Topic: RS Coax>Optical Converter (like Hosa 276)

[johnw]

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=15-1228

So this thing is only $15 and I can get it locally (unlike the 276). My guess is it isn't bit accurate, but who knows. How could I test this using a JB3 and laptop connected to a UA5? Also, I've noticed when recording with Soundforge via USB, the recording is at a lower volume. For example I was setting up my VU and discovered that there is about an 8dB difference between the laptop Soundforge file and the JB3 file when opened in Soundforge. I'm using SF5 if that matters.

[ChrisV]

Saw that post on the Oade board about this...was thinking about getting one just for patchers.   But if anyone could do some testing to see if it is bit accurate that would be cool.   I doubt it is but who knows, worth a shot

[leehookem]

I knew that they had to have one.  I went a couple of weeks ago and they didn't have a clue what I was talking about.  I did find a new RS (little bit further) that has a knowledgeable staff.

[AT853rxwh]

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=15-1228

So this thing is only $15 and I can get it locally (unlike the 276). My guess is it isn't bit accurate, but who knows. How could I test this using a JB3 and laptop connected to a UA5? Also, I've noticed when recording with Soundforge via USB, the recording is at a lower volume. For example I was setting up my VU and discovered that there is about an 8dB difference between the laptop Soundforge file and the JB3 file when opened in Soundforge. I'm using SF5 if that matters.

Am I missing something?  If you have a UA-5 you should be able to give a patcher just about anything  

[johnw]

No I probably haven't made myself clear. I record on a JB3, so there isn't an optical out available to anyone patching, only coax. Since most patchers seem to be minidisc or JB3 users, I thought it would be nice to have a 2nd optical available if needed.

Does anyone have a suggestion on how to check bit accuracy on this thing? Or why soundforge is recording at a lower volume than the JB3?

[ChrisV]

Yep, primary use would be to use the coax off my UA-5 coverted to optical since my JB3 is using the optical.   But this thing also converts both ways it looks like too.

On soundforge recording at a lower volume, that doesn't surprise me all that much because I have had similiar findings with the UA-5 doing strange things like that.  I have found 3 different volumes being outputed with the JB3 being the lowest and the RCA outs being different too with the Moniter switch on and off.   And I didn't even test what happens through USB.

[Brian Skalinder]

Does anyone have a suggestion on how to check bit accuracy on this thing?

[1] Playback a WAV from your PC through a known bit-perfect soundcard's coax out.  Feed the coax out into the digital format converter's (DFC) coax input and route the DFC's optical out to your NJB3.  Transfer the recorded file from your NJB3 back to your PC and run a bit comparison between the original WAV and the recorded WAV using a tool like EAC's WAV Compare.  Note:  EAC's WAV Compare only works in 44.1kHz, so run the test at 44.1kHz.

[2] Record through your UA5's analog inputs and feed the two digital outputs - optical and coax - to different devices.  Feed the optical output to a known bit-perfect device (device 1) . Simultaneously feed the coax out into the DFC's coax input and route the DFC's optical out to your NJB3.  Transfer device 1's recording through a known bit-perfect soundcard onto your PC, transfer the NJB3 recording to your PC, and perform  EAC's WAV Compare.

FWIW, I think the first option is an easier and better method.

[johnw]

So in order to do this, I am going to need either a known bit perfect soundcard (which I don't have) or a second recording device (which I also don't have)?

[Brian Skalinder]

So in order to do this, I am going to need either a known bit perfect soundcard (which I don't have) or a second recording device (which I also don't have)?

Yes.  Maybe you know a local fellow taper with a bit perfect soundcard and can make it a team effort?

[johnw]

I guess I should have said that I don't think mine (Montego II) is bit-perfect. Is there a list of known bit-perfect soundcards anywhere? I did a search and looked in the archive, but didn't see anything.

[1st set only]

if something is not bit perfect what is the result in the recording?

[Brian Skalinder]

if something is not bit perfect what is the result in the recording?

Best case: sounds the same on your playback system even though the 0s and 1s are different.

Middle case: sounds audibly different on  your playback system.

Worst case:  introduces artifacts into the recording - missed/dropped/misplaced sample causing dropouts, clicks, pops, etc.

From the anecdotal evidence I've seen regarding a couple other DFCs - the ubiquitous 'grey box' and CO2 - it appears worst case is the most common case if the box is not bit perfect.