QUASI Amplifier for Beginners

[AudioSenseCD]

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

 

[apexaudio]

@apex yes sir miles do i have to reverse polarity the diodes and the zener diodes and the pre drivers and vas from pnp to npn and vice versa of their location from mje340=mje350 mje150031=mje150030 location

If you want PNP outputs, you must revert rail polarity, diodes polarity and all transistors must be pnp instead npn and vice versa.

 

[AudioSenseCD]

pnp quasi

If you want PNP outputs, you must revert rail polarity, diodes polarity and all transistors must be pnp instead npn and vice versa.

sir miles kindly check if it is correct

 

[AndrewT]

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.

 

[AudioSenseCD]

@andrewT sir kindly corect the wrongs ones because i can't get what you mean plss...
regards

 

[formula 22]

Wrong!?

Hi people!
Where the schematics of this quasi amplifier, as one friend told me that she is wrong?
Cheers!

 

[AudioSenseCD]

post number 1 page 1

 

[formula 22]

resistor of 0,33ohm/5W!

post number 1 page 1

Hi
Need to add a resistor of 0.33ohm/5W on the transistor 2N3773 or 2SC2922 (for Ucc=+/-70V) in the emitter of the negative branch of power supply.
Ceers!

 

[sanju21]

APEX at 2 OHM ??

Hi there
i want to use apex550 @ 2 ohm.
what should be the optimum rail voltage.i mean i want

400 watts @ 2 ohm
800 watts @ 4 ohm (bridged) mono

is it possible? thanks in advance

 

[AndrewT]

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.

 

[sanju21]

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

what should be appropriate filter cap size
thanks AndrewT

 

[djk]

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.

 

[gorex69ers]

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.

 

[sanju21]

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

 

[formula 22]

Schematic is not correct!!??

Hi Sanju21!
Note: The schematic under point 1) has a bug, or is not correct!?
Cheers!

 

[formula 22]

Such should be (see Figure 1)!
Best regards!

 

[AN214Q]

Hi ,
I have 2SK1518 about 30pcs. in all, found it from ac servo driver pack of robotic machine.
Can this be use as output stage on this power amplifier?

please advice,

regards....

 

[formula 22]

Hi ,
I have 2SK1518 about 30pcs. in all, found it from ac servo driver pack of robotic machine.
Can this be use as output stage on this power amplifier?

please advice,

regards....

Hello!
According to the features you MJ15003 transistors with 2sk1518, if so - fit!?
cheers!

 

[sanju21]

Such should be (see Figure 1)!
Best regards!

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

 

[sanju21]

Such should be (see Figure 1)!
Best regards!

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