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Buffalo III I2S input
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88bruce  
#1 Posted : Sunday, August 28, 2011 5:02:40 AM(UTC)
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I got my new Buffalo III up and running, and initial impressions are it is a step up from
my parallel TDA1543 Dac. The problem is, I can only get it to work with SPDIF input.

I have a USB module (DDDac) which is close to the Twisted Pear USB module, in that it
uses the PCM2707, the only difference is an on-board power supply.

When I originally tried I2S, there was distorted music as output. The lock LED was on.
I tried switching the SPDIF auto-detect DIP switch to bypass (all 16 DIP switches were
originally set to the off position), but this had no effect.

I2S is hooked up as:

Gnd - Gnd
Bclk - Dck
LRclk - D1
Data - D2

I believed the Buffalo III was thinking the I2S was SPDIF. I disconnected the Bclk and LRclk,
moved Data to D1, and switched the USB module to SPDIF output. After observing the lock
LED was on, undistorted music was output.

I have the Buffalo III set up for PCM input, so jumpers JPCM1-3 give continuity on D2-5,
but I noticed there was also continuity between D1 and D2-5. Is this expected?
For I2S input, this is bridging the LRclk and Data lines.

Any recommendations to get I2S input to work?






Edited by user Sunday, August 28, 2011 6:23:50 AM(UTC)  | Reason: Not specified
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LeonvB  
#2 Posted : Sunday, August 28, 2011 5:27:39 AM(UTC)
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Quote:
I noticed there was also continuity between D1 and D2-5. Is this expected?

Did you also jumper JDSD1 and JDSD2?
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88bruce  
#3 Posted : Sunday, August 28, 2011 5:44:59 AM(UTC)
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My interpretation of the instructions is that DSD input is different than I2S in that
DSD does not use the LRclk, so I have not added jumpers JDSD1-2.

By the way, this is direct input, ie.; I'm not using Sidecar, etc.

Edited by user Sunday, August 28, 2011 6:24:50 AM(UTC)  | Reason: Not specified
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LeonvB  
#4 Posted : Sunday, August 28, 2011 6:30:48 AM(UTC)
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No that would be an error, but that would have explained D1 being connected to D2. The DSD, PCM and SPDIF schemes mentioned are mutually exclusive options when working with direct inputs. I was a bit worried you might have tried to get both DSD and PCM working.
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glt  
#5 Posted : Sunday, August 28, 2011 8:08:49 AM(UTC)
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You may try using 9bit pseudo quantizer. This effectively ties all the internal DACs to channels 1 and 2 so you can test without jumpering any inputs. Also, keep dac phase in normal
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Russ White  
#6 Posted : Sunday, August 28, 2011 8:10:29 PM(UTC)
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The only way for D1 to be connected to D2 is if both the JPCM and JDSD jumpers where used or you have a solder bridge short. Well I guess they could also have been wired together externally. :)
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88bruce  
#7 Posted : Monday, August 29, 2011 11:07:27 AM(UTC)
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I removed the Buffalo III board entirely from the case I had it in to isolate the connections.
There are no solder bridges in the area of D1 and D2, and the JDSD1-2 pads are totally
free of solder, but continuity between D1 and D2 is still present. There are also no solder
bridges on top of the board where the wire (22 awg insulated copper) exits. Could an
internal short exist in the board?


Edited by user Monday, August 29, 2011 11:22:47 AM(UTC)  | Reason: Not specified
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Russ White  
#8 Posted : Monday, August 29, 2011 11:35:37 AM(UTC)
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Not very likely, because those traces don't actually run *in* the board but on the top and bottom layer.

Is the short there when you source is not wired at all? Also can you snap some good closeups?
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Brian Donegan  
#9 Posted : Monday, August 29, 2011 11:41:33 AM(UTC)
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Quote:
good closeups


... of the chip, the input pads, RA1, and the jumpers.
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88bruce  
#10 Posted : Monday, August 29, 2011 1:04:47 PM(UTC)
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Yes, the short exists with no external connections. I removed all the I2S wiring and that did not
change anything. I used Kester 44 solder to install the PCM jumpers, so I don't believe the
jumpers were hot enough to melt the solder on the other side of the board in the vicinity of RA1.

My camera doesn't have fine enough resolution to show the detail you are requesting.

Edited by user Tuesday, August 30, 2011 8:06:03 AM(UTC)  | Reason: Not specified
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Brian Donegan  
#11 Posted : Monday, August 29, 2011 1:11:33 PM(UTC)
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Is the continuity 0-ohms?
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88bruce  
#12 Posted : Monday, August 29, 2011 1:15:43 PM(UTC)
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Yes, zero ohms.

Edited by user Tuesday, August 30, 2011 3:22:11 PM(UTC)  | Reason: Not specified
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Brian Donegan  
#13 Posted : Tuesday, August 30, 2011 3:39:56 PM(UTC)
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88bruce  
#14 Posted : Wednesday, August 31, 2011 2:29:28 AM(UTC)
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Got it. Thanks.

Edited by user Wednesday, August 31, 2011 2:40:02 AM(UTC)  | Reason: Not specified
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88bruce  
#15 Posted : Wednesday, September 14, 2011 5:11:58 PM(UTC)
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To follow up, Twisted Pear determined there was a short in the board and sent a replacement.
Basically, they backed their product.

The object of this whole exercise was to get I2S running, but after succeeding at this, I realized
I2S was inferior to SPDIF out of the PCM2707. And for SPDIF, a DPLL Bandwidth setting of
medium-low corrected artifacts created while in the default setting.

The result is a Dac a couple of steps up from my old Nos Dac.
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88bruce  
#16 Posted : Saturday, September 17, 2011 1:16:08 PM(UTC)
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I might have spoken too soon. While the Buffalo III replacement board sounds good, it
doesn't sound as good as the board with the short in it. Not quite as much clarity.

I'm using a Legato 3.1 with no output buffers for an IV stage with a similar power supply (ESP)
to the Twisted Pear BP, in that it uses LM317, LM337 regulators, but has only one bridge.
Output is +15.11VDC and -15.06VDC. Power to the Buffalo III is through a LM323 fixed 5VDC
regulator (actual 5.03VDC) which is powered by a 12VDC battery. The battery has a separate
switch from the Legato power.

If the Legato is powered only, the current draw is 200mA per rail on the power supply.
I can adjust the DC voltage on the balanced and SE outputs on both channels to zero.
When the replacement board is powered up (no input signal), the positive rail on the
Legato power supply drops to 175mA (voltage doesn't vary), and the DC voltage on the
left channel SE output goes to 2V. The right channel SE output VDC stays at zero.
Now, on power up, the previous board with the short in it didn't alter the current draw on
the Legato's power supply positive rail, or the DC voltage on the left channel SE output, so
I'm inclined to believe there might be a problem with the replacement board.

Russ, can I make a straight up exchange for my old board?




Edited by user Saturday, September 17, 2011 3:58:58 PM(UTC)  | Reason: Not specified
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Russ White  
#17 Posted : Saturday, September 17, 2011 9:11:54 PM(UTC)
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Hmmm, the problem on the board you returned was a simple solder bridge. This does not sound like anything like that.

I would double check the Legato by swapping channels etc.
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Russ White  
#18 Posted : Sunday, September 18, 2011 7:26:51 AM(UTC)
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This sounds like a faulty connection at the Legato inputs.

Also is is normal for the current draw from the legato positive rail to change when the DAC is powered up, this is because the DAC itself is now supplying some current. :)

Edited by user Sunday, September 18, 2011 7:29:32 AM(UTC)  | Reason: Not specified
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88bruce  
#19 Posted : Sunday, September 18, 2011 11:58:40 AM(UTC)
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I checked the continuity of the connections between the two boards, and everything looks
good. I also replaced the opamp on the Legato board, and nothing changed. The current
draw on the positive rail dips and stays down, which was not the case with the old board.

To be honest, I don't know what the problem is, or what I perceive to be the problem.
All I do know is that the old board did not cause any perceived problems such as this.

Edited by user Monday, September 19, 2011 3:20:15 AM(UTC)  | Reason: Not specified
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Russ White  
#20 Posted : Sunday, September 18, 2011 12:46:17 PM(UTC)
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It would not be normal for the current not to change. That would be a problem. :)

What I am saying is you can probably solve whatever problem you are seeing. If you don't connect any output stage and just measure the DC voltage at outputs at the DAC what do you get?

Can you post some pics of the Legato? Are the jumpers for omitting the buffers installed correctly?

Edited by user Sunday, September 18, 2011 12:47:00 PM(UTC)  | Reason: Not specified
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