Dx Precision, finally released... now debugged and better than HRII

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CRT have asked me Layout for Precision.... some weeks ago..

And i have said him no..... so...big magic of CRT i think...if was not CRT the magic influence, was another one i call him Arabian and he use to tell me he is not from Arabia..ahahahah, another one with name alike, but not you Stuey...relax.

But time have passed, and conversations i had with Nico, he made me understand that will be more kind to offer the whole stuff to forum folks, as we said the Precision 1 is for free and that we cannot change the "game rules".

the amplifier that is for free....not a good idea to us to block Layout for people make their own boards...i could perceive that this Nordic argument was good.

Because of that, we decide to offer all informs people asked.

My post was thinking on CRT, nothing about you Stuey.

Well.... unfortunattelly my decision resulted not so well to my personal interests in Brazil.... people already made copy, even without boards layout of informs.... and now will turn worse to me to enter with Precision II in my country... as boards almost the same are already available for free...hehehehehe...it is hard to change our behavior, even in other country, once for free, there are things that bring us back to the rails and we cannot avoid the for free tradition.

But not problems...we will keep the whole thing free to forum folks, and will be published, and will copies will be send the way was arranged between me, Nico and forum folks.

Also i have people asking for the red board, that Classic II Nordic made....pretty one, better than the Classic boards i have ordered into United States... i have already people asking the red ones...when i could not see the same interest in the blue one, the Classic boards...ahahahahah... a pitty that.

My people is powerholic in essence, and this is because they have not good knowledge.... they see power as quality, when there's nothing connected .... you can have low power with quality and high power without quality...things have not logical connections, the opposite is possible too.... the red boards show, made my people very interested, more transistors, more colour (Red), bigger board.... this means to them "more power"...ahahahah....they want Classic II... and one already give up for the Classic boards because he wants Classic II.

World is a small village...we make noise here, and whole world listen... very few brazilian folks can read in English, but they have translators, they have some good idea about English language (because school) and they can recognize and evaluate images...they can sniff power!

regards,

Carlos
 
Strong emotions, very soon to all of you...from Nordic you will receive

the nice "thousand stamps mail".... and you gonna find inside pretty boards that will make you very happy.

Dx Corporation Guarantees your happyness and strong emotions, the fast visit to heaven!

Be happy feeling the strong impact of bass in your stomach, feel the hair legs shacking with the music....listen the nice trebles and the exceptional voices you have...the thundersound that appear very strong, having some "empathy" by the 33 hertz lovely bass.

Enjoy folks, and be very happy, we have worked for that!

regards,

Carlos
 

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Here we are the Precision I (Roman letters that means "one")

made by Todd, our forum friend called TAJ.

He made a draw, a hand work, to keep data inside the forum limits.

His work quality is, as usual, excelent.

I have checked once, but will do other examinations, as there are possibilities of human mistake..... even knowing that Todd Johnson never made mistakes in his work...a very skilled, very competent professional.

Thank you very much Todd Johnson, another for free cooperation, very kind from you to be together the Dx Corporation Crew.

Well folks, a nice board for a nice sounding amplifier, good power and excelent audio quality.....boards very pretty, excelente work from Nordic, and i have my "finger" on that too, but the hard work, the efforts and the congratulations must go to Nordic that made almost all job done.

Please, if you perceive something wrong, let me know immediatelly.

regards,

Carlos
 

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Unfortunately, I am a mere mortal (at least that's my assumption) and there were some mistakes on the layout page (5 missing bypass capacitors for the back side of the board). The PCB is fine, but I've updated both.

I didn't expect Carlos to post these ones. I just wanted them checked over. Sorry for the inconvenience.

..Todd
 

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A couple of FYI's for the DIY PCB...

The pads in the driver & VBE multiplier area, (see attached picture) are really tiny. I had no room to enlarge them, so be very careful drilling them. The rest of the pads have been enlarged substantially to accommodate easier DIY drilling and sturdier solder connections.

Speaking of drilling. The holes shown on the PCB layout are not indicative of the drill size. They are just a center mark to help position the drill, and will usually be a lot smaller than the real drill size. Drill bit sizes will be left up to the constructor.


..Todd
 

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Taj,

Comments on the component layout:

There are two C3's, I think C5 100nF is mislabelled.

CIn is 4.7uF but the schematic of 29th Feb had it as 10uF electro, which is correct?

C33 68pF - Is this C13 on the schematic?

Are fuse types M205 or 3AG or can either be used?

I appreciate the effort you have put into this and I hope my comments help.
 
Hi StereoDave,

I'll check these items in the morning. Need sleep.

Since it's not my circuit, or layout, I can't authoritatively answer component questions like the fuses or the input cap. Nico or Carlos will have to answer those.

I wasn't paying attention to the fuses, sorry, just didn't notice. About the input cap, I think you're right, 4u7 got changed to 10uF recently. I'll update that if Carlos or Nico concurs.

But the mislabeled caps sound like my kinda drawing mistake. I'll take full credit for any of those blunders. I'll check them out and correct them tomorrow.

Good eye. Thanks for that.

..Todd
 
The fuses depends on your speaker impedance, depends on your supply voltage

and how good is your supply related to give you stable voltage while the amplifier will be operating into the threshold of clipping into the signal peaks.

But, there are folks that loves to listen already entering distortions.... well, the fuse selection is up to you...will be different depending your "style", and will be different depending your supply and will be different depending your output impedance.... this is up to you...your choice!...you selection.

I am showing you the current into the positive rail, the current into the negative rail (down rigth voltimeter) and into the center you can see the current going to 4 ohms speaker.... this is reproducing full UNDISTORTED power, not the threshold of distortion and not entering distortion.... means 260 watts, and the amplifier can go more and more.... those values can be good to decide your fuses.

Also, you can be that kind of listener that use "average" power levels....means musical levels.... this will reduce your power to less than 80 watts average...maybe you will prefer fuses to average if you never go up.

There are friends that have expensive speakers, not high power speakers, and they want to protect them...because of that they reduce fuses ratings...so...if they increase above, because accidents, the fuse will burn and the speaker will be safe.

I really think, that there is no perfect fuse ratio, i think the user, the builder, the constructor, the diyer must engage his own brain and decide by himself no following rigid instructions that do not evaluate all possible options.

The real good fuse will be bigger than the ones you may decide into the image i am providing you...as amplifier can enter strong clipping and current will be bigger... really bigger, depending your transformer power.

.........................................................................................................

The input condenser

Well, this one, if was something made in factories, will came to you using 1uf maximum, as they use to decide that 20 hertz will loose 3 decibels.

I think better idea is to have 2u2 (my home use), as this will allow you to have full power into 20 hertz

4u7 was suggested into the schematic as this makes you able to reproduce 1 hertz with small losses

10 uf is overkill in the reality, do not remember why this appeared into the schematic or posts here .... maybe some personnal evaluation based into audition, and this, for condensers are not precise enougth.... using 10uf you gonna have FULL POWER into 1 hertz...this is dangerous, why?

Imagine someone plug a turntable into a pré amplifier, those ones that are good ones, the English ones, from old brands from UK....they do not have even tone controls, have no filters and have no humble filters.... that tone can be around 18 hertz.

This tone will pass througth your pré amplifier and if your power amplifier was able to reproduce 18 hertz with full power, then you gonna have full power humble!!!!

This is another thing that needs to engage brain and decide your own needs.

If you want a suggestion, use 4u7....if you want to know the value i use, it is 2u2...if you want to know the value i would use if i start to assemble into a Dx Factory, it will be lower than 1uf...and the value i would make a better research about..not decided to the factory...the factory, that industry, does not exists!

Decoupling caps are to give low resistance patch to drain RF signals or oscilations that are felt into the rails, to bypass electrolitic condensers...the value can be 22n, 27n, 33n, 39n, 47n, 56n, 68n, 82n, 100n, 150n, 220n, and more, up to 10uf, non polarized, non coiled capacitors...important is the voltage that must be high.

Nico have introduce more units...they are nice to be there, more safe to you...but in normal conditions, when you have no danger of oscilations, when your Miller capacitor was already adjusted to a stable value, when you already have checked your amplifier into the scope, and perceived that has no oscilations driven by the signal...EVEN if you remove all bypass capacitors your amplifier will work fine...so...they are important, and they are not so important under normal operations.... again have to engage brain and not to follow receipt. (receita de bôlo, instruções para cozinha, seguir instruções rígidas)

regards,

Carlos
 

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That explanation of input coupling capacitors is very simplified :devilr: I mean I'm not an expert.

Somewhere I read that one should place the -3dB point at least 2 octaves below 20Hz, but I cannot remember if that was valid only for electrolytics. There are things like dissipation factor, dielectric losses, phase shifting, etc.
You're so proud of that excellent bass response of Dx Precision, so the relation to not use a proper input capacitor should not be of discussion. If one's using an expensive Polypropylene type, than low values will be fine, If I were using an electrolytic cap (I think no one seriously will do that) I'd go for at least 10µF/35V.

Just to keep things a little bit more exact :clown:

P.S.: Carlos, that wasn't meant to set your explanation in question, I know you do know a lot more than it's reasonable to write here. I just feel that if one's using wrong parts with your great design, he might miss something of the magic this amplifier will be able to do.
 
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