Seeking lower cost alternatives to Berkeley Audio Design Alpha USB converter


I am looking for a USB to optical audio converter.
The Alpha USB from Berkeley Audio Design is an external asynchronous USB to S/PDIF (or AES) interface. It's strictly a D to D converter accepting USB digital audio input and delivering digital audio output.
That's the type of product I'm looking for. However, at $1,895 the Berkeley Alpha USB is far more expensive than most similar products I've seen. Some of these products sell for less than $100.

I'm on a budget. Can anyone recommend one of the lower priced alternatives to the Alpha USB from Berkeley Audio Design?
lowoverdrive
I guess it depends on how critical performance is, but the Singxer SU-6 looks to be of good quality and is quite a bit cheaper than the Berkeley at $690.  Best of luck. 
Lots of them. 

If you can find them, one of the best budget DACs was the Parasound ZDAC which AFAIK is now out of production, but a fine DAC.
The Schiit Eitr does the same thing (USB > SPDIF coax and works very well.  

I bought one a couple of years ago but it’s now retired as I went to streamers and DACs that are better w/ USB.  I hadn’t planned on selling it - because i forgot about it, but can sell it if you’re interested. Or, you can probably by a new one from Schiit for very reasonable.  Mine is in like new condition.  Please PM me if you’re interested..  
@erik_squires
> If you can find them, one of the best budget DACs was the Parasound ZDAC which AFAIK is now out of production, but a fine DAC.  

I am not really looking for another DAC. Most of the DAC’s I’ve seen do not have SPDIF or coax digital audio **outputs**. I want a USB converter that I can connect to the digital input on my DAC.
@mgrif104 I was looking at the Schiit Eitr. You are right -- that's the functionality I'm after. However, this review turned me off to that product:
https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-schiit-eitr-us...
It says

> The Topping D10 performs the same function at less than half the price.  The D10 has the same noise profile as the Schiit Eitr but is free of its power supply induced jitter around our main tone.
I looked at the D10s, which is about $110, but I was hoping to find something without the DAC functionality so I can get the best USB to optical components for my money without spending for functionality I don't need.