Power transitor question

[gaborbela]

Hello

I would like to know can I use these power transistor with good result on 35mA bias .
http://www.onsemi.com/pub_link/Colla...MJL4281A-D.PDF
It say Gain Linearity from 100 mA to 5 A
Or better to use some slower transistor like these two
http://www.onsemi.com/pub_link/Colla...MJL21193-D.PDF
The next option would be these , I have all these 3 devise at hand !
http://www.onsemi.com/pub_link/Colla...MJL3281A-D.PDF
Someone (Mike B) said the last one tend to have hars sound !
I used before MJL0281A but no longer available .Unfortunately I burnt one side the amplifier .
These is the Avondale NCC200 clone amplifier .
Did someone tested these transistors ?
Please let me know .
Greetings !

[sumaudioguy]

Never tested that particular transistor. Topology seems to have a lot more to do with the sound than a specific device. I can use floor sweepings in this one design here and still get great sound and test specs. Not true for some of the other designs. Don't blame the device for a bad result...unless it says TI on it. Been burned by that brand every time used for the last 35 years! Never again.

[AndrewT]

Hi,
the 4281/4301 are good transistors.
They will work in a ClassAB amplifier.
35mA bias is unusually low for an EF output stage and would require 0r68 emitter resistors for optimum ClassAB bias.

[godfrey]

On Avondale's website, they recommend MJ15003 (or BUV20). Why not use one of those? Their datasheets are here: MJ15003 and here: BUV20.

Of those you listed, the slower MJL21194 would be the best match in terms of speed. The NCC200 circuit has some unusual compensation that suggests it might be picky about the speed of the output devices...

[sajti]

Originally Posted by gaborbela

HelloI used before MJL0281A but no longer available .Unfortunately I burnt one side the amplifier .

But NJW0281 is available. You replace the MJLs with them.

Sajti

[gaborbela]

Hello
I have at hand the MJ15003 but that is in metal case ! Actually I'm not a fan of the MJ13003 device , I'd rather would pick MJ15024 .
Much better after my ear .
My PC board was design to use flat case power transistor .
I replaced the burnt transistor with the faster MJL4281A and I increased the emitter resistor from 0R22 to 0R68 .
Andrew do I need that high value emitter resistor the orig was only 0R22 ?
These amplifier use only NPN transistors on the power stage !A post the schematic so U can see it .
The driver I use MJ15024 , MJ15025 .
The amp burnt because accidentally I made a short circuit with my DMM.
Now the sound is OK but I really can not do a loud test , today Sunday .
I live in a apartment I do not want disturb the people now .
Tomorrow . Probably I will test the slower power transistor to .
Thanks for your help guys.
Greetings

[Telstar]

Originally Posted by sajti

But NJW0281 is available. You replace the MJLs with them.
Sajti

I second this suggestion. They are also low-beta droop devices.

[gaborbela]

Hello
I'm more than satisfied with the MJL4281A thanks to Andrew. It does sound great , even if I would have more MJL0281A I would not go back .
The sound much open than the another side , better transparency , bass is good to .
I will replace the another side to to MJL4281A .
Can I use 54VDC power supp in 8 Ohm .
I will never drive it not even on half volume .
The bigger transformer much better quality,the reason I would like to go from 42V to 54V .
Probably it will be less a bit because 39-0-39V the transformer .
I will lose some percent after the rectification .
I will see , these is a great amp ! I like her a lot .
Greetings

[AndrewT]

Hi,
there are a number of component value changes I would experiment with.
Are you interested?

[gaborbela]

Hello Andrew
Of course, if it make my amp sound better or it will be more stable that always is a good think .
The sound now is not bad (actually I like it a lot with these power transistor) but I'm always open to improvement .
mathelaszlo2@yahoo.ca
Today I started to put together the power supply , connectors etc . Until now it was built on a piece of plywood , it was easier to replace parts or work with .
Thank you
Greetings