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Old 26th March 2013, 10:48 PM   #51
Ketje is offline Ketje  Belgium
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Quote:
Originally Posted by peterfarrow View Post
Rethink---

Raa is anode to anode at 17.7 ratio to the speaker.

not 17.7 per side, so I reckon it probably isn't 48Watts after all....

Anyone want to throw a curve ball here and sort this out...
Yes,and there is also a swing of allmost 500V on both sides in opposite fase,that's 1kV between anodes.So ...
Mona
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Old 26th March 2013, 10:54 PM   #52
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Quote:
Originally Posted by Ketje View Post
No,no,no!!
You get a swing of 249V on the anode already at 289V.That gives a swing from 289-249=40V to 289+249=538V,a total of 538-40=498V (same as 2x249).So far ok,but the same,in opposite direction on the other side,total swing over Raa 2x498=996V.Back to the sec.996/17.7=56.2V pk-pk ! That's (56.2/2)x0.7=19.6Vrms.Power on 8ohm, (19.6x19.6)/8=48W ,that's better .
With UL somewhat less.
So if everything else is ok the OPT doesn't have the right ratio.
Mona
If I understand correctly, you are finding a swing of 249V either side of a center tap at a fixed 289Vdc on one half of the primary, and the same swing on the other half of the primary, only 180 degrees out of phase. The common center tap remains at fixed a.c. potential of zero volts, thus the maximum Vp-p can only be 498V anywhere, not twice that value.
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Old 26th March 2013, 10:57 PM   #53
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Quote:
Originally Posted by Johan Potgieter View Post
If I understand correctly, you are finding a swing of 249V either side of a center tap at a fixed 289Vdc on one half of the primary, and the same swing on the other half of the primary, only 180 degrees out of phase. The common center tap remains at fixed a.c. potential of zero volts, thus the maximum Vp-p can only be 498V anywhere, not twice that value.
Agreed, however swapping EL90s gives me 25Watts RMS straight out the box, which is 14.2vrms before clipping, this is doing my head in as that is not possible from the voltage numbers we just discussed... at 500v pk-pk
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Old 26th March 2013, 11:03 PM   #54
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However it glows blue and looks nice...
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Old 28th March 2013, 04:13 PM   #55
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Ok, here is the neartly finished prototype...

6005W (EL90 or 6AQ5W) Parallel push pull prototype - YouTube

300v regulated supply using 6AS7G tubes and OA3/OB3 reference tubes is ROCK steady even at 250mA output stage current draw...

very please..

thanks everyone!
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Old 13th June 2013, 08:48 PM   #56
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Well finally, traded up the EL90 (6AQ5) tubes for eight parallel push pull 6v6 tubes, got 42 Watts over 20Hz to 20KHz

I will start a new thread because I have some other questions...
Parallel 6V6 Prototype Amplifier - YouTube
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