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AndrewT
diyAudio Member

Join Date: Jul 2004
Location: Scottish Borders
Quote:
 Originally Posted by destroyer X .............The ones watch my videos knows we can put out, at least 4 watts RMS because of 20% efficiency in class A operation.................
This is complete fiction !

A Push Pull ClassA output stage has a theoretical 50% maximum efficiency when the output is at the theoretical maximum.
eg.
with 20V supply rails and a theoretical perfectly lossless output stage the maximum output is Vpk=Supply Rail voltage.
The theoretical maximum ClassA current is = twice the output stage bias current.
Let's set the bias current to 1A.
The theoretical maximum ClassA output current is 2Apk, twice 1A bias.
The theoretical maximum ClassA power is 20Vpk * 2Apk / 2 = 20W
The supply rails are supplying 1A @ +-20V. The quiescent power dissipation of the idealised output stage is 40W.
The idealised efficiency is 20W/40W = 0.5, i.e. 50%

You cannot invent a 20% figure for efficiency and try to con Members into believing you are correct just because you stuck that rubbish in a video.
__________________
regards Andrew T.

destroyer X
diyAudio Member

Join Date: Feb 2004
Location: Recife - Brasil Northeast
Uuops!.... here you have the schematic with small modification in

the VBE multiplier resistors.

regards,

Carlos
Attached Files
 Dx Super A - final with instrum.pdf (58.1 KB, 414 views)

destroyer X
diyAudio Member

Join Date: Feb 2004
Location: Recife - Brasil Northeast
I was invited to this Brazilian forum

regards,

Carlos
Attached Images
 Estou num outro forum Brazuca..jpg (472.9 KB, 890 views)

 28th October 2012, 03:23 PM #65 destroyer X   diyAudio Member     Join Date: Feb 2004 Location: Recife - Brasil Northeast The unit goes playing all day long This is the main part of the test... the endurance, a torture. I am listening to the Dx Super A at 500 miliwatts - YouTube regards, Carlos __________________ Dx update; https://www.youtube.com/watch?v=RgXZ3s38MCIDx unbeatable amplifiers; https://www.youtube.com/watch?v=u4tGBiqMnzQ
AndrewT
diyAudio Member

Join Date: Jul 2004
Location: Scottish Borders
power is only 1 watt.... in pure class A, but this is not a tragedy, as we can increa

Quote:
 power is only 1 watt.... in pure class A, but this is not a tragedy, as we can increase bias (double) and then we will have 2 watts each channel
Carlos,
how ?
If the bias is set such that there is 1W of ClassA output power available then doubling the bias current increases the available ClassA power to 4 (four) times.

250mA bias ~= 500mApk of ClassA current & that = 1W of ClassA into 8r0.
500mA bias ~= 1Apk of ClassA current & that = 4W of ClassA into 8r0.
__________________
regards Andrew T.

Last edited by AndrewT; 28th October 2012 at 05:39 PM.

destroyer X
diyAudio Member

Join Date: Feb 2004
Location: Recife - Brasil Northeast

resistor wattage.

regards,

Carlos
Attached Images
 Remarks about Dx Super A.jpg (902.7 KB, 811 views)

 28th October 2012, 08:01 PM #68 destroyer X   diyAudio Member     Join Date: Feb 2004 Location: Recife - Brasil Northeast Adjustment...i have made a mistake We must measure 25 milivolts DC in each of the 4 power emitter resistors as voltage drop in stand by mode, no signal entering the power amplifier. If we have only one pair in the output, then we should adjust 50 mV and check the other power emitter resistor. Sorry.... i am becoming old...this is happening with me. regards, Carlos __________________ Dx update; https://www.youtube.com/watch?v=RgXZ3s38MCIDx unbeatable amplifiers; https://www.youtube.com/watch?v=u4tGBiqMnzQ
 28th October 2012, 08:51 PM #69 destroyer X   diyAudio Member     Join Date: Feb 2004 Location: Recife - Brasil Northeast Five Brazilians already built the unit and they said sounds wonderfull and they just cannot switch off...so good is the sound.... i have also felt this way.. i just cannot switch it off anymore. I am in two Brazilian foruns, and another one is remote controlled (ahahahaha!) Two of them forgot the heatsinks to the second VAS transistor (BD139) and to the drivers (BD139 and BD140).... they all need, in special the second VAS. regards, Carlos __________________ Dx update; https://www.youtube.com/watch?v=RgXZ3s38MCIDx unbeatable amplifiers; https://www.youtube.com/watch?v=u4tGBiqMnzQ
 28th October 2012, 09:25 PM #70 destroyer X   diyAudio Member     Join Date: Feb 2004 Location: Recife - Brasil Northeast We are working together in perfect harmony...me and Juan Vargas Well...he is producing the layout and i am bothering suggesting modifications. Soon we gonna have his layout posted here..... we are working hard. A video will be posted answering questions Juan has made.... if i like the layout or not..then i am bothering asking him to move parts.... he is very calm with me..if was the opposite i would send him to hell with one way tickets..but he is very nice...much more nice than i can be. Carlos Mergulhão is the words you should type in the Youtube's adress line..then you will be sent to my channel. regards, Carlos __________________ Dx update; https://www.youtube.com/watch?v=RgXZ3s38MCIDx unbeatable amplifiers; https://www.youtube.com/watch?v=u4tGBiqMnzQ

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