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IanCanada's Latest RPi GB Goodies Impressions... and your tweaks, mods and hints...
IanCanada's Latest RPi GB Goodies Impressions... and your tweaks, mods and hints...
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Old 21st April 2019, 05:47 PM   #181
Markw4 is offline Markw4  United States
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Speaking of hints and tips for the RPi dacs, odd there don't seem to be any good recommendations for powering the dacs other than from batteries (whatever happened to the super cap fad?).

Anyway, the dac board itself does need three separate 3.3v regulators to sound as good as it should. DVCC and VCCA could each be powered by LDO regulators (if, say, one wanted to compare linear power supply SQ to that of using batteries). However, ES9038Q2M dacs often don't sound good with LDOs used for AVCC. One could probably use an AD797 opamp more or less as ESS recommends and perhaps use a dedicated LDO to provide the opamp 3.3v input reference voltage. http://www.esstech.com/files/4514/40...PCB_Layout.pdf

Only precaution about using AD797 (which can sound great used for AVCC power) is that they can get unstable if the power rail impedance is too low (maybe a good way to see if the effective source impedance of batteries is really all that low at the loads ) If stability issues, something like OPA1611 could be tried.

For the output stage, haven't tried to compare batteries myself, but a simple test to see if the effective power rail source impedance is low enough to make the opamps sound their best might be to put some large-ish value film caps from each of the +- output stage power rails to ground very close the power input terminals of the output stage board. If no audible change in sound quality, then the batteries are probably doing quite well. If any improvement in SQ at all from adding film caps, then PS source impedance as seen by the output stage may be a bit higher than optimal.

Be very interested to see if anyone tries any of the above besides me. I don't have a battery setup so unfortunately I can't compare. I tried LiPO4 for AVCC once on one dac and that was enough of that unstable AVCC sound for me. Probably no surprise either. Even if using an opamp supply for AVCC, the ESS recommendations I linked to above suggests putting the AVCC supply as close to the dac chip AVCC pins as physically possible, so as to keep wiring from having any adverse SQ effects (which it can).

Last edited by Markw4; 21st April 2019 at 05:50 PM.
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Old 22nd April 2019, 11:38 AM   #182
jacklee is offline jacklee  Hong Kong
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Default Taking it to the next "level" (continue)

Just a quick note on powering the 3 rails of the DAC HAT separately. This removes the last bit of digital noise from the sound and I highly recommend it.

Initially I removed the 3 decoupling caps mini-tabs and powered the 3 rails directly using batteries. I later on added the decoupling caps mini-boards back and prefer that as it sounds smoother and with better resolution.

If anyone is planning on doing the same mod I recommend keeping the decoupling cap boards in-place. Just cut the PCB bridge near the "in" label should separate the 3 rails. A simple continuity test using a multimeter will confirm that.
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Old 22nd April 2019, 08:36 PM   #183
wlowes is online now wlowes  Canada
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Default PS mania

Jacklee, I have no doubt your separate PS adds magic.

I wonder if a dedicated PS to the clock on the FIFOPi would also add. It would be easy to remove the + & - pins and supply power separately from the main board. Need to check if the clocks are powered all the time or only when selected.
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Old 23rd April 2019, 07:57 AM   #184
jacklee is offline jacklee  Hong Kong
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Quote:
Originally Posted by wlowes View Post
I wonder if a dedicated PS to the clock on the FIFOPi would also add. It would be easy to remove the + & - pins and supply power separately from the main board. Need to check if the clocks are powered all the time or only when selected.
That's very likely will impact the sound. My understanding is that the clock not in use is switched off by the ENABLE pin. Whether the clocks themselves are powered all the time I'm not certain but I don't think that matters.

Please do share your experiences if you plan to do the clock mod.
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Old Yesterday, 02:38 PM   #185
aguaazul is offline aguaazul
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IanCanada's Latest RPi GB Goodies Impressions... and your tweaks, mods and hints...
I have 2 sets of CCHD-957 & NDK @ 45/49’s & both Ian’s old and new clock adapters in their stock form.

There have been many capacitor suggestions. I have used the Cornell Dublier caps in other projects to great results.

I need a little direction please. Folks have thrown around the Black Gate: BG NX HiQ .33u 50v caps, don’t have any.

The included ceramic caps are getting poor results, so I’m looking for definitive capacitor suggestions.

I do have the Nichicon 370-AUDIO-KIT (0.22 uF to 330 uF). Plenty good audio caps in there I can run.

Have an Airwork station, have built for practice a few SMD test boards to pretty good results (not so good with SMD LEDs).

With this open option, what would you do? Suggestions welcome.

Aguaazul
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Old Yesterday, 02:50 PM   #186
Markw4 is offline Markw4  United States
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Quote:
Originally Posted by aguaazul View Post
The included ceramic caps are getting poor results, so I’m looking for definitive capacitor suggestions.
Why do you think the problem is with caps?
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Old Yesterday, 03:30 PM   #187
aguaazul is offline aguaazul
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IanCanada's Latest RPi GB Goodies Impressions... and your tweaks, mods and hints...
Quote:
Originally Posted by Markw4 View Post
Why do you think the problem is with caps?

Just from reading online. Perhaps they are just fine. But I'd like to try something else.
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Old Yesterday, 04:26 PM   #188
Markw4 is offline Markw4  United States
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Quote:
Originally Posted by aguaazul View Post
Just from reading online.
Well, if a film cap added to one clock also affects the other clock, then it would seem likely that tacking a small film cap across one of the clock socket power pins on the back of the fifo board might work just as well. Probably somewhere between .1uf and 1uf. Smaller caps will be more effective at higher frequencies, but which cap(s) works best is a trial and error search problem. Might help if the voltage regulator was closer to the clocks and dedicated to the clocks only. Caps might only be able to help so much if something else is the main underlying issue. Just sayin'

May I ask what source material are you listening to? Also, have you tried turning down the software volume just a bit, maybe 3dB? Most of the volume control should be done using the dac digital volume control, but sometimes reducing the volume level slightly before the digital signals arrive at the dac can help some. Other things can help too, if you think sound quality needs to be a little better.

Last edited by Markw4; Yesterday at 04:29 PM.
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Old Yesterday, 11:05 PM   #189
wlowes is online now wlowes  Canada
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Default WOW!

Quote:
Originally Posted by jacklee View Post
That's very likely will impact the sound...
Please do share your experiences if you plan to do the clock mod.
I did it and WOW! Like upgrading from regular NKD SD to SDA. Not a subtle change in my system. All the usual sound improvement that comes from lower phase noise oscillator. Pin point 3d sound stage. Separation, rich natural sound, black background. Ian's FIFOPi has now exceeded my best result with BBB and Ako S03 which was very good.

So here is the set up using mains power.
The clean PS to FIFOPi is a small Hammond 229 transformer, super soft rectifiers, CLCLC filtering using a 13x1800uf caps producing 8v DC. A salas shunt takes it down to 5v. Then Ian's TPS7a4700 reg down to 4.1v. This feeds the clean side of FIFOPi and Ian's I2SPCM bd. So the FIFOPi is using the onboard LT3042 reg. There is a separate feed from the TPS7A4700 reg to a second 4700 based reg soldered directly to the 45mHz clock adapter. It takes the 4.1v down to 3.3v. I removed the power pin from the clock adapter so they share ground but not power.
Also for full disclosure, the clock adapter has the 3 ceramic caps removed from the bottom and has one .68uF FCA cap on the bottom and a single .46uF BG HiQ cap on the top power to ground.
Also both the 4700 regs have BG caps per some earlier threads.
I am not advocating that 4700 regs are better than LT3042. I just happen to have the 4700 regs available from my last build so its a 'run what you brung' kinda deal.

I am writing this after listening for about 10 mins. The regs were previously used for a long time but were idle for a few months so I don't expect a lot of run in improvements but again the sound improvement was not subtle. I'll report after a few days if there is any appreciable change.

I expect similar improvement is possible for battery users.
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