Pro-Ject Pre Box S2 Digital: MQA HW decoding at reasonable cost

[trl]

Really interested thread about this DAC, I'm looking further for someone testing it with a linear PSU as well.

I like the idea of dual ES9038 DAC; with a bit of tinkering and re-wiring this could be a decent balanced DAC as well (well, at least by looking at chip specs and ESS recommended design).

[trl]

I would suggest more than 5V batteries, then a DC-DC step down low noise & low dropout regulator. You really need a very stable power supply for the DAC. Also, try not using the power banks with lithium batteries inside...they tend to have lot of ripple & noise from their SMPS DC-DC buck converters!

[trl]

59 minutes ago, Mark Dirac said:

Thanks trl. If what you want is stability, then you cannot get a more stable supply than batteries plus a low-inductance capacitor. Now - that may not be good enough (low impedance at all frequencies? In-rush current control? Something else?) - but it will be stable.

Batteries are not stabilized over time, so now you might get 1.24V/element and after few hours you could be getting 1.19V/element. So, I still think a 7.2V battery followed by a low-drop & low-noise regulator could be better.

[trl]

It's a ES9602Q small headphone amplifier chip that can be used for monitoring and low-volume listening, especially for high sensitivity cans. Most likely an external headamp might help if using planars or high impedance headphones.

[trl]

7 hours ago, left channel said:

A new and very comprehensive review, via @MagnusH in his pinkfishmedia incarnation:

https://headfonics.com/2018/03/pro-ject-audio-pre-box-s2-digital-review/

 

 

Not sure I fully understand the "stepped attenuator" syntagm; AFAIK volume control it's done inside the ES9018 chip, so the volume is not controlled analogically via a real resistive stepped attenuator. 

 

P.S.: I usually associate the "stepped attenuator" with an expensive resistive attenuator device, so please take my above statement with a grain of salt.

[trl]

Perhaps a new firmware might correct this tiny issue with the "wake up".

[trl]

@fgribas: Why do you want to use a power bank to power your DAC for? I found a couple of USB ports on my desktop computer with less than 1mV RMS of AC ripple & noise, which is quite acceptable.

 

I've attached 6 pics from 3 devices tested by myself recently:

- pics 1&2 from a CANYON +5V power bank: 20.2mV AC ripple & noise

- pics 3&4 from a DURACELL +5V power bank: 0.482mV AC ripple & noise

- pics 5&6 from a LENOVO 90W power adapter with USB hub included: 0.664mV AC ripple & noise

 

However, after looking at the FFT (2nd pic for each device) you'll realise that both power banks are SMPS (DC-DC boost boost converters) and the best FFT is from the LENOVO USB hub.

 

However, you could find a low-noise USB port in your computer if you dive deep into this...or you could purchase a +5V linear PSU from eBay. Also, DIYAUDIO forum has a couple of good users building cheap and very good +5V LPSU. One thing's for sure: stay away from power-banks, unless you have a scope around to measure how +5V signal looks like...or if the power bank is really designed for audio (7.2V battery with linear regulators inside!).

[trl]

2 hours ago, buonassi said:

[...]

• capacitors - questionable quality[...]

These are 2.000h rated caps able to handle AC ripple extremely well, that means after 2.000h @105C AC ripple handling will get cut in half. I would really not care about these caps, honestly.

 

Have you seen the Cap-Top or CapXon caps from inside JBL, Mackie a.s.o. audio equipment?

[trl]

The review from ASR was indeed quite positive, showing a very good performance and a very low noise on outputs.