What's the best way to connect a coaxial SPDIF microphone interface to a PC?

[Delicieuxz]

I have an API A2D microphone preamp interface that I need to get connected to my PC for music recording. I bought a Creative Labs Titanium HD sound card, because it supposedly has coaxial SPDIF, but I haven't been able to get it to work with that sound card. I just get this screeching noise coming through the speakers when I have the API interface running:


View: https://vocaroo.com/1cn67SeJ36Ie

In the clip, I switch the API A2D control switch through the various bitrate settings, which is when the frequency of the noise changes.



In that clip, when I sets the API A2D to 192k bitrate, the screeching noise wasn't there. But after changing the clock speed in the Creative Labs software, the screeching sound started occurring on the 192k setting, as well. Also, when playing with the software, sometimes the screeching would not happen on one setting or another - but it seemed to be random which bitrate setting the screeching wouldn't be on, it didn't correspond to what the software was set to. And when it wasn't making that noise on a particular bitrate, I tested playing audio into a mic and through the A2D, and no audio was coming through my PC speakers, even though the API A2D preamp and AD meters appear to be receiving the sound normally.

After enough playing around with the bitrate in the software, I got it so that both the software bitrate and the API A2D bitrate are set to 44.1k, without that screeching noise coming through the speakers. So I tested it in my DAW by monitoring a track with the input source set to Digital-In L. But no audio came through the speakers. Then, when I set the input source to Aux L, I got that same digital screeching noise coming through the speakers.


View: https://youtu.be/2pJo073_CCA



The API preamp interface worked with my previous PC, which had an Auzentech Prelude sound card with coaxial SPDIF. But I can't use that sound card with my new PC as the Auzentech sound card is PCI, non-express, and my newer motherboard doesn't support that.

Coaxial SPDIF is kind of an outdated connection that isn't supported in newer stuff, which makes it tough figuring out a good connectivity setup for my API interface. The Titanium HD is supposed to support coaxial SPDIF, AFAIK, yet it isn't working for me.

One solution I've thought of would be to get a sound card that supported optical SPDIF, and then use and adapter to convert from coaxial SPDIF to optical SPDIF. The only current Creative Labs sound card which supports optical SPDIF-in is the AE-9, which costs half a grand. It'd suck to pay that just to connect my interface.

Another solution could be to sell the API A2D and buy some 500-series API preamps and a good AD converter. But that could end up being expensive and I really like the API A2D's features and design.

Another idea I've had is modding the API A2D's outputs, to give it ADAT, USB, or whatever works output. I don't know if that's possible, but if it is, it'd be nice to do.



Rear and front of the API A2D:

The Titanium HD's features:

 

[Delicieuxz]

One thing that makes me wonder is that the Titanium HD's RCA inputs are labelled as optical in / out. But those are coaxial connectors, aren't they? Optical SPDIF looks like this:

So, are those not actually coaxial SPDIF connectors on the Titanium HD then? If not, is there an adapter to get them to work with coaxial SPDIF?

 

[uOpt]

There are cheap coax to optical converter boxes. The conversion is rather trivial and no need for expensive equipment, it won't damage sound.

I have various USB soundcards with optical S/PDIF in. My specific model is no longer available, but other models are. Cost $10-20 and again, no concern about sound quality since it is all digital.

 

[toast0]

One thing that makes me wonder is that the Titanium HD's RCA inputs are labelled as optical in / out. But those are coaxial connectors, aren't they? Optical SPDIF looks like this:

View attachment 614057

So, are those not actually coaxial SPDIF connectors on the Titanium HD then? If not, is there an adapter to get them to work with coaxial SPDIF?

There's mini toslink, which apple used on some computers, where it works as a 3.5 mm jack, or optical, with goofy cables. Here's an adapter to go from mini to regular toslink. A quick read of the sound card manual suggest that's the case here. Need some sort of optical cable that plugs into an rca port (which might be mini toslink ?)

,

 

[Delicieuxz]

There are cheap coax to optical converter boxes. The conversion is rather trivial and no need for expensive equipment, it won't damage sound.

I have various USB soundcards with optical S/PDIF in. My specific model is no longer available, but other models are. Cost $10-20 and again, no concern about sound quality since it is all digital.

A sound card with good DA conversion is important for quality playback. I'm kind of hooked on Creative Labs, not because I think their company is great, but for their "crystalizer" feature, which I always have running for gaming and general entertainment. Sound is pretty dull without it. Their sound card software suite is pretty good.

A Creative support rep has told me they'll see if just the AE-9 sound card can be sold to me, without the mic pre component. It'd be pretty awesome if that's possible. I haven't found any used AE-9s without the desktop preamp module, but there is a used AE-9 desktop preamp module for sale on eBay without the sound card. I'm guessing someone else has no need for the module but wants to keep the sound card. I wonder if the desktop preamp module is even usable with anything other than an AE-9 sound card and Creative's driver software for the AE-9.

There's mini toslink, which apple used on some computers, where it works as a 3.5 mm jack, or optical, with goofy cables. Here's an adapter to go from mini to regular toslink. A quick read of the sound card manual suggest that's the case here. Need some sort of optical cable that plugs into an rca port (which might be mini toslink ?)

View attachment 614140,

Interesting. And this forum post digging deep into the Titanium HD's components confirms that's the situation: https://www.avsforum.com/threads/finding-the-spdif-pin-on-a-sb-x-fi-titanium-hd.1844161/

"The RCA Analog Line-In doubles as Mini-Toslink ports inside the center of it (combo jack). The Red port has an optical Output Transmitter(TX) and the White port is the optical Input Receiver (RX)."

So, I need a coaxial -> optical adapter, and then one of these cables: https://www.amazon.ca/gp/product/B09Y5QBZLT/ref=ppx_yo_dt_b_asin_title_o00_s00 , https://www.aliexpress.com/item/1005005243398553.html
Or the smaller adapter: https://www.aliexpress.com/item/1005003816868872.html

It's good to have that sorted out.

 

[Delicieuxz]

I got a coaxial -> optical converter and a toslink -> mini-toslink cable, and now the sound is passing to my PC all good.

 

[uOpt]

I got a coaxial -> optical converter and a toslink -> mini-toslink cable, and now the sound is passing to my PC all good.

Congrats!

 

[Delicieuxz]

Congrats!

Thanks!