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Old 31st August 2011, 09:23 AM   #591
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Quote:
Originally Posted by Nico Ras View Post
Hi Miib,

I do not think it is a competition between which output stage is the best, but more so to offer different variations so that constructors have a choice.

In my humble opinion the character of the amplifier is dominated by the front end.

There is such a controversy regarding sound of MOSFET vs BJT, but I could not conclude that I heard any significant difference between the two output stages, only that they sounded excellent.

It would be like comparing performance differences between a red Ferrari and a yellow Ferrari.

Maybe I am getting too old.

Regards

Nico
That's a quite interesting feedback since i have a good On semi matched MJL1302/3281 stock laying around. Using them in SSA and waste money on purchase lateral mosfet could me make seriouly happy. Designing PCB is not a issue for me, since alex provide somme elegant exemple to adapt. The most issue for is the schema using regular BJT and Vbe multiplier.

Marc
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Old 31st August 2011, 01:36 PM   #592
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Quote:
Originally Posted by Idefixes View Post
That's a quite interesting feedback since i have a good On semi matched MJL1302/3281 stock laying around. Using them in SSA and waste money on purchase lateral mosfet could me make seriouly happy. Designing PCB is not a issue for me, since alex provide somme elegant exemple to adapt. The most issue for is the schema using regular BJT and Vbe multiplier.

Marc
Pcb needs room for emitter resistors also. It's 60 pages since and there is no shared and tested full bjt pcb yet. I might do it for myself but my skill is not enough to achieve it yet.
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Old 31st August 2011, 05:17 PM   #593
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Quote:
Originally Posted by terranigma View Post
Pcb needs room for emitter resistors also. It's 60 pages since and there is no shared and tested full bjt pcb yet. I might do it for myself but my skill is not enough to achieve it yet.
As I said redrawn the PCB forBJT use is not an issue for me (I do it for Brother of quasi to switch from TO3 to TO264 transistors). The issue for me is to have the right schema with the right value...

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Old 31st August 2011, 09:35 PM   #594
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Hi, I am on redrawing Alex rev 1.4 pcb based on Nico simple L-mosfet. When we compare Nico schema and Alex PCB : we can see that 1µ/10nf/1k/100nf are before Fuse on schema and are after on Alex PCB. What is the right situation or it doesn't matter?

Marc
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Old 1st September 2011, 12:33 AM   #595
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Here my mix based on Nico/Alex work but with Exicon double die. I try to apply MiiB advise

Click the image to open in full size.

Click the image to open in full size.

The board mesure 148x130mm. The board allows installation of 50mm large smoothing cap. and is equiped with double rectifier bridge.
I have minor changes in mind around BD139/140
Marc
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Last edited by Idefixes; 1st September 2011 at 12:39 AM.
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Old 1st September 2011, 01:21 AM   #596
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I think you have to stick face to face Q1-Q3 and Q2-Q4 like alexmm has done.
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Old 1st September 2011, 05:38 AM   #597
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Quote:
Originally Posted by terranigma View Post
I think you have to stick face to face Q1-Q3 and Q2-Q4 like alexmm has done.
They are face to face. I needed toom to route traces. To made them touch, you just need to bent a little leg or to insert ą little aluminium pieces between them. In this way you couple them thermaly.

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Old 1st September 2011, 06:39 AM   #598
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Wyh dont you turn the caps 180 degrees...and make a simpler GND..??
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Old 1st September 2011, 07:28 AM   #599
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Quote:
Originally Posted by MiiB View Post
Wyh dont you turn the caps 180 degrees...and make a simpler GND..??
That's evident as nose in middle of the face (as we said in franch) that I didn't see this simplification of my alex work adaptation. My pcb is overall a output and rectification rearrengement from alexxmm 1.4. As i a have double rectification bridge i don't need anymore some traces on existing on alex pcb and so it allows the smoothing cap rotation. Good advice thanks. It will be done this evenning. Miib have I correctly apply your suggestions for R13/trimmer? Could you advise me with some value for this section. Yesterday I go to my basement stock to pick u somme parts for this one : the two 300va 2x25V toroļdals, 4u screw mallory 23.000µf/ 40V smoothing caps, 2u 230x200x40mm heatsink. As the pcb is ok it will be etched.

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Last edited by Idefixes; 1st September 2011 at 07:32 AM.
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Old 1st September 2011, 07:38 AM   #600
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I have not done simulation with the BD 140/139 pair.. so I think you must experiment a little..

You can measure the current in the output stage over the fuse..With my driver set simulation suggests something like 250 ohms...(I would use the trimmer to find the right value an than change to a fixed resistor)

Also the resistors setting the Driver stage current can vary a little.. in my simulations (with different drivers) 140 ohm gives app 20 mA which will be just fine..
good luck.
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