Apex AA14 Amp Class A 24V Supply

[chermann]

nope...its not so good...47nF is still oscillation...not big.....but...

 

[minek123]

how to calculated this thiele network for taht...i guess the 0,5µH are too less....normally about 1µH, or?

Check out Self's book "Audio Power Amplifier Design", page 358/359 (6th edition, chapter 14 on 'output inductors').

 

[minek123]

Here is what Cordell says about RL network:

 

[chermann]

thank you minek...
read and learn 😊

 

[chermann]

I have got the page from my brother because i do not own that book.
here :

 

[chermann]

next try....1µH and 6R8 (good to know that i had some old AVR´s..)

the simulation is looking more worse then the real amp...
in the simulation i realized that i have done a typo...if i made a comma it is not working and therefore i use 5µH(typo)...this is nonsense.
if i check and try out some values i found that with so with 4ohm its about 1µH and 2R and its fine...with 8R its a bit worse.

i will check at the real amp and post it in the next hours.

 

[chermann]

test with 220nF looks okay...and i have to switch off this lamps

square wave 5W into 6R

 

[chermann]

with 470nF it is not really nice..
what do you think?

is that okay...or enough damped?
square wave 5W into 6R

 

[chermann]

i measured the slew rate with the stronger Thiele and its just about 4,3V /1µsec
with the smaller filter - 0,5µH//3R3 i have got 8,85V/1µsec

i did the measurement again with a other cable to couple the signal into the amp and i have got better results.
you see it on the scope that the yellow line...input gets with bad cable a ringing too.

here you see the smaller Thiele network with square wave 10khz and 220nF...for me it is very good.
second pic is the slew rate with 20Vrail and no cap load...just 6R

 

[chermann]

nope...its not so good...47nF is still oscillation...not big.....but...

#post 141...

this comes from the light in the office...switch that off!

 

[chermann]

here is the sim file for slew rate
8,8V/1µsec...exactly the same 😊

 

[chermann]

LT file
R8 2k15 for lower the gain to 21DB
10kHz square into 6R with 220nF
Thiele 0,5H//3R3

 

[chermann]

as written in another thread...my speakers are not critical too

here

 

[minek123]

Except for extreme cases, speaker cable capacitance will be much less than 220nF, so it should be ok.

For a 20W amp, SR around 10 if perfectly adequate.

 

[chermann]

i did a short fg check....with 700mVrms input i got 2,8Vrms into 6R so it is about 1,3WATT...
with 8,2Vpp at 1kHZ its about 5,8 at upper fg
low fg is under 1Hz...top is 200kHZ

 

[chermann]

question:
i see my other amps using bigger caps at the C5 position.
does it help to large the C5 from 100µF to 1000µF /16V?

 

[Vrystaat]

next try....1µH and 6R8 (good to know that i had some old AVR´s..)

the simulation is looking more worse then the real amp...
in the simulation i realized that i have done a typo...if i made a comma it is not working and therefore i use 5µH(typo)...this is nonsense.
if i check and try out some values i found that with so with 4ohm its about 1µH and 2R and its fine...with 8R its a bit worse.

i will check at the real amp and post it in the next hours.

chermann, I have read before that it is better to mount the resistor on the outside of the inductor, a while ago.

 

[chermann]

hi Vrystaat,
really...i see it very often inside the coil.....nevertheless this Thiele is a prototyp.

 

[chermann]

Hi
i want to check the OLG and phase.
I did the dummies step by step by minek...his example is working but at the actual amp i get always the question of trans stop time?
i have got after add traces --> olg () trace...therefore i had a line...

what do i am wrong?

 

[chermann]

lt spice file