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

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Here is the machine....enjoy the sonics... superior sonics.

Around 170 watts into 8 ohms

More than 250 watts into 4 ohms

Clear trebles, without excesses.

Deep and controlled bass

Huge dinamics

Silent amplifier, very low noise...almost nothing to ears.

Huge and tested.

Dx Precision II was made also, the new one i cannot show schematic because sold to a local factory..but i can explore too...maybe, finding a partner (Nordic) we will make some of them.




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Transistors are 2N5401, 2N5551 into the differential

Also the first VAS transistor.

To VAS output and drivers, use the good ones:

2SC4793 and 2SA1837.

Into the output the Sankens work better, but, the Toshibas 2SC5200 and 2SA1946 can do the job in a confortable way too.

Bias current, stand by current is 60 miliamps

Off set can be adjusted to be lower than 500 microvolts.

Yeah!... smashed High Resolution II, also the Dx Standard and 80 percent of the forum amplifiers.

Construct 5000 dollares quality amplifier paying 200 dollares in parts.

Wanna better one..... have to go to Hugh Dean....he had helped me to design this one.

Thanks Giamie, dear fratello, ... Also Doctor Self because some ideas...and thanks Nordic (help and support) and also Duda (parts).

The input diodes are dangerous....having oscilation cut the damn thing out!


This will depends from Nordic.

In the reality we are focused into the Dx Precision II..... but..maybe he will make boards for this one just released.

This is up to Nordic.... i will not produce boards for this one because working as production line superviser (for 3 weeks only) into the factory that started to produce Precision II.


its about time

to see some real amps ( considering power ha ha ha ) from you carlos!!!!
its a very nice thing to see someone who managed to produce quality reliability with simplicity and afordable cost to procced to biger machine .....

i am going to be one of the first to buy ..... to listen ....and ofcourse to abuse your amp in my small pa application

merry merry xmas to very very creative carlos !!!!!!

thank you carlos
Disabled Account
Joined 2006
Hi Carlos

Nice amp design, I am pretty sure it will have great sound - see you have changed your opinion Self and are using some of his ideas. The better you amp gets the more ideas i see from Self there.Self does not spoonfeed all his knowledge to others, he only points you in the direction; you have to explore. I dont know whether you are aware that he designs comercial amps which are relatively cheap,have won various awards and with great sound for the price.

I view amp design a bit like hugh from aksa does, hormonic content very important (His amps overdo it a little bit, what he calls musical i call a tad of colouration,too sweat; i compare to the live real thing) and make some cash on the side modifying amps and cd players, my favourites are rotels. Relatively cheap, well built with excellent choice of parts that offer quite good sound for the money. They can become magic with some tweaking!!! The less thd and tim the better but always with a close eye on the harmonic content.

The amp i use is a middle of range 12 year old tweaked rotel which i have compared together with a couple of musicians (sister included;piano) to various amps (some big dollar high end) and including a aksa 55 belonging to a friend. This amp simply blows the aksa away, its in a different class. Some simple amps can be made to sound very good indeed, compensation is critical and component choice important.

I have a roughly built dx II, and a hint try 2sa1016k/2sc2362k for ltp and 2sa1406 or 7/2sc3600 or 1 for vas, even on this new design. Compensation can then be tweaked too and this is what hugh and now also you seem to have mastered.
Maybe ill try this one too later, but i have been playing around for last 9 months with a design similar to roender (i got my idea from ad817/ad797) have not fully mastered the sound yet, but have to say folded cascode gives clean fast and powerful sound. Roender has some excellent ideas, his input pair does sound marvillous and probaly his whole design too.

Nice to read your posts always some humor in them. I am portugese too but born bred and educated in same country as "Nordic".

Good that many friends have readed the thread.

I am a little busy repairing my car.... so... i will answer you all latter.




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My seven years old Volkswagen needs some repair

ball bearings, oil, steering box terminals, fuel tank floating piece,alignment, fuel injection cleaning, spark plugs substitution and more...more...more...more.

135 dollares will be the cost.

Brasil is wonderfull...in other country you may pay 2 times more.

My car is the same as the white one you see in the picture bottom.

I will answer, each one of you in a couple of hours.




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Thank you all folks.. nice support to the amplifier

And really sound very good... this one is Precision, the published schematic.... there's another one, Precision two that is better.

But also very complicated... a lot of parts.

thank you si-jopie, Giaime, Nordic,Sakis,Homemdder and twaksak.

I could read you all...very nice comments..good Sakis, nice Homemodder, very good help twaksak..also jopie.

Now, let's give time... the amplifier seed is into the ground..we will see how many interested and soon we will have folks offering boards for us.

My part in that one...the Precision, was already made...constructed and tested, after many different prototypes..monthes of hard work...now finished...also the model II gave a lot of work and it is still producing some hard work to me.

Model II, the Precision II will start to be constructed into January.... and will be a mess to organize there..suppliers and that stuff...also boards will be made there..but i cannot use those boards and show the schematic because agreement...maybe i will sell it in the future...but not now a days.

Now a days is time to follow the Precision constructors, to help them with the new amplifier.

When you see one guy posting that constructed..there are more 3 guys doing it into the shadows... and those, use to receive help into direct mail... those use to produce hard work, because when i can talk to hundreds into the forum... direct mail is one by one.


Prototype have not burned..and i made it work hard.

But you are not the first to comment this.

And i have to thank you by the kindness to inform this to us.

Here is some protection.... this way people will feel more safe..one transistor more and one resistance is not the problem.

Also the transistor can be other one, a more huge one, and the resistance can be splitted in two units to adjust better the operational point.... also a trimpot can be used to tune each unit into the clipping threshold.

But this was already discussed, deeply, into the Dx thread.

Into the Dx amplifier thread there are many posts about this subject...from UK, Graham Maynard and Andrew T.. they have already explored that weekness, and suggested modifications.

Was tested and did not blow without the protection...but to avoid this same old story once again..here is the protection.




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diyAudio Member
Joined 2005

Carlos, how can we build your amplifiers if new versions are introduced 2 each day?? I can't keep up! My trash can is full of crumpled up paper from notes I write down about the the most recent version. :xeye:

I will stop my revisions at HRII.55v. :angel: When I've finished building that one (and all the other amplifiers I'm building) then you will be at DX Amp version 2050 (in 2008). I will then build that one.

I am glad you continue designing, and I'm glad you started a new thread for this one!

Merry Christmas, Boss, I will gladly send you some Christmas weather. We have too much here. Your palm trees will not like it.

A little bit of ice and snow would be helpfull here.

Sorry Todd..... i have wait 3 monthes to publish this Precision... the next one have secret schematic... so you are not really delayed....only one!

I am using ventilator running all day long.... 3 to 4 showers each day... we are melting here.

I am really perceiving my place more hot than some years ago... also ocean level is higher.... waves are already hitting the front ocean buildings... soon we will have to construct ocean barriers because of that.

We still have people burning leaves here, in the place to let them into the ground.

This one finished... as i have complained he was poluting my air.




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Re: A little bit of ice and snow would be helpfull here.

destroyer X said:

A little bit of ice and snow would be helpfull here.

I am using ventilator running all day long.... 3 to 4 showers each day... we are melting here.




Here we ad lot and lot of snow, some part of the Montreal city are still under snow, here is a photo.

I'm happy for you that you did finished the final version of the Dx precision.




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