Can I build up these Darlington transistor if I use two BJT transistor ? - diyAudio
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Old 15th July 2010, 05:34 AM   #1
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Default Can I build up these Darlington transistor if I use two BJT transistor ?

Hello

It is possible to build up successful (to get the same quality sound) the BDX53C /BDX54C medium power darlington transistors .
Data sheet with the internal circuit available here !
http://www.datasheetcatalog.org/data...onics/4103.pdf
The reason I want to build up these darlington I want to get high power darlington close to the BDX type
For example
I chose for driver MJE15030 /15031 Minimum hFE=40
For power transistor MJW21195 /21196 Minimum hFE=20
The BDX53C/54C min hFE=750
If I do these calculation I get close hFE 40x20=800
I also have at hand MJL21193/94 similar like another power transistors but with more power .
Of course I ad the 10K & 150R resistors and also a diode .
Any comment , help , advise please
Thank you very much
Cheers
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Old 15th July 2010, 07:35 AM   #2
Enzo is offline Enzo  United States
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You probably could but have you considered alternative darlingtons like TIP102/TIP107?

And I don't know what kind of power you want to weild, but the larger TIP142 and TIP147 are very common in power amps in the music industry.
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Old 15th July 2010, 02:50 PM   #3
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Thanks for the advise
The Tip has different internal circuit .
It uses 5K resistor instead 10K , but I tested and is not the best replacement !
TIP142 pdf, TIP142 description, TIP142 datasheets, TIP142 view ::: ALLDATASHEET :::
I want to get some darlington for these amplifier (picture attached)
BDW83C /84C would be the best choice but no longer available BDW84C at least not in good quality . Like ST , Texas I. or Philips only some Chinese cheap bad quality. Or some fake ST.
Now I have these amplifier , I like it a lot . I use BDW93C / 94C a bit powerless since those are medium (small) power darlingtons . Also I want to crank up the bias min 400mA. Of course with lower PS .
I tried to parallel them but impossible to match (at home) the darlingtons and sound bad with the unmatched power transistors !
If you look at the BDX53C/54C data you can see that darlington was design for audio to.
http://www.datasheetcatalog.org/data...onics/4103.pdf
There are some high power darlintons like MJ11015 /16 but the same problem .
The internal resistor value are different and it sound awful .
I tested , the best it would be to use two BJT and build the darlington .
Thanks for the advise one more time

Greetings
Attached Images
File Type: bmp first%20diy%20amplifier[2).bmp (185.1 KB, 64 views)

Last edited by gaborbela; 15th July 2010 at 02:55 PM.
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Old 15th July 2010, 04:31 PM   #4
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Quote:
Originally Posted by gaborbela View Post
Thanks for the advise
The Tip has different internal circuit .
It uses 5K resistor instead 10K , but I tested and is not the best replacement ![snip]Greetings
Generally, the lower this resistor is, the better the high frequency performance of the Darlington. In what way did you test it?

jd
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Old 15th July 2010, 04:49 PM   #5
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Hello
Yes you right , but in the bass region became very light .
Otherwise these amplifier sound incredible with the BDW93C/94C now .
I'm just listening , huge bass nice mids tube like sound . But only with 100mA bias .
I still worried these small transistor will blew up .
I can use 18V power supply but I will end up with a 5W amplifier .
If I replace the power transistor different type what is on the schematic the sound become total different .
Thin , no longer soft tube like . I have a lot of great ON semi high power and driver transistors at home . I do not believe is impossible to build up these darlington with the same resistors etc .
I just need some advise because I never did it before .
Greetings
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Old 15th July 2010, 05:24 PM   #6
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BDX53C/54C are available from OnSemi, Farnell here in the UK sell them.
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Old 15th July 2010, 05:39 PM   #7
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Thank you
I know but those are low power darlingtons unfortunately .
To use them in parallel I supposed to match them which is not so simple .
For me BDW83C /84C would be great . But 84C no longer available , just some fake ST or cheap useless Chinese parts ..
I ordered from Germany Reichelt BDW83C/84C but cheap garbage .
From ST company the smaller BDW93C/94C works great but low power ..
I would like to rase the bias up to 400mA.
That is the reason I need high power darlington

Cheers

Last edited by gaborbela; 15th July 2010 at 05:43 PM.
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Old 15th July 2010, 05:41 PM   #8
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Quote:
Originally Posted by gaborbela View Post
Hello
Yes you right , but in the bass region became very light .
Otherwise these amplifier sound incredible with the BDW93C/94C now .
I'm just listening , huge bass nice mids tube like sound . But only with 100mA bias .
I still worried these small transistor will blew up .
I can use 18V power supply but I will end up with a 5W amplifier .
If I replace the power transistor different type what is on the schematic the sound become total different .
Thin , no longer soft tube like . I have a lot of great ON semi high power and driver transistors at home . I do not believe is impossible to build up these darlington with the same resistors etc .
I just need some advise because I never did it before .
Greetings
Well one thing is that with different devices you probably need to figure out the best bias setting and adjust it to that. Did you do that already?
Different speed devices may also lead to instability or oscilatory behaviour which can alter the sound strongly. You would need to check that.

jd
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Last edited by jan.didden; 15th July 2010 at 06:29 PM.
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Old 15th July 2010, 05:48 PM   #9
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Hello
Yes you right , I do not own oscilloscope so any test like that not possible .
I did listening test and not a good replacement parts .
Cheers
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Old 15th July 2010, 06:30 PM   #10
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Quote:
Originally Posted by gaborbela View Post
Hello
Yes you right , I do not own oscilloscope so any test like that not possible .
I did listening test and not a good replacement parts .
Cheers
OK, so they may be good parts IF you re-adjust the amp. That will always be an issue, whatever replacement parts you get, unless they are the originals.

jd
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