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

[sakis]

É about to produce an A40 by NP i just recovered some pcb from the past and i said "ok what the hell lets do it "
the ones who know me also now that i am a typical AB 2SA130-3281 person but lets do somethng class A for a change ...

the particular post exists as asubject to pass forum also but since this is a solid state isuue lets talk about it here ....

the story is about darligtons .....feel free to join in !!!!

quoted from pass forum
-------------------------------

TIP142-147 BDV66-67 and related cousins ....

the bad reputation about these devices lays arround one thing only ..... durability and stability .....

But where this comes from ????
most people that had circuits working with these devices missed one thing :
Draligtons have diferent makes depenting on the make , the application , the original order , costumer specs and so on and on and on ....

meaning that if you have 2x2N3055 in one amplifier and the first is ONSEMI and the other is MOTOROLA you have a chance .... but if you have a TIP 142 from philips and TIP 147 from SGS it simply doesnt work ....

the bigest reason is that you dont know which is the exact configuration between the driver and the output tranistor .... one is made with A resistor other is made with B resistor and so on and on and on ....

if its a lofi application all is fine but if the circuit/application creates stress to the outputs then death and smoke is just a matter of time .....

Never the less let us not forget that darligtons often can be taken as mosftes IE if the design is not proper for them oscilation is waiting arround the corner....

Take as a fact that almost non of comercial equipment ever used this familly except some philips amps and some BO sets that if broken the repair is a nightmare .....

Funny part .....

somewhere in the net exists the john fisher amplifier that clames 100-150w power with the lowest part count you can ever imagine he he he he I think that this amp must be constructed by so many (built with 142-147 ) and now days i think that all these people support and keep demands for production of 142-147.. family .....
the "thing" has a very catchy title he he he

[sakis]

i ve met with one of these amplifiers created by elektor and used BDW83-84C as outputs ...... if i had to name this amplifier i could just as well name it : THE ULTIMATE SONIC KILLER !!!!

been constructing this amp for 3 times in the far past last time i think 8years still own it and having to change the outs to a more reliable MJ11015-16 which actually improved a lot as about durability and done nothing about the sound ( expected )

may be now days with more expirience i will take a look at it gain to see if there is something missed or done the wrong way .

What is trully noticable about this design is that has everything tha will kill your sonics
---- strange input configuration
---- then classic and effective VI limmiters ( from asafety aspect )
---- large base caps located in the output transitors
---- finally huge 1R 10W balast resistors that actually support my above comment that a darligton will behave in a strange way depending on temperature drive and others even though given as a fact thata in a elektor design the best of material is to be used

compaired to the above NP selections of output resistors 0R68 in a configuration of 2 xTIP142+2XTIP147 used as outs looks more than proper

then again elktors design is AB issue and A40 is a classA issue there i can presume and please someone correct me that if darligtons are too busy keeping on with 400ma idle/device may be they dont have time to oscilate .... hell !!!!! i lost my sleep on this ......

sudenly and out of the blue this post and this schematic comes up very related and have alot in common as an idea with the A40 even though one is classic double darligton and the other is sziklai double darligton please find attachment and related link at the end .....

strange but the claims that with BD249-50 and other related slow devices circuit is woorking but with modern fast transistors runs in to oscilation problems

finally remains a another question about something i read in the forum that as an idea to each output BJT having its own driver provides amzing drive to an amplifier

thanks
regards sakis
New Amplifier design

[sakis]

here is the elector circuit

[sakis]

http://www.quasarelectronics.com/ima...-kit/1077d.pdf

that actually must be an elktor design stolen by the greek company smart kit electronics that claims that a pair of BDV 66-67 OR TIP142-147 can do 100-120W@4R

due to the usual catchy title the amplifier has been selling alot through the years (worldwide !!!! ) also depending on the quality of material given inside the kit , proper assembly and handling ( the kit featured alternative options for building inside related to the output resistors and the configuration of the VI limmiter for 8 or4R respectivelly ) this amp was a ticking bomb ...

since outs inside the kit was simply what was available in the smart company and since in the instructions wasnt clear enough how importand was the VBE multiplier to be common heatsinked with outs most of these kit amps ( if not all ) actually failed if stressed just a bit ....

thanks for your time
all input is very welcome

sakis

[Lumba Ogir]

sakis,

finally remains a another question about something i read in the forum that as an idea to each output BJT having its own driver provides amzing drive to an amplifier

Yes, there is a problem with driving paralleled devices. Less amazingly, each master device does not have its own driver, does it?

[wg_ski]

Originally posted by sakis
strange but the claims that with BD249-50 and other related slow devices circuit is woorking but with modern fast transistors runs in to oscilation problems

Looks like he just threw whatever models he had into the simulator. And then tuned up the lag comp until it "worked". The topology was good (as Nelson Pass commented), but it really needed the right (faster) transistors to get the performance it's capable of. And the compensation would have needed rework. Give someone who knows what they're doing five minutes with an oscillating prototype and they'd have it working. With the fast transistors.

[wg_ski]

Originally posted by sakis
[due to the usual catchy title the amplifier has been selling alot through the years (worldwide !!!! ) also depending on the quality of material given inside the kit , proper assembly and handling ( the kit featured alternative options for building inside related to the output resistors and the configuration of the VI limmiter for 8 or4R respectivelly ) this amp was a ticking bomb ...

since outs inside the kit was simply what was available in the smart company and since in the instructions wasnt clear enough how importand was the VBE multiplier to be common heatsinked with outs most of these kit amps ( if not all ) actually failed if stressed just a bit ....

Again, this amp was often the victim of builders who didn't have a clue what they were doing. And were looking for a cheap 100W amp. With the Motorola TO-3's instead of the plastic ones which are often fakes, not mixing output tranny brands, proper heat sinking with both outputs and the Vbe servo on the same heat sink (not two separate heat sinks for the NPN and PNP) the darn thing is near foolproof. I built those things in high school.

[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 ....

[Michael Chua]

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

I've never been successful paralleling darlingtons. Maybe every darlington with its own driver is possible but not very practical.

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

Are you referring to the TDA7250? It is normally used to drive a pair of TIP142/147. For higher power, you can substitute with MJ11015/16.

[sakis]

Originally posted by Michael Chua


I've never been successful paralleling darlingtons. Maybe every darlington with its own driver is possible but not very practical.

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

as legentary NP says ....the one and only !!!!!

i am constructing this as we speak ....will see