Dx Optimus is being prepared... dynamic bias.. Class A to AB

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Dx Optimus is beeing prepared... dinamic bias.. Class A to AB

having more watts into class A.... bias is controled dinamically receiving audio from output and controlling the VBE multiplier resistance (voltage drop).

I am just starting...it is working into simulator and i have to study to decide the stand by current and to adjust the decreasing.... say... to decide what power will return to AB mode.

Well.... it is just a simulating monster...working...but cannot guarantee quality before construct.

Next days i will be studying using simulator and calculator machine...and hate that part...and they the good work will start.

I will publish IF, result good.... It will be something that remembers Dx Standard and the HRII..... around 50 watts into 8 ohms.

No... i have not discover nothing ...this was used by JVC down the eigthies...i will just adjust, adapt, match, tweak and make it work..just that!

regards,

Carlos
 

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On the run..... just doing

we gonna see if this will result good or a big sheet.... of papper filled with sketches.

regards,

Carlos
 

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Exactly.... the same idea and automatic bias circuit Gradiente does

and my Dx HR II and Dx Standard mixed all together.

This idea was called Super A.... and it just control stand by bias dinamically...bias is increased till you reach 5 watts RMS (this is adjustable tweaking the circuit) and then return to the standard Class AB biasing.

But..my Dx Amplifier uses "increased volume triggered bias level"... already much more bias than other amplifiers.... the efficiency is lower than others, but it is an increased tipo of class AB amplifier when you increase volume to 10 watts and more.

The idea is not mine, the circuit i am tweaking is not mine.... as i said was JVC...and those early days of brazilian audio industry, Gradiente had association with JVC and used to build licenced JVC schematics...so..JVC and Gradiente are not different.

The circuit, the idea is not mine..but the adjustment i will give to it will be mine, and this will make the difference.

Also my amplifiers does not sound alike Gradiente (not enougth high frequencies to my taste)..... i hope!

This one will sound my way.... will be brigth into trebles alike HRII and will not have any artificial high frequency increasing device.... no trick capacitor.

ahahahha.

regards,

Carlos
 
Well... square wave is not music...if was i would be very happy

But i am satisfied...waveshapes from 1 hertz to 30 kilohertz are very good.... slew rate seems very good into 20 kilohertz.

It is turning good.... slowly will be better.

Picture using shirt....celebration.... Optimus have just born.

regards,

Carlos
 

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Yes... i know that Randy Slone made the OptimOs

Mine is Dx OptimUs....using U..... latim name.... optiMOS maybe it means optimus plus MOS.

Well... i do not know..... i have not watched Randy schematic.

Mine is Dx....base into the Dx Standard and HRII... a very different circuit.

Name here is "DX OPTIMUS"

Observe from Slone home page...his amplifier is OPTI-MOS... mine is Dx Optimized bias amplifier.

regards,

Carlos
 

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fab

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Re: Dx Optimus is beeing prepared... dinamic bias.. Class A to AB

destroyer X said:

...No... i have not discover nothing ...this was used by JVC down the eigthies...i will just adjust, adapt, match, tweak and make it work..just that!

regards,

Carlos

Hi Carlos,

The JVC Super A integrated amplifier was the first amplifer I bought in 1982. I had the 40Wrms version. At the time I did not have the good source and good speaker to really appreciate its sound. When I made my quasi complementary V-MOS DIY amp, it already sounded more detailed than my JVC...

However, I suppose that you can have your own design with the Super A principle that can be quite different than the JVC and hopefully even better :)

Good luck and keep us posted.
:cool:
 
Yes Fab and Lumba Ogir.....may be mufled too

We never know till we listen.

thank you,

regards,

Carlos

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

I am listening the Dx Standard.... the young kid...the first i have made, and it is not mufled...so.... not my speaker and not my ears.... some amplifier really sounds mufled compared with others...if you do not compare..you may listen your life long without realise that.

Carlos
 
Good way to call your non optimistic moment.

ahahaha.... cautious optimistic... your therms, the way you twist the reality is wonderfull...ahahahahah!

I was remembering... recall.... "Lippy the Lion and Hardy Har Har"

great!

I have increase my Dx Standard bias to 800 miliamperes to listen..... oh pain!.... what a hell awfull sound..... without life... alike my non coloured picture.

Was you that sent me this optimistic energy dear Lumba?

I have used 3 volts RMS into the peaks.... operating class A... aaagh!

I do not know why i use to insist to try class A.... i think i am a very big, enormous idiot... loosing my time.

But will try to fix.... just a battle... war not lost yet!

regards,

Carlos
 

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I am thinking to increase the transistors speed

To use faster ones and low capacitance VAS.... to reduce Miller capacitors and feedback capacitors...to have good response into 300 Kilohertz... all that to be sure no problems to audio band high frequencies.... when we have 300 Kilohertz maximum into 3 dB... results less distortions into the audible range... sadly...because this frequency response is also an oscilating addicted circuits too.... because very obvious reason...if it can work (audio is also oscilation)...if can amplify 300 Kilohertz... for sure can oscilate into this frequency too... and our transistors, modern ones, goes easy to 100 Megahertz.... this is very problematic...because there are oscilations triggered by the audio...you see waving over the traces into the scope...superimposed oscilations..lower level but they are there.

Capacitances and inductances you have into the board copper lines (parasitic capacitance) ... distances you have from transistor leads (capacitance)... copper lines near others (capacitance)...copper lines longer than 5 milimeters (inductances).. and we have miliohms of resistances too.... so... we have some "tuned circuits" into boards.... Tank circuit..oscilating devices when you have associated capacitances and resistances...and this exists into boards, components, and leads... so... if you face, lets say.... small capacitances alike 3 picofarads (this is half inch, two legs wire, 1 milimeter diameter twisted one over the other...or some copper lines in parallel... 2 inches ones!... them you have the condenser.... other circuit parts will "produce", will "behave" alike inductances...then ready!...you have an oscilating system... the RF tank circuit oscilating into Very High Frequencies..upper 100 megahertz... and transistors beeing able to do that..for sure they will do!

Also using emitter resistances you can increase treble.... reducing input condenser, limiting low end to have 3 dB less into 20 hertz (this is considered flat) you will perceive the unit as having more mids and trebles (Psycho acoustic effect...brain effect... ratio of tones loudness).

The way we have to reduce crossover distortion is to increase bias to class A.... and it is a good idea to have class A into the power you usually use to play your music (maximum of 2 watts RMS each channel i could perceive).

Class A amplifiers are very hot... and do not have power...so..if you switch from class A to AB you gonna have power... this way you join both "worlds" together..... bring "Greeks and Troyans happy" and may listen something sligthly better than good sound.

What moves me?.... passion and foolish... alike everybody in this forum (majority)

Carlos
 
No... i do not use to drink.... even straigth lines are inductors

In the reality straigth lines does not exist... it is a concept inside human brain.... a line is a sequence of interrupted dots.... lines goes turning curved, bouced, rounded... straigth lines into our Universe does not exist..if you trace a line from your town to the nearest town it will be a curve over the globe...... globe is rounded, so lines over it are rounded too... we have gravity... into the Universe we have gravity from everywhere, this turns straigth line impossible... even the black hole forces ligth to became rouded ... ligth does not propagate straigth.

So... your piece of copper line into a pcboard is a very small inductor...BUT... can be combined with others in series and parallel and produce an interesting value of inductance..and this one associated with capacitances creates all the mess.

Every two pieces of metal, placed near together, even having air gap between them... will result into air cores capacitors.

I do not use to drink.

Hic!

Carlos
 

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Thank you Lumba.... in the reality i do not think different

I have just some hopes... this moves me.... hope!

Well..... how the circuit works:

First the circuit has a normal VBE multiplier circuit to adjust bias, can have a trimpot and so on... this one has a NTC.... a resistance that is reduced when receive heat... into the position it is assembled....it will reduce the resultant resistance into the BD139 circuit... the main bias control, the manually adjustable one.

Other transistors are receiving audio rectified...so.. they receive DC that changes their operational point.... when iddle you adjust current to .... let's say....hummmm...600 miliamperes... and when you increase the audio output volume... power increasing, then you will have DC enougth to drive the transistors that will reduce resistance from colector to emitter.... this reduced resistance will reduce bias...so...having audio level...bias is reduced.. this way you will go to Class AB operation.

Boys... circuit is not mine...i can adjust it, tweak it, make mine modifications, decide other currents, decide different thresholds ..but it is from JVC...i am just using it as a non profit amplifier, opened to the public, a genuine DIY amplifier, using the technology we have in our world, offered into the internet, opened wide world to everybody.

So... the qualities or defects of this circuit is not my responsability and also does not represents i am a great designer.... i have not made this one...my value is as a tweaker.. the one work hard and burn fingers...i have not created this one.

regards,

Carlos
 

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Bias circuit behaves alike a resistance...you have the main current to be used into

The VAS colector to emitter junction.... this current is adjusted by the bias circuit... even a single resistance can do this job for you.

This VAS colector to emiter current will be modulated, will variate and will be sent to drivers and output transistors.

So... the bias circuit, transistorized or not, is the one provides current to the VAS.

But also, and more interesting, it adjust a DC potential into it's extremes...when current crosses this resistance it develops voltage... and this voltage use to be 2.4 volts into my kind of outplut circuit..the one i use (not discovered by me .... of course).

Into my output circuit... a very used one... Doctor Self use and a lot of folks use this one..emitter follower...or darlington output.... well..you need to set 0.6 volts to each transistor (around that..from 500 to 640 into AB amplifiers.... and more into Class A amplifiers... and lower into class B amplifiers..those one uses almost nothing as bias).

As each upper output line transistors (NPN) are two...then you need 1.2 volts (0.6 plus 0.6).... and the lower transistors (PNP) also will need 1.2 volts (0.6 plus 0.6)... this means 2.4 volts must be developed into this bias circuit..the bias resistance...it behaves alike a resistance...the obligation is to develop 2.4 volts and into the decided current needed to the VAS to drive the output circuit.

Why 2.4 volts and not positive 1.2 Volts and negative 1.2 Volts.

That idea of positive and negative depends your reference..if your reference is zero volts (output line...you have there milivolts, almost nothing)..then you split those 2.4 into two parts..and the polarity will be given because the base to emitter junctions connected to the output line that will create the 0.6 plus 0.6 zener effect because of semiconductors junction.

If our reference was 1 positive volt..then you gonna have positive 0.2 and negative 2.2 volts... all depends the reference..nothing born negative or positive....there are not red positive electrons and blue negative ones...they are all negative into the atom

All the work is this one.... this "resistance" can be something that reduces it's resistance when receiving heat from the heatsinks.... and this will be usefull to control the amplifier...if not... the transistors turns hot and current increases.... when the current increases it turns more and more hot.... this make the transistor internal resistance to reduce and the current increases even more...this goes this way till the destruction....so...if the bias can reduce its resistance (reducing bias), will protect the amplifier.

This is very easy... dedicated not to Engineers or advanced guys.. this is for beginners only...to help you my dear Mr. Incognitus.

No one explains nothing... they think everybody has born already knowing everything... this is not truth... there are a lot of folks, alike me, that need some informations to evolute.

regards,

Carlos
 
To the ones interested...as 300 hit seems a good interest into 2 days

Will explain the equivalent circuit attached.

This is the equivalent circuit.... made with resistances.

You can use resistances... they will make the job...not the dinamic job, but they will fix your current into 600 miliamperes (around that), and will feed each transistor with 750 milivolts (if they share the same ammount..normally they do not share the same ammount)

regards,

Carlos
 

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