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27th April 2011, 01:21 AM
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#1 |
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diyAudio Member
Join Date: Nov 2002
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6sl7 6sl7 dynaco driver board
Tried making a driver board for my dynaco stereo 70 and well it doesn't have much power.
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27th April 2011, 01:35 AM
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#2 |
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diyAudio Member
Join Date: May 2005
Location: Victoria, B.C.
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Looks like you forgot something.
 jeff |
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27th April 2011, 01:40 AM
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#3 |
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diyAudio Member
Join Date: Nov 2002
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Ok? What?
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27th April 2011, 01:55 AM
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#4 |
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diyAudio Member
Join Date: May 2005
Location: Victoria, B.C.
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WAG is your driver stage doesn't have enough swing for the finals. Also, what's the scoop on the screen taps connected to the feedback loop? Hard to see the schem. (voltages etc.)
jeff |
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27th April 2011, 02:46 AM
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#6 | |
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diyAudio Moderator
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Quote:
__________________
If there's a sucker born every minute, where do the rest of them come from? |
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27th April 2011, 03:46 AM
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#7 |
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diyAudio Member
Join Date: May 2005
Location: Victoria, B.C.
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Ok, thanks.
jeff |
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27th April 2011, 11:21 AM
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#8 |
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diyAudio Member
Join Date: Nov 2002
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voltage map
input tube 6SL7 pin 1) 0 pin 2) 142vdc pin 3) 1.262 pin 4) 0 pin 5) 142 pin 6) 1.244 pin 7 h pin 8 h 6SN7 pin 1) 141vdc pin 2) 194 pin 3) 141 pin 4) 141 pin 5) 194 pin 6) 141 pin 7) h pin 8) h power supply voltage feeding the 100k plate resistor (6sl7) is 277vdc voltage feeding the 22K plate resistor on the 6sn7 is 331vdc |
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27th April 2011, 01:00 PM
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#9 |
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diyAudio Moderator
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You've only got 50V or so across the 6SN7. Not good. Get the B+ higher.
Morgan Jones reported that when he separated the supplies for the input voltage amp and split load inverter, he had some instability, so watch out for that. I might consider upping the B+, using it in common for the two stages, and increasing the 6SL7 plate resistor. As you have it drawn, the feedback is quite low- this may or may not be what you want, but you should be aware of that.
__________________
If there's a sucker born every minute, where do the rest of them come from? |
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27th April 2011, 03:00 PM
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#10 |
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diyAudio Member
Join Date: Nov 2002
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Just finish making some changes
Changed the input tubes 6SL7's plate resistors from 100K to 200K Upped the power supply voltages from 331vdc to 387 and 277 to 342 Voltage map 6SL7 Pin 1) 0 pin 2) 115 pin 3) 1.24 pin 4) 0 pin 5) 117 pin 6) 1.23 pin7&8 heater 6SN7 voltages pin 1) 115 pin 2) 267 pin 3) 120 pin 4) 117 pin 5) 265 pin 6) 122 pin 7&8 heater Sounds a lot better now. Do I need more plate voltage on the 6SN7's? Do you have suggestions for feedback? This is my second try and designing a driver circuit. Picture of my 6SL7/6SN7 driver board. Picture of my 6SL7/6SL7 driver board. The 6sl7/6sl7 has a 6sl7 input with a 6sl7 long tail. While it sounded very good I will make a change to the plate resistors on the input tube and see how it sounds. Last edited by Original Burnedfingers; 27th April 2011 at 03:08 PM. |
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