Audio problem on USB device

[spin]

I am using an SDR receiver, seen from Debian as a USB sound card.
Software read signal from USB sound card, decode it and play audio on A20 built-in audio card.
All is working without any problem and CPU load is low (20-30%).
Audio is processed by Alsa but also using Pulseaudio there is no change.

If I use another USB device, as a Wi-Fi USB module, audio is chopped but CPU load in lower than 50%.

Same problem using any other application using audio and Pulseaudio. Or using Jackd. When there is some audio exchange (redirecting audio using Jack or recording from monitor in Pulseaudio, audio become chopped and system become very slow.

Is this a "too big requirement" for an A20?

Regards

Franco Spinelli