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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, 02:18 AM   #1
stocktrader200 is offline stocktrader200  Canada
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Default 3 x 3 Tube amp 30 watts

First try with Tubes and the sound is outstanding
I now have to build the board for it.

12AX7 Voltage amp stage followed by 6922 or ECC88 driving NPN transistors
Surprisingly it didn't need any global negative feedback
I also have to prepare a case for it !!
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Old 15th January 2015, 02:59 AM   #2
ballpencil is offline ballpencil  Indonesia
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I like it! Just subscribing to hear what others would say.
Is there any risk of damage to the output transistor from EMF spikes from the transformer?
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Old 15th January 2015, 04:12 AM   #3
stocktrader200 is offline stocktrader200  Canada
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I have not been able to kill it going no load to short at full output.
but 500+ volts of back emf may do it.
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Old 15th January 2015, 04:41 AM   #4
ballpencil is offline ballpencil  Indonesia
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I would do it with ECC88 front and swap the 2N5551 phase splitter with another ECC88 to make it all ECC88 tube (honestly, it would be 6N23P). I don't think i need the 12AX7 gain. Maybe B+ can be lower a bit that way.

How do you determine "it didn't need any global negative feedback"?
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Old 15th January 2015, 05:25 AM   #5
stocktrader200 is offline stocktrader200  Canada
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Listening test, backed up by good looking waveforms on the scope.
12AX7 sounds really nice. 2N5551 replacement may add extra tube sound but given gain there is unity I don't think it matters much.
Tube swapping may change the tone noticeably
3 x 3 name comes from 3 triodes and 3 NPN transistors
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Old 15th January 2015, 05:49 AM   #6
davorin is offline davorin  Croatia
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Have anybody data sheet for transistor MJE14007?
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Old 15th January 2015, 06:05 AM   #7
ballpencil is offline ballpencil  Indonesia
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Do the output transistors need any heatsink? How large?
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Old 15th January 2015, 06:39 AM   #8
ballpencil is offline ballpencil  Indonesia
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I think OP meant MJE13007.
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Old 15th January 2015, 06:45 AM   #9
gingertube is offline gingertube  Australia
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I would be worried about the 160V rating of the 2N5551.
Try a MJE340 instead.
Cheers,
Ian
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Old 15th January 2015, 08:22 AM   #10
costis_n is offline costis_n  Greece
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Quote:
Originally Posted by ballpencil View Post
I would do it with ECC88 front and swap the 2N5551 phase splitter with another ECC88 to make it all ECC88 tube (honestly, it would be 6N23P). I don't think i need the 12AX7 gain. Maybe B+ can be lower a bit that way.

How do you determine "it didn't need any global negative feedback"?
I agree. 75K does not give the best linearity for ECC83. You obviously made it low to lower the gain. So use an 6N23P which has lower mu, and likes lower voltages.
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