Wadia iTransport and jitter - RH review

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mr_bill

Wadia iTransport and jitter - RH review
« on: 29 Mar 2009, 03:15 pm »
If you just read Robert Harley's March review of the iTransport on AV Guide, you may be thinking like me - this is a great transport (if you have a good dac that reclocks/rejects jitter).

Robert plays with the big expesnive equipment and is an very revered reviewer and if he says that the iTransport sounds better than CD transports, then I believe him.

So, what's the big concern over jittter then, if the Wadia measures so poorly in jitter and uses a cheaper high jitter chip?

I'm beginning to think all this talk about high jitter and this transport being so much better than this one is a lot of hooey.

The discless transports (Duet, Wadia iTransport) seem to have an edge - don't they!? 

Read the review.

champ10

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Re: Wadia iTransport and jitter - RH review
« Reply #1 on: 27 May 2009, 04:22 pm »
The current issue of stereopile has an update from JA which adresses the high jitter output of the iTransport.

I have to admit that I have found this all equally baffling. I also tend to trust RH. Especially since I have compared my iTransport to exactly the same source he did. (Esoteric P-03,D-03,G-0rb) And I came to the same conclusions he did. BEFORE he published his findings.

I know jitter matters. I just dont understand the discrepency here. Maybe there is an advantage to HDD vs. cd that we arent seeing yet?

art

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Re: Wadia iTransport and jitter - RH review
« Reply #2 on: 9 Jun 2009, 06:36 am »
As a manufacturer, I have to be careful what I say. But let me put this in a way that many of you can probably relate to.

If we put out a product that had as much jitter as the Wadia, do you think that it would get a good review?

Yeah, we all know the answer to that.

JA's assertion appears to me that jitter is the DAC's problem to deal with. Again, if our latest product had that much jitter........


BTW, out latest product has less jitter than the last CD transport that we built.

Getting back to the technical side of things:

There are 2 ways to take care of the jitter the transport creates. One uses a ASRC. Some of us designers feel that any ASRC is going to do something to the sound, and what it does isn't always for the better. The internal math functions of them is simply not enough to do the job the right way. IOW, without lots of internal truncation of data. You can not pass HDCD data through one, if that gives you any clue as to how much they operate on the sound.

The other way is with a secondary analog PLL. (An ASRC is essentially a PLL, done in the digital domain.) The harder the PLL has to work to correct the incoming data, the more likely it will be to affect the sound in an undesirable manner.

All PLLs have a range, both upper and lower, over which they are effective. To be really effective, they have to go very low. But this affects lock-up time. The worst jitter is the really nasty stuff that is close to the carrier frequency.

All of the jitter tests use test tones, of one sort or another. Things change a lot with music present. There is an extremely high correlation to jitter and the music. If you were to listen to the PLL pin on any SPDIF RX chip, you can make out what you are listening to.

So, in practice, while a "good" DAC can handle the incoming jitter and clean it up, it is not a perfect cure-all.

Make any sense to you guys?

Pat

mr_bill

Re: Wadia iTransport and jitter - RH review
« Reply #3 on: 9 Jun 2009, 01:38 pm »
Yes, and thanks for that answer.
Hurry up and get your Duet transport mod finished! :D

art

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Re: Wadia iTransport and jitter - RH review
« Reply #4 on: 9 Jun 2009, 05:22 pm »
Uh.....I have some PCBs here with some errors on them. Have to make some changes the old-fashioned way.

Been meaning to mention that in the Duetta thread, but I forgot! Willing to part with those for a decent discount. Interested?

pat