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Old 30th June 2004, 05:24 PM   #11
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The impedance pertubations were actually higher, when viewed on the TDR.

Jocko
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Old 1st July 2004, 05:20 AM   #12
Prune is offline Prune  Canada
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The problem is that the nice pulse transformers I use for termination on the DAC side aren't cheap, and terminating each of the inputs with them before feeding into a multiplexer is not something I can afford. That's why I only used one transformer after relays. Also someone pointed out where to buy 50 ohm coaxial relays, but S/PDIF is 75 ohm. On top of this, my manual and remote control system is set up for latching relays, and I've never found any 75 ohm latching relays.
I wonder if I just leave the non-coax relays I have in, would there be any improvement if I were to shield them with grounded foil, or would that make it even worse?
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Old 1st July 2004, 07:35 PM   #13
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I used relays for the same reason.

Foil over them??? I don't see any reason for it.

There are so many things that cause reflections, that you might have more than you realise already. I have seen some DACs where they run several inches of twisted pair wire into some big caps (physically, not electrically), and then some PCB traces....and finally into the RX chip.

(And a chip that I hate, but we won't go into that..........)

But speaking of which.....it causes a boatload of relections all by itself.

Bottome line......

You would be amazed by how much crap you can get away with, and still have it work. The jitter may be off the scale, but it will work.

You probably have around 1 nSec jitter in your setup to begin with, even with everything working at 100%. So you add another nanosecond or so.......

Getting that extra amount out takes lots of work, and fancy test equipment. Trust me.

Jocko
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Old 1st July 2004, 07:50 PM   #14
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Default If you only needed one input......

And were concerned about reflections........

And had has much money as The King of Chip Amps.........

(Like any of us do!)

You could build one of these:

Input return loss is >30 dB.

Jocko
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Old 1st July 2004, 08:20 PM   #15
tiroth is offline tiroth  United States
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I'll take three. Thanks.

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Old 1st July 2004, 09:22 PM   #16
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Default OK......then.....

Take up a collection, and I'll build more.......

Jocko
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Old 1st July 2004, 09:28 PM   #17
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Thumbs up Groupbuy

I take two!
Looks neat.
Well done Jocko!
How about a ......."groupbuy"?. (hardly dare to speak out the word!)
Edit: what is that black squarish thingy?
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Old 1st July 2004, 09:35 PM   #18
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Default Sure you are still interested???

Any and all profits go the the Jocko Homo Avoid Bankruptcy Pizza Fund.

Here is the back view.......big enough to see, but too small for the "vacuum cleaners" to get the component values.

Heh-heh.


Jocko
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Old 2nd July 2004, 12:22 AM   #19
tiroth is offline tiroth  United States
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Default Re: Groupbuy

Quote:
Originally posted by Elso Kwak
Edit: what is that black squarish thingy?
Transformer I would guess. I think I have this schematic on a napkin somewhere...
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Old 2nd July 2004, 07:37 AM   #20
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Default Re: Sure you are still interested???

Quote:
Originally posted by Jocko Homo
Any and all profits go the the Jocko Homo Avoid Bankruptcy Pizza Fund.

Here is the back view.......big enough to see, but too small for the "vacuum cleaners" to get the component values.

Heh-heh.


Jocko
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Jocko

I'll take 4; pl email.

Fred
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