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Old 15th November 2012, 05:42 PM   #1371
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Default Yes, they will arrive in a matter of 15 days

But shipment from December may be a problem, because Christmas..them may delay a little bit more.

Do not forget to say the value is below 50 USD ... say Christmas gift to an old friend.... write this outside the envelope, inform what you have inside... do not say has 30 transistor same model, this may look it gonna have a shop as destiny...say 10 units model XXX, 10 units model YYY and 10 units model ZZZ.

Do not exagerate dear Evette.... i really already have a lot of units, all them, or the majority, came from you or Dudainc...i am really needing these BD139 and BD140.... mainly BD139.

2SC2240 and 2SA complementary...yep..good ones..but voltage is not that high and current is also not that high...this way i am going with BC546/556 to the small transistors and BD139/140 for mid power ones and the output i use the strongest ones NJL4302 AND 4281.

I am old and neurotic...i use only BC546... sending me others, probably they will be there sitted without any use for them.

They work fine, they accept a big voltage..... no reason to change something is producing great results.... why to put Watermellow in that big tree that has so small fruits?.... big tree should have big fruits as a watermellow, but if fell down into our heads we perceive God has made a good design when have decided this stuff that way.

Yeah.... the man can keep the speaker..just send me the girl i have pointed before (hehehehe!)...i will show her my transistors.

regards,

Carlos
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Last edited by destroyer X; 15th November 2012 at 05:44 PM.
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Old 15th November 2012, 06:07 PM   #1372
wiljj78 is offline wiljj78  Philippines
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Uncle Charlie, I know your transistors are very powerful LOL....
Playing those speakers indor its enought to shake your doors and windows and another hard time for you to retune your Super A again with those girls dancing Gangnam style LOL…..
Regards,
Willy

Last edited by wiljj78; 15th November 2012 at 06:15 PM.
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Old 15th November 2012, 06:58 PM   #1373
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Default All right wiljj78

I will show them your speakers too.

heheheheh

regards,

Carlos
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Brazilian Airways Christmas Message to all of you!
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Old 17th November 2012, 03:54 PM   #1374
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This thread is alive again?!?

My amp is finished since about a year, I used it since then and I have no complain to report.

I may investigate in the modifications Bonfis did as I'd like to increase idle current. But I'll need a scope to identify any sign of oscillations...

Will a 20MHz scope do it, I mean in the audio world? Will it show me any high-speed oscillations, or do I need to go 60MHz+

Martin.
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Old 18th November 2012, 08:10 AM   #1375
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Default It can actually be tuned to result in a different performance

we can do that using simulator, but the best results happens when we do that listening.

The idea is to adjust some components to reduce third harmonic compared to the second... this will give you something people called "tube" alike sonics, because tubes measure very badly but sounds very good to human ears... these harmonics are pleasant and do not bother us..the ones we hate are the third, fifth and seventh harmonics...these ones we hate..but they should be present too, because if they are not present...sound becomes stérile...lifeless.

There's a consequence when we do that... the sound opens in an extraordinary way... the brightness into the treble comes giving some "shine" into the treble as they become thinner compared to the previous, former, reproduction filled with harmonics till the top...this makes the sound fat and a little bit unprecise... timbre becames a little bit damaged because other frequencies (beatings, the harmonic results) goes together changing the pitch of the tone... so, a bell is not the bell sound.....it looks we have installed hundreds of very small loosen rivets on it that goes shacking and producing a sand grains sound when sand grains hits some aluminium can after you shake it...you now...the fundamental sound from the bell has added a sand noise.... could you get it..becames "fat" of harmonics.

We have this effect... i used to reduce "total" harmonic distortion without care with the "harmonic distribution" that means how much fifth compared to fourth...how much seventh compared to sixth...and how much third compared to second harmonic...that ratio is important.

But what was the result dear Cannonica.... the amplifier, the Dx Super A that has a highly superior tuned circuit...became sharp as a razor blade, cutting the air alike a supersonic whip... old tweeter ressurrect becoming alive and hitting our ears with celestial sonics from heaven.

But it becomes nearby the threshold of oscilation.... any foolish you make and your amplifier gonna drain all your power supply energy producing an astounding oscilation that may kill some transistors or may produce some kind of damage.... and this happened not because i am 52 years skilled...but because i was lazy... one more discovery by accident...that opposes and dennies the say that good results depends on 80 of perspiration and 20 percent of wisdom... sometimes depends on accident, the imponderable.

I was tweaking a Dx Blame ST, already transformed in Dx Super A (*) when i have faced the sublime moment of lazyness.... the Dx Blame ST is using a single pair in the output.... when the Dx Super A is using two pairs in the output.... then i felt myself lazy to install the second pair and i persuade, wrapped, cheated myself saying to myself that would be a good idea to compare a Dx Blame ST under the same conditions...so... left side Dx Blame ST, and rigth side Dx Super A and both with the same transistors, same supply, same enclosure, same speaker, same filters, same rectifier, same wiring...well.... totally and absolutely equal.... but simulator said to me that with two pairs in the output would be much easier to reduce third harmonics....i was stubborn and i decide to work into the simulator to get the result i wanted.... and i make it.... but when installed i found the amplifier dangerous... touching the input with my finger tip (AC from mains wiring irradiates electro magnetic energy in 60 hertz that travells into the space and hit my body.... and my body has hemoglobine that is full of iron, also we have water and salt inside our body, so, we are metal too, and antenna....my finger tip had developed a DDP of 60 hertz signal, a human tone generator).... then touching i have listened the hum (60 hertz) and a high pitch tone and the "devil's whip"... the sound of radiomagnetic propagation opened... and this only Radio Amateurs knows, the sound alike whip cutting the air... the "chirp" sound that seems oscilation...i had to revert some of my modifications because the sound resulted poor and stérile...i found that we need to dope, to pollute a little to become good to be listened...this was done listening and working hard.... fully perspiration stage.

There's a video where i have faced an accident because of that.... it is in portuguese, but as you are clever and i use some mouth noises to explain effects and defects, you may get it:

Abre teu olho amiguinho a - YouTube

Your amplifier is dangerous because the voltages and currents it works..the power reserve it has into the stock of electrons.... if something become unstable there you may have huge damage.... because of that i dare not to tweak it...but i can give you some clues if you want to assassinate your amplifier by yourself, or to achieve absolute success or producing a superior option... all this depends your grade of madness and boldness.

Doctor Hugh Dean..... in my mind a great Doctor, despite he has not that degrée, always said to me that we need to go to the threshold of oscilation to produce good amplifiers....he just forgot to tell me that we must go to the threshold and then give a step back on that.

I am now produce a video showing where you should tweak.... but i would also say to you Cannonica.... that i highly appreciate you my dear friend and i gonna miss you....if you do that some amplifier may be destroyed and you will be hated till the end of the days and you may disappear from our forum ashamed because of that.... i will repeat to you...i would not dare to do that into high power amplifiers..too much dangerous.... you may need special protections..because if you have a chirp sound when switching MP4 player power one, sending this sound to the amplifier...hehehehe..you gonna see smoke signs alike a native indian made to communicatte with other...you gonna do that inside your expensive circuit....but if succesfull...you gonna meet God in the heaven and will listen the celestial voices from the angels... alike a did...before the hell thing burned because i forgot the fuses (the supply rail wires melted and shorted and destroyed my MP4 player instantaneously)

regards,

Carlos


* JVC circuit modified by uncle charlie, or cracked, or evolute, or modified, or stollen or mischaracterized or disguised or filched.... depending how much you love me or hate me you will call one of these previous names with the installation of some parts that make it Super A (reduce bias when you increase volume... start in class A and then go to class AB)
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Brazilian Airways Christmas Message to all of you!
https://www.youtube.com/watch?v=HFGM5K-WWnY#t=135; Unbeatable!; https://www.youtube.com/watch?v=u4tGBiqMnzQ
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Old 18th November 2012, 09:11 AM   #1376
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Default Here you have it Cannonica, BMW, A. Wayne and several

other very nice guys.

Simulators for audio - how to tweak - YouTube

regards,

Carlos
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Brazilian Airways Christmas Message to all of you!
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Old 18th November 2012, 12:38 PM   #1377
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Carlos, you're very inspired when you write!

The changes I want to do are minor, see the pic attached. And be sure that when I do that, I always start the amplifier with resistors in place of the fuses.

Martin.
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File Type: png more mods (Bonfis).png (92.3 KB, 166 views)
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Old 18th November 2012, 03:20 PM   #1378
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Default Thank you..... but my last discoveries opposes a little

when compared to this schematic i sent you long time ago.....i imagine i did it.

Stop resistor is something you should decrease instead of increase.... try 10 ohms.

That capacitor should be reduced to 100pf and observe if you have oscilations.... it gonna be easy.... the protective resistors will show huge current and trimpot will not control the current under oscilation... a huge current will be drained and output transistors will become hot in a matter of seconds.....if happen, then increase the capacitor back again... i was very careful land i was working in the safe side...the value there is 120pf...i have increased to 180pf to 220pf for safety reasons..because scared.

When an amplifier enters oscilation, we face a very interesting effect..the rise of temperature is so fast the transistor has not time to transfer the heat to the heatsink, so the transistor case become very hot to be touched.

Well..this name, oscilation sounds terrible..but if we analise... an amplifers are oscilators that goes oscilating following (tracked) by the input signal....but only when tracking input signal...when it do that by itself, producing a tone or a carrier (high frequency) then it is abnormal and we use this terrible name....but the amplifier is also an oscilator....it oscilates all time long..oscilates from positive rail to negative rail...the audio swing.

The increase of current is a good idea too..but be prepared because it gonna work very hot because of that.... from these three suggestions, now a days the only one has my support is this last one, to increase (a little) the stand by current.... a little.... 35 percent maximum increase.

regards,

Carlos
__________________
Brazilian Airways Christmas Message to all of you!
https://www.youtube.com/watch?v=HFGM5K-WWnY#t=135; Unbeatable!; https://www.youtube.com/watch?v=u4tGBiqMnzQ

Last edited by destroyer X; 18th November 2012 at 03:24 PM.
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Old 18th November 2012, 05:20 PM   #1379
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Sparking my interest again ... Interest + effort = DX MK3.2

I'm using 40 volt PSU , as i can use this for other projects , if used on the MK3 it will be for output stage , as i believe vas stage was best with 54 volt supply , is this true Carlos ..?

i would like to run sperate regulated supply for vas , would you be willing to post up a schematic to do so with the necessary mods to the main board to seperate supply , i will most likely use mods you sugested above 140 pf instead of 100 , 10 ohm resistors and of course up the bias and compare ..


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Old 18th November 2012, 05:50 PM   #1380
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Default I am now a days focused into the Dx Super A

So, i will not labour into this one... i am suggesting people to make their own efforts to upgrade it and update it.

To use separate supply you just remove the diode and install one supply into the power transistors colectors and the other one enters left side hole where you had the rail diodes.

I do not think this is needed... waste of time Wayne.

These things require global modification, almost a redesign...and the one i have redesign is the Dx Super A circuit...you can copy from the Dx Super A some ideas but you should simulate to check this stuff.

I am not "in" this project anymore...now i am taking care or other ones...this amplifier is finished for me...alike a complete mission...i am in other ones now a days.

regards,

Carlos
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