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3 x 3 Tube amp 30 watts
3 x 3 Tube amp 30 watts
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Old 15th January 2015, 03:43 PM   #11
Tubelab_com is offline Tubelab_com  United States
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Is there any risk of damage to the output transistor from EMF spikes from the transformer? ........I have not been able to kill it going no load to short at full output.
I have made some similar amps. I tried BJT/tube "darlington pairs" and mosfet/tube pairs. I liked the sound of the BJT better, but hard clipping with a guitar preamp plugged into the input and a guitar speaker load would blow one of the BJT's every time. (MJW21194's). The mosfet version was blow proof but I used some huge 900 volt Fuji Mosfets that are no longer available.

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Old 15th January 2015, 05:25 PM   #12
stocktrader200 is offline stocktrader200  Canada
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I think it may be the emitter resistor I used to set the idle current to 50 ish ma may be why the amp is holding up. I think I would need to drive a large cap to get resonance or ,as you said , create a condition of uneven drive to the 6922's with severe clipping.
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Old 22nd January 2015, 07:28 PM   #13
stocktrader200 is offline stocktrader200  Canada
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the MJE14007 dissipate about 10 Watts each
200v at around 50 ma
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Old 22nd January 2015, 09:06 PM   #14
ballpencil is offline ballpencil  Indonesia
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Still can't find MJE14007. Are you sure it's not MJE13007?
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Old 22nd January 2015, 11:53 PM   #15
Junm is offline Junm  Philippines
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MJE13007 is commonly used in PC power supplies...I also can't find any datasheets for mje14007 or e14007.
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File Type: pdf MJE13007.pdf (36.3 KB, 36 views)

Last edited by Junm; 22nd January 2015 at 11:59 PM.
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Old 23rd January 2015, 04:27 AM   #16
stocktrader200 is offline stocktrader200  Canada
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sorry, My mistake it is MJE13007G 400v 8A npn in TO220 package
hfe curve is straight , slightly rising, from 10ma to 1.5 A as opposed to
a parabolic curve.
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Old 23rd January 2015, 10:11 AM   #17
ballpencil is offline ballpencil  Indonesia
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Can you show some pics? Especially interested in heatsink size for the 13007
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Old 25th January 2015, 03:46 AM   #18
stocktrader200 is offline stocktrader200  Canada
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its about 6 inches by 2 inches with 1 inch fins
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Old 15th March 2019, 05:44 PM   #19
Mosquito is offline Mosquito  Argentina
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very nice, and since I have at hand all the tubes and transistors, I'm going to prototype one channel. Only thing I can figure is how it can put out 30W with 200v HT and 3500 /8 OT
((200X200/3500)X2) = 23W or near, w/o considering losses) sure I'm missing something..
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Old 15th March 2019, 06:30 PM   #20
Fenris is offline Fenris  United States
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If each transistor dissipates 10W (50ma x 200v) and each triode is about 1W (best guess from the datasheet), we've got 22W class-A, max. Letting the real world in, we would probably get a 240v p-p swing across the OT. With a voltage ratio of 20, that means 24v p-p at output. Power would then be about 12.5 watts if my math is correct. That's about what I simulate for my hybrid power pentode design, although mine is at less voltage and more current.
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