HDMI to TTL with isolation
We made this HDMI to TTL interface to improve the transport conditions of i2S and DSD signals. HDMI transport is superior to TTL, in fact TTL should not be used at all outside of chassis. i2S is better than SPDIF as the signals are separated where SPDIF combines them together.
Also included in the interface is a isolator chip (ISO7240) that will keep the ground from HDMI and TTL sides separated. This will prevent ground issues and reduce noise. USB isolators are currently limited to 96kHz sample rates (USB Full speed), so i2S isolation is the only isolator type that can handle high samples rates, up to 384kHz.
The isolator supports 4x signal transmission (i2S or DSD) and 2 x control signal (DSD128 flag and DSD/nPCM flag) isolated by photocoupler (optical isolator).
The TTL connections:
- HDMI to TTL interface supports i2S and DSD
- 4kV pp isolation
- ISO7240 isolation chip
- Supports up to 384kHz sample rates
Roland Rittau –
In my search for a module that translates an I2s over HDMI LVDS signal to standard I2s, I found and ordered this module.
For the power supply of the module you still need 3.3 volts, because the current consumption is less than 100mA, you can buy a cheap 3.3v ultra low noise module.
What can I say, the module works perfectly, the transmission via HDMI and this module is significantly better than the other interfaces. It is important to have the shortest possible HDMI cable, for me 15cm – 50cm worked perfectly.
For those who are not (yet) familiar with this, this module is required if a device, such as a Gustard U12 or U16, outputs an I2s signal via an HDMI connection and the DAC has a "normal" I2s input (5 or 4 pin). Since the I2s signal is transmitted as an LVDS signal via HDMI, it cannot be fed directly into an I2s input (5 or 4 pin) on a DAC board. You need a converter like that.