Hello World! I'm new (enthusiast) in Hi Fi community (in general). I possess a pair of AR10Pi and a pair of cheap B&W DM302, Sansui AU-4900 integrated amp and another cheap integrated amp of exotic brand (Continental Handels) that's class A from mid 80' (made in Japan). I'm planning to invest in better pre and better power amp in near future. I'm not fooling myself that I'm going to setup turntables and play discs ... That's why I've decided to buy/build a DAC. Actually not only a DAC but all-in-one solution with built-in offline player and online streamer.
So I'll connect my cheap and compact DAC to Raspberry Pi with I2S (the problem of not getting 24 bit stream over I2S is solved now).
I have a question if is possible to galvanic isolate I2S connection and how.
I'm chosing between Sellarz Audio's DAC-24192-ABR and Audiophonics' I-Sabre DAC ES9023 Raspberry Pi A+ B+ / I2S.
Please, write down your opinion on both DACs, their PSU, clocks, signal path, used elements (especially caps) IC implementation and sound if you tried one of them.
Both are asynchronous.
I see some advantages buying Sellaz Audio's as it has integrated high precision clock (AUdiophonics' has it too) and ultra low noise regulator circuit. What do you think? The built quality seems good too.
I understand that IC amplifications is limited and not as good as analog. I know that signal is very vulnreable (especially for loss of dynamic) at it's source where the voltages are lowest.
I'm planing to use this DAC with separate pre or integrated amp and not with power amp directly (I dunno input voltage sensitivity of my two integrated amps).
What do you think, what can be modified on this board? And why (thanks for short explanation).
What do you suggest for powering this (with RPi) at 5VDC? If I galvanic isolate I2S connection I can power it with cheap linear PSU (as DAC has ULN regulation already). Correct me if I'm wrong.
I have basic knowledge and skills in electronics (I know basic proprieties of elements, I can do some basic calculations, I'm good in soldering but I do not understand logic behind analog signal processing/amplification). I have some good handbooks and I'm willing to learn more. And definitely it's not going to be my only DAC. Next step (I hope in this year) will be in direction of building top performing DAC with budget up to 1k.
All the best,
Matija
So I'll connect my cheap and compact DAC to Raspberry Pi with I2S (the problem of not getting 24 bit stream over I2S is solved now).
I have a question if is possible to galvanic isolate I2S connection and how.
I'm chosing between Sellarz Audio's DAC-24192-ABR and Audiophonics' I-Sabre DAC ES9023 Raspberry Pi A+ B+ / I2S.
Please, write down your opinion on both DACs, their PSU, clocks, signal path, used elements (especially caps) IC implementation and sound if you tried one of them.
Both are asynchronous.
I see some advantages buying Sellaz Audio's as it has integrated high precision clock (AUdiophonics' has it too) and ultra low noise regulator circuit. What do you think? The built quality seems good too.
I understand that IC amplifications is limited and not as good as analog. I know that signal is very vulnreable (especially for loss of dynamic) at it's source where the voltages are lowest.
I'm planing to use this DAC with separate pre or integrated amp and not with power amp directly (I dunno input voltage sensitivity of my two integrated amps).
What do you think, what can be modified on this board? And why (thanks for short explanation).
What do you suggest for powering this (with RPi) at 5VDC? If I galvanic isolate I2S connection I can power it with cheap linear PSU (as DAC has ULN regulation already). Correct me if I'm wrong.
I have basic knowledge and skills in electronics (I know basic proprieties of elements, I can do some basic calculations, I'm good in soldering but I do not understand logic behind analog signal processing/amplification). I have some good handbooks and I'm willing to learn more. And definitely it's not going to be my only DAC. Next step (I hope in this year) will be in direction of building top performing DAC with budget up to 1k.
All the best,
Matija
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The ES9023 DAC has on-board opamps. They can't be bypassed so the way to make them corrupt the sound the least is give them no load to drive and the cleanest possible power supply. Thus a JFET buffer followed by an ultrasonic filter is called for. To clean up the power supply I'd install LC filtering with plenty of low ESR electrolytic and ceramic caps directly across the power rails of the chip.
Does the board have a JFET buffer or does the ES9023 drive the low-pass filter directly?
Yes its possible to isolate I2S using transformers - 3 Pulse Engineering S/PDIF transformers should work but I haven't tried it. You would need to add logic to modulate the data line (an XOR gate with one input fed from the clock) and I'm not sure if the word clock frequency is high enough to pass through one of those trafos. I will go and check though.
<edit> Having checked the specs for the PE65612 they're good for 20V-uS which means you'd have to attenuate the word clock to around 1V peak-peak and then have a comparator at the receiving end to get back to logic levels. A bit of a work-up I must admit.
Ah I see there's only an LC filter for power, not for the signal.
Yes its possible to isolate I2S using transformers - 3 Pulse Engineering S/PDIF transformers should work but I haven't tried it. You would need to add logic to modulate the data line (an XOR gate with one input fed from the clock) and I'm not sure if the word clock frequency is high enough to pass through one of those trafos. I will go and check though.
<edit> Having checked the specs for the PE65612 they're good for 20V-uS which means you'd have to attenuate the word clock to around 1V peak-peak and then have a comparator at the receiving end to get back to logic levels. A bit of a work-up I must admit.
Ah I see there's only an LC filter for power, not for the signal.
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I think that this board doe not have JFET buffer but I did ask the seller about this technical detail.
Yes, is a lot of work for media player + DAC under $150 in total. As Raspberry Pi A+/B+ have integrated non-linear PSU for powering CPU I'm afraid that I'll get noise from this it even if I'll be using low noise PSU. A/B model version had linear PSU for that. Another risc is to get noise over shared main (external) PSU but there is LC filter for that.
This is my first project and good point to start learning, that's why I've decided to modify it with I2S isolation. It will take me into study (it far exceeds my level of knowledge).
Yes, is a lot of work for media player + DAC under $150 in total. As Raspberry Pi A+/B+ have integrated non-linear PSU for powering CPU I'm afraid that I'll get noise from this it even if I'll be using low noise PSU. A/B model version had linear PSU for that. Another risc is to get noise over shared main (external) PSU but there is LC filter for that.
This is my first project and good point to start learning, that's why I've decided to modify it with I2S isolation. It will take me into study (it far exceeds my level of knowledge).
Thinking once again about I2S isolation, these chips from Analog Devices are probably a much better bet - ADUM3300 datasheet and product info | Triple-Channel, Digital Isolator, Enhanced System-Level ESD Reliability (3/0 channel directionality) | Digital Isolators | Analog Devices
Hi the Subbu V3 PSU is too light for that. You could use this one when it becomes available:
http://www.diyaudio.com/forums/digital-source/264185-squeezebox-touch-psu.html
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