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Old 14th August 2013, 04:57 PM   #461
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Join Date: Sep 2005
Originally Posted by ashok View Post
Blew the Darlingtons by using it at +/- 42 V and over 350 mA bias current. Didn't really do it intentionally but happened due to a set of goofs while fiddling with the board. But it did run for quite a while in that condition ! Not bad !

The stereo board will most likely use LatFet's . I have to choose between LatFet and Bipolar. Since I need a new power amp for my new coaxial OB speaker , the LatFet would be ideal. Bass will come from a sub.
42V rail voltage 2X over the limit at 350mA bias. Especially with small size heatsink like yours on the picture.
Btw the BDW83C/84C can handle a bit more power.
At least you gave a try to these project.
Did you had the chance to test the amplifier with the advised semiconductors?
I mean BC550C/560C or JFet on the input, MJE243/253 for VAS.
The TIP darlington I pick to replace the BDW because cheap and available almost all store.
Using JFet instead bipolar the mis and upper area of the sound has more body, add some warmness to all over and the sound got more natural.
The MJE rock solid here since I tried many other driver like
Toshiba 2SA1930/2SC5171, 2SA968B/2SC2238B and some other from Toshiba, I'm a big Toshiba fan.
MJE150## from On Semi, also MJE240/250, BF469/470, Also BD139/140 from Philips these I blew up due to the high voltage.
The amp sounded nice with some those drivers to but to me not even came close to the MJE243/253
I didn't gave up on these little amplifier, I was busy to adopt the CCS to test here, according to LC that took his amp another league.
I made the layout for that, I will post it soon.
Btw I follow the other topic with the HEX fet, Toshiba Fet, and discrete darlington.
All the 3 mentioned type perform better some area than the well developed LC's LATfet amp. The Toshiba 2SK1530/2SJ201 and Sanken version outperform the LC amp almost every area not just in the bass even do was used cheap regular resistors, caps etc.
I do want to compare one of that version with my darlington.
I do have Toshiba fet at home also HEX fet but according to the test Sanken and Toshiba fet worth every penny in these topology even do those aren't cheap.
Now I have to remind I did tested these amplifier with discrete (built up)darlington and sounded so bad compare to the darlington I gave up any further test.
Ashok you helped me alot, now I know the amp does not oscillate, also according to you it got more stable by using that the 22R resistor.
Thank you for that.
I'm back here soon since I have the layout, I ordered some clad board already for further test.
I'll post the layout for the Toshiba and the darlington after these post.

Greetings Gabor
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Old 14th August 2013, 05:45 PM   #462
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Location: 3RS
Hi G,
I have 2SK1530/2SJ201 also. But I don't have MJE243/253 yet. Will certainly be experimenting with this basic amp plus mods in the days to come. It looks interesting . I don't have the BC560C yet. At least I can't find my old stock but will be getting some soon.

Must thank you for bringing to our notice the performance of this circuit. Will post on significant changes when I make them. Hopefully others will try this also. It is already being worked upon on a coupe of other threads I think.
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Old 14th August 2013, 09:03 PM   #463
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If you want to test the Toshiba mosfet here is the circuit, all do it was tested in the same circuit where the Sanken BJT was used. Since the layout was ready for the discrete darlington (Sanken or other power BJT) borys just replaced with these Toshiba
The result was excellent!
I think for these mosfet like to the LATfet and HEXfet enough a simple VAS stage so these was modified according to that.
These layout with a small change can be used for HEXfet, Darlington and for Toshiba mosfet to.
I post the layout now, there is some minor mode since the designer use 1/4W resistor.
Also I modded so I can use the power darlingtons and I hate fuse on PC boards..
The layout must be open with the paint program, print setup 34% and that is the correct size.

ashok the MJE243/253 to my darlington layout only. Here was not tested!
Attached Images
File Type: png BG1-HexFet_Toshiba_Brd1.png (82.3 KB, 382 views)
File Type: png BG1-HexFet_Toshiba_Brd2.png (72.9 KB, 376 views)
File Type: png BG1-HexFet_Toshiba_Sch.png (60.5 KB, 372 views)
File Type: png BG1-Daelington.PNG (139.4 KB, 367 views)

Last edited by gaborbela; 14th August 2013 at 09:06 PM.
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Old 14th August 2013, 09:09 PM   #464
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One more
The layout designed by Marc, so he deserve all credit for.
I just made some small mode.
Greetings G
Attached Images
File Type: png BG1-HexFet_Toshiba_Brd1.png (103.3 KB, 313 views)
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Old 24th August 2013, 02:02 AM   #465
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I went over on the layout and found a small error which was fixed and the two smoothing capacitor was disconnected from the signal ground and connected to the right place in these case to the main ground.
Now these layout is for one pair power darlington or one pair Toshiba mosfet.
See the circuit for the difference between the two power stage.
If you use Toshiba mosfet max rail voltage 40V in Class A/B
If you use darlington like BDW83C/84C or similar power rate max rail voltage 36V at 100mA bias.
Please do not exide the rail voltage or the bias under any circumstances.
It will blow up the one pair of the mentioned darlington can not be pushed higher.
If you need more power please double the output (must be matched).
The layout need to be tested, so if you go on and build it please take the time to check the circuit before you power it up.
After with the CCS test if the result is good or better than my orig I will make layout for two pair darlington or Toshiba mosfet.
On the PC board there are no fuses be careful
Greetings Gabor
Attached Images
File Type: png BG1-HexFet_Toshiba_Brd1.png (80.0 KB, 108 views)

Last edited by gaborbela; 24th August 2013 at 02:04 AM.
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Old 24th August 2013, 02:18 AM   #466
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Location: 3RS
I'm still on holiday but visited some local parts dealers ( in Colombo). I got two pairs of 2SA1216 and 2SC2922. That's all he had ! Couldn't find any other devices we normally use except 2sc1845 and 2sa992.

Has anyone used the 1216/2992 in this circuit ? Need to determine what supply voltage I can use.
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Old 24th August 2013, 11:00 AM   #467
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In a similar topology those Sankens was tested, they perform very well and sound gooood according to Marc.
All do these circuit has CCS (have a feeling you not after that) with the discrete darlington at 40V 100mA very stable.
Take a look at here
FET-hex explendit amplifier
I will have to test and compare with my old darlington amp to know more about these circuit.
These circuit similar but still a lot differ from mine.
Feedback, capacitor values, transistors, other resistor values etc.
You can see all that.
The good think you can use the transistors from these circuit if you do not want any CCS.
Greetings Gabor
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Old 24th August 2013, 12:00 PM   #468
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I'll post one more time the layout.
I made some minor adjustment, so these is the final. To get the right size please save it, open with paint, print setup 33% or 34% and print.
Any question please do not hesitate to ask.

Greetings G
Attached Images
File Type: png BG1-HexFet_Toshiba_Brd1.png (80.0 KB, 65 views)
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Old 25th August 2013, 08:28 PM   #469
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Join Date: Jun 2011
Has anyone considered the NTE253MCP? Matched pair of power darlingtons.

$4.59 a pair here

NTE253MCP NTE253MCP pdf NTE253MCP datasheet NTE NTE253MCP NTE253MCP 4.59 American Microsemiconductor NTE253MCP available at 4.59. FREE UPS ground shipping or more.
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Old 25th August 2013, 08:53 PM   #470
Cuda is offline Cuda  France
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Thanks Gabor for your Email

Some one know how using SANKEN STD03 darlington with thermaltrack and remoce the VBE multiplier ?

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