[googlephone]

I just did some modding on my SB Duet and SN Dackit. I replaced the digital RCA connectors with BNC connectors. I then made my own BNC cable using 75ohm RG6 coax. This is the real deal. I can't believe what a major difference this made. I used to think that jitter was snake oil used to sell products, but this $25 upgrade has made such a huge difference in my system. The highs are under control, bass has more substance and everything just seems to be much clearer. I'm assuming this is due to the fact that my DAC does not do anything to reduce jitter.

Has anyone else done similar mods? I'm sure this is not necessarily new news, but just have not seen much talked about the benefits of a true 75ohm digital signal provides. By the way, the cable is also 1.5m. I've read in many discussions that this is ideal for digital cables.

spdif

 

[FallenAngel]

Yes, real coax should be used.

About 5m is optimal.

 

[cobaltmute]

You need to track down Jocko Homo. He can give you all the details about the 75 Ohm situation.

I have read that not all BNCs are 75 Ohm as well.

 

[iriverdude]

I asked about this a bit ago (repalcing RCA with BNC) my DAC has BNC as well.

 

[Pars]

BNCs come in 50 ohm and 75 ohm, with 75 ohm somewhat harder to find. 50 ohm seems to be used for test equipment, etc. Do some searches on diyaudio or diyhifi and you will run across Jocko and others thoughts as to SPDIF interfaces and pulse transformers, etc.

http://www.head-fi.org/forums/f6/add...ransit-129132/

This thread may be of interest.

 

[googlephone]

I made sure my BNC connectors were definately 75ohm. Now you got me curious about trying a longer cable.

thx

 

[googlephone]

Okay I tried 4m and then 3m. In both cases the sound quality degraded. The harshness in the upper frequencies returned. So now I'm back to 1.5m. Maybe later on I'll see how 2m and 1m sound. It appears that there may be a sweet spot for the length. Luckily RG6 is fairly cheap to allow for experimenting.

 

[stew1234]

Would it make a difference if the internal wire from the BNC connector to the board is still normal wire?

Or would using a cut from the signal cable and using that inside from the BNC connector improve anything?

 

[DKJones96]

Are we talking digital or analog here?

 

[Pars]

Quote:

Originally Posted by stew1234 /img/forum/go_quote.gif Would it make a difference if the internal wire from the BNC connector to the board is still normal wire? Or would using a cut from the signal cable and using that inside from the BNC connector improve anything?

Coax would be better. You can get mini coax (RG79 IIRC; check the impedance because there is also a 50 ohm variant).

Quote:

Originally Posted by DKJones96 /img/forum/go_quote.gif Are we talking digital or analog here?

Digital.

 

[DKJones96]

Oh, alrighty. The talk about highs being better and such threw me off.

 

[googlephone]

I was worried about internal wiring also, so I just replaced the wire with the center portion of the RG6. I was attempting to maintain as much of the 75ohm as possible. Took it from the BNC connector to the circuit board on both ends. Beyond that I could not go any further.

 

[linuxworks]

I wish I had your ears, google guy

no matter WHAT I do to spdif, the results are always always the same.

maybe we live on different planets?

I guess I should be happy that I don't need to 'worry' about transmission lines for digital audio. either that or my dacs just re-clock no matter what signal I put in.

don't know. but I've never in my life heard any diff any spdif cable made. not ever. maybe I should just be happy with *that*

 

[googlephone]

Honestly I'm not a big believer in cabling. I was actually using a cheap video cable as my coax digital cable. I was in the mind set of digital is digital. I did a quick comparison between the coax and optical and really didn't find any difference. I demo'd the Audio-GD Ref1 from a local Head-fi'er and really enjoyed the improvement. I went ahead and put in an order. I kept reading on the Audio-GD site about the improvements from BNC vs Coax so I figured I just do a simple swap between RCA and BNC from my Squeezebox Duet controller. I figured since I was doing this I might as well upgrade my SN Dackit and build a simple 75ohm cable out of RG6. Just basic cabling I had lying around. Little did I know that this small mod would provide such a significant improvement to my system. I'm very tempted to do another demo of the Ref 1 against this cheap DAC. I'm sure the REF 1 will still be an improvement, but not a significant as before.

I do believe that since the DAC is very inexpensive and does nothing to reclock that my improvements will probably be more significant that others with more sophisticated DAC's. Also I was starting off with such a poor cable so improvements for me may be a little more exaggerated.

Now I'm curious to see if I will be able to hear the difference with other mods such as power cables, RCA's, and such. I have to say after upgrading to the HD800's tube rolling is completely a new experience for me. The subtle differences in the past a more noticeable now.

 

[linuxworks]

you've seen the wiring I use in my hackings

I'll grab junky old ribbon cable, rip it into 2 wire pairs and use that for spdif board-to-jack wiring.

I never heard a problem from that. and that's just about as bad as you can get.

am I missing parts of the music? I don't think so, but how can you *know*?

too much involves the mind. I don't trust that, as a yardstick.

if you could use the 'overly sensitive dac' as a test device in the RMAA test, maybe you could actually show, graphically, where the problem is? you said it was not subtle, therefore it would HAVE to show up in something like an RMAA. I know RMAA isn't the last word in audio tests and its pretty simpleminded in what it does, but any 'major' diff you hear should have something that also shows, as a diff, somewhere.

care to try it?

rmaa is free software and you only need the dac and maybe another 'reference' dac; then send the cheap cable's output to both dacs (in 2 runs) and capture the graphs.

you do need to have access to a decent (same quality as your best dac) a/d box, as well, since you're going to 'listen' to the analog-out of the dac and the only way computers can do that is via an a/d converter, sending that digital signal back into the pc. RMAA does all this for you, you can use 2 boxes just fine (2 spdif interfaces on the pc).

I'd love to see the results from this.