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Old 1st March 2013, 04:47 AM   #2541
Luke is offline Luke  New Zealand
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Quote:
Originally Posted by stolbovoy View Post
Why? What if he will keep the total bias the same? Even if the total bias current will be twice of original will it put the drivers outside of SOA?
Exactly, these drivers at 60V will deliver 5 amps, even if you halve it for high heat its plenty to reliably drive 4 outputs into high bias class A.
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Old 1st March 2013, 10:00 AM   #2542
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Luke View Post
..........at 60V will deliver 5 amps............
Check the datasheet!
There's no way that 50W device can handle 300W, not even for 100us.
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Old 1st March 2013, 10:30 AM   #2543
Luke is offline Luke  New Zealand
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Quote:
Originally Posted by AndrewT View Post
Check the datasheet!
There's no way that 50W device can handle 300W, not even for 100us.
apologies, I was looking at the outputs datasheet

The driver will handle near an amp at this voltage.
With the outputs having an hfe of 40 at 60v, this driver could push 4 output transistors to 20 amp and only be required to deliver 500mA. To me this is seems quite doable. Is my math right?
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Old 1st March 2013, 10:32 AM   #2544
AndrewT is offline AndrewT  Scotland
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That's better.
Do a proper temperature derated SOAR into a reactive load for the drivers, just as you should do for the output devices.
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Old 3rd March 2013, 04:35 PM   #2545
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So is it possible to double transistor amout? Or if I do that should I add more driver transistors? I have JIM's PCB so It seems to be quite easy to just add (double them too) more drivers to backside of PCB to help drivers load?
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Old 4th March 2013, 01:23 AM   #2546
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Why would you want to double the output transistors for this amp when this amp as designed was able to drive the Apogee Scintilla at 1 ohm loads???
I would think that it would only be required if you wish to increase the supply voltage,but then the whole amp should be somewhat redesigned and optimized.
One of the reasons this amp became legendary in it`s ablity to drive safely 1ohm loads is the fact that it uses two drivers per bank..
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Old 21st March 2013, 08:55 PM   #2547
Fix is offline Fix  Sweden
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Just a quick post, and a hello !

My amp still works fine and I used it for many many hours.
Still impressed.

Might build another... :-)
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Old 23rd March 2013, 05:14 AM   #2548
Luke is offline Luke  New Zealand
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Quote:
Originally Posted by jushuota View Post
So is it possible to double transistor amout? Or if I do that should I add more driver transistors? I have JIM's PCB so It seems to be quite easy to just add (double them too) more drivers to backside of PCB to help drivers load?
Hi Jushota,

I think you could, but for what gain?
if you tell forum members what you are trying to achieve you may getter better advice.
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Old 27th March 2013, 06:21 PM   #2549
spurlte is offline spurlte  United States
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Default SOAR

Quote:
Originally Posted by AndrewT View Post
That's better.
Do a proper temperature derated SOAR into a reactive load for the drivers, just as you should do for the output devices.
What is "SOAR?"
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Old 27th March 2013, 06:33 PM   #2550
K-amps is offline K-amps  United States
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Subtle or Arbitrary reaction.


or maybe try wiki: http://www.lmgtfy.com/?q=soar+%2Btransistor

Last edited by K-amps; 27th March 2013 at 06:37 PM.
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