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Old 24th November 2011, 05:29 PM   #1681
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Default Synchronous Clocking/Hum Update

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Originally Posted by barrows View Post
I confirmed that the MC lead was introducing the hum into the output, disconnecting it and going back to the onboard clock eliminates the problem.
I have ordered some micro coax (U.FL) cables and jacks for the clock distribution. Russ, or anyone knowledgable here, is it advisable to connect the shield at both ends of the cable, or should I try just connecting it at the source (USB receiver board) end?
Thanks in advance!
OK. So first I moved my USB receiver so that it is closer to the B-II, the I2S lines are now about 7 cm, and the masterclock line (on U.FL micro coax) is about the same. At first I tried only terminating the shield at the source end. At this point the hum was much reduced, but still audible with the ear at about 10" from the woofer cone, in both speakers. Now many might be OK with this level of hum (inaudible, even at on the quietest night, at the listening position, and certainly below the noise floor of even my lowest noise recordings), but knowing that there was virtually none before trying the synchronous clocking, I kept tweaking...
I decided to ground the shield for the MC cable at both ends: I carefully soldered a micro bnc to pad R17, and ran a short ground lead to it, then I used a 5 cm U.FL cable between the boards. Now the hum is entirely gone from the R channel, and the L channel only has hum audible with the ear within 2" of the woofer cone. The hum now present is likely due to pickup in the analog output wiring, as the L channel leads are closer to the transformer side of the chassis. I will probably experiment with shielding in the chassis to reduce the hum on the L channel, but it is likely now entirely inconsequential...

I would recommend anyone experimenting with synchronous clocking to go ahead and ground the clock distribution cable at both ends, and to use some U.FL or W.FL coax cables.

Russ, great news on the teleporter. When you say no problems with longish runs of cat 5, do you just mean no dropouts or loss of lock, or have you looked at MC and Bit Clock waveforms on the 'scope and seem no degradation in the waveform? Seems almost to good to be true! Any potential advantage to cat 6 with the additional shielding?
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Old 24th November 2011, 05:51 PM   #1682
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Quote:
Originally Posted by barrows View Post
Russ, great news on the teleporter. When you say no problems with longish runs of cat 5, do you just mean no dropouts or loss of lock, or have you looked at MC and Bit Clock waveforms on the 'scope and seem no degradation in the waveform? Seems almost to good to be true! Any potential advantage to cat 6 with the additional shielding?
I mean both. There is no degradation at all that I can detect.

LVDS is perfect for the application.

No need for CAT6 but any twisted pair type cable will work pretty well.
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Old 25th November 2011, 08:11 AM   #1683
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How can I connect the Buffali II in syncronous mode?

D.

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Old 25th November 2011, 11:20 AM   #1684
Angelm is offline Angelm  Bulgaria
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Russ, Brian my Buffalo II has problem with locking S\PDIF. I listened the dac half year without any problem. I tried everything. Different USB to S\Pdif converters, regular CD...
Finally I disconnected everything and powered the dac from battery. The power amplifier was also disconnected from main supply.
The laptop was running on battery and the LOCK diode still blinking. Is there anything I could try to solve the problem?

Thanks,
Angel
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Old 25th November 2011, 04:12 PM   #1685
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Default Synchronous Clocking

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Originally Posted by Nikon1975 View Post
How can I connect the Buffali II in syncronous mode?

D.

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Doing this is described elsewhere in this thread, go back and take a look for pictures, Bunpei has been doing this for awhile with the SD Transport. First, you need an I2S source with masterclock output, and I would not consider trying this unless you are confident that your source is low jitter, as using a synchronous clock eliminates the ASRC and its "jitter reduction" on the ESS chip.
To provide a synchronous clock, first depower the oscillator on the B-II board, by either removing the clock Trident, or if not using Tridents, removing the associated inductor on the underside of the board (see trident instructions for finding this inductor). Then the Masterclcok signal lead can be soldered to the pad at R17 between the ESS chip and the Oscillator on the board-use your meter to learn which is the right pad for the clock input to the ESS chip. As mentioned previously, I recommend using a coax cable for clock distribution (U.FL works well) and grounding the shield at both ends. Keep the clock distribution cable as short as possible (as well as the other I2S leads).
I am no expert, but this is working well for me. If more expert readers feel a need to comment, or have opinions on "better" ways to do this, please chime in!
BTW, I am curious why my B-II has no resistor at R17, is this a change that was made, or should R17 be present?
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Old 25th November 2011, 04:54 PM   #1686
avr300 is offline avr300  Denmark
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Barrows

R17, look here

Buffalo II- R17 required? - Buffalo DAC - Twisted Pear Audio Support
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Old 25th November 2011, 05:28 PM   #1687
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AVR300!

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Old 26th November 2011, 02:31 PM   #1688
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In my case, R17 is installed. Do I have to remove it to connect the master clock?

D.
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Old 27th November 2011, 03:41 AM   #1689
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Quote:
Originally Posted by Nikon1975 View Post
In my case, R17 is installed. Do I have to remove it to connect the master clock?

D.
No, but you probably don't have a good reason to have it there in the first place.
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Old 27th November 2011, 08:25 AM   #1690
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No, but you probably don't have a good reason to have it there in the first place.
Russ,

Your answer puzzle me. I have the BII with 100 MHz crystal. Is R17 there by mistake?

Please clarify,

D.
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