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Old 27th August 2011, 05:43 PM   #511
radio is offline radio  Macedonia
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Hi all!
BRAVOOOO ~ !!!
excellent topic !!
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Old 27th August 2011, 06:05 PM   #512
Ruwe is offline Ruwe  Europe
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Quote:
Originally Posted by Lazy Cat View Post
When you start to power up the unit there are well known current limiting starting procedures (serial rail resistors, bulb lamps, current limited PWS, etc) but always you have to know where is the BIAS trimmer starting position, the schematic gives you an idea, always, and it goes slowly from 0 to let say 100mA per output device. One eye is on scope screen to detect possible oscilation, DC offset, ... it is very straightforward method.
Thanks,
What puzzles me though in your SSA BIGBT Basic circuit is the tempco location. It's not actually directly connected to the gates of the driving IRFs.

I'll change the question : Is more voltage across the tempco giving more DC current in the output transistors (as usually does in most conventional amps), or it's the other way around?
Sorry to bother you again, but I can't understand it clearly in this current feedback circuit.
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Old 27th August 2011, 06:13 PM   #513
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Hi A.Wayne. I have settled on the Lateral MOSFET version. It appeared quite early in the posts and Alex did design a very nice board for it.
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Old 27th August 2011, 06:57 PM   #514
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Hi Ruwe

Currents inside CFB loop are explained here.

If you have SSA Basic version, BIAS is regulated inside CFB loop with a current bypass element like in a simple trimmer form, as a case from the post #1, or with tempco device to track down the bypass current with temperature (in proportion with quiescent current of the output devices). It is not classical Vbe multiplier to change voltage potential but it has to change CFB bypass current.

In more complex SSA version the VAS quiescent current is constant and classical VAS Vbe multiplier or integrated thermal-track diodes are used.
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Old 27th August 2011, 08:07 PM   #515
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by Nico Ras View Post
Hi A.Wayne. I have settled on the Lateral MOSFET version. It appeared quite early in the posts and Alex did design a very nice board for it.
Just curious , why lateral Mosfets , Sonics..?

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Originally Posted by Lazy Cat View Post
You are welcome Ruwe.

Well my track record in BIGBT kill is zero. Two months ago one friend accidentally made full short circuit when connected single speaker cable with 4mm banana from GND to OUT. We heard very loud bang but at the end only one FUSE was replaced. 5% of WBT connector evaporated in the air but all BIGBT's were intact (1xmosfet, 4xNPN, 4xPNP devices, on each rail). The amp has no other current protection than 10A/T fuse.

When you start to power up the unit there are well known current limiting starting procedures (serial rail resistors, bulb lamps, current limited PWS, etc) but always you have to know where is the BIAS trimmer starting position, the schematic gives you an idea, always, and it goes slowly from 0 to let say 100mA per output device. One eye is on scope screen to detect possible oscilation, DC offset, ... it is very straightforward method.
What schematic is this one LC and it's best when amp is only protected by PSU fuse , well for sonics ...
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Old 27th August 2011, 08:23 PM   #516
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Hi a.wayne,
Al of my amplifiers of late uses Laterals, they simplify the schematic and they are fast. I have also built the one I described a little later using MJ15001/15002 as output devices, but I could hear no significant difference that would convince me to move away from L-Mosfets.

In fact I do not believe that there would be any significant difference between the IGBT system and mine either. I think that the significance in the apparent clarity and transparency is speed, bandwidth and phase and not harmonic distribution or order. But then that is my subjective observation.

Nico
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Old 27th August 2011, 08:33 PM   #517
a.wayne is offline a.wayne  United States
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Thanks for the response Nico, I had given this a look and was curious to hear your thoughts .


http://www.irf.com/technical-info/wh...oosewisely.pdf
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Old 28th August 2011, 06:24 AM   #518
radio is offline radio  Macedonia
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Quote:
Originally Posted by Nico Ras View Post
Hi a.wayne,
Al of my amplifiers of late uses Laterals, they simplify the schematic and they are fast. I have also built the one I described a little later using MJ15001/15002 as output devices, but I could hear no significant difference that would convince me to move away from L-Mosfets.

In fact I do not believe that there would be any significant difference between the IGBT system and mine either. I think that the significance in the apparent clarity and transparency is speed, bandwidth and phase and not harmonic distribution or order. But then that is my subjective observation.

Nico
Hi Nico Ras!
You can give your schemaic amplifier with MJ15001/MJ15002?!
I make that comparison?
Thanks
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Old 28th August 2011, 07:54 AM   #519
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Originally Posted by radio View Post
Hi Nico Ras!
You can give your schemaic amplifier with MJ15001/MJ15002?!
I make that comparison?
Thanks
I used the schematic of Lazy Cat in # 183. Used MJE340/350 and MJ15001/15002
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Old 28th August 2011, 08:50 AM   #520
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I used the schematic of Lazy Cat in # 183. Used MJE340/350 and MJ15001/15002
Sorry I lied, the drivers are BD139/140
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