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Old 21st December 2012, 11:50 PM   #251
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Hello
Wahab I would like to have a few question to you.
First I see you left out the 330pF capacitor from the modified darlington and the lateral Fet circuit to.
I think that was purposely. Can you gave me some hint, I do not miss that capacitor just I want to know is not an error.
Do you think these topology would work with out major mode with power BJT like the mentioned Toshiba 2SC2500 and complementary?
Please let me know before I etch the PC board, I'll give a try to the lateral version just to compare with the Darlington.
I see these topology getting more and more popular on the forum.
Also I got a lot of resistance from DIY-ers because the Darlington devices (what I like(because I heard in the amp).
I wish we could invent the newer Sanken darlington with the thermal track but not much valuable information on the NET about them.
Tomorrow I start to work on the Hitachi PC board, protect fro oxidation, drill the holes etc.
Some of my fund are hold by pay pal, I do not want to spend more from my pocket.. I already spent ## ### over the years on DIY parts.. These include DIY speakers, cables etc.
I want to order the resisters and the needed transistor.

Greetings Gabor
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Old 22nd December 2012, 09:00 AM   #252
wahab is offline wahab  Algeria
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Hi Gabor ,

Well , this capacitor (along with the 2.2K resistor) will reduce the high
frequency -3dB cut off to 130Khz , down from the 240Khz if it wasnt there.

I suspect that it was added as RF filter rather as well as slew rate limitation ,
as in Europe the radio broadcasting AM band start at 150Khz or so with
emitters less powerfull than in the 70s , but still being a problem for
whom is living not too far from the antennas , so if you have nearby
RF transmitters it can be usefull to implement the said capacitor.

Other than RF concerns , this also limit the signal slew rate to cope
with the BDW83/84 6us slow turn off.(2us or less for the BDW93/94)

Replacing the darlingtons with two drivers and two 2SA1943/2SC5200 pairs
wont improve the perfs by a sizeable amount providing the comparative monolithic
darlingtons are not beta starved , in wich case there will be
a difference when driving lower impedance loads than 8R , and this likely
is the area where Sankens could have an hedge over the STMicro BDWs ,
wich are requiring tests before mounting to eliminate low beta samples.

As for popularity of darlingtons , or rather lacks of , i think that it has
more to do with urban legend than real technical ground , seems that
experiences with decades old slow devices like TIPs or Motorola s early
production where kept as definitive conclusions for all possible monolithic
darlingtons , past , present and future ones....
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Old 22nd December 2012, 09:36 AM   #253
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by wahab View Post
As for popularity of darlingtons , or rather lacks of , i think that it has
more to do with urban legend than real technical ground , seems that
experiences with decades old slow devices like TIPs or Motorola s early
production where kept as definitive conclusions for all possible monolithic
darlingtons , past , present and future ones....
May be the old slow darlingtons were not designed for audio so that they made a bad sounding amps. But iff they are made specially for audio then imagine: if IC, with hundreds of components, can be made "better" than discrete, why not darlington with only 2 parts? The only limitation is thus how the driver's emitter tied up at the output along with output emitter.

Does the latter fact limit the possible performance of the darlington? Technically, may be not. But I have never heard such output topology that sound good enough. (I prefer to modify my vintage amps output stage, with the cost of increased THD)

And I have those fast darlingtons specially designed for audio. And I have made a circuit that perform incredibly well in simulation (P3A input stage, but with different models). But the sound was just another darlington sound.

Anyway, I'm looking forward to any good designer to design a good sounding darlington amp to make me understand more about it. Until then, I'll stick with my urban legend opinion
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Old 22nd December 2012, 10:08 AM   #254
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Hello
Thank you wahab
I did added back that capacitor at least to the darlington (not to the lat FET version) in case if needed good to have the room on the PC boars so I can mounted it properly.
The guy who mode the circuit (at least he told me he designed it) he advised to use Texas Isnt. BDW
Unfortunately on that time it became obsolete so the best ever replacement ST Micro.
From Philips also 20 years a go had some BDX darlington in TO3 case (I think those were more popular in audio) but became obsolete also.
Thank God I found some ST BDW83C/84C (I think is orig because those were produced for order bent and shorter leads)..
May be I will order more after I test them if the seller still has them.
To me TIP was OK replacement but probably how you wrote the BDW types are better..
From other corp not worth to buy not even for half a price, probably only the Sanken SAP15P & complementary..
http://www.farnell.com/datasheets/3147.pdf
These are popular darlinton even in audio but to redesign these amp does not worth that much all!!!!
There is a German made MBL high end amplifier (not cheap at all) that still use the BDX type darlington (probably Philips produce to them in a large quantity) but in the market no longer available.. May be the lat FET will sound as good as the darlington and the problem will be resolved once in for all!
All do people say mosfet has softer bass than BJT, I will test it. I have mostly mosfet amp design from Mr. PASS and the Hitachi Lat mosfet amp(s) If is true the mosfet tend to have soft bass good to have at least a good sounding BJT (with good bass)
I did like the sound of the darlington very much!
Thank you one more time
Greetings Gabor
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Old 21st February 2013, 07:31 AM   #255
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Any progress on the amp ?
I've just drawn up a schematic using Jap transistors and TIP142/147 based on your last schematic but with slightly modified parts values. Supply will be off board. Will attempt to make the board as small as possible.
Hope to have it ready in a few days.....if the work doesn't get stalled by unforeseen circumstances !
If it works Ok I might replace the 142/147 with 2SK1058/J162 and see what happens.
Cheers.
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Old 21st February 2013, 09:15 PM   #256
wahab is offline wahab  Algeria
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TIP142/147 ? I guess that when you ll use other devices
there will be an audible difference...
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Old 21st February 2013, 09:36 PM   #257
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Wouldn't it be better to use these Darlingtons (see bottom of the page) than the old industrial craptanium from Texas, Philips or Motorola?
SANKEN ELECTRIC : Power Transistors : For Power Amplifier

You're right, Wahab. There will sure be an audible difference in that comparison.
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Old 21st February 2013, 11:28 PM   #258
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Hello
My advise to you please use first those transistors I used at my last test!
That will give you a base to compare some other Darlingtom, Lat fet etc...
Reason I write these because that was tested and works properly.
Al do Sanken produce some nice device not much information about and the chip inside built up not the same as BDW83C/ 84C or TIPs.
My last test I made with the TIP147/142- the result was incredible.
Yes I compared the TIP with BDW93C/94C and no audible difference at all! The TIP142/147 more rugged than the BDW93C/94C..
I know there are some new and better darlington chips out there but if not compatible with the orig after you get the idea the amp sound bad, not working properly etc.
If you use 2 pair power transistor please try to match them.. There is a matching instruction some page back from Wahab!
I didn't tested yet the modded circuit, was modified by Wahab. I need some clad board to etch the PC boards for that and the lat fet version to.
My advise to you please use the last circuit was posted by me at post #251.
U can use for input JFet or BC550/560 C grade.
I advise first use for VAS MJL243/253.. Reason I did tested several driver transistor here and to me MJL is the favorite.. Including some famous drivers from Toshiba...
After you can change use what ever you like but again you have a comparison base.
Be careful if you want to use lat mosfet because need some mode!!!!
Mr. Wahab already mode the circuit so we can use lat mosfet but that is not tested yet!
I was unable to work on my project (I'm a disabled person, all do I'm getting better now), sometimes I can't work at all.
I'd rather wait until I feel better and when I put together a project I know I have done to the best of my ability.
Please do not mode the amplifier until you do not test the orig! After if you feel you can improve it please do so, I'm not against that. I just want you to avoid you run into in to some trouble or get a bad result!
I spent ### hours with these amp I know what I'm talking about.
Another think, all do these look a small amp please do not undersized the heatsink.
Greetings Gabor
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Old 22nd February 2013, 02:25 AM   #259
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Right Gaborbela. I will use the TIP142/147 as I have many of them and have no other use for them right now. Second...if things should blow due to errors then it is a small loss. The Lat Fet's are expensive and so are other power devices.

I have some decent power amps to compare it by. Will let you know what happens. I've been curious too.
Cheers.
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Old 5th March 2013, 02:46 PM   #260
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Work has been held up ! Will be able to continue only mid March.
However I see that a very similar circuit is being tested by Lazy Cat and others on the VSSA thread. Interesting !
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