Streamer with variable digital output

I am still not convinced that any of the streamers mentioned or recommended in this thread, other than the Node, have the VARIABLE DIGITALOUTPUT (not screaming just emphasizing) required by the GAN1. None of the documentation explicitly states that they do. 

The majority of DACs and streamer/DACs, including the afore-mentioned streamers, utilize digital attenuation for volume control. This allows users to adjust volume and transmit scaled-down signal samples to external DACs through various digital outputs (usb, Toslink, coaxial, etc.) and analog outputs (SE or XLR). Additionally, users can switch to a fixed volume control mode to bypass altering the signal when sending it to an external DAC.

Now, there is on-going debate about the degraded quality of the scaled down signal samples through digital attenuation due to the lowered dynamic range (DR) and signal-to-noise ratio (SNR) at higher levels of attenuation.  To that end, some manufactures, like RME, claim "In reality, current circuitry overturns the theory, and the SNR at the output of such a device (referred to an analog volume attenuator) is no better than a digitally controlled one"  Gustard R26 / A26 also uses digital volume control but supplements a feature that, when turned on, utilizes analog attenuator to mitigate the dynamic performance loss at low listening level.  As a result, digital volume control is not considered a significant drawback, especially in higher-end products.

WiiM Pro and Pro Plus will both attenuate their SPDIF digital volume and are bit perfect digital transports. The only difference between the two is the DAC section which for the OP’s purposes is irrelevant. I have both Bluesound Node and WiiM Pro that I use digital direct to my DSP active speakers and attentuate volume in the app. WiiM and Node are both Roon ready as well. Another alternative. 

Tune into 8:21

https://www.youtube.com/watch?v=28GQzI5meB0

Even WiiM Mini that does not have coaxial output could pump digital signal into Gan 1 and control volume from finger tips. I'm using the Wii Mini here to address the OP's fear but, in terms of sound quality, I don't recommend it because it lacks bass and sounds lean.

I am still not convinced that any of the streamers mentioned or recommended in this thread, other than the Node, have the VARIABLE DIGITALOUTPUT (not screaming just emphasizing) required by the GAN1. None of the documentation explicitly states that they do.

Ifi Zen Stream works into Gan 1 and controls volume.