[Folsom]

Are there any BNC connectors from Digi that will work? I would rather go BNC just for it's much better ability with digital.

[hagtech]

ARFX1063.

jh

[Folsom]

Thanks!

[rajacat]

Are there any BNC connectors from Digi that will work? I would rather go BNC just for it's much better ability with digital.

Why is BNC better than RCA with digital?

Raja

[hagtech]

Why is BNC better than RCA with digital?

Yes and no.  Theoretically, you can do a better job with a BNC.  But it has to be a 75 ohm type (video), not the more common 50 ohm version.  You see, it is all about continuous impedance matching along the line.  Any discontinuities will cause perterbations (reflections) of the signal transitions.

So yes, if you design a perfectly terminated 75 ohm BNC it will perform better.  On the other hand, doing so in a HAGUSB is difficult, because the panel mount requires a 1/2 inch of connecting wire or cable to the PCB.  This short path is probably just as bad as the RCA jack in the first place, which isn't really so bad.  This is taking things to the extreme.  More importantly, you want the receiving end to be terminated well.  The trasmitter side is not as critical.

I realize this is as clear as mud.  But you have to look at the entire picture, not just one connector.  It all depends on implementation.  I made the RCA jack short and tight in the HAGUSB, so its impedance mismatch would cause minimal signal degradation.  You'll hear far greater differences depending on what you use for a connecting cable.

jh

[rajacat]

Thanks for the theoretical explanation.

Raja

[Hawthorne]

Hi Jim

Ive Just ordered a Hagsb and await delivery. What coaxial cable can you recommend to use with it?
I have a Van Den Hul hybrid with ferrite rings on both sides. Could you advise on something of higher quality, i.e. what do you use

Thanks

Jack.

[hagtech]

I can't make any recommendations for digital cables.  There are a gazillion different ones out there and I've tried maybe 0.5% of them.  In the shop I use video cables.

jh

[dougigs]

If I can add my $0.02:

With regard to cable: you want one that actually has a 75 ohm characteristic impedance (cable type RG59 or equiv) and has genuine 75 ohm connectors. Also, **You want to make sure it's longer than 1 meter** Short cables are bad news for SPDIF etc -- you're not going to have the proper characteristic impedance with a foot-long cable, and you'll get more reflections and therefore more jitter. Long=good.

I get cables from Canford in the UK -- very good cable-makers, used by the video industry. I buy the cable below, which is preposterously expensive -- 11 pounds each (20 bucks), but I think it's worth having something truly reliable for something as nice as the HAGUSB. It's really good quality cable, in a nifty turquoise colour:

http://www.canford.co.uk/commerce/productdetails.aspx?productid=38-982

[dougigs]

And with regard to USB connectors:

With due respect to Jim, the Digikey part he cites isn't a great match for the HAGUSB. First, it's a 50 ohm jack, and you want genuine 75 ohm if you're going to bother with this(though, I should add, you want to make sure your DAC has a genuine 75 ohm termination -- I can give you discussion threads that tell how to mod this).

But more significantly, there's a line of very good quality Amphenol 75 ohm jacks that fit very neatly into the HAGUSB PSB... I used Digikey part A24602-ND (there are others with similar design -- you want the plastic insulator so it's not grounding itself to the case). Take your needlenose pliers and carefuly pullthe leads out of the plastic so they're sticking straight out, not right-angle anymore. Then you can slide the PCB directly into the slot in the jack, and carefully bend the leads so they go into the output holes... You wind up with a total lead length of about 3 to 4mm, and a snug solid fit that is almost as solid as the RCA).

[dougigs]

Oh yeah -- How to tell 50 ohm (computer network/oscilloscope) plugs from 75 ohm (RF/SPDIF) BNCs:

The 50 ohm always have a solid white-plastic sleeve around the pin in the middle of the jack -- not just around the bottom, but around the whole pin. 75 ohm leave the pin/socket naked (because air is a higher impedance dialectric than plastic). Also, 75s cost more: 6 to 9 bucks for a jack, typically.


Also: if you order those Amphenol jacks, note that you have to order the panel mounting hardware as well -- that is, the nut and te lock-washer. These are .5" hardware, if you're getting imperial. Some suppliers like Farnell stock this if you search for "BNC hardware." And you want to have these mounted solidly to the panel.