RF Attenuators = Jitter Reducers

[rfbrw]

For the Krell owning types.

[regal]

Originally Posted by wakibaki

jkeny

Does a capacitor pass AC but not DC? It's a FACT. .

it depends , in the real world we don't deal with DC, there is always some amount of sub 1hz frequency that passes thru caps and presents itself as DC (for all practical purpose.) And all caps have leakage.

I guess what I am saying is in text books things are cut and dry, but after you close the books and start working you will learn its not all black and white in the real world. If you keep a closed mind you will never grow as an engineer.

Just because an SPDIF is terminated at 75 ohms on the receiving end doesn't make it perfect. I think you need to spend some time on the bench with a scope.

[jkeny]

Originally Posted by abraxalito

Curious - how do you know what jitter sounds like? Have you managed to isolate the effects of jitter so you're sure you're hearing it on its own? If so, I'd like to know how you did this.

I modified a Hiface unit & the only change was to provide a clean clock supply - huge difference in sound - it agreed with all others who report the same - it agrees with the various descriptions of the sound of jitter that I've read - you even seem to know this yourself in your soundstage statement below - what else do you want to attribute this one change to?

My guess here is its also affecting the RF intermodulation, not just the jitter. I get 'slight edge and sibilance' from not paying attention to RF issues. I do agree that jitter affects the definition of soundstage images. So I hypothesise that you're reducing two effects here, not just one.

Oh great, so you agree that it's reducing jitter & NOW you have another effect that you are attributing to it using guesswork. I've already pointed out that there are measurements of the reduction in reflections - why do you have to GUESS that something else is at work?

[jkeny]

Originally Posted by rfbrw

For the Krell owning types.

Oh yeah baby, it's bigger & industrial looking, so it must be better - I'll have two of them & hopefully they are very expensive so then I'll know that they are better than the $12 ones & can tell everybody so

[jkeny]

Wakibaki,
I'm not suggesting that anybody wilfully did anything - just mistakenly made the same assumption you do & said "there's a 75R in there so our termination is perfect" - as Regal says a bit of measurement may reveal otherwise. Have you ignored the TDR plots I've been mentioning throughout all this which shows reflections in a "properly terminated" system & how these were measurably reduced when an attenuator was used? This termination was done according to the application note in the TI DIT4192 datasheet (& don't tell me that I now think I know better than Texas Instruments - just look at the plots)

[abraxalito]

Originally Posted by jkeny

I modified a Hiface unit & the only change was to provide a clean clock supply - huge difference in sound - it agreed with all others who report the same - it agrees with the various descriptions of the sound of jitter that I've read - you even seem to know this yourself in your soundstage statement below - what else do you want to attribute this one change to?

Nothing to do with 'what I want' here - why make it into something personal? Cleaning a clock supply will also have the effect of reducing the RF content on the supply don't you think? Tell us more about how you cleaned the supply and what the cleaned supply was connected to on the board - I guess a clock osc but anything else besides that?

Oh great, so you agree that it's reducing jitter & NOW you have another effect that you are attributing to it using guesswork. I've already pointed out that there are measurements of the reduction in reflections - why do you have to GUESS that something else is at work?

Its because of what I said earlier - perhaps you did not read carefully, So I'll say again - because in my experience sibilance is not caused by jitter, its caused by RF intermodulation. Reductions in reflections result in lower jitter you think? Any measurements to demonstrate that?

[jkeny]

Originally Posted by abraxalito

Nothing to do with 'what I want' here - why make it into something personal?

That's just a turn of phrase nothing else!

Cleaning a clock supply will also have the effect of reducing the RF content on the supply don't you think? Tell us more about how you cleaned the supply and what the cleaned supply was connected to on the board - I guess a clock osc but anything else besides that?

It went from a regulator to a battery supply but I'm not going to argue with you on this - you have your opinion that's fine!

Its because of what I said earlier - perhaps you did not read carefully, So I'll say again - because in my experience sibilance is not caused by jitter, its caused by RF intermodulation. Reductions in reflections result in lower jitter you think? Any measurements to demonstrate that?

First, I'm sure you understand that reflections arriving at the receiver during the decision window will superimpose a voltage onto the transition signal which will cause the decision point to shift to where it should be. Is this jitter? As to measurements - look at the TDR plots on DiyHiFi.org - it's plain as day!

[abraxalito]

Originally Posted by jkeny

It went from a regulator to a battery supply but I'm not going to argue with you on this - you have your opinion that's fine!

So you cite avoidance of a non-existent argument as an excuse to avoid answering my question? Put your analyst on danger money baby

First, I'm sure you understand that reflections arriving at the receiver during the decision window will superimpose a voltage onto the transition signal which will cause the decision point to shift to where it should be. Is this jitter? As to measurements - look at the TDR plots on DiyHiFi.org - it's plain as day!

Ah but not 'plain as day' to me as I haven't been invited to join diyhifi even though I've applied. Without membership the attachments are invisible - one practical outworking of Jocko's paranoia.

[jkeny]

Originally Posted by abraxalito

...................
Ah but not 'plain as day' to me as I haven't been invited to join diyhifi even though I've applied. Without membership the attachments are invisible - one practical outworking of Jocko's paranoia.

So you don't disagree about how reflections cause jitter, then! If that's the case then reducing them should be a good thing, no?

[abraxalito]

Originally Posted by jkeny

So you don't disagree about how reflections cause jitter, then!

I'm not sure how you got that from what I said. I'm open to being convinced but as I've seen no evidence I'll remain sceptical.

If that's the case then reducing them should be a good thing, no?

Reducing reflections in isolation I'd say would be good. However, padding the line does not do that, as Jan has already pointed out. So I remain somewhat sceptical.