QUASI Amplifier for Beginners

[AndrewT]

Better still, if Yehan cannot design, then he should not be modifying an existing design.
It seems to me that the best Yehan can achieve is to copy exactly an existing known and recommended design and build without any changes that may compromise the performance.

 

[djk]

+1

 

[olafk]

Oops!… I Did It Again

I built the amplifier with two pairs of transistors and it works with +-40V DC. The Sound ist great.

Thanks apex, very nice for beginners (like me ;-)

Olaf

 

[AN214Q]

I built the amplifier with two pairs of transistors and it works with +-40V DC. The Sound ist great.

Thanks apex, very nice for beginners (like me ;-)

Olaf

Hi,

Can we use NPN and PNP power transistor in the output stage on this project?

Regards...

 

[JojoD818]

Hi,

Can we use NPN and PNP power transistor in the output stage on this project?

Regards...

I bet you can, with some modifications of course. However, as the thread title suggests, it is a QUASI-complimentary amp.

 

[formula 22]

I built the amplifier with two pairs of transistors and it works with +-40V DC. The Sound ist great.

Thanks apex, very nice for beginners (like me ;-)

Olaf

Hi olafk!
According to this schematic, where you worked?
Since the standard schematic error is ( take a look topic?!)
Such should be!!!
Cheers!

 

[formula 22]

100W/4R class-AB amplifier

Hi, all!
Thus the amplifier can work in class AB!!
Tnaks

 

[olafk]

Hi formula,

the amplifier is running without any modifications and works very well. I did not made so mutch tests - may be i will find some things.

Regards
Olaf

 

[AndrewT]

Formula,
you don't need to change the protection diodes across the output.
1n4002 work perfectly well at limiting the back emf to <Vrail+0.7V.

 

[formula 22]

100W/4 class-AB amplifier

Hi, all!
Thus the amplifier can work in class AB (see schematic-1)!!
Tnaks and cheers!

 

[AndrewT]

Not very well.
Probably badly.

 

[formula 22]

Not very well.
Probably badly.

Why well not?!
A higher "quiescent current" (about 100mA), audio amplifier goes to the class-AB!
Class-AB less THD distortion, ....
Andrew cheers!

 

[AndrewT]

No Tempco
ClassB ish
Odd feedback

 

[sudhir kumar]

hi Apex sir,
Currently using this amp with 5 pairs of 2n3773,supply 40-0-40 AC 1.5kv traffo,20,000mfd caps per side on 4 ohm load. sounds good to my ears even as full range amp but currently coupled with your 2x12 inch subwoofer enclosure in a three way system.
What output power i should expect from this ?

 

[apexaudio]

hi Apex sir,
Currently using this amp with 5 pairs of 2n3773,supply 40-0-40 AC 1.5kv traffo,20,000mfd caps per side on 4 ohm load. sounds good to my ears even as full range amp but currently coupled with your 2x12 inch subwoofer enclosure in a three way system.
What output power i should expect from this ?

250W on 4 ohm load with 40-0-40 AC, can you post pictures of your sub?

 

[olafk]

Very hot

Hi,

I built the amplifier (picture see post #663) with two pairs of 2N3773 and I use +-60V DC. Now the Transistors MJE350/340 become to hot. I can touch them for only 3-4 seconds and I think it is a bit critical.
Should I reduce the voltage (have regulated power supply) or are there any other things I can do? I changed the heatsink to a bigger version for TO220 like the MJE15030, but gave no better result.
Can anybody help me?

regards
Olaf

 

[apexaudio]

Hi,

I built the amplifier (picture see post #663) with two pairs of 2N3773 and I use +-60V DC. Now the Transistors MJE350/340 become to hot. I can touch them for only 3-4 seconds and I think it is a bit critical.
Should I reduce the voltage (have regulated power supply) or are there any other things I can do? I changed the heatsink to a bigger version for TO220 like the MJE15030, but gave no better result.
Can anybody help me?

regards
Olaf

Nice work, MJE340/350 work in class A and must be hot but use 100R resistor instead 56R around MJE340 and this will reduce current in VAS CCS and disipation on MJE340/350 also.
Can you share your pcb?
Regards

 

[olafk]

Hot

Hi Apex,

thanks for the advice. I will test it after work this evening.

regards
Olaf

 

[olafk]

PCB

Hi Apex,

it works. Thankyou.
Here is PCB.

regards
Olaf

 

[apexaudio]

Hi Apex,

it works. Thankyou.
Here is PCB.

regards
Olaf

Nice PCB, thank you.
Regards