Symetrical schematics are alike plague in Brazil, do you like them?

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Brazilian epidemic, contagion, plague, pestilence!

This the national standard, to me seems a plague, all
copies of the Leach amps ... some of them, the copies, includes
the same part number, same board layout, same resistances and capacitance
and sometimes same capacitor values..they use more modern transistors
disguise, but actually copied and neither took the
work to make a good copy .... epidemic seems to me .... as
contagion spread throughout the national territory,
all factories dozens of professional models... all them with the same ..
circuit .... I do not like the sound .... seems to me, synthetic , alike the
comparison of natural orange juice with Tang synthetic powder.
But there are those who prefer tang.
I have assemble..the ones i can remember, 5 amps in this same style,
then gave up permanently .... you had some
very good experience with this type of amplifier?
those symetrical ones, double differential ... made comparison with others?
Have you appreciated this one...this topologie, this style?

They are multiplying..alike viruses....3 new factories each month...there are already
hundreds in operation, all them using the same circuit...something you could see
in Marshall Leach pages.

Now a days, the almigthy Selenium (second most important speaker factories in Brazil..next to Bravox) bougth two factories, and now they are also
producing the same kind of circuit.

I have simulated...fourier is fine..harmonic distribution not so nice.... THD very high...
even using other transistors and voltage regulation in the rails, series rail resistances
and tweaking values..i could not have decent distortion..now a days..amplifiers are
distorting less than 0.009%

Do you disagree?.... tell us why...have tested....had experienced moments of satisfaction with
these kind of amplifiers?

regards,

Carlos
 

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I remmeber i have assembled, using huge transformer, a Cygnus model

I had almost 200 watts rms..undistorted ... and pumping two selenium speakers, they were under my bed...bed had holes and feet..distant from the floor...look alike this one you see in the picture..but that bed had drawer and parts were inside..transistors, capacitors and all stuff.

The bass punch was nice...i used to be layed down feeling vibration..another amplifier was pumping treble and midranges.... passive filters in the input...independent volume controls.

Two big Selenium drivers, 15 inches each one of them...200 watts each one..in series, each one of them 4 ohms.... inside their own tuned enclosures, having ports and tuned to 30 hertz.

One day i decide to try a small amplifier... from Elektor...boostrapp one... that one Elektor published that you could use several supply voltages, and they have provided a chart for you to substitute resistances.

I have connected the 30 watts amplifier, the Elektor..to these speakers..and believe it or not....more punch, more deep bass..things started to shake.

I have tried to increase low frequency response increasing feedback condenser (gain) and input condenser in the symetrical one..but no good result.

This is the reason why i dislike...stucked!... clogged!..obstructed..jailed..confined!..sound does not go out from the speaker..remains there..strange thing.

Speakers, to mids and highs where on a shelve... separated amplifier and volume controls near the bed...you can see the way that bed ways (that other bed i had)... holes to remove upper plate, space below and holes to exaust air (tuning the whole thing)..inside strong 3 inches extructure made of plywood and two main divisions..a non vibrating thing...very strong bed that other one was..this one i am using is not so strong..reason why have no speakers inside.

regards,

Carlos
 

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They are multiplying, someone may say, because they are good

I can agree this is a good signal...the population aproval, but, they have not the chance to compare, as the same style of sonics are playing everywhere, football stadiuns, parties, ball, carnival, celebrations, electricall trio (mobile power units assembled inside big trucks..... plays loud.... treble is fine...also voices...i dislike the bass only.

Those Brazilian amplifiers, use to put out 40, 50, 60 volts and even more than that, and some of them can face 3 ohms or less output impedance... they are used in groups, say... ten, twelve or more amplifiers distributing sound to several speakers.

I think they are appreciated because loud.... some others tried digital amplifiers and some Class H, but population have not accepted.

regards,

Carlos
 

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We love music..we have hundreds of these trucks, so, speaker, amplifiers

and music are important for us.

We have a say here, first in portuguese because translation is difficult:

- "Atraz do Trio Elétrico só não vai quem já morreu!"

Behind (following, walking with) the Electrical Trio, the one does not go, is because already died (living beings cannot resist).

Visit Brazil, a lovely country, happy and friendly people..violence exists..in New York too!

regards,

Carlos

An externally hosted image should be here but it was not working when we last tested it.
 

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And these amplifiers...do you like them?

My people likes...i am exception i think..... and i want to contact other "exceptions"..to produce the "rarities, the exotic ear group..bad taste tribe!"

You know...for me...all this is fun...i do not mind...i like blonds, but there are exceptions.

regards,

Carlos
 

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The question is: Would blonds like you? :D

These class B and AB amplifiers are becoming popular because they can be mass produced at low cost and without having a clue about electronics.

Class H and class D are lower cost but there are fewer people capable of getting these circuits right and dealing with mass production problems (like sourcing magnetics, dealing with component tolerances without trimmers, mixed thru-hole and SMD in power PCBs, EMI, etc).

It's not a matter of customer acceptance, people tend to buy the most cost effective product.
 
You can make a very good or very poor Leach amp out of substantially the same components. If you "don't have a clue about electronics" it can be on the poor side.

Carlos - your simulation is flawed. First, the VAS -and therfore the front end -is seriously and intentionally out of balance. Tsk, tsk tsk. Eva's going to put you to bed without any supper. Second, the MJE1503x suck as VAS transistors unless they're buffered (miller capacitance is too large and nonlinear). Heck, use the models for the BD139 if that's all you have. Third, with only one output pair you're suffering from beta droop at high power - even with an 8 ohm load. Put in the rest of them (just use the area scaling factor if your simulator limits the # of transitors). The good professor solved this problem by using a triple. Fix some of this and you'll get better than 0.797%.
 
in addition to wg_ski's comments, there looks to be a pretty significant error in the schematic. the top mje15031 after the diff amp looks to have it's collector and emitter connections reversed. i would guess this stands out in the sims at least for dc operating point?

mlloyd1
 
Thank you folks...all comments readed, and will take a look at the schematic

Yeah...schematic is reversed..but the simulation schematic seems good..at least current is ballanced, also voltage and small off set.... output waveform good enougth.

Girls.... that's what we like...cannot post too much...only electronic girls...or audio electronic stuff.

regards,

Carlos
 
These kind of amplifiers, when correctly implemented are
way better than doug self s so called blameless.
I published such a design that you eagerly criticised
since it seems that you didn t manage to make a single one
work well enough, so you branded the amp bad rather than
asking yourself some questions about your ability to implement
such a design, prove is that you didn t use a single technical
argument to prove your point.

http://www.diyaudio.com/forums/solid-state/155993-awb50-simple-power-amp.html#post1998594



Contrary to a single differential that will be very tolerant
of mistakes and will still work relatively fine, a symetrical
differential , although very simple , ask for a little more
skills to produce the good resuts..
 
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I see Wahab... 50 years building was not enougth

needing more skills...well... i have only to call Wahab!

You built that one Wahab..and have not build Blameless...or the opposite...and was enougth to conclude..what a brain man..you know..when i grow up i wish i will be alike you.

Man... when you met this man you use to talk... i think you do not even know him.... the man..Mr. Skill, give him my regards... and also my complains..as he is present in more modern guys when was not with us..the old folks..the veterans.

heheheh

regards,

Carlos
 
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Hi,
the complementary LTP input stage is similar to what Leach has used.
But the rest is completely different.
No Cascode
Dual output from both LTPs
Dual output driving a folded Cascode.
Drivers as VAS
No triple EF (Locanthi T).
Global over full frequency instead of LF feedback
No HF feedback loop excluding last stage.
 
needing more skills...well... i have only to call Wahab!

You built that one Wahab..and have not build Blameless...or the opposite...and was enougth to conclude..what a brain man..you know..when i grow up i wish i will be alike you.

Carlos

I did build a blameless well before Doug Self highjacked
the idea and used it as his typical design...
I wasn t even an adult at the time.

Anyway, if you need some explanations about the
subtilities of the symetrical siblings, will be a pleasure
to give some explanations..

Andy_c , who is infortunately no longer by there
did some smulations to compare the blameless to
a symetrical differential, and did found that doug
self prefered design was better, prompting many by
there to applause the technical comparison that were
in fact badly flawed in the behalf of the blameless.;

I did recheck the comparisons, and it appears that the
symetrical differential is better even if it use less
negative feedback..
 
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Highjacked?.... really?... Doctor Self did that?

heheheh.... maybe you are kidding.

Slone made a Blameless..do not know if he made in advance compared Doctor Self..or the opposite... in the reality...in our modern world, it is very difficult to find the ones have really created something new...maybe Dunlap....but even his design, others may say was not him.

Well..it is not impossible two persons, different places and same time to have the same idea.... things are intuitive and some evolution are obvious.... alike some consequence...if installed CCS to the differential..then why not to the VAS, to the Drivers and so on?.

First stage differential....why not the second stage too?...so... consequences, obvious developments..when one is publishing the differential, other was creating the differential VAS.

But for sure you are skilled..... a good engineer Wahab...there are the Practice Skill...the theoricall Skill and the ones have both.... there are the one have scientific approach and the Imaginators.. as "they think".... they have a lot of opinions..some of them have never touched a soldering iro..have never compared anything....but they think a lot.

You are good.... fast you have found that 220 would be the best value to the my amplifier, the first Vas emitter load.... you realise very fast...because good theorical or practice skills, or even both of them.

It is interesting to know what people "think" about that...but also, would be more interesting to know and to listen, the ones made the complete job... the ones have analised the schematic, the ones have calculated, have simulated, have assembled, have listened and have compared the way i did..... this way..i will know thougths from another one that had the same kind of experiences compared the ones i had.

I remember 5 amplifiers, in the reality five variations around the same schematic..as Marshall Leach has two main models and these ones i am talking about are sligtly different.... my people have supressed something...reduced, simplified a little...in the reality...i have not registration of all i have made..but for sure more than 60 amplifiers with double symetrical input i have assembled, and listened, and compared.

Much more than 5000 units made.... now a days i am super lazy, doing 3 or 4 a week (200 per year or less)...but was not so slow this way...around 1.7 each day was the average.... then calculate what this means in 50 years.... i am thinking in 5000 thousand..but calculating you see that can be much more than that....6 times more.

And always i found this one not good....always i found the boostrap ones much better..also the ones with chips not very good, and the ones with EF sounding better.

Well.... people alike you Wahab, that is a little bit old and have build hundreds and thousands can say something...so...i respect that you say it can be even best than Blameless... sadly, my years of research cannot confirm what you said...so..there's something strange on that.

regards,

Carlos
 
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So many multiple repeated times i have realised one amplifier was not all that good

while comparing..when before i was satisfied with that beated amplifier, that i feel strange when i perceive that there are folks with golden ears or super powers that can discover that without listen, and without compare.

I have learned, and that is the most absolute truth that is now a days the north of my life...that we do not know how good is an amplifier before compare it with others.

We may think, we may imagine, we may believe...but we really do not know..TILL we make comparison.

We have troubles to say about the best..... as we need to refer to others..best compare to what one? is the question that comes imediatelly...so.... all is a result of comparison..good, better, best, worse...all this is relative, and depends two things..the one is better and the one is not the best.

My amplifier is the world best considering all i could listen, all i could buy, or build....but of course..may exist one or much more than that able to beat it.... i had not that chance to listen

I do all i can..people present schematics and i run to build and to test...but i know that some folks do not build, do not listen and go spreading "I think so" all around.

When people use "i think so"...turn to myself i suspection person that do not think with precision... imaginative and biased..without practice and testing of his own theories and beliefs.

regards,

Carlos
 
After 50 years building I'm sure you have very good building abilities (at least for building amplifiers in the way they were 25 years ago, because you seem to completely reject all the progress made in the last 25 years :D)

Creativity and open scientific mind are different abilities. You can build amplifiers for 50 years without developing them. In fact I think you lack both, and it's probably too late in your life to develop them.

I have not been doing anything for 50 years because I'm way younger. However, after 4 years learning class D by myself now I'm the designer of one of the smallest, lightest, most efficient, most cost effective and most powerful subwoofer plate amplifiers currently in the professional audio market. It's (conservatively) rated 4000W @ 2 ohms with greater than 90% efficiency and only 7lbs weight (including heatsink, faceplate and DSP).

This claim is not as eloquent as yours, it's much harder to reject.

Be creative. Make real achievements.
 
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with respect to all previous posters and to you my friend uncle charly ...
it is often that we miss the obvious
\
which in this case is simply that this is probably a bad or simplified copy of some chinese amplifier that actually works or worked in the first place ...after its been allready a bad copy which probably bad copy means that either schematic or parts are now canibalized compared to the original schematic you are simply watching the results ...

Eva most of the times i agree and respect your technical skills ...in this life i will probably never achieve such an approach ...BUT i disagree about the evolution ...even a dynaco amplifier can be evolved to something better ...better parts ..better pcb ....better topology but yet again same idea and nothing inovative ... that is very true ...
 
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