ACA mini mosFET/BJT input, thread spun off from here: [https://www.diyaudio.com/community/threads/diy-aca-mini.379037/post-7946869]

[No ideas]

What if we added capacitors between the bases of the output diamonds?

 

[No ideas]

Here is how we can use BJT input for ACA Mini.
It is a diamond input. And IRFP240/9240 output.
Distortion is acceptably low.

View attachment 1430746

Can you define acceptably low? <1% ?

 

[No ideas]

is unequal power consumption normal?

 

[lineup]

Can you define acceptably low? <1% ?

THD 0.037%

 

[lineup]

What if we added capacitors between the bases of the output diamonds?

Is not needed.
Actually there is no need for compensation.

 

[No ideas]

THD 0.037%

The original ACA mini had 0.035% thats like almost the same

 

[No ideas]

Is not needed.
Actually there is no need for compensation.

Heard it improves voltage swing

 

[lineup]

Probably it does @No ideas
I have seen people add such a capacitor.
However the improvement would be very small.

 

[No ideas]

Still cant seem to bias it right

 

[No ideas]

i dont know which pot i should turn first and where should i hook up my meter, i even struggle with biasing it in simulation and getting the bias current below 800ma

 

[Mark Johnson]

There's a YouTube video showing how to bias the ACA mini, maybe it might be something to investigate. (link)

I assume you did a Google search for "ACA mini" with site:youtube.com

 

[No ideas]

i did not becuse its a thread about a modified version and the bias current may be diffrent, i cant get a nice sine wave with anything below 500ma of bias current, must be an issue with the mosfets

 

[No ideas]

I believe we would need more information about why the irf520/9520, maybe i need more bias becuse of the irfp240/9240's higher R-on? Id preferably use irf540/9540 due to their even lower R-on and the fact that i have them.

 

[No ideas]

i think the issue here is the jfets

 

[No ideas]

ive got my jfets in the mail and im wondering if i should try to build it? it seems that it will run hotter at 8W per transistor compared to the original 5W per transistor. it seems that this design depends a lot on the choice of parts.

 

[WhiteDragon]

Id preferably use irf540/9540 due to their even lower R-on and the fact that i have them.

If I remember right IRF9540PBF and IRF640PBF should be a better pair Rds On 200m and 180m

As with 9540 /540 are typically like many others usually 600m and 180m typically miles about using "matching" N and P channel part suffix


This circuit doesn't really do much better than .1 to .5% distortion
you could basically pull a stereo out of a old Buick and get radio/cd/bluetooth/aux input with 100x the performance lol
just use a 12 to 14 volt switch mode instead. About 10 bucks at a junkyard for a stereo. power supply about 15 to 25

 

[WhiteDragon]

All I got for BJT driver

 

[No ideas]

If I remember right IRF9540PBF and IRF640PBF should be a better pair Rds On 200m and 180m

As with 9540 /540 are typically like many others usually 600m and 180m typically miles about using "matching" N and P channel part suffix


This circuit doesn't really do much better than .1 to .5% distortion
you could basically pull a stereo out of a old Buick and get radio/cd/bluetooth/aux input with 100x the performance lol
just use a 12 to 14 volt switch mode instead. About 10 bucks at a junkyard for a stereo. power supply about 15 to 25

I have an tda7377.
Most things nelson pass makes have awfull numbers yet people still like them, also i didnt knew the 640/9540 was a better match.