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Topic: Hifiberry DAC+ and jitter and linear PSU issue (Read 4352 times) previous topic - next topic
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Hifiberry DAC+ and jitter and linear PSU issue

Hi,
I am new in the audio community. Of the month I am a happy user of Raspberry pi with Hifiberry DAC+ > Objective2 amp > Beyerdynamic DT 880 PRO system. Unfortunately I have read a lot of posts on "audiophile" forums and now I am little bit confused. Fortunately finally I found this forum. I would like to ask two questions:
- does the issue of jitter on raspberry pi (i2s) really matter? Or can I relax myself? After reading this forum, it looks that this is not an issue. But If this is truth, why do they realised Hifiberry DAC+ PRO?
- do I need linear PSU or can I stay with standard raspberry power supply?
Thanks in advance for all comments.

Re: Hifiberry DAC+ and jitter and linear PSU issue

Reply #2 –
I have found this blog too. But this is about DAC+ PRO, not about DAC +. That is what I am asking and why I am little bit confused.

Re: Hifiberry DAC+ and jitter and linear PSU issue

Reply #3 –
Quote from: gizegoiz on
- does the issue of jitter on raspberry pi (i2s) really matter? Or can I relax myself? After reading this forum, it looks that this is not an issue. But If this is truth, why do they realised Hifiberry DAC+ PRO?

I2S on the RPi is created using a 19.2MHz crystal oscillator, which cannot create the bit clock for 44.1kHz using an integer number of clock cycles, so jitter is intentionally created by the Broadcom chip by varying the divisor to create the bit clock. This problem does not occur with a 48kHz sample rate or multiples thereof.

The Archimago blog post Saratoga links to above will help you understand things, but keep in mind he tested the DAC+ Pro.

Jitter is one of those things where you have to decide whether hearing a difference is important or just knowing it exists bothers you. In the general audio section here, there's a sticky on how to do such a listening test. But I don't know whether a favorite software solution here, Foobar2000, works with Linux. I'm guessing you're using Raspbian, or is it something else? I'm sure others here know.

Edit: Oops, just saw that you already know the Archimago blog.

Re: Hifiberry DAC+ and jitter and linear PSU issue

Reply #4 –
So basically that pro DAC just includes its own PLL, which is why it doesn't have that problem?

Seems like repeating that blogs measurement of a pure tone would make it very clear how valuable the PLL is.

Re: Hifiberry DAC+ and jitter and linear PSU issue

Reply #5 –
Quote from: saratoga on
So basically that pro DAC just includes its own PLL, which is why it doesn't have that problem?
The DAC+ Pro has 2 crystal oscillators, one for 44.1/88.2/176.4kHz and one for 48/96/192kHz.
The idea of a pure tone test is useful, but there is certainly jitter (intentional) on the I2S using 44.1kHz. The DAC+ Pro is only 40 euros (about 40 bucks), so even if you try a critical listening test and decide you can't hear anything, the Pro won't break the bank (sorry, assumption).

Re: Hifiberry DAC+ and jitter and linear PSU issue

Reply #6 –
But with dac+ pro raspberry runs as clock slave.

Re: Hifiberry DAC+ and jitter and linear PSU issue

Reply #7 –
Quote from: gizegoiz on
But with dac+ pro raspberry runs as clock slave.
?? The I2S would be. Is that a problem? If so, you can configure the DAC+ Pro to be slave, but then why get it?

Re: Hifiberry DAC+ and jitter and linear PSU issue

Reply #8 –
Quote from: bobbaker on
Quote from: saratoga on
So basically that pro DAC just includes its own PLL, which is why it doesn't have that problem?
The DAC+ Pro has 2 crystal oscillators, one for 44.1/88.2/176.4kHz and one for 48/96/192kHz.
The idea of a pure tone test is useful, but there is certainly jitter (intentional) on the I2S using 44.1kHz. The DAC+ Pro is only 40 euros (about 40 bucks), so even if you try a critical listening test and decide you can't hear anything, the Pro won't break the bank (sorry, assumption).

Yeah but it sounds like he already owns the older model, so he is trying to understand if an upgrade makes sense.