yeo's USB-Converter, I2S output...

[assendor]

Hello yeo, 

My knowledge when it comes to I2S/EIAJ/Spdif/AES/EBU is more than limited.
I can see that the USB-Converter can either output Spdif or I2S.

Simply apply shorting of R16 to get I2S output, instead of R12 to get Spdif.

Well this is Great, but what is I2S... and how do you use it, and ...
Here is a describsion found on some website:

An I2S bus design consists of three serial bus lines:
- a line with two time-division multiplexing (TDM) data channels [SD],
- a word select line [WS],
- and a clock line [SCK].

Now if this is correct, how do you use this signal?
Let's say on the simple chip TDA1543??

It is so frustrating to be completely in the dark here,
it is also irritating to be forced to use Spdif, just because my skills does not
allow me to do otherwise.

   Another thing also very interesting, Tony mention something about using a
transport with output EIAJ, and then he uses the Asyncronus reclocking as
done on Monica2.. And loves the sound above all other.
Did I understand this right?

   Sorry if the questions are completely horrid, but it is hard to find any useful
info about the subject.
Or I'm just to stupid to understand what I find...   

Thanks for any input, anyone..

-Jonas

[yeo]

hi jonas

i2s communication is used by some dac chips, like tda1543, tda1541...

the chip i prefer, tda1545, unfortunately uses eiaj, so some conversion has to be done as the usb receiver used can only output i2s or spdif. 

if you hook up to tda1543, then it's pretty easy. there's an article on my site "computer audio is so much fun" that shows how it's done.

that said, no stock on the usb convertor for a while now!

monica2 uses asynchronous reclocking. there's also an article on my site (not by me though) where this diyer managed to incorporate asynch reclocking to his monica 1 dac. it consists of a flip flop for the word select, data and bit clock (the 3 lines you'll use in i2s too) being clocked at very high frequency clock, usually 80mhz or higher.

the jitter is not reduced this way but it's "spread out". as such, sensitivity to cable is reduced by this.

the transport tony uses is i believe the cdpro2. the controller could output eiaj as it's designed/built/programmed by our own mr kok here.

thus you could retrieve eiaj without having to go through spdif and all its associated muck.

no problem at all answering your questions. i'll be glad to help out!

yeo

[assendor]

Thank you yeo,

   That was really helpful information, even if this makes me understand there's
even more to learn here....

   Now what is also to wonder here, how high is the quality of the I2S
signal coming from the PSM2706 Chip?
It is to be assumed that from the computer everything is "Perfect"?
It should be MUCH MUCH better than any commercially available Transport.

Now mr kok's system/Player tweak most certainly is another story.

   This Combination of your USB-Converter and then Feed this I2S signal
into a DAC that can understand this Language,
Wouldn't that be better than almost any transports capability to transfer a
100% perfect signal to the DAC.

Does the USB contain any errors here?
Can there be in any way be added any errors via the USB system?
Is there any CRC check here in any way, or is it just likely there is no errors
implied over a USB-cable?

   You know I've always loved the USB-Monica, and it is suspected that the implied
errors from the SPDIF when using other systems is the answer to this.
Also we know that different quality cables sound different when using SPDIF.

When it comes to using CD-players of different kinds as a source, there is always
different sound from each one??
Now this makes me suspect they don't read, or do something to the data on the way from the CD to the DAC.
This makes it interesting to be sure the Computer does not do the same thing,
or at least how to reduce this to a minimum.

You did write something about why you choose a Synchronous reclocking
on USB-Monica, But I can't seem to remember why this was.

Monica3 has NO reclocking, how would Monica3 sound connected directly to
the USB-Converters I2S signal, or this might not be so easy Since Monica3 only can understand EIAJ.
But if we took the EIAJ from USB-Monica and applied it to Monica3,
would this work at all=??

Oh this was enough Blah blah..

thanks again yeo.

-Jonas

[yeo]

hi jonas

well, i wouldn't know how good is the data integrity but the fact that i use the same circuitry with my own i2s-to-eiaj conversion circuitry in the usb monica, which number hundreds in the world right now, so i guess it's all good! 

now we experimented with usb cable as well. there is differences in sound.

there was this cable, with gold plating etc, and touted as best in sonics etc. this cable sounded WORST.

the best cable we heard had ferrite clamps at both ends (or is it one end? can't remember.)

the digital receiver used in monica3 already has such a low jitter figure so i don't want to mess it up with all the extra stuffs.

you got to understand this. circuit wise, eiaj onwards, there is no difference between monica3 and usb monica.

the only difference is the interface circuitry.

usb monica --- usb convert to i2s, then convert to eiaj.
monica3 --- spdif convert to eiaj.

so differences is just in the interface circuitry.

yeo

[assendor]

Hello yeo,

   thanks a lot for taking the time to clear this stuff up, since I don't stand a
chance understanding all these Digital conversions stuff.

Nice to know that USB-Monica is doing well...
She sounds Wonderful to me, so of course others would think so to.
Now it would be interesting just for the fun of it, to check out other combinations.

   USB-cables matters too then... ERRR; So OK.,
Wonder why this is?
Since you mention there where some USB-Cable being better that had some
Ferrites,,, Could this mean that Noise entering the receiver is making the difference=?? Either in signals or in the 5v powering??

   You probably do know that my USB-Monica has separate power for the
USB- receiving circuitry, Not using any power from the computer.
I thought there was a difference when adding Os-Cons to the power supply from
the computer.
I though there where even more improvements when powering it separately. (Except some difficulties getting the computer to communicate
if power loss, then power back on in the USB-Circuitry.)

   When it comes to the USB-Converter, this has also been stuffed with loads of OS-Cons to improve computer powersupply 5V.
When experimenting with this, the improvement was there.

So there is no differences in Re-Clocking between Monica3, and USB-Monica then?
They are the same two DAC's, only one has SPDIF interface, and the other has
USB-Interface. OK got it.
Don't know where all the other mezz in my head came from? 
Maybe my brain is broken or something.. HAHAHA, What else to do but laugh.

Hey got an idea here...
If we where to use Monica2 connected I2S wise to the USB-Converters I2S
output,,, Where should this I2S be put in...
It would be interesting to hear how Monica2 sounded using USB as source,
since it has asynchronous Re-Clocking, and USB-Monica has not.

What would be specially interesting is to find out if there is any clocking errors
introduced on the way from USB??? Cause with asynchronous this then could
sound better.

What do you say? Is this just stupid, or is it not possible at all+?

   I've seen several places, and think you have mentioned it too, that I2S
directly is far better than to convert it to Spdif, then back to I2S again...
The Clock is not either messed up as much when using I2S directly,
Could this be correct??
Maybe it is, since Spdif has a lousy way of recovering the clock.. this is something
read around.. maybe here among other places.

-Jonas

[ole]

The USB cable only matters as far as RF pollution is concerned, I think. Even if you have a separate supply for the USB receiver, you still have the ground and data lines to worry about. I don't think the cable itself makes any difference like it would for analog or spdif interconnects.

The most straightforward solution would be  an optical USB connection, separating the PC ground from the rest. That is quite expensive, though, and introduces yet another power supply for the optical receiver.

Yeo mentioned a ferrite clamp on one of the sonically better USB cables. I just tried this, I used such a clamp from an AV cable, so I wound the USB cable twice through it and listened. The difference is quite audible, much like improving Vref stability further - which is not surprising, as the ferrite clamp supposedly dampens RF spikes on all lines running through it, including ground.

Highly recommended, and dirt cheap!

Ole

[assendor]

Hello Ole,

How Fantastic, Amazing... Can't wait to check it out.

Guess this will be the case also for the USB-Converter then, is this the one you are using?
No you have USB-Monica, right?

The USB-Cable from my computer is 5.meters, then there is a Serious Heavy Duty cable going straight to ground from the Plug in the USB-Monica Circuit board. (Pretty sure this Earthing did make a difference?)

It is now clear to us all that noise here is something making this solution also improvable,
no matter how digitalized the transfer is.

Ferrite clamps... Did you take all the pairs in the USB-Cable, including ground and winded them
around this Ferrite Clamp?

Cheap tweaks are the best, and you Ole are superior at coming up with such solutions anywhere.

thanks a lot.

   OH, BTW, if we used a USB-Cable, did what Ole explains here, then connect the USB-Converter,
using the SPDIF output with a Pulse trans, then SPDIF cable, and a Pulse trans again, would
the improvement of the Ferrites still be noticeable..

Is it only poisoning the Analogue part of the USB-Monica, since it is connected to computers ground,
or is the contamination of the signals also happening on the Digital side in the Chips`?``

IS it possible to put a Inductance of lets say a Henry, in series with the USB-Ground, when it enters the
Monica-DAC?
Would this disturb anything?+
The +5volts should be possible NO matter what to Put an Inductor in series with, this could possibly
destroy something if it disconnects during operation, due to discharge of the Inductor.
Surely the caps would take care of this, but maybe no need to test to see if it really is OK.

-Jonas

[ole]

I have USB Monica / Mojo.

The ferrite clamp is just clamped on to the whole USB cable, with the USB cable passing through it twice. Think of side A and B of the clamp, then the cable comes from the PC into side A, leaves it on B, goes back into A, leaves it on B, then continues to the DAC. A loop around, so to say. This increases the suppression effect.

A ferrite clamp or ferrite bead is not a pure inductor. It is a non-linear element which partly neutralizes spikes in a conductor passing through it, while not affecting lower frequencies. So I've been told. How that exactly works is a little over my head, though - still, it's quite effective. There is a good reason why you find them on nearly all notebook switching power supply cables, and often on USB cables that come with better quality peripherals.

An inductor in the ground loop will probably make the USB interface stop working, as the return path is then blocked for the data lines which carry RF.

My guess is that it will have a positive effect on the USB-converter, too, as RF pollution on the USB power supply may affect the SPDIF timing.

Ole

[ole]

Just for the fun of it I added a second ferrite clamp to the USB cable, on the DAC side. I didn't expect much, but in fact it got a LOT better. More detailed, more ambience, darker background. I'm not sure what is going on there, but I really like it!

In some other forums I found several people commenting on negative effects of ferrites on USB audio cables. While I took those with a grain of salt (big bucks for cables involved, little technical background), it sure made me think - why do I hear what I hear, and others apparently don't?

Did anyone here try ferrite clamps on USB cables?

Ole

[yeo]

hi ole

you make good use of your holidays!

the better sounding usb cables i have heard, all have ferrite clamps at both ends.

and it makes sense. ferrites absorb those emi/rfi noise.

now what's really interesting is, what will happen if we wrap the usb cable with the ers emi/rfi absorbent paper?

yeo

[ole]

I put yet another ferrite clamp in the middle of the cable, so it's now a total of three. It got still better, although not as much as with the first two. I tried another clamp on the DC supply to Mojo/Monica, but that didn't change anything.

Just how much junk travels along the USB cable, and isn't there a better way to get rid of it? Ready made optical USB solutions are really expensive.

What is the actual problem here - the dirty 5V USB power from the PC, noise on the data lines, the ground connection between Monica and PC, or all of them?

Ole

[yeo]

hi ole

i believe the data/signal frequency is quite high, in megahertz range, so the noise are all in the mhz range. quite a tall order to ask electrolytic capacitors to filter out everything!

also the fact that the longgggg usb cable acts as an antennae, transmitting and receiving more such noise. if ferrites help, i believe the ers paper should do wonders. wrapping the esr paper over the air core inductors of charlize really helps. and again, the switching noise emitted from the ta2020 chip is in the range of mhz.

i believe the self powered usb-eiaj module should reduce this noise problem somewhat. a good fast power supply regulator can help mitigate this. but do give me time. the previous design i drew isn't useful at all. need to redo and fork out the money for another new pcb layout.

yeo

[ole]

No, no, I didn't mean to rush you to change your design. This seems to be a general USB problem, not specific to Monica. Thinking of it, part of the problem might be that the 5V supply return is the same as signal return and shielding - essentially, we are feeding the RF signal from the data lines into the Vdd at Monica side, at least the part that drops over the resistance of the ground wire. That's bad. No wonder if the ferrites improve it. A major improvement would really be self-powering.

About self-powering USB-EIAJ, you previously mentioned device detection problems when booting the PC with Monica powered off. Why not just use a simple relay switch? If the coil is not powered, draw power from USB bus. If coil powered, draw power from local supply. Coil is connected to local supply. That should do it, or are there other issues?

Ole

[yeo]

hi ole

there is a sequence to powering on/off the usb receiver chip. i'm aware of this.

but the biggest problem i'm facing now is that in my new design/pcb, the computer won't even recognize it is a usb audio device! it just says "unknown usb device". so something is wrong.

i have soldered/desoldered the 32 pin extremely small tqfp pcm2706, rewired a few pins... etc. so i'm actually stuck at this stupid step of getting the pc to recognize it!

most likely i'll chuck away this design and redo since i made quite a mess out of it.

ha ha! i must be one of the most clumsy guy around!

yeo

[ole]

Hi Yeo,

This was really bugging me, so I disconnected the USB 5V supply by lifting one leg of the L1 ferrite on USB Monica. I then made a simple 5V supply with LM78L05, connected to the 12V Mojo supply before the regulator, over a 150R resistor and another ferrite for decoupling, and I also put the recommended buffering cap before the LM78L05 and a small ceramic cap to the output.

With this mod, I have to power on USB Monica first, then the PC.

Result is everything I hoped it to be. Much increased resolution, better soundstage depth. Just like adding the ferrite clamps on the USB cable, but a lot more pronounced.

I highly recommend this to anyone using USB Monica!

Ole