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A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
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Old 21st September 2014, 04:02 PM   #3011
Julf is offline Julf  Europe
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Quote:
Originally Posted by carlsor View Post
Philosophically speaking, I need to make peace with the idea of cleaning up the I2S signal from a $40 computer with a $285 reclocker. I'm waiting for someone like Acko to design a low jitter small computer.
Do we have any objective evidence that jitter really is an audible issue with the RPi?
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Old 21st September 2014, 04:37 PM   #3012
palmito is offline palmito  United States
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A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
Quote:
Originally Posted by carlsor View Post
Philosophically speaking, I need to make peace with the idea of cleaning up the I2S signal from a $40 computer with a $285 reclocker.
The $285 reclocker costs that if you buy it assembled/tested. If you buy the pcb alone ($25 last I checked) and populate it with the minimum required parts (follow Enrico's build instructions, the S03 is a generic solution, when configured for the ddac is uses less parts than when configured for other dacs) I don't think it will cost anywhere near $285. If I remember right, the XO is the most expensive part, about $30 (but you could buy a $10 part if you can live with higher jitter). However, it does require smt soldering which might not be your cup of tea.

Quote:
Originally Posted by carlsor View Post
I'm waiting for someone like Acko to design a low jitter small computer.
This might be what you are looking for:

GB: SDTrans384 - A micro SD card digital transport

I looked at it a while ago and didn't look forward to having to change memory cards to play music. However, Acko uses this and swears by it, as do other people who have used it. I have never listened to it.
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Old 22nd September 2014, 04:59 PM   #3013
G600 is offline G600  France
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Today is a sad day, it looks like the left channel of my built is dead...

Is there a way to test the DAC chip ?

Doede, is it possible to buy bare decks (pcb + surface mount components only) ?
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Old 22nd September 2014, 05:12 PM   #3014
nige2000 is offline nige2000  Ireland
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Quote:
Originally Posted by G600 View Post
Today is a sad day, it looks like the left channel of my built is dead...

Is there a way to test the DAC chip ?

Doede, is it possible to buy bare decks (pcb + surface mount components only) ?
I've been able to replace the dac chip
The hard bit is taking off the old without damage

But check for bias voltage first
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Old 22nd September 2014, 05:21 PM   #3015
palmito is offline palmito  United States
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A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
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Originally Posted by nige2000 View Post
The hard bit is taking off the old chip without damage
Without a hot air station, this might be the easiest way, if you have room to maneuver. You will still have to carefully clean the lands before soldering the new chip.

Chip Quik: Easy removal of surface mounted devices
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Old 22nd September 2014, 05:28 PM   #3016
G600 is offline G600  France
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I have just triple checked, voltages are good everywhere I measured.

Replacing the chip is not for me, with my lack of tools, practice and likely lack of skills, I find that unsoldering an SMD regulator is very hard...
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Old 22nd September 2014, 07:15 PM   #3017
dddac is offline dddac  Germany
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just email the guys from audio creative. But beware, the board and smd parts are (unfortunely) the most expenisve parts of the kit...

for a quick check, measure the current to the right and left channel. can be done by measuring over the first 10 Ohm series resistor. expect aprox 500mV. at leadst they should be very similar. this will help finding furher issues? also check pin 20 for 2.4 volt. last methode, change the I2S signals from left to right. this all will give you enough clue what is wrong
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Old 22nd September 2014, 07:39 PM   #3018
G600 is offline G600  France
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Thank you for your help Doede, this is a fine debugging guide !

Hum, spoke too fast, I've removed those 10 Ohm resistor a few days ago, following Mr Lowe's tip for Belleson implementation...

Last edited by G600; 22nd September 2014 at 07:48 PM.
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Old 22nd September 2014, 08:07 PM   #3019
dddac is offline dddac  Germany
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just insert them again ;-)
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Old 23rd September 2014, 04:30 AM   #3020
Rax is offline Rax  United States
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Quote:
Originally Posted by carlsor View Post
Cascoded JFET circuit is shown in post 2622 on Aug 28.
Ross
oh... I see (a possible cause for confusion). Typically, what is called a "cascode JFET CCS" is below. As the single JFET CCS, it's a simple insert in the pin 20 circuit ("two legs"). I don't think there is a combination of JFETs that could work well at 2.4V.

What you have in post 2622 is what I lumped at some point under the name "separately biased CCS," as these ones require a B+ tap (have "three legs").

Just to clarify our terminology...

Radu.
Attached Files
File Type: pdf Cascode JFET CCS.pdf (7.7 KB, 88 views)

Last edited by Rax; 23rd September 2014 at 04:36 AM. Reason: clarification
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