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 Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 19th May 2005, 08:58 PM #1 diyAudio Member   Join Date: May 2005 Location: charente Ongaku Hi, Excuse my English. I would like to build the amplifier ongaku but it misses the powers (mA) of the power tranformer in the schematic. Is anybody know that? Thanks
 19th May 2005, 09:20 PM #2 diyAudio Member   Join Date: Apr 2005 Location: New York Salut Du Bonnieure, I have an Ongaku Schematic without the values either, but the B+ feeding the 211 says 860V. If you neglect the DC resistance of the primary winding of the output transformer, you could calculate the max current the tube could draw. With newer 211 (75W dissipation limit) that will put the maximum current at the operating point around 87mA or so. Older tubes had a dissipation limit of 100W and therefore the max quiescent current value would be around 116mA. This is all a "back of the envelope" calculation, but if you lack the real values, you could get a rough estimate like this. It will be an overestimation. Take into account that the same secondary winding is used to feed one half of the 5687 tube with 460V also, so find out the max possible current that tube can take at 460V and you have another maximal estimation. Add up everything and voila! Cheers, Rada
 20th May 2005, 08:49 AM #3 diyAudio Moderator Emeritus     Join Date: Jan 2003 Location: Near London. UK Welcome to the forum du bonniere. I don't want to rain on your parade, but if you're not able to determine how much current a SE 211 amplifier needs then I have doubts as to your ability to safely construct something using 860V. There are no degrees of death, but you just don't get a second chance with 860V, whereas an error with 300V will cause a few sparks but possibly not much more. Could I humbly suggest that it might be better to gain some experience by building a SE 2A3 amplifier before progressing to 211? __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
 20th May 2005, 03:36 PM #4 diyAudio Member   Join Date: May 2005 Location: charente Hi, It is not my first amplifier but the overone was KIT. No problem for 1000V, because I work every day with 400V. A power transformer is expensive and I want to be shure. Here is my estimate: 5V, 10A ( 2A*4 5AR4 Ih) 12V 2A ( 0,5*2 Ih 5687+0.2*2 Ih 6072 ) 10V, 5A ih211 10V, 5A ih211 150V,0,6A because 2*0,3A max 380/0/380 V, 300mA (2*120Ma max 211 current + 2*90Ma max 6072 current) Are you OK Thanks for your help bruno
 20th May 2005, 07:48 PM #5 diyAudio Member   Join Date: May 2005 Location: charente Sorry 5V, 10A ( 2A*4 5AR4 Ih) 12V 2A ( 0,5*2 Ih 5687+0.2*2 Ih 6072 ) 10V, 5A ih211 10V, 5A ih211 150V,0,6A because 2*0,3A max 380/0/380 V, SIZE=3]500mA[/SIZE] (2*120Ma max 211 current + 2*90Ma max 6072 current) Are you OK Thanks for your help bruno
 21st May 2005, 06:23 PM #6 diyAudio Moderator Emeritus     Join Date: Jun 2002 Location: U.K. Welcome Bruno, I think it might have been mentioned here before, but I'll mention it again... Above 500 or 600v things start to behave differently. Things you thought were good insulators seem to fail (such as the sheaths of components). The voltage rating of most resistors is exceeded. Sparks start to jump a visible distance. Be very careful
 24th July 2005, 08:15 AM #7 diyAudio Member   Join Date: May 2005 Location: charente Hi, my Ongaku is finished. You can see some pictures here: http://fr.pg.photos.yahoo.com/ph/dub...IiSWDBNL91cYOw There is no problem, no noise. I have just to change a 5ar4 that i have broken The sound is warm and powerful, very realistic. About the power transformer, the good way for 5AR4 is not just one output 5V but 4*5V with a good isolation ( 1500V mini). You have characteristics of my transformer in the pictures. goodbye
 24th July 2005, 05:27 PM #8 diyAudio Member     Join Date: Nov 2004 Location: Back to Italy Nice. I will never have the guts to work with these utterly high voltages. Gianluca
 24th July 2005, 07:21 PM #9 diyAudio Member   Join Date: Feb 2005 Location: MI Easy......... Take that tube current from other posts & include the other tubes as well. With a choke input filter, the transformer can deliver close to the AC output current rating, but with a capacitor input, derate to 60% current. After this excersize, add a minimum of 25% reserve capacity for good regulation of the B+ (high voltage). A tube rectifier will add series resistance, so find the PSU Designer II power supply simulator at Dungan Amps site to target the power supply voltage. I find the simulator fairly accurate.
 25th July 2005, 10:05 AM #10 diyAudio Member   Join Date: Dec 2003 Location: Flensburg, Germany Maybe somebody else needs it..... Here are the original values from Audionote: 1x 0-150V 150mA 1x 6.3V-0-6.3V 2.5A 1x 380V-0-380V 260mA 2x 0-10V 5.25A 4x 0-5V 3A

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