JohnW
pfm member
This is indicative of low input mains voltage - maybe heavy load due to winter heating / electric ovens....
If you Push and Hold the level knob during power-up the MDAC will display the input voltage - we have about 15.8V here....
MDAC First Listen (part 00110100)
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This is indicative of low input mains voltage - maybe heavy load due to winter heating / electric ovens....
If you Push and Hold the level knob during power-up the MDAC will display the input voltage - we have about 15.8V here....
I've been experimenting recently with RPi power supplies over the break. I have been powering my RPi3 with a linear power supply for some time but took it further...
Firstly, a nice chap in Denmark told me that an immediate improvement in sound quality can be achieved by bypassing the standard miniUSB power socket and connecting the 5v supply directly to the GPIO pins (pin 2 = 5v; pin 6 = GND). This is very simple to effect and did, indeed, offer an immediate improvement.
The chap in Denmark then went further. He found that the Pi's onboard voltage regulator (to supply 1.8, 3.3 and 5v to various parts of the board) could be improved upon. He removed the existing regulator and built his own with better quality regulators, capacitors and heat sinks and continued with the GPIO connections for the 5v and wired the other two voltages directly to the appropriate points on the board. A further improvement. I have followed this path and can confirm a small but noticeable incremental improvement.
The chap in Denmark's latest move has been to replace the onboard oscillator with a very high accuracy external clock board which he is also pleased with. I think I'll draw the line at that one for now.
For the record, I run RuneAudio on my Pi. I never get pops, clicks or other distractions - just beautiful music controlled from my tablet or phone.
Lastly, if there's anyone in (or in reasonable travelling distance of) Cambridgeshire who would like to have a listening session with their quality streamer against my modified Pi, it would be interesting to compare my unit's performance against a known reference.
Apologies is this is felt to be slightly off topic but the RPi appears to be experiencing a reprieve for the FDAC so thought it might be of interest.
Firstly, a nice chap in Denmark told me that an immediate improvement in sound quality can be achieved by bypassing the standard miniUSB power socket and connecting the 5v supply directly to the GPIO pins (pin 2 = 5v; pin 6 = GND). This is very simple to effect and did, indeed, offer an immediate improvement.
The chap in Denmark then went further. He found that the Pi's onboard voltage regulator (to supply 1.8, 3.3 and 5v to various parts of the board) could be improved upon. He removed the existing regulator and built his own with better quality regulators, capacitors and heat sinks and continued with the GPIO connections for the 5v and wired the other two voltages directly to the appropriate points on the board. A further improvement. I have followed this path and can confirm a small but noticeable incremental improvement.
The chap in Denmark's latest move has been to replace the onboard oscillator with a very high accuracy external clock board which he is also pleased with. I think I'll draw the line at that one for now.
For the record, I run RuneAudio on my Pi. I never get pops, clicks or other distractions - just beautiful music controlled from my tablet or phone.
Lastly, if there's anyone in (or in reasonable travelling distance of) Cambridgeshire who would like to have a listening session with their quality streamer against my modified Pi, it would be interesting to compare my unit's performance against a known reference.
Apologies is this is felt to be slightly off topic but the RPi appears to be experiencing a reprieve for the FDAC so thought it might be of interest.
TwoSeventy
pfm Member
The reason I put together a Raspberry Pi streamer is that my Windows based setup was playing up and didn't work consistently well headless. The surprising thing was the improvement in sound quality. I had ordered the iFi supply at the same time but it was due to arrive later so I got a generic supply first and then replaced this with the iFi supply. The Raspberry Pi with the generic supply sounded better than the Windows setup and further improved with the iFi supply. As the Raspberry Pi is connected asynchronously via USB with an Olimex isolator in between it is curious that sound quality differences exist at all.
Measurements of MicroRendu -> iFi iDAC2 with various PSU's incl iFi's:
- - > http://audiosciencereview.com/forum...asurements-of-sonore-microrendu-streamer.577/
TwoSeventy
pfm Member
Thanks. I am using the Raspberry Pi with the MDAC with it's regular power supply and still not sure how an asynchronous isolated USB connection can be affected by the streamer (Raspberry Pi) and different power supplies.
JohnW
pfm member
When you hear the effect Detox has on the Async USB sound quality then that's even more surprising!
What I've termed "Second order" effects such as RF and Ground loops - even Jitter on the Asycn USB Data stream have a surprising impact on audio quality.
JohnW
pfm member
If I read the thread correctly? the perfomance is MUCH worst with iFi PSU?
It appears the typical problem of the SMPS "Y" Cap injecting Earth leakage currents account for the horrendous 60Hz related noise when using the iFi Switching supply.
TwoSeventy
pfm Member
Other points of view on the iFi power supply and the MicroRendu testing:
http://www.head-fi.org/t/761310/ifi...tra-low-noise-ac-dc-adapter/150#post_12663948
http://www.head-fi.org/t/761310/ifi...tra-low-noise-ac-dc-adapter/150#post_12663948
iFiAudio published their own measurements, and an explanation of audio science reviews results, here
http://www.computeraudiophile.com/f...t-nothing-part-4-uploaded-and-complete-28982/
Essentially they argue that the audio science guy had misconnected his test kit.
clivem2
pfm Member
That's one in the eye for Amir....
JohnW
pfm member
Well I've never met Amir in person, but reading his posts and I already dont like the guy as he has a personal agenda and projects a huge ego.
I shake my head when I see the very basic mistakes he makes, and then poor conclusions - he exemplify's one of these "Internet" experts which people are only too eager to follow because he "reinforces" something that they want to hear.
HOWEVER - in the case of the iFi PSU he has "stumbled" on one of the major problems of SMPS PSU in that due to the need to "localise" the internal RF current path requires a Capacitor ("Y" Capacitor) between the Primary side (Mains input) and the "isolated" secondary side (Load output). This Capacitor DIRECTLY injects mains leakage currents into the Load (Audio System) - not only mains current but nasty RF noise etc.
http://archive.eetasia.com/www.eetasia.com/ARTICLES/2004NOV/B/2004NOV16_POW_TA.pdf?SOURCES=DOWNLOAD
iFi measured there PSU with the "Earth" lifted on the AP measurement system - if the "load" device / system (audio system) is Earthed (as most systems are) then I'll expect you will have much the same results as Amir measured.
iFi must know this and are just trying to pull the wool over buyers eyes...
I'm more then happy to measure one here - I could be wrong (but I'd say there is 95% chance I'm not).
JohnW
pfm member
By the end of this month, you can try an MDAC2 "Streamer" PCB, it will be able to be operated "standalone" for software development ahead of MDAC2 release.
misterdog
Not the canine kind
http://www.pinkfishmedia.net/forum/showpost.php?p=3009287&postcount=437
Right click the post number.
Right click the post number.
Hi John,
I'd love to try the MDAC2 Streamer PCB, and provide feedback. I'm also counting down the days until the Detox arrives, as I'm using the USB input.
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