QUASI Amplifier for Beginners

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#581
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thx Mr. Miles for this quasi amp

if you teach me sir how to do a PNP quasi i will update sooner or later i'm glad that we have you Mr. Miles thank you very much.

regards
 
#584
not correct.

you have used the PSU Zero Volts (between the capacitors) as an Audio Ground. no no.

you have swapped the +ve & -ve supplies.

you have no emitter resistors in the emitter leads of the four leftmost output devices. no no.

you have the mains fuse and the mains switch in the two different Mains Lines. no no.
 
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#590
400W into 2r0 is equivalent to 40Vpk and 10Apk into your 2r0 load.
Expect +-50Vdc to be suitable.
Two amplifiers from the same PSU will require ~60Apk transient current demand.
Design for that 60Apk, or you won't get decent performance from the speakers.
 
#591
So i can use the apex550 at +-50 rail voltage at 2 ohm load without any changes in design.(i will upgrade power transformer & capacitor for more current)
transformer will be 36-0-36 volt secondary
what should be secondary current rating of transformer for one mono bridged channel(total audio power will be 800 watt) how did you calculate 60Apk :scratch1:

what should be appropriate filter cap size
thanks AndrewT 🙂
 
#592
I recommend twice the VA rating on the transformer as you expect watts out, say 1.5KVA for your amplifier. You could get by with a fraction of that but would have to raise the voltage and it could overheat with large duty-cycle signals.
 
#593
I like the quasi type circuit . It has a good bass response. Our vintage audio amplifier 1979 AKAI AA-1115 uses a Quasi type output. it uses rubycon capapitors, 4 NPN 2SD313 output transistor. Presently this amplifier still sounds good.
 
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#594
Stucked again

hi guys
i have some queries

1) In the scematic there are 2 capacitors 2.2 uf & 100 uf
http://www.diyaudio.com/forums/atta...uasi-amplifier-beginners-apex-550w-classb.jpg

But in layout they are shown as 1 uf & 47 uf respectively
http://www.diyaudio.com/forums/atta...amplifier-beginners-apex-550w-class-b-pcb.jpg 😕

which one is correct?

2) In scematics emitter of mje15031 is directly connected to speaker output
But in layout it is connected with 0.33R 5W resistor in between.
which one is correct & why ,because i have seen this in other designs also.

3) What is the wattage of resistors which are not mentioned?

thanks

i should have chosen electronics as my subject :headbash::headbash:
 
#599
formula 22 said:
Such should be (see Figure 1)!😉🙂
Best regards!
Click to expand...
thank for reply formula 22,
i am unsure of adding a 100R & 0.22R resistor.
as i have assembled the circuit (point to point hardwired without pcb) & ran the amplifier on rail voltage 40 vdc & it sounded great without any problem.
now i want to use pcb but it's layout differs from the circuit given (which i mentioned in my post #594.
SIR, i am not questioning your knowledge,it's just that i am noob & doesnot understand the logic.
& does anyone has links for correct pcb diagram.
SORRY formula 22 if anything i said offended you
 
#600
formula 22 said:
Such should be (see Figure 1)!😉🙂
Best regards!
Click to expand...

thank for reply formula 22,

i am unsure of adding a 100R & 0.22R resistor.
as i have assembled the circuit (point to point hardwired without pcb) & ran the amplifier on rail voltage 40 vdc & it sounded great without any problem.
now i want to use pcb but it's layout differs from the circuit given (which i mentioned in my post #594).

SIR, i am not questioning your knowledge,it's just that i am noob & doesnot understand the logic.
& does anyone has links for correct pcb diagram.

SORRY formula 22 if anything i said offended you
 
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