You cannot send native DSD over HDMI. The only way to send it over HDMI is to convert to PCM. DSD 64 (1x DSD at 2.822 MHz) converts to 352 KHz when converted to PCM. You need to downsample 352 KHz to a sample rate your Denon accepts - like 192 KHz or 176 Khz. 176 KHz would be better if your system supports that. So, try downsampling 352 KHz in DSP Studio.