RF Attenuators = Jitter Reducers

[jkeny]

Unfamiliar with it.

Does it have an ASRC? Are you happy with it's performance? Do you not know the in & outs of your measuring equipment?

I'll probably change over the analog output to the passive circuit published by Jan Didden as soon as I have a few weeks at home. With well-established levels, restricted bandwidth, and a healthy voltage level, I seriously doubt that the output section is the limiting factor; that's why 3/4 of Gary's page concentrates (rightly, IMO) on the input section where this is not the case.

He's fairly uncompromising & categorical in his condemnation of the analogue output stage!

edit: If you're talking about the DCX input receiver (not the case for my other DAC), I have had problems at spdif levels, but far fewer with higher voltages. It's never done the "dull sound" thing, and I've only had it go frying eggs once. The high output of the Hiface is an advantage here.

Ok so you have issues with SPDIF input into the DCX - the attenuators will reduce the SPDIF level so might this be a problem for the DCX? for listening? Can I ask, if it doesn't sound right how can it be used to measure other devices?

So your M-audio 24/192 is impeccable?

 

[guido]

Guido,

Similar to your analyzer is the tipical TDC, time to digital converter, which is used a lot in physics.

And yes, it can be used to collect the same histograms, like the TIE histograms here. We used these to measure jitter in our experiments a lot of time. Typically these have 45 psec resolution, that is the finest binning.

But there is an important point: seemingly also the scope would have a similar resolution, 25 - 40 - 100 psecs. But. An interpolating algorithm is used, so the crossing time can be extrapolated by a much better precision.
The higher level scopes are good down to 1psec jitter resolution, the best ones are having like 500 femtosec jitter noise floor.

I have seen the built in 50psec rise time square signal generator's jitter: it was gaussian, 1sigma was 1.5psec. In the above histograms it would be a thin line.

Another point: a TDC like instrument collects only histograms, you loose the "private" information of the individual edges, so no time trend reconstruction. Also no FFT of it, no phase noise plots.

Again: a TDC has to be started / stopped at each time. That is, triggered. Also this procedure, producing the trigger, is producing it's own jitter contribution. Not by accident the discriminators used for it are a topic on it's own.
Also conventional scope "eye diagrams" are having the scope trigger jitter included.

In the plots above this is not existent: there was only one trigger at the beginning.

Ciao, George

Ok, ok. Here's one plus for my acient beast: it was only 80 euro's or so and not 35k

 

[sendler]

Any other SPDIF out?

Of which the most educating is the TIE trend trace and the phase noise plot,

Does your M-Audio card have an SPDIF out or is there some other digital source that you have handy to test that we can compare to?

 

[jkeny]

Sendler, are you asking Joseph K to measure an M-audio 24/192 or do you just want another jitter TIE plot to compare the Hiface plots to?

 

[aardvarkash10]

So your M-audio 24/192 is impeccable?

My understanding is that SY has proposed comparative measurement testing - DUT in circuit, DUT out of circuit. Given this, its largely irrelevant whether a source (or sink) is "impeccable" sonically - just that it is consistent.

More important is whether the test equipment can resolve at a suitable level to extract meaningful data, and then of course to logically analyse the data for causation.

As far as listening tests are concerned (and taking as a given that solo, heads-up listening is barely testing - more noodling...), barring gross errors, the same surely applies - the aim is to identify a difference.

 

[jkeny]

My understanding is that SY has proposed comparative measurement testing - DUT in circuit, DUT out of circuit. Given this, its largely irrelevant whether a source (or sink) is "impeccable" sonically - just that it is consistent.

If it can't measure low level details how can it be irrelevant, otherwise why not just use the Realtek motherboard native sound output for measurements?

More important is whether the test equipment can resolve at a suitable level to extract meaningful data, and then of course to logically analyse the data for causation.

Is that not what I'm asking above?

As far as listening tests are concerned (and taking as a given that solo, heads-up listening is barely testing - more noodling...), barring gross errors, the same surely applies - the aim is to identify a difference.

Again, if the unit is sonically inferior how can sonic differences be identified?

I'm flummoxed - objective measurements surely must show that the measurement equipment is of a sufficient standard - are you saying that this isn't the case? I think we've already seen that the DCX2496 isn't up to the job even though SY has stated that it measured perfectly. Now he is changing the output stage after it came under scrutiny - an admission that it is not up to the job. He has also admitted that the DCX has a problem with SPDIF level signals. I'm really amazed that people so tied to measurement are now found to be using measurement equipment so unsuited to the task! - This really calls into question all the measurements previously performed with this unit.

What about the M-Audio 24/192 - what should we know about it's shortcomings?

 

[aardvarkash10]

If it can't measure low level details how can it be irrelevant, otherwise why not just use the Realtek motherboard native sound output for measurements?

Absolutely what i said - just further down the post.

Again, if the unit is sonically inferior how can sonic differences be identified?

To put it crudely, the inferiority or otherwise of a device "sonically" (generally a VERY arbitrary and subjective test) is irrelevant AS LONG AS IT CAN REASONABLY RESOLVE AND IS CONSISTANT.

Try this line - take a plastic trumpet. Play it, and listen to it. Its awful sonically of course, but thats the nature of the beast. Now take a standard trumpet mute and put it on the plastic trumpet. Can you hear a difference? Can you describe the difference?

If you can hear a difference, then its reasonable to conclude that the change is due to the use of a mute. The "quality" of the instrument is irrelevant to our test here.

I'm flummoxed - objective measurements surely must show that the measurement equipment is of a sufficient standard - are you saying that this isn't the case?

Absolutely - and if you have concerns about the equipment, it behoves you to state really clearly what those concerns are, preferably including a set of minima for specs that are required. Hectoring about perceived qualities of the equipment is unlikely to satisfy you or SY.

I think we've already seen that the DCX2496 isn't up to the job ...This really calls into question all the measurements previously performed with this unit. What about the M-Audio 24/192 - what should we know about it's shortcomings?

See above. If you think the device is incapable of performing satisfactorally, explain CLEARLY why and give some guidance for the specifications required to satisfy you.

Disclosure here - all this stuff is technically MILES above my head. I wouldn't know a SPIDF from a spliff. In fact the latter may well be the cause of my inability in this area. None-the-less, i can follow a line of logic and I'm trained in conflict resolution and mediation which requires me to see both sides of any argument, hence my interest here.

Cheers!

 

[jkeny]

......

........

Absolutely - and if you have concerns about the equipment, it behoves you to state really clearly what those concerns are, preferably including a set of minima for specs that are required. Hectoring about perceived qualities of the equipment is unlikely to satisfy you or SY.

No, I'm not the one that is making the claim that I can measure anything that can be heard - it behoves those that do to prove it! I'm not hectoring, simply querying the equipment being used or should this not be done in your opinion?

See above. If you think the device is incapable of performing satisfactorally, explain CLEARLY why and give some guidance for the specifications required to satisfy you.

Obviously the equipment isn't suited - both the analogue output stage & the SPDIF input stage are found wanting? Again, it's not up to me to specify what the specs should be BUT when I see agreed inferior equipment being used for measurement it makes me query the veracity of the measurements being proposed.

Disclosure here - all this stuff is technically MILES above my head. I wouldn't know a SPIDF from a spliff. In fact the latter may well be the cause of my inability in this area. None-the-less, i can follow a line of logic and I'm trained in conflict resolution and mediation which requires me to see both sides of any argument, hence my interest here.

Cheers!

I hope you can follow the line of argument & the logic.

Really, all the measurements that show the effects of attenuators have been already given with the equipment used & test set-up. This is the direct measurement of the effect. This was rejected & analogue measurements proposed. It is not unusual to query the equipment being used & those that proposed the analogue measurement to be able to stand over the equipment (or at least understand the parameters & limitations of it).

 

[aardvarkash10]

well then if you are unwilling to state what IS required to carry out the test to your satisfaction you can expect to be dissatisfied with the results SY brings back.

Moreover, you won't have any comeback. Just like its not enough for someone to stand on the sidelines and sling accusations at you about your device, its not enough for anyone to rubbish a test without clearly and unequivocally stating what IS required to carry it out properly.

This shouldn't be a ******* contest - it should be a quest for answers. That means everyone involved has to make positive input surely?

 

[jkeny]

well then if you are unwilling to state what IS required to carry out the test to your satisfaction you can expect to be dissatisfied with the results SY brings back.

Moreover, you won't have any comeback. Just like its not enough for someone to stand on the sidelines and sling accusations at you about your device, its not enough for anyone to rubbish a test without clearly and unequivocally stating what IS required to carry it out properly.

This shouldn't be a ******* contest - it should be a quest for answers. That means everyone involved has to make positive input surely?

Look I'm not the expert in analogue measurement - others claim they are - it is up to them to say what they use & how it does the job. Sorry if you don't want to understand this but this is a typical tactic!

The DCX is inferior & all it's measurements are in question - so I suggest you revisit any results from this equipment!

You are now trolling so no more answers from me!

 

[SY]

Can I ask, if it doesn't sound right how can it be used to measure other devices?

So your M-audio 24/192 is impeccable?

I think, with levels set correctly and a digital input, that the Behringer sounds fine, so I disagree with the premise of your question. I was less happy with the analog inputs.

I use the M-Audio 192 for measurement, not the Behringer. Yes, from an audibility POV, the 192 is impeccable. When I use the Behringer, it functions as a crossover as well- when I listen to the 192, I use an analog electronic crossover based on the Heretical preamp and a gyrator, which is also described on my website.

Any other details about my listening system you need to know?

Now he is changing the output stage after it came under scrutiny - an admission that it is not up to the job.

No. It's an admission that the output level is too high- it's set up for studio levels, not home levels.

 

[aardvarkash10]

hmmmn. O-kay then...

Lets review...

You are not an expert in anologue measurement, but you know what won't work.

The DCX is in question, but you can't or won't give specifics on your concerns.

And I'm a troll.

You have the answers to your concerns in your own hands, but seem unwilling or incapable of applying them. Sorry if you don't want to understand this but this is a typical tactic.

Cheers and good luck withthe experiment.

 

[jkeny]

I think, with levels set correctly and a digital input, that the Behringer sounds fine, so I disagree with the premise of your question. I was less happy with the analog inputs.

You disagree with Gary Pimm's analysis of the analogue output stage & his reports about the sound?

I use the M-Audio 192 for measurement, not the Behringer. Yes, from an audibility POV, the 192 is impeccable. When I use the Behringer, it functions as a crossover as well- when I listen to the 192, I use an analog electronic crossover based on the Heretical preamp and a gyrator, which is also described on my website.

Any other details about my listening system you need to know?

So can you tell me the test set-up - what DAC will you be playing the Hiface through & measuring the analogue output?

No. It's an admission that the output level is too high- it's set up for studio levels, not home levels.

It's trivial to adjust for this level in your measurements - why change the output stage?

 

[SY]

It's trivial to adjust for this level in your measurements - why change the output stage?

I use the Behringer in my system for listening. It's inconvenient to have a 7V output and keep the volume control turned down low. A few Rs and Cs fixes the problem.

The comparison in measurements of the analog outputs between the modified Hiface and the cheap Chinese unit will be done on both DACs.

...the requirement of handling the full range of pro-sound voltages on the input and output seriously compromise the unit when used for home levels. For best performance the input and output circuits should be configured to match the needed gain structure of your system.

Seems he and I agree.

 

[wakibaki]

And I'm a troll.

Yes, but still afloat. I see jkeny has conveniently forgotten that he has already lost this argument.

w

 

[ThorstenL]

Hi Jospeh,

A TEK 7354. 35 000 Euro, in case You wanted to ask... Stock, without the jitter analysis package. That can cost another 10000 in a worst case.

You know that from now on I officially hate you, right!

Nah, I'm not small. Good on you. Maybe if I need something tested I can fly over and convince you to do it together after hours, using this nice, nice Tek 'scope?

Maybe my company can afford one a year or two after all this economic crisis ** has blown over...

Ciao T

 

[abraxalito]

Second, both of the DACs I actually use measure better than -115dB to the noise floor and THDs below 0.002%.

This claimed -115dB - its read right off the FFT baseline as before right? And you're still acting coy about how many bins in the FFT?

I'm not much impressed by internet stories and ex cathedra proclamations from self-appointed gurus with, ahem, honesty issues.

Let's unpack this a little. I'm presuming that the 'self-appointed guru with honesty issues' is T right? So where's the authority you ascribe to him?

 

[wakibaki]

You are not an expert in anologue measurement, but you know what won't work.

The DCX is in question, but you can't or won't give specifics on your concerns.

aardvarkash10 has torn a large hole in your forensics.

Tell us under exactly what conditions the differences are audible.

I see ThorstenL, despite his bluster, nevertheless declines to undertake testing himself.

I see Joseph K is happy to submit shots from which he infers a difference, but is unable to produce shots which demonstrate a difference in the analog output.

jkeny will tell us which equipment produces the audible difference.

ThorstenL and Joseph K will tell us what standard of analog test will satisfy them.

Between us we will contrive to test the equipment to a standard agreeable to all.

jkeny, ThorstenL, Joseph K; respond to these points or once again be seen to be being insincere.

w

 

[ThorstenL]

Hi 'baki,

ThorstenL, Joseph K; respond to these points

I see no points to respond to. Given the lack of credible test equiment involved and the lack of sensible protocols for the DB Testing, including any calibration in either test that sets confidence levels and that would allow to verify that the test can at least distinguish differences know to be measurable and/or audible, I can only regard this whole thing as a very funny joke and laugh even louder, as the alternatives seem to negative and impune severely on the characters of several of those involved.

So I respond with:

Splendid Joke old man, not laughed as much since Monty Pythons "Nudge Nudge, Wink Wink" Skit and the Norwegian Blue Parrot, which the whole things seems to largely resemble, really dogs bollocks of all jokes...

Ciao T

 

[ThorstenL]

Hi 'baki,

I see ThorstenL, despite his bluster, nevertheless declines to undertake testing himself.

I'm under some contractual obligations not to. Actually I can undertake testing all sorts of things (I often do), but in many cases I would be breaching confidentiality agreements, non-disclosure agreements and other undertakings if I did make the results public. In the case of almost anything USB Audio that is not Musiland I have signed NDA's far and wide.

But I would be happy to advise on appropriate procedures and equipment for the tests, both technical and listening, if the tests are meant to provide meaningful results that have at least some claim on significance.

I could also advise how to set up tests to provide reliable if spurious negative results, but it seems that side of things is well in hand.

BTW, you are also quite funny, but not as funny as Sy, sorry old man, not even place two, that goes to the geezers over at Jocko Homo's place.

Ciao T