A Darling.......ton Story ....

[wg_ski]

Originally posted by sakis
is that eventhough MJ11015-16 are suposed to be a quiet good device manufactured by On semi now days ...also one of the devices that you dont meet fakes often and also a quite ruged device .....

i wonder why we havent seen any big amps using a few of these in parallel to obtain relativelly high power ....

the only application i remember seen this devices is one fender or marshal amplifier and one rumanian or something kit amplifier that uses some tda to drive the MJs

comments please ....

Most of the 015/016's I can get now are made bt ST. Those are just as good as On's. If you can get ST's TIP142's you're in pretty good shape but good luck on that . The last batch of 142's I got were junk and I ended up using them for relay drivers.

How about the 11032/11033 (the 50 amp units with pins too big for a TO-3 socket) for driving 2 ohms? I've got a couple pairs of old stock Motorolas. Now those would be worth doing something with a series/parallel output stage and +/-80V......

[sakis]

thats very nice of you ....but actually i am not willing to construct anything like that .... since five years ago when i first met with the John Fisher amplifier ( ha ha ha ) i think i am never going to construct anything with these devices ....

the only reason i am constructing the A40 is because i think that with relativelly slow devices like tip 142-147 i think that they will keep busy biased at 350ma each or more so they wont have time to oscilate

i ve been constructing a gozillion amps but never done a class A ...

as we said above ...i am a AB 2SA1302-3281 person ....

regards and thank u
sakis

[Michael Chua]

Originally posted by sakis
take a look at papa's design the A40 it uses 2 pairs of tip 142 -147

Thanks for the reminder. Must try it one day.

Let me know what DC Offset at the output is when you finish building the A40.

[sakis]

that ....

transistors was what was available in the workbench (tip142-147), wiring was a mess , power supply was poor , my scope and my generator create an earth loop ( my setup is kinda messy cause my company east electronics just mooved to amazing huge office and nothing is really ready yet )

then caps used were good quality and all to92 transistors were matched to an amazing figure of 5% ( !!!!! )

then yeap !!! the ofset was a sweet 5mv !!!!

another thing though is that this remained very low eventhough some times i put the rails to almost 40 volts while keeping an eye to the bias

i hate darington smoke ....smels more nusty than mosfet ....

(i burned so many mosfets trying to operate legend 4 amplifier in 60+60 vlts that i can actually tell you the brand of the mosfet by smell ha ha ha ha ha )

[mjf]

hello.
i have built an a40 with tip141/146.........
there is a schematic i found in a texas inst. amplifier book (from the eighties i think),the output transistors t11,t12 are tip 141/146.......(t9,t10 =bc182,bc212 ; t6= bc182 ; t5 = bd135 ; t1...t4 = bc212.
greetings..............

[sakis]

might have a potential ....

has everything included ..... ccs , guarded vas , vilimiters and so on ..... why not ....

sonicwise speaking ..... i wouldnt expect miracles from it ....but why not ??? looks like a working circuit

[mjf]

hello.
it is a standard application power amp ,designed by tex. instr.
they compared the costs of a discrete output stage (tip33/tip34,bd137/bd138 plus resistors) against the tex. darlington tip's.............the darlington's were a few percent cheaper...........
greetings........

[sakis]

...now here is some one that knows his ways around darlingtons ... this car audio amplifier was given to me by a friend ...

It uses 2 pairs of BDW 83C-84C/ch with all the well known stability issues BUT!!!

---uses 1 Ohm ballast resistors quite big but better safe than sorry .. differences that occurs from the nature of the darlington may consumed there

---uses Bd 139 as vbe multiplier which is a s good as any other NPN transistor but for sure offers the best and secured way of mounting on the heatsink .

--- uses a Vi limiter

--- uses Miller caps located as close to the outputs between B -C

now ... to my understanding ...if you want to make darligton multioutput amplifier this is the one and only way ....

regards sakis

[AndrewT]

All 4 output halves appear to have a trimmer resistor tacked on.
Why?
Can you identify what they have trimmed?

[sakis]

amplifier needs some repair it goes on fault condition even though outputs and drivers are ok ... probably some protection or PWM issue

i suspect that trims has o do with bias since there is no trimmer but will check and post my findings here

kind regards sakis