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Old 27th March 2007, 11:47 AM   #581
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Default I know you are experience with computers, heat, overclocking and so on


But please...do not forget to install protective rail resistances....even those 20 ohms will fit...to avoid problems as bias may be too advanced, or off set too much out of the correct value.... start with the off set in the mid range position and adjust the bias one to minimum resistance.

regards,

Carlos
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Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg
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Old 27th March 2007, 11:48 AM   #582
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Default One day we will celebrate with a barbecue


And we will do it inside computer chassis...ahahahaha!

revenge...as it gave you hard work in the past...revenge!


regards,

Carlos
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Old 27th March 2007, 11:52 AM   #583
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Default What is the current entering that amplifier?


Yes..you already know that...as you are experienced Nordic..but there are young folks reading this thread...beginners as i was 40 years ago...and those simple things are "big help" for some of them.

regards,

Carlos
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Old 27th March 2007, 11:56 AM   #584
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Default Mydaugther Larissa, 10 years old, use to help me with my toys


She helped me to calculate this amplifier...that Dx amplifier..and she use to correct me...she already knows equation that i have teached to her.... and she do those things better than i can.

She knows how to calculate the entire amplifier...this topologie.

She is the main Dx corporation designer!....ahahahahha....can you believe....and it is true.

And there are folks pride because they know how to calculate resistances in parallel...my daugther makes more!

I want to present you my daugther.

regards,

Carlos
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Old 27th March 2007, 12:00 PM   #585
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Default She has not special..average intelligence and interests are normal for her age


But she loves to hold soldering iron with her daddy...and to understand the trails the electrons goes.

She use to revise my texts...to check my constructions searching for shorts and wrong connections..also she helped me when designing the Dx amplifier...she was the calculator operator.

More than my daugther...she is the chief of Dx Corporation Enginneering projects department...hehe

Just that.

regards,

Carlos
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Old 27th March 2007, 01:44 PM   #586
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Heh, Carlos handy, just got to keep her indoors for the next 60 years or so....

Hope you use real wood for the barbeque, I always laugh when I see people useing charcoal... yuck.

Is it better (less likely to blow up) to use the slower transistors - tip41?

I'm about halfway done putting the pcb and circuit in eagle... so far it looks consistant...
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Old 27th March 2007, 01:47 PM   #587
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Default Here the last schematic, adapted to your needs Nordic


As the heatsinks are not so "enormous" as we hope, ....so.....the diodes will be helpfull to keep temperature under safe limits.

there's a fixed 47 ohms resistance...will be needed to reach the current, as 100 ohms alone is not enougth together those three diodes.

The VAS transistor, i think you will use a 200 Megahertz unit...the old and good BD139....but he may oscilate, as gain is good and it has that possibility, to oscilate in hi frequencies...better not to give it this chance including a capacitor (better Silver Mica....ceramics can work too) from 22 to 27 picofarads.

Those "radio frequency" transistors,...able to work till 200 Megahertz are eagger to oscilate...they need only to be biased and sensing the inductances and capacitances we have in our circuit boards they start to oscilate...the capacitances with inductances join together to construct a "tuned circuit"...and this will produce certain frequency of oscilation that are proportional to this capacitance and inductance....because of slew rate they are used...but....hummmm..can be a problem.

The input do not need so big capacitor as 4.7uF...if you prefer, you can reduce it to 2.2uf or even sligthly lower without losses in the low end.

I hope this helps you.

regards,

Carlos
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Old 27th March 2007, 02:03 PM   #588
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Default No!..... TIP41 is not better...it is just more safe


Using small leads into the BD139...good pcboard..with small copper lines...small in length and not near one each other.... installing the Miller one....BD139 will be sligtly better in sonics....but that difference is a hell difficult to perceive.

TIP41 decision was because easy to find... good gain...over 100 normally.... price is low... dissipation of the To-220 case is nice...and to be more safe...just that.

You can use your BD139...Klaas have used and he like it.

So...was tested by me and by Klaas...will fit your needs.

I think BD139 is wonderfull transistor...almost so good as MJE340 and MJE350....they are cousins...also BC630 and BC649 are younger cousins...alike young kids...less power they can hold only.

Capacitances of BD139 are very good.... this transistor is a guaranteed of quality by itself..used since the seventies...good ones.

Also the differential input...if you use the PNP BD140.... will work fine too.

Sorry..i use charcoal and i fire it using liquid or Gel alcohol.... good smelling wood is not so easy to find...but in our future meeting we will use the wood you suggest...since it turns handy for us....barbecue receive only salt...big salt grains only....and the salt goes in the moment the meat goes to the fire...and then, after some minutes, it is removed shacking it.... the surface is fast toated to avoid too much losses of blood..this turns meat more tender.

regards,

Carlos
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Old 27th March 2007, 02:41 PM   #589
Nordic is offline Nordic  South Africa
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Try old wood form grapevines... I must say over the years it is getting a bit more expensive finding nice wood for a braai, our word for barbeque, it is a South African speciality... especialy lamb chops, which is hardly eaten in some parts of the world... weird....

I have a feeling I should go for tip41 etc... because I am too dumb still to deal with many variables.... I need to be very sure.

Like you said before it is uncertainty which make people abandon projects midway...

Very confusing signals when you say, use this part, but wait, it is more likely to go nuclear and blow up your house if you get it wrong.

Thanks for the tip on input cap, haveing a problem finding the right size in 4u7... have not checked the filter values, so will take your word for it...

Tonight I'd like to get the final BOM done, so that I can go shopping tommorrow...


Thanks for the patience auncle Charlie, the circuit above,

I am at the output stage now, of entering the board into eagle, and still no problems... used tip41, as it does not have all models... will have to check pin legs with whatever I use....

I can allready see BC640, would go exactly oposite from the way they are drawn on the board... for input stage... at least I can't get those 2 wrong....
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Old 27th March 2007, 03:17 PM   #590
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Default TIP41 is hardly used to output...but dissipation is small...this amplifier would need

Two pairs...each one will need one emitter resistance.

Good idea is to go for the more safe decisions...and then...near future, you can tweak, and substitute here and there...to make your own experiences and to produce your own conclusions about those things.

Everything will be fine...just give it a triple check...you already found the first damn problem...those BC639 can produce errors because their leads position.

And you are finishing....make one board with new parts and the second one with used parts..... another Myth will go down...used, junk parts, work as new...and sounds absolutelly the same.

Life is wonderfull...each day we learn a little bit more..... and i use to read other forum folks...there are a lot of things i do not know and i go learning.... i am very happy as i could make my own...and sounding excelent..you will see that.

What was the chip amp you have made...if LM3875...hehe...Dx amplifier will eat it in the breakfast...easy...fast and LOL.

No!... they are not bad...the opposite, they are excelent..producing a nice work beeing so small and having so small distances between leads....problem there are the protections..they interfere with sonics.

regards,

Carlos
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