[groovyd]

We have something special for you today. Lots of things have been said about jitter, and here's our take on the case.


SPDIF iPurifer^®: Jitter Performance Test Results - Part 1/2





Background

To show what the SPDIF iPurifier® can do and how it can improve DACs from the inexpensive through to the very expensive, we used the ‘Jitter Generation’ function of the Audio Precision 2 test system to create a ‘J-Test Signal’ (the industry standard for testing and widely used by magazines, including Stereophile, USA).




The Audio Precision 2 artificially creates a specific, known amount of jitter and then measures how much it is reduced by the SPDIF iPurifier®. Hence it is quite quantifiable AND informative as a measurement tool.






The Methodology

Audio Precision 2 (AP2) generates a signal with 64,130pS of jitter (measured via loopback into AP2) using a square wave waveform at 250Hz. The specific settings are simply chosen to create a gross amount of easily visible jitter. The test results are scaled to be comparable with those by Stereophile (USA).

DACs Tested

The majority of DACs (>80%) in the market use either AKM or Cirrus Logic SPDIF receiver chips, hence one DAC using each of these was selected.

The DACs tested are listed below:

1. DAC 1: AKM based, AK4113 Receiver & AK4490 DAC Chip, RRP US$400

1. DAC 2: CS based, CS8416 Receiver & CS4398 DAC Chip, RRP US$500

1. DAC 3: BB/TC based, TC Audio DICE Chip as Receiver & PCM1792 DAC Chip, RRP US$5,000

The last DAC was included because of two reasons; very high asking price, which indicates its high-end shelf affiliation, and its SPDIF inputs’ specific ‘anti-jitter’ circuitry. It was interesting to see how well it’d work next to DACs with ‘vanilla’ input circuitry.

Stay tuned, there's more!

but here's the thing... any usb hub will remove jitter. they all re-clock.

 

[iFi audio]

but here's the thing... any usb hub will remove jitter. they all re-clock.

USB hubs aren't designed with audio in the first place and oftentimes can make sound audibly worse, on the contrary to our iPurifiers.

 

[gvl2016]

What is the point of reclocking in front of an asyncrhonous USB input anyway? The post linked above btw is for the SPDIF iPurifier, which is a completely different product.

 

[iFi audio]

What is the point of reclocking in front of an asyncrhonous USB input anyway?

Because asynchronous data transfer isn't the be-all and end-all problem solver. There's far more going on than this and we've been vocal about it for years. If you want to know more, please search REclock/REbalance/REgenerate.

 

[gvl2016]

I just wish there was more objective proof on the effect of these devices apart from the manufacturer's claims and subjective reviews.

 

[iFi audio]

I just wish there was more objective proof on the effect of these devices apart from the manufacturer's claims and subjective reviews.

Please take a look at AMR and iFi audio offer. Over the years we released many products, provided very generous insight into our kitchen table (a number of times with measurements where it was helpful to understanding what we actually did) and explanation what these actually are. Our reputation is based many happy customers and all this in general, not claims exclusively. All things considered, we deserve some credit.

Fun fact: you can counter measurements with other measurements and these with yet another measurements.

 

[groovyd]

USB hubs aren't designed with audio in the first place and oftentimes can make sound audibly worse, on the contrary to our iPurifiers.

But the iPurifier3 just uses any old cheap and off-the-shelf usb 2.0 hub IC. How does your usage of it make it any different then a $5 hub that uses the same off amazon? Mind posting photos of the internals front and back and highlighting the components and what makes them exceptional in the context of the circuit? I don't really feel like taking mine apart to prove anyone wrong without them having the chance to prove themselves right. I am an electrical engineer and firmware developer by the way with a masters in signal processing so please let's just skip straight to the facts and drop the superfluous fluff.

 

[gvl2016]

All things considered, we deserve some credit.

Indeed, it's more of a curiosity if USB "conditioners" are still as relevant today due to advances in USB tech.

 

[Jazmanaut]

Please take a look at AMR and iFi audio offer. Over the years we released many products, provided very generous insight into our kitchen table (a number of times with measurements where it was helpful to understanding what we actually did) and explanation what these actually are. Our reputation is based many happy customers and all this in general, not claims exclusively. All things considered, we deserve some credit.

Fun fact: you can counter measurements with other measurements and these with yet another measurements.

Links please!

 

[iFi audio]

But the iPurifier3 just uses any old cheap and off-the-shelf usb 2.0 hub IC. How does your usage of it make it any different then a $5 hub that uses the same off amazon?

Now wouldn't you like to know our secret sauce, would you?

It's not about single components per se but what one does with them. As an engineer you probably know this.

Mind posting photos of the internals front and back and highlighting the components and what makes them exceptional in the context of the circuit?

The description of what makes our iPurifiers exceptional is to be found at http://www.ifi-audio.com/

I don't really feel like taking mine apart to prove anyone wrong without them having the chance to prove themselves right.

Then please don't do that. To us the proof that we did our job right is a generous number of satisfied customers. Some of them early on were very skeptical about what we do, but gave our USB products a go and are happy. If you're not, we can't please everyone. We try though, we really do!

so please let's just skip straight to the facts and drop the superfluous fluff.

We've introduced our tech already and we implement it wherever we can, please take a look at other USB components by us. The same things we do in a number of products.

Indeed, it's more of a curiosity if USB "conditioners" are still as relevant today due to advances in USB tech.

They are. Some DACs are more immune than others, but vast majority can be improved.

 

[Arniesb]

What is the point of reclocking in front of an asyncrhonous USB input anyway? The post linked above btw is for the SPDIF iPurifier, which is a completely different product.

I listen dacs with galvanic isolated, async dacs... None can bring to the table as ifi usb solutions can do. Not even close.

 

[gvl2016]

I had the original USB iPurifier in my chain and it made no difference at best, and frankly I thought it made the sound worse so I got rid of it. These arguments are pointless, we need instrumented tests with concrete DACs to support these kind of claims.

 

[technobear]

I had the original USB iPurifier in my chain and it made no difference at best, and frankly I thought it made the sound worse so I got rid of it. These arguments are pointless, we need instrumented tests with concrete DACs to support these kind of claims.

The iPurifier2 is a far more sophisticated device than the original iPurifier was. I own 3 of them and if any one of them breaks or goes missing, it will be replaced immediately with a new one. All the technical information required is already presented on the iFi Audio website but quite honestly all you need to do is use your ears. If you can't hear the difference then maybe your hearing is simply not that acute or maybe your kit isn't up to the task - an iPurifier2 won't turn a lousy DAC into a great one or enable your headphones to perform beyond their capabilities.

One thing worth noting is that like all electronics, these things perform better when warmed up. A half hour should be enough.

 

[gvl2016]

With this type of devices that (may) affect the sound near the noise floor your ears are a very bad instrument to evaluate their effects. How do you know that whatever that you're hearing is not a sign of added distortions and/or noise? Like I said, these arguments lead nowhere.

 

[Krutsch]

... quite honestly all you need to do is use your ears.

If you can't hear the difference then maybe your hearing is simply not that acute or maybe your kit isn't up to the task...

A-a-a-n-n-n-d... there it is.