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Old 26th June 2010, 08:06 PM   #21
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Quote:
Originally Posted by abraxalito View Post
Take a look by all means, but don't try that at home. This is quite a good example of how not to do a DAC output stage - in particular the decoupling. Are all those thick (power) traces ground fills?
Board looks different, schematic is just that - schematic...
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Old 28th June 2010, 09:07 AM   #22
novec is offline novec  Norway
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Quote:
Originally Posted by abraxalito View Post
Are you really sure sensitive analog circuits are going to be better off with multiple built-in 2MHz oscillators? Especially as each reg has its own and they won't be synchronised.
Sure? Never :-) But I'm trusting Pierre on this. If he says it's good, it's good enough for me. And the specs do look nice.

I'll start off with two DAC boards, with and without SRC, and shuffle things around a bit to be able to experiment with Iref resistors and PSU resistors and caps. They'll still be separate boards so I can test both zapfilter and LM4562 output stage.

If I keep the PSU resistors for each rail, how do I decide on the values? DIR draws 2x 8.3 mA, SRC draws 2 + 66 mA. DAC Idd draws 23-45 mA depending on sampling frequency and ~35 mA Icc. There's no separate power data for the three Vcc rails.

Last edited by novec; 28th June 2010 at 09:22 AM. Reason: PSU resistors
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Old 28th June 2010, 09:26 PM   #23
novec is offline novec  Norway
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Ok, I'm having a little difficulty understanding the Denon circuit... I can see that the first six opamps are the regular I/V and summing circuits, and IC406-1 single ends it all. But what's IC406-2 and all the transistors for?
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Old 29th June 2010, 12:33 AM   #24
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Quote:
Originally Posted by novec View Post
But what's IC406-2 and all the transistors for?
IC406-2 looks to be a switchable gain stage (0dB, 6dB) but I can't think why its needed. The transistors on the output side (TR402/3) are for pop/click suppression on power up/down or output muting (which is the same thing). Notice they're the 'wrong' way around - I dimly recall that a transistor connected in such a way has a lower saturation voltage.
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Old 29th June 2010, 12:36 AM   #25
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Originally Posted by novec View Post
And the specs do look nice.
Yes they do - how clever of them to limit the specified noise bandwidth to 100kHz when that little charge pump runs at 2MHz
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Old 29th June 2010, 01:34 AM   #26
jcx is offline jcx  United States
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does the player include HDCD decoding? - the standard requires gain change
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Old 29th June 2010, 03:13 AM   #27
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Hi Guys...
I'm just keeping an eye on this thread... my design includes some complicators... I decided to regulate each voltage rail separately.. +5Va, +3V3 digital, +5VaR, +5VaL... using LT1763-xV, and analog outs are via OPamp.. LME49722 (4562 version2)...

I was thinking about hires sources of signal: maybe SRC is just a jitter reclocker than anything... is not 24/48K enough? If so, I would get SRC out and put a PMD100 in the circuit, the clock is supplied like "the Flea" and is near.

just thoughts... not to disturb your thread. :-)

About Denon: yes, 2930 and family has HDCD... that output is for gain purpose of HDCD lower out. Mine is a little different as 2930 uses PCM1791.
But the DAC project is intended to be used with SD card player.


Regards.

Hisatugo.
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Old 29th June 2010, 03:34 AM   #28
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Smile taking part of it...

to who may interest...

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Old 29th June 2010, 08:16 AM   #29
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Quote:
Originally Posted by abraxalito View Post
IC406-2 looks to be a switchable gain stage (0dB, 6dB) but I can't think why its needed. The transistors on the output side (TR402/3) are for pop/click suppression on power up/down or output muting (which is the same thing). Notice they're the 'wrong' way around - I dimly recall that a transistor connected in such a way has a lower saturation voltage.
M'kay. Just wanted to make sure I didn't have to mess with it.

Quote:
Originally Posted by abraxalito View Post
Yes they do - how clever of them to limit the specified noise bandwidth to 100kHz when that little charge pump runs at 2MHz
Sulplise, sulplise

Quote:
Originally Posted by Hisatugo View Post
Hi Guys...
I'm just keeping an eye on this thread... my design includes some complicators... I decided to regulate each voltage rail separately.. +5Va, +3V3 digital, +5VaR, +5VaL... using LT1763-xV, and analog outs are via OPamp.. LME49722 (4562 version2)...
I was considering the same, but decided it was too overkill, even for me... With ten channels, that's 20 more regulators.

Quote:
Originally Posted by Hisatugo View Post
I was thinking about hires sources of signal: maybe SRC is just a jitter reclocker than anything... is not 24/48K enough? If so, I would get SRC out and put a PMD100 in the circuit, the clock is supplied like "the Flea" and is near.
I'll want to try 192 kHz upsampling with the SRC, but its main function is reclocking. But as stated earlier, I'm suspecting (and hoping) the Lynx AES16 source clock is clean enough to skip the whole SRC.

Quote:
Originally Posted by Hisatugo View Post
just thoughts... not to disturb your thread. :-)
This kind of "disturbance" is exactly what makes diyAudio forums great

Last edited by novec; 29th June 2010 at 08:22 AM.
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Old 29th June 2010, 03:42 PM   #30
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Originally Posted by jcx View Post
does the player include HDCD decoding? - the standard requires gain change
That's exactly what it is.
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