Audio GD New NOS 7 2016 Edition Impression Thread
Aug 29, 2016 at 6:37 AM Post #151 of 286
   
I assume you have read my posts "http://www.head-fi.org/t/803111/xmos-xu208-usb-bridges-the-latest-gen-has-arrived/3094"
 
There are two 3.3V ldo on the clean side, one for the XOs, the other for cpld. The one for XOs require the cleanest power. You certainly can remove the two ldo and use two external uV grade lps to drive the XOs and cpld directly, just make sure use shielded cables. Single digit uV noise level is not so easy to maintain at a distance over 20/30 cm. Grounding should not be a problem as long as you don't form a ground loop which will pick up EM waves. As for myself, my 0.8uVrms LT3042 just arrived yesterday, now I'm waiting for the circuit boards.
 
Soldering should be easy; Removing the two ldo on the other hand might be a little tricky if you haven't done this before. So please refer to "http://www.head-fi.org/t/803111/xmos-xu208-usb-bridges-the-latest-gen-has-arrived/3108".

 
I may be getting greedy, but after researching power supply to use for the output section of F-1, most I am looking at have noise rating in the uV range, and looking at ADP150 the noise is 9uV.  To get most out of this I am now thinking I should either feed the 3.3V directly from external PSU or else use LDO which is rated 1 uV or less.  The SMT soldering is not something I have experience with, also costly if I need to find hot air rework equipment.  Still using the LDO near the board might be worth pursuing.  I may try to source already assembled LDO though to minimise how much SMD soldering I need to do.
 
I guess the question is how much is to be gained by using this setup vs just replacing with the AD150s and feeding an external LPSU are per your original mod.  <1uV LDO don't seem to be cheap or many options available.
 
Aug 29, 2016 at 7:45 AM Post #152 of 286
Hi, I succesfuly did sidegrade from DAC19  to NOS19. There is a big and change in sound. Very interesting so far. I Will post some impresions after some time. Maybe also some comparison between DAC19/NOS19. 
BIg thanks and cheer to audio GD. The guide for upgrade is perfect! And fortunatelly there was no problem at all.
 
Aug 29, 2016 at 10:15 AM Post #153 of 286
   
I may be getting greedy, but after researching power supply to use for the output section of F-1, most I am looking at have noise rating in the uV range, and looking at ADP150 the noise is 9uV.  To get most out of this I am now thinking I should either feed the 3.3V directly from external PSU or else use LDO which is rated 1 uV or less.  The SMT soldering is not something I have experience with, also costly if I need to find hot air rework equipment.  Still using the LDO near the board might be worth pursuing.  I may try to source already assembled LDO though to minimise how much SMD soldering I need to do.
 
I guess the question is how much is to be gained by using this setup vs just replacing with the AD150s and feeding an external LPSU are per your original mod.  <1uV LDO don't seem to be cheap or many options available.

 
First a little background about LDO's total output noise: a simple estimation is as followed,

------------------------------------------------------------------------------------------------------
Vout_total = sqrt[ Vout_n^2 + (Vin_n * PSRR)^2 ]
Vout_n:  LDO's output noise (9 uVrms @ 10Hz ~ 100kHz; ADP150)
Vin_n:    LDO's input source's noise
PSRR:   LDO's power supply rejection ratio or ripple rejection (55 ~ 70 dB @ 10Hz ~ 100kHz; ADP150)
 
(Note: only estimation, in practical integration over the whole bandwidth is required; also coupled noise from other sources must be taken into consideration too)
------------------------------------------------------------------------------------------------------
 
Take SU-1 as example: it use LM2940 as 5V LDO (54 ~ 72 dB @ 120Hz; output noise = 150 uVrms). Let say its input have 10 mVrms rippe/noise and assume LM2940's average PSRR ~= 60 dB or = 1/1000.
 
V5v_total = sqrt[ 150u^2 + (10m / 1000)^2 ] ~= 150.33 uVrms
Now look at 3.3V stage, let's also assume average PSRR ~= 60 dB (1/1000)
V3v3_total = sqrt[ 9u^2 + (150.33u / 1000)^2 ] ~= 9.0013 uVrms    ---- 5V from LM2940
V3v3_total = sqrt[ 9u^2 + (0u / 1000)^2 ] = 9 uVrms                      ---- ideal 5V source

Now you can see an only decent LM2940 (150 uVrms) will result to almost identical last stage noise level as a 0 uVrms ideal source. That's why Singxer choose LM2940 (more cost effective).

So depending on complexity, you can;
 
(A) Remove only isolation/swiching power supply (Mornsun B0505S) and connect (+5V, Gnd) to any decent (<100 uVrms) external 5V power supply; 1uV LPS won't provide any advantage. This is supposed to give you same level of performance as SU-1.
 
(B) In addition to (A); also replace LDO for CPLD with an ADP150. Because of both LDOs are ADP150, you can comfortably power the two LDOs with Lithium-ion battery. This is my current configuration.

(C) In addition to (A) and remove both LDOs; use ~1 uVrms LPS to directly provide 3.3V power to the XOs. This is what I am planning to do.
 
This is a pre-assembled module (at least the smd parts) --- "http://www.diyinhk.com/shop/accessories0/73-08uv-ultralow-noise-dac-power-supply-regulator-33v5v-1ax2.html", but right now it seems out of stock.
 
Right now I can only find two around 1 uV LDO; LT3042 and ADM7154: LT3042 has reverse input protection which is very useful if powered by battery, also its input can range from 3.8 ~ 20 V. Its PSRR @ 10 Mhz is a little below 60 dB. As for ADM7154, its input range is 3.8 ~ 5.5V, but its PSRR @ 10 Mhz is a little over 60 dB. Also its evaluation kit "http://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/eval-adm7154.html#eb-overview" is only 49 USD, much more reasonable than LT3042's 150 USD demo board. So there is option (D) replace LDO for XOs with ADM7154 ev kit and power the ev kit and  the other LDO with a decent external LPS.
 
Aug 29, 2016 at 11:14 AM Post #154 of 286
   
First a little background about LDO's total output noise: a simple estimation is as followed,

------------------------------------------------------------------------------------------------------
Vout_total = sqrt[ Vout_n^2 + (Vin_n * PSRR)^2 ]
Vout_n:  LDO's output noise (9 uVrms @ 10Hz ~ 100kHz; ADP150)
Vin_n:    LDO's input source's noise
PSRR:   LDO's power supply rejection ratio or ripple rejection (55 ~ 70 dB @ 10Hz ~ 100kHz; ADP150)
 
(Note: only estimation, in practical integration over the whole bandwidth is required; also coupled noise from other sources must be taken into consideration too)
------------------------------------------------------------------------------------------------------
 
Take SU-1 as example: it use LM2940 as 5V LDO (54 ~ 72 dB @ 120Hz; output noise = 150 uVrms). Let say its input have 10 mVrms rippe/noise and assume LM2940's average PSRR ~= 60 dB or = 1/1000.
 
V5v_total = sqrt[ 150u^2 + (10m / 1000)^2 ] ~= 150.33 uVrms
Now look at 3.3V stage, let's also assume average PSRR ~= 60 dB (1/1000)
V3v3_total = sqrt[ 9u^2 + (150.33u / 1000)^2 ] ~= 9.0013 uVrms    ---- 5V from LM2940
V3v3_total = sqrt[ 9u^2 + (0u / 1000)^2 ] = 9 uVrms                      ---- ideal 5V source

Now you can see an only decent LM2940 (150 uVrms) will result to almost identical last stage noise level as a 0 uVrms ideal source. That's why Singxer choose LM2940 (more cost effective).

So depending on complexity, you can;
 
(A) Remove only isolation/swiching power supply (Mornsun B0505S) and connect (+5V, Gnd) to any decent (<100 uVrms) external 5V power supply; 1uV LPS won't provide any advantage. This is supposed to give you same level of performance as SU-1.
 
(B) In addition to (A); also replace LDO for CPLD with an ADP150. Because of both LDOs are ADP150, you can comfortably power the two LDOs with Lithium-ion battery. This is my current configuration.

(C) In addition to (A) and remove both LDOs; use ~1 uVrms LPS to directly provide 3.3V power to the XOs. This is what I am planning to do.
 
This is a pre-assembled module (at least the smd parts) --- "http://www.diyinhk.com/shop/accessories0/73-08uv-ultralow-noise-dac-power-supply-regulator-33v5v-1ax2.html", but right now it seems out of stock.
 
Right now I can only find two around 1 uV LDO; LT3042 and ADM7154: LT3042 has reverse input protection which is very useful if powered by battery, also its input can range from 3.8 ~ 20 V. Its PSRR @ 10 Mhz is a little below 60 dB. As for ADM7154, its input range is 3.8 ~ 5.5V, but its PSRR @ 10 Mhz is a little over 60 dB. Also its evaluation kit "http://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/eval-adm7154.html#eb-overview" is only 49 USD, much more reasonable than LT3042's 150 USD demo board. So there is option (D) replace LDO for XOs with ADM7154 ev kit and power the ev kit and  the other LDO with a decent external LPS.

 
Thanks so much, this will greatly help me in selecting an appropriate LPSU and spend money where it matters and not waste.  Maybe beyond some of the ebay pre-built LPSU (those seem more 3-4mV typically).  I might be better off to keep things simple.  A good LPSU never seems to go astray so I might look for something with at least a couple of rails and decent performance if I am going to the effort and expense of assembling even pre-assembled stuff (but try not to go overboard in cost) and have something I can be proud of.  Hopefully I can learn something from this process as well...  again many thanks I will bookmark your post for future reference.  I will practice SMD solder and desolder on some unwanted electronics.
 
Aug 30, 2016 at 1:35 AM Post #155 of 286

 
LT 1963 rechargeable adjustable battery power supply 60 Rmb
 
Aug 30, 2016 at 10:35 PM Post #157 of 286
World taobao please search: 1.2   6.5v  can you find !!
 
Aug 30, 2016 at 11:23 PM Post #159 of 286
bigsmile_face.gif
charger
 
Aug 30, 2016 at 11:25 PM Post #160 of 286
this price 60 rmb with battery and 8.4volt charger!!!!!
 
Aug 30, 2016 at 11:31 PM Post #161 of 286
  this price 60 rmb with battery and 8.4volt charger!!!!!


Sorry... more questions... (I am your neighbor but cannot read Chinese)....
Do you need remove the batteries to charge, or can charge while the batteries are on the card?
Can you use the device while the batteries are actively charging?
 
Sorry again, but many thanks in advance.....
 
Aug 30, 2016 at 11:57 PM Post #162 of 286
while charging ,battery can stay,automaticly power off if low battery,have 2 leds also .Don't know can use in charge process,or not.Better not i think.
 
Aug 31, 2016 at 9:33 AM Post #164 of 286
This is another choice "https://world.taobao.com/item/529586432965.htm?fromSite=main&spm=a1z3o.7695460.0.0.z7iccN"
 
Input: AC 9~12V
Output: DC 5V
First stage: LT1963 (40uV), Second stage: LT3042 (0.8uV)
Price: 88 RMB
 
Can easily be modified as DC/battery input, first stage output 5V, second stage output 3.3V
 
Just bought two.
 
Aug 31, 2016 at 9:39 PM Post #165 of 286
Better to get something like this http://www.diyinhk.com/shop/audio-kits/89-08uv-ultralow-noise-dac-power-supply-regulator-3357v-15ax2.html
 

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