Apex A40 fundamental improvement. (Sandy)

[U130421]

There is no difference between suggestions from you and my method.
Why put two items instead of just one.

You must put the generator back to the input, as the original circuit.

 

[SandyTodorov1]

Not true

 

[arpagon]

@kokoriantz - look at Bob Cordell's book about simulating the amplifier's OLG.
Otherwise, Sandy is right of course - I think I told him about this method for OLG simulation
Well, if you use LT Spice, there is a method with Tian's probe but this is a different beer...

 

[SandyTodorov1]

PSRR without the filters of the power supply (yellow) and with them.

 

[U130421]

Not true

Add at least a series capacitor with the generator to allow DC feedback establish the operating point. The same as A40 is not a Marantz, your amp is NOT a A40 , it is a different amp needs to be baptized.

 

[SandyTodorov1]

Obviously you do not understand how this method works.

Well no name for now.
I do not respect CFA amps when it comes to audio amplifiers have no advantage.
Just I wanted to show you how you can improve the parameters by eliminating the drawbacks of APEX-A40

 

[shabusf]

Hi Sandy,
Do you think that we can improve the measurements on original Apex A40 with just changing the transistors(to a more compatible ones )?. Could you please share your thoughts.

Also, I made the original Apex A40 using BC550/560, and I do love the sonic quality Better than my Onkyo A807 stereo amp. But if there are any scope of improving it further I would like to have a try.

Thanks
Sha

 

[SandyTodorov1]

Here's the result of replacing MJE340 / 350 with appropriate. Change and C2 470pF - 100pF

 

[arpagon]

Ето резултата от замяна на MJE340/350 с по подходящи. Промяна и на С2 470pF > 100pF

My friend is actually telling that this is the result of changing the MJE340/350 pairs with some better ones. And the C2 capacitor's value was also decreased from 470pF to 100 pF.


@Sandy: Адаш, I think I correctly translated your words, did I?

 

[sajti]

And replace D3 or D4, and D5 or D6 with red LED. That improves the quality of the current mirror stage.

Sajti

 

[SandyTodorov1]

D3 or D4, and D5 or D6 No problem transistors operate at low current <10mA
2T3169=BC169=BC239=BC549

 

[sajti]

D3 or D4, and D5 or D6 No problem transistors operate at low current <10mA
2T3169=BC169=BC239=BC549

But not the BC547C/557C...
Sajti

 

[SandyTodorov1]

Saturation them equally

 

[sajti]

Saturation them equally

No. Check out the topic about the quasi saturation!

Looking for a small signal NPN with no Quasi Saturation: MEASURED DATA

Sajti

 

[SandyTodorov1]

2T3168/3167 = BC548/547
2T3238/3237 = BC548/547
Transistors Low Voltage <50V no problem with saturation and work well in Ucb = 0V Ic<10mA

 

[sajti]

2T3168/3167 = BC548/547
2T3238/3237 = BC548/547

Ok. I gave it up.

Sajti

 

[SandyTodorov1]

The replacement of the D4 and D5 or D6 red LED will not improve anything and will worsen the use of power.
Will start limited at low voltage.

 

[shabusf]

Thank you Sandy for your valuable suggestions on transistor. I do have the suggested ones in my parts bin Will have a try once I get some free time.

Regards
Sha

 

[Elvee]

Obviously you do not understand how this method works.

Well no name for now.
I do not respect CFA amps when it comes to audio amplifiers have no advantage.
Just I wanted to show you how you can improve the parameters by eliminating the drawbacks of APEX-A40

Interesting design and ideas, but you should probably not present them as related to the A40: in fact, you could have used any regular AB amp as a starting point, but that's not even necessary: your amplifier seems to offer excellent performances, and it is sufficient in itself


There are lots of much less interesting and innovative designs around, but their authors present them in more attractive, less brutal way, and they get much more appreciation from the community, even if it is not really justified.

Another aspect to take into account is the real world.
Sims are OK, and are a great tool, but there is no substitute for reality, because physical designs always show peculiarities and quirks that a sim does not reproduce, and in general, the measured performances are significantly inferior, because many minor, higher order effects are not modeled in the sims.
Presenting a working prototype (even if it looks ugly) and its measured performance will earn you more interest

 

[SandyTodorov1]

That is already something that is different from APEX-A40.
And with a new name.