Sakura Amp Modification

[tony]

let us carry on.......

Q: with the 35volt rails, how much power can the circuit deliver to say an 8ohm load?

A: assuming rails won't sag and that Vce sat is 0, then we have 35volts peak, or 25volts rms, therefore at 8 ohms, power is about 80 watts...in reality power will even be lower because of losses...

Q: will adding extra ouput trannies increase power?
A: no, but the SOA is mitigated, lower ohm loads can be driven more safely.....

[Johannah Aleksandria]

heto, hinalungkat ko...
http://www.electronicslab.ph/forum/index.php?topic=23173.0

Vce = VR22 + VR23

; VR23 = Vbe

So let's look at VR22,

VR22 = I_22 X R22

; I_22 = I_23 ; they are in series

So, I_22 = Vbe/R23

VR22 = (Vbe/R23)R22

Final Equation:

Vce = (Vbe/R23)R22  +  Vbe

Taking Vbe = 0.6

Vce = (0.6/1.2)2.7  +  0.6
      = 1.95 volts

[tony]

^good  analysis, +1 point for you......sana kanina mo pa inilabas yan.....nagdrama ka pa......

mine is a shortcut computation......remember that these are just computations....the real life voltage could be somewhere in between....

[pEN DoTA]

 

Q: why is there a need to add emitter degeneration resistors?

A: because those resistors do not change in value with current and temperature unlike the transconductance which varies all over the place.....

Q: why do we want transconductance to be stable? what is the benefit?

A: reduced distortion and wider bandwidth...

+1 ka master. dagdag kaalaman na naman.

[pEN DoTA]

Vce = VR22 + VR23

; VR23 = Vbe

So let's look at VR22,

VR22 = I_22 X R22

; I_22 = I_23 ; they are in series

So, I_22 = Vbe/R23

VR22 = (Vbe/R23)R22

Final Equation:

Vce = (Vbe/R23)R22  +  Vbe

Taking Vbe = 0.6

Vce = (0.6/1.2)2.7  +  0.6
      = 1.95 volts

+1 ka din sir.

[tony]

continuing with the analysis of the output stage:

at 80watts into 8ohm power level, peak current = 35/8 = 4.375 amps...
base of output trannie therefore requires Ib = 4.375/35 (lowest hfe rating is takes into consideration) = 125mA, this is the peak current required from our driver....

[tony]

the driver stage:

using the 2SC2073 driver it has a minimum hfe of 40, therefore drive current to its base needs to be = 125/40 = 3.125 mA.....

using a 2SC4837 which has an hfe of 100, drive current decreases further to 0.125mA....

Q: what is the significance of all this?
A: having devices of higher gains reduces loading on the previous stage, so that that stage if more free to do its thing, that is to swing voltage....

[tony]

Vce = VR22 + VR23

; VR23 = Vbe

So let's look at VR22,

VR22 = I_22 X R22

; I_22 = I_23 ; they are in series

So, I_22 = Vbe/R23

VR22 = (Vbe/R23)R22

Final Equation:

Vce = (Vbe/R23)R22  +  Vbe

Taking Vbe = 0.6

Vce = (0.6/1.2)2.7  +  0.6
      = 1.95 volts

if you want to be anal about it, there is a small flaw in your analysis:

; I_22 = I_23 ; they are in series,

to be more accurate about it:

I_22 = I_23 + Ib (base current)

so in reality, I_23 is always smaller than I_22,

so we assume that Ib is <<< I_23 so that it is ignored....in order that your argument to be true....

for trannies with hfe >>10 this is very true...

[???]

Vce = VR22 + VR23

; VR23 = Vbe

So let's look at VR22,

VR22 = I_22 X R22

; I_22 = I_23 ; they are in series

So, I_22 = Vbe/R23

VR22 = (Vbe/R23)R22

Final Equation:

Vce = (Vbe/R23)R22  +  Vbe

Taking Vbe = 0.6

Vce = (0.6/1.2)2.7  +  0.6
      = 1.95 volts

Ilabas na kasi ang computation at ng matuto kaagad kami at marefresh ang iba pa naming basic. I too rely on computation kasi nakakapagbigay ng shorcut at basis.  Plus 1 sir hengil at tony.

Basa mode uli. 

Sana idissect pa ng masyado.

[???]

And +1 to sis johannah for bringing this up. Marami sana kaming matutunan.

[Skyjham]

good day po sa lahat!

  ask ko lang po kung pano mag share ng photo dito,not allowed kasi to post link


thanks po

[Woots29]

post mo lang link without http then kami na bahala dun

[Skyjham]

ok po try ko thanks ng marami

[Skyjham]

modefied av-502
[IMG//i256.photobucket.com/albums/hh180/Skyjham/konzertAV-502.gif[/IMG]

[BANNEDMemberAccount]

[Johannah Aleksandria]

modification na ba to for higher power?

[Johannah Aleksandria]

good day po sa lahat!

  ask ko lang po kung pano mag share ng photo dito,not allowed kasi to post link


thanks po

Tanong ko lang sir, ilang volts na ba gamit sa mod?

[tony]

modification na ba to for higher power?

rail voltages are the same so no.......

[Skyjham]

[IMG//i256.photobucket.com/albums/hh180/Skyjham/konzertAV-502modefied.jpg[/IMG]

[Skyjham]

ito naman po ung pang modefy sa amp ng mga component kung sakaling sira ung mamahaling IC amp,
av-735 po yan upto 60 vdc po VCC

[IMG//i256.photobucket.com/albums/hh180/Skyjham/IMG_7873.jpg[/IMG]