[tonyptony]

Lemme guess.........you are using a 1 meter pigtail.

Pat, was this one for me? If so, I am not. Remember, I'm in the business too. I'm using a 2 meter SM Corning Cable with the best ST connectors they offer and ends prepped and polished for the lowest possible reflection. I specified quite precisely what I was looking for and they supplied it. Fortunately I paid a realistic price for it, not what it would have gone for in the audio market.

[Nuuk]

Update. After a few days listening with the 100uF DC blocker, I realised that it seemed to be messing with the timing of the music so I have been trying other options.

I think that I am going to stick with the 0.22uF Evox Rifa SMR (Polyphenylene Sulphide). Not quite so much bottom end but everything else is very good. 

[art]

Lemme guess.........you are using a 1 meter pigtail.

Pat, was this one for me? If so, I am not. Remember, I'm in the business too. I'm using a 2 meter SM Corning Cable with the best ST connectors they offer and ends prepped and polished for the lowest possible reflection. I specified quite precisely what I was looking for and they supplied it. Fortunately I paid a realistic price for it, not what it would have gone for in the audio market.

So I don't have to type this twice, your answer can be found here:

http://www.hifisentralen.no/forum/index.php/topic,20260.msg395498.html#msg395498

No idea what most of the members there think of me. Guess it helps to know the language. Oh, well.

Pat

[Polarbear]

No idea what most of the members there think of me. Guess it helps to know the language. Oh, well.

Pat

Hi Pat

I want to thank you for your contribution on the Norwegian forum. Best thread in there for a long time
By the answers it seams like they don't mind your attendance at all. And their question are mostly objective. But some of the members have a hard time finding any consensus in the litterature and technical papers available.
I say: keep it up 

Cheers
bjørn

[art]

Thanks for the kind words.

As I said, I am impressed both by the members' ability to communicate in English, and their knowledge level. I think some of the US-based forums could take a lesson in civility from your forum. But, I think a lot of that goes hand-in-hand with knowledge level. I won't mention any nut house by name, but I think most everyone will get the joke.

Pat

[art]

This is a bit o/t, but for those of you who still think that there are 75 ohms RCAs.............

Edit: Senior citizen moment.

Here, take this guy's words instead of mine:

http://www.diyaudio.com/forums/showthread.php?postid=1550065#post1550065


Only I don't have to measure them on the TDR to prove they aren't 75 ohms. It isn't worth the effort to prove the obvious.

Pat

[crooner]

Pat,  what is your preferred connector for true 75 ohm terminations?

[art]

As a testament to the value of Audio Circle, there is still a tremendous amount of traffic on the site that hosts the data that I posted here. When AC was down, or only open to registered members, the traffic was nil.

Now that it is open to all again, the traffic has spiked up to previous levels.

I don't know which I am more surprised by: that this thread still generates such interest, or that AC is so heavily read by folks just passin' through.

We should all thank the folks who work so hard to keep this site running. I can't imagine what a challenge it was to recover from their server/hosting issues. Not sure what we would do without. (We kinda got a preview of that, and we didn't like it!)

Thanks to JohnR and the rest.

Pat

[Firefly]

art, one question:
If we increase supply voltage of 74HCU04 to 5V, then output voltage will increase.
Resistor value can be increased from 249 to 300 Ohm & secondary can be terminated with 75 Ohm, is this correct?

[art]

No.........not quite............

If you make part of the divider 300R, then the other resistor would need to be 100R to make the impedance 75R.

But........you have to factor in the output Z of the chip as part of that 300R. When you go from 3.3 V up to 5 V, the output Z goes down. I think the mod used a 249R. (It has been a while.) The output Z was probably at least 35R, maybe closer to 40R. At 5 V, it is probably down around 20-25R. So, be sure to include that in the equation.

You also have to design the divider so that you have the proper output voltage, as well as impedance. You are shooting for 1 V p-p, unloaded, or 0.5 V p-p loaded w75R. Not a hard math problem, best solved by plugging in common values, and seeing the result. I would rather have an output a tad lower and with 75R impedance, than the perfect voltage at the expense of impedance.

Pat

[Firefly]

art, thank you. Agree, proper termination is more important than 0.4 or 0.5 or 0.6V on secondary.
I used to work with fotons, interferences, reflections & high order aberations  , no experience with digital transformers, can you help me? I will do my homework & learn, but need some help with formulas, how to calculate values.

[art]

This thread is over 3 years old, and we are still getting hits on our site, from it. (OK, some may be from other sites who have linked to this thread.)

Some of the pictures/graphs are closing in on 10,000 views. Wish I had a penny for each one!

Pat

[multibit16]

It was (still is )  a very interesting and helpful thread Pat and without the BS, me along with others really appreciated you taking the time to post it.

[user68]

This is the most informative and interesting thread I've found on Squeezebox mods. I'm going to mod both my receivers adding the BNC and S22083 transformer in one and, in case I can't get the voltage/impedance output right, will only take out the ferrite bead in the other. Then I'll compare the two.

I've read all the posts over the 3 years several times but a couple of things still aren't clear to me.

According to Pat's advice, should the 0.22uF DC film blocking cap be connected in series with the 249R resistor before or after the transformer primary at pin 1?  I can't see a consensus from the two circuits posted by different members.

Did Pat advise putting a ferrite bead on the positive supply voltage of the HCU04 or was this a further modification?

I will appreciate advice to get it right.

[art]

This is the most informative and interesting thread I've found on Squeezebox mods.

Thanks. Judging from the traffic on our site, a great deal comes from this thread. Years after it first appeared.

I'm going to mod both my receivers adding the BNC and S22083 transformer in one and, in case I can't get the voltage/impedance output right, will only take out the ferrite bead in the other. Then I'll compare the two.

I've read all the posts over the 3 years several times but a couple of things still aren't clear to me.

According to Pat's advice, should the 0.22uF DC film blocking cap be connected in series with the 249R resistor before or after the transformer primary at pin 1?  I can't see a consensus from the two circuits posted by different members.

OK, some of my engineer buddies may quibble (but only because they have measurement gear that you do not or will ever have), but for the DIYer, whichever way makes for a tight layout. That is more important.

Did Pat advise putting a ferrite bead on the positive supply voltage of the HCU04 or was this a further modification?

I will appreciate advice to get it right.

I believe there already is a ferrite bead, on pin 14. Leave it.

Pat

[Firefly]

No ferrite bead on pin 14 in stock form. Only 100nF cap to ground.

[art]

I'll take your word for it. I have looked at so many different things, they all run together, after a while.

The ferrite bead will only help to keep the various caps from resonating, with the trace inductance. I can not remember the last time I built something that did not have some sort of isolation, between stages.

It would also help to keep some nasty HF stuff, from getting into that chip. However, the real culprit is the LF stuff, and the ferrite is of no help, with that.

Even if you power it, from its own supply, there will still be a fair amount of correlated jitter. This is what happens when any clock and the SPDIF signal share the same chip.

Pat

[Firefly]

Trust me, no ferrite bead on pin 14. Only C83 to ground.
And no beads on other chips. They all share the same 3.3V source


Yes, jittery output "Boinggg, boinggg,....". After warm up things get little better, only "boing, boing,.." 
1G to the rescue. I prefer LVC. Or is HC better?

Separate reg from +5V input to +4V. Similar to Hynes reg, but improved. SMT NPN's to isolate each load and land to +3.3V.

No use for noisy voltage reference (1000nV@1Hz) for me  "Mission impossible" to filter 1/f noise out.

[art]

OK, no ferrite bead.............having looked at so many things, for so long, it all starts to look the same.

Anyway..............congrats. We have over 10,000 views, for some of these pics. Never had any idea it would be this popular, and for so long. Some pics are barely to 8000 views, but still impressive that so many of you guys have found any of this useful.

Pat

[Firefly]

closer view, 74HCU04 removed