Some pictures.
Sorry, do not find square 1kHz in my archive. I've 50Hz and 20KHz.
All these measures were done with the first prototype and a SMPS.
I've to find time to redo the measures with the final boxed version.
I still have some PCB if you want to try.
Regards,
Stef.
Sorry, do not find square 1kHz in my archive. I've 50Hz and 20KHz.
All these measures were done with the first prototype and a SMPS.
I've to find time to redo the measures with the final boxed version.
I still have some PCB if you want to try.
Regards,
Stef.
Attachments
Last edited:
Thank you! I will make a new board, put the bridge farther away at the end of the board.
What do you mean by "mini version ran, but very unstable" ?
While testing with your 4ohm load, please show the signal on your power supply line as well. Please indicate volts/div and it would be good to see input signal.
I also suggest to move bridge coil in vertical plane. As it is now, it is far too close to cascode stage.
How is your power supply designed ? It is CRC ? Which output voltage ?
Please also change R29 and R30 to 100ohm.
Regards,
Tibi
The output transistors burned out spontaneously twice.
I ordered a new board yesterday. A better layout. The coil has been stowed further away. When I get it, I'll try to get it running.
There are two power supplies. One is a 33v transformer, the other a 55v CRC.
Use an output fuse while testing the amplifier and take care on static charge handling.
I specifically asked if you use CRC filtering, because scope waves indicate clearly that you have a power supply problem.
CRC must NOT be used in a class B amplifier or A/B amplifier.
You can use CRC in a class A, class D, but not A/B or B.
Regards,
Tibi
I specifically asked if you use CRC filtering, because scope waves indicate clearly that you have a power supply problem.
CRC must NOT be used in a class B amplifier or A/B amplifier.
You can use CRC in a class A, class D, but not A/B or B.
Regards,
Tibi
R29 and R30 are part of a capacitor multiplier made with Q13 &Q14 and must be set between 10ohm - for a fast turn on and 100ohm-for a slower turn on.
During power on sequence, capacitors C13 and C14 will charge trough R19 and R30 till the point where mosfets turn on and internal Rdson of each mosfet will bypass these resistors. This create a short transient region that must be kept short. Therefore C13 and C14 under 220uF and R29 and R30 under 100ohm.
If you have power on issues, reduce R29&R30 to 10ohm and C13&C14 to 47uF.
Regards,
Tibi
During power on sequence, capacitors C13 and C14 will charge trough R19 and R30 till the point where mosfets turn on and internal Rdson of each mosfet will bypass these resistors. This create a short transient region that must be kept short. Therefore C13 and C14 under 220uF and R29 and R30 under 100ohm.
If you have power on issues, reduce R29&R30 to 10ohm and C13&C14 to 47uF.
Regards,
Tibi
Hello Tibi,
When you were talking about a dual ground plane, were you talking about this kind of thing?
Regards,
Stef.
EDIT: for smk7
10K for R29 and R30 was an error.
I think too that R23 is now 8k2 (but not sure).
Attachments
Yes, that's good to follow and read this thread. 😉
I'll correct this in a future github update.
Regards,
Tibi
Yes. Use small group of many vias, where is possible, to connect top to bottom.
Regards,
Tibi
To fill the various holes? (Just to be sure).
I didn't dare to do it with the vias weighing that it could introduce pervert effects. I'm also doing a contest to use as few vias as possible. 😉 In the new version of the Mini that I am preparing for March, I have reduced the number of vias from 8 to 1.
Do we really need to add top ground plane on all the GND zone or only as in my example around the opamp?
Stef.
I didn't dare to do it with the vias weighing that it could introduce pervert effects. I'm also doing a contest to use as few vias as possible. 😉 In the new version of the Mini that I am preparing for March, I have reduced the number of vias from 8 to 1.
Do we really need to add top ground plane on all the GND zone or only as in my example around the opamp?
Stef.
parasitic capacitance may appear. It is necessary to make transition holes in the polygons. This is my understanding.