Apex A40 fundamental improvement. (Sandy)

[U130421]

why you don't like MJE340/350? Because American?

 

[U130421]

This is the performance of the current mirror by the "Bad designer ". The Marantz , with the same transistors, is 0.006% for a gain of 2 but higher frequency response. By respect to the very kind people of Bulgaria , I retain to show yours.

 

[SandyTodorov1]

why you don't like MJE340/350? Because American?

No bad transistors.
There are bad designers placing transistors in inappropriate places.

 

[SandyTodorov1]

Big problem MJE340 / 350 no evidence of Ft and Ccb

 

[SandyTodorov1]

H22b Ccb (PNP)

 

[SandyTodorov1]

There is no difference in the two methods of compensation h22b !2/!3
Just use the method that requires less elements.
I used method has better PSRR

 

[SandyTodorov1]

The use of R1 instead of the current generator matters worse considerably.

 

[Itco]

MJE340/350. The first transistors with missing information about ft and Cob. Don't care if they are american or not. They suck!
I already replace them in my Apex A40, and the sound is much better.

 

[SandyTodorov1]

Evidence it is foolish to use MJE340 / 350 Ic ~ 10mA

Measured:
------------------
MJE350-24pF
MJE340-14pF
------------------
KSA1381-3.8pF
KSC3503-2.0pF
2SA1538-4.5pF
2SC3953-2.2pF
------------------
2SA1220-45pF
2SC2690-26pF
BD139C-21pF
BD140C-38pF

 

[ssavi]

Hi Sandy I replaced the transistors,and i changed the capacitor the difference is absolute.

P.P.
Съжалявам, че не пишеш в българския форум

 

[desislavov]

if i get you right , i must change transistors from post #28 in yellow box`s ?

 

[SandyTodorov1]

Yes, but if they change, they don't play so beautifully anymore.
But he's going to play it right.

 

[bullittstang]

Yes, but if they change, they don't play so beautifully anymore.

But he's going to play it right.

I’m not sure what your comment means? Do other things need to be changed with the transistors to be the best modification?

 

[SandyTodorov1]

Comments kidding.
Audiophiles do not like little distorting amplifiers.

 

[bullittstang]

Comments kidding.

Audiophiles do not like little distorting amplifiers.

Gotcha!!! Totally agree, either needs perfect distortion or perfect cables to get said distortion! LOL!

 

[sEBYres]

software

Comments kidding.
Audiophiles do not like little distorting amplifiers.

Hello Sandy, what software you use for simulation?
Thanks!

 

[SandyTodorov1]

Altium Designer 19.1.8

 

[SandyTodorov1]

Some audiophiles measure THD of 10W decided to give such simulations.
I think that if you can measure THD of 10W this is very bad amplifier.

 

[r_merola]

Just to clarify.

Do you really simulate this circuit with 1MOhm resistors polarizing zener diodes and the current source in upper and low side the very first stage (R7 and R10)?

I tried it in LTspice and it did not work there - Zener polarization error. I changed both 1MOhm resistors to 33K and I got simulation results.

It do really have very low simulated distortion, but very high DC offset even using coupling capacitors as suggested here.

Do you know how to analyses square wave amplifier response? Your square wave from first post shows problems. I could solve it with best compensation values.

The greatest problem with CFA is just DC offset and Marantz created a really good solution for this issue.

By the way, I think the real value of 680pF is 68pF and with this value almost all Marantz schematics performs very well. The problem rise because some capacitors manufactures mark 681 for 680pF and 680 for 68pF and others mark 680pF and 68pF as final value in component.

Regards and Happy New Year

 

[SandyTodorov1]

Upload a photo of your schedule to see where your error.