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Old 8th July 2013, 03:13 PM   #21
AndrewT is offline AndrewT  Scotland
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then you must prevent blowing up your input stage transistors.
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Old 8th July 2013, 04:13 PM   #22
Leify is offline Leify  Sweden
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I bought the pcb's here at the store and apperently you can cascode them. So can it handle the +- 52 V rails?

Appreciate all answers,

Br
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Old 9th July 2013, 02:31 AM   #23
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F5Turbo Article says Yes. Can you handle the heat?
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Old 9th July 2013, 05:45 AM   #24
Leify is offline Leify  Sweden
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I have not bought the cases and heatsinks yet so that problem can be solved. However that I wrote in the beginning of this thread is that I want to have a lower bias for aiming to about 30W class A and the remaining in class AB. That could work right?
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Old 9th July 2013, 10:10 AM   #25
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i say no. you need more then 2 output pairs to handle the heat. 52V*0.9A bias pr device=46.8W dissipation pr device. that is to high.
you can however run it with alot lower bias. like 0.5A pr device (26W dissipation). but it will only give you 16W class A at 8ohm.

Last edited by AudioSan; 9th July 2013 at 10:16 AM.
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Old 9th July 2013, 11:54 AM   #26
AndrewT is offline AndrewT  Scotland
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30W of ClassA needs ~1.4A of total bias.
A 2pair output stage with each passing 0.7A is ~35W /device.

That allows upto 2.8A of ClassA output and then it transitions to ClassAB for the higher currents.
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Old 9th July 2013, 12:16 PM   #27
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0.9A was for the 50W v2. a general answer regarding if one can build a v2 with 52V rails.
v2= 2pair output 50W class A amp.
and one would need to change source resistors so that the diodes dont kick in way too soon. or drop them all together. but then its not a v2 anymore.

Last edited by AudioSan; 9th July 2013 at 12:22 PM.
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Old 9th July 2013, 03:32 PM   #28
Leify is offline Leify  Sweden
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Thanks guys,
So if I understand it right it's not possible to have +-52V rails and 30W class A and remaining in class AB what it now will be. What do I need to change specifically to make that happen. Sorry for all these maybe "stupid" questions but I'm new at this and need help.

Br Leif
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Old 9th July 2013, 05:52 PM   #29
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it is possible. but i would drop the diodes. and cascode the front end.
it will be alot of extra heat doh. 0.7A pr device and 52V rails give you those 30W class A. with a dissipation of just over 140W pr ch(36W pr device). so you will need some monster sinks

Last edited by AudioSan; 9th July 2013 at 05:55 PM.
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Old 9th July 2013, 06:04 PM   #30
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Quote:
Originally Posted by Leify View Post
Thanks guys,
So if I understand it right it's not possible to have +-52V rails and 30W class A and remaining in class AB what it now will be. What do I need to change specifically to make that happen. Sorry for all these maybe "stupid" questions but I'm new at this and need help.

Br Leif
It is possible but you will have to refigure the source resistor value to drop the apporopriate voltage needed to have the diodes near turn on. The easier way is balanced. You get voltage on the cheap.
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