Asynchronous I2S FIFO project, an ultimate weapon to fight the jitter - Page 321 - diyAudio
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Old 20th March 2014, 10:11 PM   #3201
AR2 is offline AR2  United States
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Quote:
Originally Posted by TNT View Post
AR2, what the resistance (and impedance) of the "primary" in the way you use the trafo?

//
Hi TNT,

As I described somewhere earlier, I use no resistors before the primary. DAC is interfaced with jFet buffer board and than at the buffer's output there is Lundahl 1674. I consider this an optimal configuration in loading DAC and using transformer. Also in this configuration this DAC does not need any termination on secondary, per data sheet and confirmed on my network analyzer. What I suggested for Ian to try just like I did, was to try Lundahl without buffer board, and the only way to safely do it was reversing Lundahl so it it was used as 4+4:1+1. As reversed, secondary provided higher impedance to DAC without need for resistors. The disadvantage is attenuation of the signal. I would not use it this way because of several reasons, but it is the good way in listening the effects of buffer (if any). This transformer could be used as 1+1:4+4 or 1+1:2+2. This is not a good candidate to use Rasmundsen's method where signal is severely attenuated with resistors, and than voltage is amplified through transformer with high ratio. There are several possible ways to do interface DAC with transformer, and doing it with buffer is one of them. It is my preferred method. The only "compromise" is that signal goes through buffer, vs just transformer winding and resistors, but in my case that is through two small jFets and couple of resistors, since buffer is balanced and with no caps in a path of a signal.
The sound is not as thin as with transformer only, and I really do like it.

Best
AR2
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Old 20th March 2014, 11:00 PM   #3202
TNT is offline TNT  Sweden
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Excuse me AR2.. I red your schematic backwards.
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Old 21st March 2014, 12:26 AM   #3203
AR2 is offline AR2  United States
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Originally Posted by TNT View Post
Excuse me AR2.. I red your schematic backwards.
Not a problem at all.
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Old 22nd March 2014, 02:43 PM   #3204
asaf23 is offline asaf23  Russian Federation
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Hi,
I'm trying to connect the isolated I2S output of WaveIO into the FIFO input directly.
I get the WaveIO isolator power supply from J5 of the FIFO board according Ian's suggestion in the post #1348.
J5 is labeled as "DC 5V OUTPUT" but instead of 5V there is almost the same voltage as an input DC (6V in my case).
Please, any advise?

Regards,
Andrey
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Old 22nd March 2014, 09:23 PM   #3205
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I received the cable UFL RG 178 (8cm) for the master clock,well built cable,clean,in comparison with the 1,37 MM (that of G.B) feeling a greater dynamic range.
Click the image to open in full size.
mc partagé sur ZimageZ
Ian cards(FIFO-I2StoPCMconvertorBoard) are connected with coaxials cables
Click the image to open in full size.
coax partagé sur ZimageZ
Amanero-FIFO-I2StoPCM-diyinhk power regulator-A123 replaces the DSP card in the Audio GD Ref 7.1.
Click the image to open in full size.
ref partagé sur ZimageZ
The implementation is not yet finished,I want to connect the cards with cables UFL,fix properly in the frame,connect BEAGLEBONE Black in I2S directly to the FIFO (when bit perfect).
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Old 22nd March 2014, 09:43 PM   #3206
mcluxun is offline mcluxun  United States
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Hey Ian
I'm working on the i2c isolator on the i2s isolator board.
Are the in/out pins used when it's populated with SI860 ?
Thanks
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Old 22nd March 2014, 10:35 PM   #3207
ULNOCXO is offline ULNOCXO  Europe
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Quote:
Originally Posted by 1audio View Post
Femto Clock is a serious misnomer targeted at insecure audiophiles. It all depends on how you measure them. The oscillators that can meet those numbers are not really available for commercial products. When I tried to get them I was told that they were a controlled commodity and I could only sell them inside the US. Typical SOTA commercial performance at 22 MHz works out to about 1.6 pS RMS jitter 10 Hz to 100 KHz. Getting it below that requires very low close in phase noise- -100 dB or less at 10 Hz. Getting that low close in phase noise is very hard and expensive. However phase noise at low frequencies has far less impact on audio. The DAC's internal processes actually limit the performance such that past a pretty accessible level (NDK, Crystek) you won't get improved performance. However good execution will trump even the best conceivable clock used badly. Ian's efforts here are among the best you will find in audio.
1audio,
I agree on the above points that you explained in a very clear way; I just want to put my two cents in.
Very low noise oscillators are generally not for commercial products, but we are near to obtain all the necessary authorizations for this purpose.
We executed a specific test to compare oscillators with different phase noise profiles and a lower close in phase noise showed significantly better audio quality reproduction.
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Old 23rd March 2014, 07:36 PM   #3208
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Quote:
Originally Posted by hochopeper View Post
@all

In other news, I have ordered some prototype PCBs for a PSU design that I hope might be of use to FIFO builders ... two isolated supplies on one PCB (one for each side of the isolator board ). LM317 pre-regulator and TPS7A4700 output. By using pre-regulator we get additional PSRR at audio freq but also ability to control volt drop over the TPS7A4700 so that it's not trying to dissipate too much power itself. Will have positions for CRC snubber between transformer and rectifier also. Will post back here with details when I have built and confirmed the prototype is working! I'll also be building some of the tools that Frex has designed for PSU noise measurements so we can see how close we get to datasheet spec for the regulator.

Regards,
Chris
Hi Chris

Do you have some informations about your build
Regards

Phil
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Old 24th March 2014, 02:54 AM   #3209
mcluxun is offline mcluxun  United States
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Hey Ian
My FIFO board stopped working today, I doubt the onboard regulator failed.
When feed with 6v dc the board outputs 6v to the clock board, and the read on 5v output header(J5) is 6v too.
The power led on board is dimmed too.
Is there any chance I can try to save it?
Thanks

Last edited by mcluxun; 24th March 2014 at 02:56 AM.
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Old 24th March 2014, 04:06 AM   #3210
Ceglar is offline Ceglar  Australia
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Quote:
Originally Posted by asaf23 View Post
Hi,
I'm trying to connect the isolated I2S output of WaveIO into the FIFO input directly.
I get the WaveIO isolator power supply from J5 of the FIFO board according Ian's suggestion in the post #1348.
J5 is labeled as "DC 5V OUTPUT" but instead of 5V there is almost the same voltage as an input DC (6V in my case).
Please, any advise?

Regards,
Andrey
This is correct what you say. J5 will be the same as the actual input voltage minus some very small drop - much closer to 6V if you power FIFO with 6V.

I did also ask Lucian about this (WaveIO) and he suggested that 6V was within tolerance of the chip. FIFO manual specifies working input voltages between 4.5 and 6.7V. In the end I set the regulator to 5V.

Manual also says FIFO has resettable fuse onboard.. .. ..

Last edited by Ceglar; 24th March 2014 at 04:11 AM.
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