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Old 9th November 2012, 10:54 AM   #4591
ide2003 is offline ide2003  Indonesia
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+ 1
here we have followed one's journey, I have applied some of John's ideas
some worked very well some not, at least we don't have to go climbing all the mountains
and I thanks John for that

Last edited by ide2003; 9th November 2012 at 10:57 AM.
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Old 9th November 2012, 12:49 PM   #4592
wlowes is offline wlowes  Canada
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Thomas Edison ran 11,000 experiments before he perfected the light bulb. Billions of people have benefited from his persisent journey. I for one have appreciated the journey that ecdesign has shared with us. The ideas that lead to dead ends are equal in value to those that yield perfection. It is the process of discovery and continuous improvement.
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Old 9th November 2012, 01:32 PM   #4593
SSerg is offline SSerg  Russian Federation
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I have an answers for your remarks, colleagues.
But I want previously to receive the reply from author.
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Old 9th November 2012, 04:38 PM   #4594
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This is not a forum for dialectic confrontation but for inventing, sharing and building nice gear to enjoy our beloved music. People who contribute freely to our enjoyment must be thanked and encouraged...

John has explained most or all of his decisions and he declared at each major change why the former project was surpased by the later so the former was dissmissed and abandoned.
I don't think anybody has to write a long statement as mea culpa and strike his chest every time a project does not lead to an optimal outcome. There are things that are obvious and don't need to be written down to be understood...
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Old 9th November 2012, 05:45 PM   #4595
oshifis is offline oshifis  Hungary
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And don't forget the principles described in the initial post (and the details in the subsequent first couple of posts) are way much better than found in most commercial DACs. Even if someone has different ideas, he still could learn a lot from this thread (or come along with his better solution - if there is any).
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Old 10th November 2012, 11:17 PM   #4596
ash_dac is offline ash_dac  United Kingdom
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I've tried going through the posts, and found a few informative posts but I still need some clarification re the tda1541a grounding. The datasheet has the DEM caps to a ground, then a 100N cap' tied to ground from the -5 to -15V pins. The tech data has power supply rejection ratio -58db on -15V -84db on -5V.

The datasheet also lists 5V decoupled to joined analogue and digital ground yet says -0.3V to 0.3V difference between the analogue and digital grounds.

I suppose what I'm asking is are there two grounds required? My first thoughts were where do those DEM cap grounds go?

Appologies for any lack of understanding in advance!
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Old 11th November 2012, 12:13 AM   #4597
Shinja is offline Shinja  Japan
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SSerg

poobah pointed out the problem of "direct interpolation" at #85 and so on.
Quote:
Originally Posted by poobah View Post
When you apply linear interpolation... mechanically or in the digital domain you are adding signals that weren't in the original... and this is noise. It will be most apparent at frequencies of fs/4 to fs/2.
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Old 11th November 2012, 09:53 AM   #4598
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Hi ash_dac,

Quote:
I've tried going through the posts, and found a few informative posts but I still need some clarification re the tda1541a grounding.
Pin 5: analogue ground, this includes ground for active divider decoupling caps.

Active divider decoupling caps require -separate- GND route to pin 5. Active divider decoupling caps need to have low inductance (SMD film caps) and must be placed as close to the TDA1541A pins as possible, underneath the chip. Active divider decoupling cap value: 1uF, free running DEM oscillator frequency: 60 KHz (approx. 1nF between pins 16 and 17).

Pin 14: digital ground, reference for I2S input signals.

Local power supply decoupling:

Use 1uF SMD film (1210 size) in parallel with 220nF NPO, locate the decoupling caps underneath the chip for shortest possible wiring (lowest induction, most effective decoupling). The NPO cap is soldered directly to the PCB, the film cap is soldered directly on top of the NPO cap.

Capacitor between +5V and analogue ground.
Capacitor between -5V and analogue ground.
Capacitor between -15V and -5V.
Capacitor between -15V and analogue ground.

Un-interrupted ground plane is essential.

Analogue ground and digital ground are connected to the ground plane.
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Old 11th November 2012, 11:36 AM   #4599
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John, fDEM of 60KHz? What brought along this odd frequency? Not a multiple of either ws or bck....
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Old 11th November 2012, 11:56 AM   #4600
Sandor is offline Sandor  Italy
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I've found some SMD 1uF caps (1210 size) that could fit for active divider decoupling.
They all are 16V, is this safe?
Better a PPS (polyphenylene sulphide) or FCA (acrylic) dieletrcic?
All other types (higher voltage, different dielectric) are too big for soldering directly on the pins of the TDA1541.

Last edited by Sandor; 11th November 2012 at 12:23 PM.
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