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Old 19th May 2005, 08:58 PM   #1
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Default 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
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Old 19th May 2005, 09:20 PM   #2
Radames is offline Radames  United States
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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
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Old 20th May 2005, 08:49 AM   #3
EC8010 is offline EC8010  United Kingdom
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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?
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Old 20th May 2005, 03:36 PM   #4
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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
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Old 20th May 2005, 07:48 PM   #5
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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
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Old 21st May 2005, 06:23 PM   #6
dhaen is offline dhaen  Europe
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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
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Old 24th July 2005, 08:15 AM   #7
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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
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Old 24th July 2005, 05:27 PM   #8
Gluca is offline Gluca  Italy
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Nice.

I will never have the guts to work with these utterly high voltages.

Gianluca
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Old 24th July 2005, 07:21 PM   #9
amperex is offline amperex  United States
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Default 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.
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Old 25th July 2005, 10:05 AM   #10
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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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