapper Posted August 29, 2004 Share Posted August 29, 2004 No, it has to do with turn on transients from the power tubes. I believe it is the indirectly heated ones that have a slower voltage build up. Rick Quote Link to comment Share on other sites More sharing options...
sunnysal Posted August 29, 2004 Share Posted August 29, 2004 mullard did make a gz-37 which should work fine in place of a 5U4G, it has the addtional benenfit of a slow, ramped turn on like a 5AR4 its only real imprtant difference is that is draws 3A versus 2A for the 5U4G...I am using a mullard gz37 now in my amp instead of a 5U4G...regards, tony EDIT: craig is of course right, you should check with your amp maker before trying any other tube types...btw I had a U52 in my amp for a while, it was the best sounding rectifier I ever tried in the amp...regards Quote Link to comment Share on other sites More sharing options...
NOSValves Posted August 29, 2004 Share Posted August 29, 2004 Jim, Write the amp builder and ask him what GZ series tubes his transformer can handle and what they will do to the voltages in the amp in respect to the other tubes. He is the only one that can answer the question for you with any certainty. Craig Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted August 29, 2004 Author Share Posted August 29, 2004 Thanks everyone, you've all been so helpful...I appreciate that (and Allen, I don't blame you for not selling your gorgeous rectifiers)! I will write Edmund Lam and ask him what'll work best with my amp's circuitry and power supply. Should be quite interesting what he says. Quote Link to comment Share on other sites More sharing options...
Dflip Posted August 29, 2004 Share Posted August 29, 2004 Deals to be had, a pair of GEC U52's for a starting bid of $150 for the pair on ebay. Also a Brimar 5U4 engraved running at $51 and counting for a single with less than a day to go. The 274B were hitting $750 or so and still going. The engraved Brimars are the least expensive of the lot and they will run you 5-7 times the cost of your Sylvania blackplates. Jim, now when did you say we were going over to Allan's place and freeing the slaves, er I mean giving the tubes a right to work in a bush league state. Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted August 30, 2004 Author Share Posted August 30, 2004 LOL! Seeing how happy and well pampered his babies are, I'd doubt if any of 'em would wanna be down here and work for minimum wage! I'll check out those auctions, even if most of 'em are way over my head. Quote Link to comment Share on other sites More sharing options...
Deang Posted August 30, 2004 Share Posted August 30, 2004 Allan, I'm sorry to tell you this -- but I believe all of those tubes are fakes. Quote Link to comment Share on other sites More sharing options...
Allan Songer Posted August 30, 2004 Share Posted August 30, 2004 I would have a hard time paying these prices! My 274B tubes came in a big lot of mostly worthless TV tubes for $50 at the Rose Bowl swap meet about 15 years ago. There were about 100 tubes and the only things worth a damn were the three 274B and some RCA 12BH7. I bought the U52 out of Australia back in the early 1990's when they were "only" $50 each. The Brimars I got on the VERY early days of ebay (1998 or 1999)---I bought 6 of them for about $80 from a guy in Manitoba. But you know what? Those 1940's black plate coke-bottle Sylvanias are right up there with ANY of this exotic stuff and you can still get them for about $10 ea.!!!!!! Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted August 30, 2004 Share Posted August 30, 2004 Hi, Jim: This is quick since I need to get ready for school. There are a number of 5 volt rectifiers that would work in your amp. Trying different rectifiers is among the easiest way of altering the plate voltages on both input/driver/and output tubes. I have used all of the tubes mentioned above in my Moondogs, as well as most of them in the Horus. 5Y3s are also great rectifiers, but are more moderate in terms of power. The dropping resistors in the power supply will of course influence things, and I should say that I also altered the values of those somewhat when experimenting with different rectifiers. Erik Quote Link to comment Share on other sites More sharing options...
MSklipsch Posted August 30, 2004 Share Posted August 30, 2004 "No, it has to do with turn on transients from the power tubes. I believe it is the indirectly heated ones that have a slower voltage build up." Rick ---------------- Right. It takes more time for the filaments to heat up the actual cathode tube, sumthin' like that. You can watch the difference, 5U4 filaments come up within a few seconds. A EZ-81/6CA4 takes about ten. I would guess that a directly heated rectifier tube would be more noisy, it's probably why you see chokes in the PS after the said tube. (Well, most of the time.) However, I did swap a 5Y3 for a 5V4 in a SE 6BQ5 amp. It made it worse, dunno about that other than it's a lame circuit from get go..... I know folks collect tubes because they are rare, but that kind of money for rectifier tubes? Must be nice to have money to burn like that. I'll stick with television half-wave dampers, they do a pretty good job when you think about it. And nobody wants to collect the damn things...... Quote Link to comment Share on other sites More sharing options...
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