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Old 5th April 2013, 05:33 PM   #4031
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For those, like yours trully, that know nothing about IGBTs:

IGBT tutorial: Part 1 - Selection

Cheers,
M.
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Old 6th April 2013, 10:11 AM   #4032
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Quote:
Originally Posted by maxente View Post
I known it's a must an osciloscope, but unfortunately i don't have one
Borrow one, it is essential.

Basic rule to connect newly made DIY amp to power supply, is to connect both DC rails via serial resistors 22-33 Ohm/10 W which serves to protect the amp and output transistors from failure in a case of a wrong assembly or oscillations. This also enables to perform measurements in such abnormal conditions safely.
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Old 18th April 2013, 01:12 PM   #4033
maxente is offline maxente  Romania
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Today I have some time to measure some voltages
First I connect to GND all the pcb traces used for normal rectifier and replace those fuses with 33ohm/10W resistors
This is good because oscilations are gone, now i can measure voltage on any point of schematic with no problem at all
Here is what i measure so far
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Old 18th April 2013, 07:38 PM   #4034
Hlaford is offline Hlaford  Croatia
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I wonder, BC550 and BC560 at Rbb~150 ohm are maybe not the best match to BF471 and BF472. Perhaps some lower Rbb transistors would further decrease the noise floor?

Just a thought.
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Old 23rd April 2013, 02:20 PM   #4035
400kg is offline 400kg  Turkey
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Default ssa edit

hi dear Lc
whether you want to use such an arrangement to ssa
Is there a spot you want to correct?
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Old 23rd April 2013, 02:31 PM   #4036
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Uploading as image (from @400kg).
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Old 23rd April 2013, 04:19 PM   #4037
Belaji is offline Belaji  United States
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Default Another SSA Variation

Here's my take on LC's great amp!
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Last edited by Belaji; 23rd April 2013 at 04:34 PM.
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Old 23rd April 2013, 11:36 PM   #4038
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Quote:
Originally Posted by maxente View Post
Today I have some time to measure some voltages
First I connect to GND all the pcb traces used for normal rectifier and replace those fuses with 33ohm/10W resistors
This is good because oscilations are gone, now i can measure voltage on any point of schematic with no problem at all
Here is what i measure so far
So now you have good starting ground to calibrate SSA to working conditions.

You're not so far away, indicated from your measurements values, DC offset should change in both directions and finally set it to zero. Bias through each output BJT should be 100 mA and when you'll come to this conditions, you can freely disconnect safety serial resistors and connect SSA directly to PSU via 5A/T fuses.
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Old 23rd April 2013, 11:38 PM   #4039
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Quote:
Originally Posted by Belaji View Post
Here's my take on LC's great amp!
WOW nice take, just needs to be realized. Any obstacles?
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Old 24th April 2013, 12:03 AM   #4040
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Quote:
Originally Posted by 400kg View Post
hi dear Lc
whether you want to use such an arrangement to ssa
Is there a spot you want to correct?
Yes, according to all experiences gained from SSA, TSSA and VSSA I would change input current injection point, since that improves thermal stability into rock solid as in VSSA.

That complexity of the amp would be disastrous if it would have unstable output bias and if it would walk around zero DC like a drunker, also in this way you won't need any DC servo at all.

So how to make it hehe, let me see your approach and if you cannot transform and adapt it, I'll help.
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