quasar amplifier by dr bora 1000 watt

[boraomega]

Nice results Joselito! Several people built it without any issues and it should work OK. What was the cause of your trouble with amp in the beginning? First you reported it is distorting and in a next post you are saying it sound nice and clear?!?!

 

[joselito San Juan]

Engel,

The diode drawn is reverse or short circuit it should be otherwise.

Edwin

 

[joselito San Juan]

Sir Boraomega,

It was a power supply problem where my friend Edwin here had plugged the transformer to a 100 vac source instead of the 220 vac. With that condition the power amp is low voltage and perform poor with 1000 watt 8ohm load. With the right power source it drives the load strong and clear. Thank you for the brilliant design you shared to us.


Engel,

I used the original IRFP240 specified by Sir Boraomega and had no chance of locating the IRFP460s. My friend Edwin now is also building one for him, he is not yet registered in the forum. Thanks

Joselito

 

[bkastel1]

IRFP250

Hi,

could you use IRFP250 instead of IRFP240? I have tons of IRFP250 available.

Thanks,

Borut

 

[walter1252]

joselito,
sir bora noted not to use irfp460 to me because of parasitic oscillation issue,what fets you use?
how do you implement the diode is this right?
pls see attachment

 

[pallab]

sir,i have 8 pair IRFP460 ..so is there any problem if i use these IRFP460 instead of IRFP240 in D Bora LEGEND QUASOR amps???? please reply me..

 

[pallab]

sir,i have 8 pair IRFP460 ..so is there any problem if i use these IRFP460 instead of IRFP240 in D Bora LEGEND QUASOR amps???? please reply me..

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

so..how many components i have to replaced in this circuit???

please some one reply me.....

 

[pallab]

sir,i have 8 pair IRFP460 ..so is there any problem if i use these IRFP460 instead of IRFP240 in D Bora LEGEND QUASOR amps???? please reply me..

image link..
https://www.facebook.com/photo.php?fbid=820846387967382&set=a.609485605770129.1073741838.100001260869231&type=1&theater

so...how many components i have to replaced in this circuit...to run it +-90v rails????please some one help me..

 

[boraomega]

For work on +-90V you do not have to change anything. I am suggested that you use IRFP240 only.

 

[boraomega]

FQA32N20C might be even better choice for output than IRFP240.

 

[pallab]

irfp460

FQA32N20C might be even better choice for output than IRFP240.

sir,please
tell me why irfp460 is not applicable for this project???

 

[boraomega]

Because of higher internal capacitances. Several people (not all!) got serious problems when using IRFP250, 260, 460 and other types.

 

[Rembulan]

Because of higher internal capacitances. Several people (not all!) got serious problems when using IRFP250, 260, 460 and other types.

Sorry DR Bora I got confused mind to explain

 

[destroyer X]

If was designed by Bora, then it is good!

No doubts about it...i have tried several models, and all them sounded great!

regards,

Carlos

 

[wattaniya]

hi boraomega,
in this schematic u mentioned 220pf condenser,,right side of the image down, can u translate to english.

can i replace mje Numbers with a1837, c4793?

 

[boraomega]

Translation: "220pF capacitors between C and B of both MJ15035 are to be soldered under the board (on copper side) with short leads and directly on transistor pins."

If you have no better option, you can try with a1837, c4793 pair but they are way inferior.

 

[boraomega]

No doubts about it...i have tried several models, and all them sounded great!

regards,

Carlos

My old faithful friend, great designer and even greater personality!

Respect old friend!

 

[wattaniya]

hi boraomega thank u for the reply,
pls can u tell me how to adjust the bias?
in my experience -adjusting bias with in positive rail 10 ohm 1watt resistor instead fuse,
for one pair 250mv across reading in 10 ohm resistor, 25ma/pair,
so 8 pair x250mv=2vdc. is this correct?

is this layout is correct?

 

[boraomega]

Do not forget that entire amp - all stages - are connected to main supply and if you measure total current in a rail it will contain currents of drivers and pre-stages as well. Therefore, you should add at least about 60-80mA to nominal 200mA of output devices bias. Also check that you have about 5-6mV (+-20%) across each of 0,22ohms source resistors. It won't hurt or have negative influence on amp if you set higher bias per pair (not more than 50mA/pair)... just quiescent dissipation (and heating) will be slightly higher.

 

[wattaniya]

hi boraomega, thanks for the reply,
why the positive rail and negative rail disconnected middle in the pcb.
in the schematic the rails are not disconnect.