Noise problem on diy H-Bridge

[bigbluecoconut]

Hi,
i made a self oscillating full Bridge amplifier,
(20-50V) oscillating at 250KHz. 🙂
In standby it works like a charm, low power consumation (<1W).
And no noticeable noise at the speaker.
Pic and schematic. attached.

But when i connect my Phone,
or Ipod and start a song, it produces a lot of noise, 😡
but the music sounds well.

When i stop the music, it the noise continues for 3-4s, then stops.
With the Ipod i have less noise than with my phone.
So it must come from the audio source.

But i dont know how to solve this problem.
(same audio sources are working well with a TAS5630).
Can anyone help me with this problem?

Regards
David

 

[rayma]

when i connect my Phone,
or Ipod and start a song, it produces a lot of noise

Could be noise coupling from the comparator back to the input stage, since they
share the 5V supply and grounding. Try a separate 5v supply for the input stage,
and keep the op amp and comparator grounds separated.

Also bypass the 2.5V offset voltages for the input stage with 10uF or more, and
add two ~10k series resistors from the 2.5V nodes to the op amp inputs.

 

[bigbluecoconut]

I tried, what you wrote, but it didnt change anything. 😉
But then i removed C7,C9, R8 and replaced R1+R4 with 10k (instead of 470r)
At the input stage.
It reduced my noise problem alot, but not enough...
But i dont think, its a good idea to increase the input impedance more...