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Old 25th October 2012, 02:44 PM   #4541
CeeVee is offline CeeVee  Portugal
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ahhh

so glad to find it ...
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Old 25th October 2012, 02:54 PM   #4542
SSerg is offline SSerg  Russian Federation
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Quote:
Originally Posted by -ecdesigns- View Post
TDA1541A datasheet page 4...
Hi, -ecdesigns-

Right, however:
"When input OB/TWC input is connected to VDD1 the two channels of data (L/R) are input simultaneously via DATA L and DATAR, accompanied with BCK and a latch-enable input (LE). With this mode selected the data must be in offset binary. The converted samples appear at the output at the positive going transition of the latch enable signal."
That is to say signal LE also important, at least once, at mode of the simultaneous data loading.

Apropos, recommend to read if there is possibility van de Plassche monograph. He is one of the developer TDA1540/1541(A) family.

That will say about garbling the square-wave pulse (the post # 4530)? Possible, HF decline, about which spoke guido in post #32, is connected with reduction SR?

Since begin given subject passed 6 years. Some your beliefs could change. Could you lead certain summation, like post #73? On what decisions stopped you on given moment?

Serg
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Old 25th October 2012, 03:41 PM   #4543
Shinja is offline Shinja  Japan
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try to playback fs/4 or fs/2 frequency signal.
haha
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Old 25th October 2012, 04:37 PM   #4544
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hi ecdesigns, so humbled that you replied to my post

i currently have the receiver chips bypassed to a te7022- 1541 via i2s. after one listen i figured that all the bad rep 1541 gets is due to the 7220.

the hiss was solved by swapping out some caps in the ps. no doubt it's a poorly designed one...

could you please outline for me the reason for different output transistor choices from mark3 and upwards?

thanks
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Old 25th October 2012, 04:44 PM   #4545
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I just did a bit of googling, and this is the thread I meant, look at post #35 and #123, it's a full recipe of a tda1541a dac.

Any good TDA1541A DAC kit?

Actually, be sure to read the WHOLE thread, not just the recipe! It talks about grounding, decoupling, layout, power supplies, I2S conditioning, DEM reclocking, the whole bloody thing. It's a gold mine!
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Old 25th October 2012, 05:00 PM   #4546
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thanks studiostevus. im off to do my homework~

edit: can the same dem circuit used for ws? why is bck chosen over it? in my humble experiement with grundig reclock i found taking the signal from ws to have a better soundstage than bck.

Last edited by PreSapian; 25th October 2012 at 05:08 PM.
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Old 25th October 2012, 05:14 PM   #4547
ide2003 is offline ide2003  Indonesia
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Quote:
Originally Posted by studiostevus View Post
I just did a bit of googling, and this is the thread I meant, look at post #35 and #123, it's a full recipe of a tda1541a dac.

Any good TDA1541A DAC kit?

Actually, be sure to read the WHOLE thread, not just the recipe! It talks about grounding, decoupling, layout, power supplies, I2S conditioning, DEM reclocking, the whole bloody thing. It's a gold mine!
ahaa, yes, have that good thread as well, reminder for my local audio friend
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Old 26th October 2012, 10:23 AM   #4548
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Hi SSerg,

Quote:
That is to say signal LE also important, at least once, at mode of the simultaneous data loading.
I use time multiplex mode and two's complement (/OB/TWC connected to 5V) exclusively.


Quote:
Since begin given subject passed 6 years. Some your beliefs could change. Could you lead certain summation, like post #73? On what decisions stopped you on given moment?

1) Direct interpolation was abandoned mainly because of trebles roll-off.
2) External DAC concept was abandoned because I wasn't able to fully block source jitter.
3) SD-transport concept was developed to approximate an ideal digital audio source.

The main reason I kept changing the design, designing and building one version after the other was increasing / changing mains interference spectrum that resulted in varying DAC performance levels. I wasn't aware of this at first, and this has lead to wrong conclusions.

I attached an oscillogram showing my mains voltage when interference levels are lowest. Most irritating interference is the approx. 2.5 KHz signal riding on the mains. This interference swithes "on" and "off" with random intervals.

The interference is generated outside my house as it persists when my house installation is completely disconnected from the mains.

Ken Newton reported similar mains distortion, perhaps this mains interference is a global thing.

I would be very interested if people from other countries have similar distortion on the mains. If you have a scope the interference can be measured safely by connecting the scope probe tip to a sheet of copper. This will pick up 50 or 60 Hz mains frequency and the interference riding on it (when present). Measure for longer time period like a quarter of an hour because this interference switches on/off periodically.

Knowing the cause of the problem I redesigned power supplies so they are immune to this interference.

Similar, I had to design yet another masterclock that is immune to (power supply) interference. It will always produce ultra low jitter, regardless of external conditions and clock loading.

Next oscillogram shows the 11.2896 Mhz output signal. It's a pure sine wave with very low distortion (fundamental).

The third oscillogram shows the BCK attenuator output signal. The signal is band limited in order to minimise ground-bounce. The positive transient that's very important for sample timing is speeded up to maximum in order to ensure maximum trigger certainty.

The final oscillogram shows the band limited and attenuated DATA signal. This signal is derived straight from the DSP on the SD8-transport.
Attached Images
File Type: jpg mains.jpg (100.3 KB, 495 views)
File Type: jpg hf-out.jpg (89.9 KB, 481 views)
File Type: jpg att-bck-out.jpg (87.3 KB, 469 views)
File Type: jpg att-data-out.jpg (85.8 KB, 467 views)
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Old 26th October 2012, 10:41 AM   #4549
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If you already use yours MCU and have a grip on the data/clock traces, why won't you use TDA in simultaneous load mode?

How do you know your's clock is low jitter, i mean have you measured it with an equipment which has less jitter than your clock?
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Old 26th October 2012, 04:28 PM   #4550
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Quote:
Originally Posted by -ecdesigns- View Post

The main reason I kept changing the design, designing and building one version after the other was increasing / changing mains interference spectrum that resulted in varying DAC performance levels. I wasn't aware of this at first, and this has lead to wrong conclusions.

The interference is generated outside my house as it persists when my house installation is completely disconnected from the mains.

I would be very interested if people from other countries have similar distortion on the mains.
Hi John,
Mains interferences are well known phenomena, very old news.

On my stereo/home theater setup there are 4 isolation transformers, the secondary windings are balanced to the ground, with capacitors filters after the secondary windings. Their positive impact on the sound quality of my setup is big.

Some (if not most) of the interference on the mains is on RF. As we know, RF spreads also by radiation, not only by conduction. Ideally, RF interference should be killed, or minimized, before they enter any audio gear.

On the part of designing and building audio gear, RF interference should be killed, or minimized, right at the mains voltage entrance to the equipment, with a good shield completely surrounding the mains filter. In addition to that, the power supply should be very well filtered, since there is no practical mains filter that kills completely all RF interference present on the mains supply.

Extra care should be taken when designing mains filter, to ensure that such a filter is capable of withstanding consumption variations by the equipment, without fluctuations to its' output voltage.

In addition, the equipment housing, or case, should have a very good and efficient RF shielding, since there are RF waves in all (or most) house rooms. Those RF waves come from radio, TV and communication equipment outside the house, as well as from sources inside the house, like cellular phones, cordless phones, computers, refrigerators motors, TV sets, all equipment that have switching power supplies and all equipment having digital circuits. Most of the commercial equipment do not have adequate shielding (it's too expansive).
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