Hello,

I took my Buffalo DAC to a friend with oscilloscope and we saw an interference/osciallation at Placid outputs when powering WaveIO USB>I2S module. Yet it works fine when connected to Buffalo IIISE so it's Placid+WaveIO combo behavior. Also there's no problem when powering WaveIO by simple 7805 regulator for example.
I also tried older placid HD 1.0 and it actually shows less of interference, but it's there nevertheless.

What can be of an issue? The way I understand it - it's the reaction of Placid to the load it sees? Needs more capacitance maybe? Can you suggest something please?

Edited by user Saturday, August 22, 2015 3:07:57 PM(UTC)  | Reason: Not specified

It could be extreme reactance(L or C or LC parallel) of the load. A small resistor in series with the regulator could help.

Hello again,
I finally got to test and measure my interference problem. So here are the results:
There is 300mV ! interference measured around 500khz with oscilloscope on Placid 2.1 outputs when powering WaveIO USB>I2S converter. Placid is fine by itself when no load connected or when powering B3SE

Adding a capacitor at the output solves the problem, as is the 0.5ohm resistor (got to try smaller values soon).

But honestly - i'd be happy if more "elegant" solution is possible. Any way I can tweak Placid itself to calm it down?

Also strange thing is that older Placid HD has twice smaller interference as compared to 2.1 version in same situation. Why is that?

Edited by user Monday, November 9, 2015 6:37:00 AM(UTC)  | Reason: Not specified

Here:

Edited by user Monday, November 9, 2015 6:33:05 AM(UTC)  | Reason: Not specified

Looking at that photo of yours - it's really different i think..
Forgot to say that i don't see similar "distortion" on I2S line, but with optical isolator i guess it should be expected...

Sure, what is amount of "distortion" (shall we call it this way?) you have on yours in mV?
Do you power WaveIO with separate/dedicated Placid? How do you connect your I2S isolator grounds?
I run all grounds to buffalo and only take +5V for isolator chip (IL715) directly from Placid powering the buffalo. My WaveIO has dedicated placid 2.1 powering it (with separate transformer secondary).

Yesterday I tried smaller cap and 0.068uF (Vishay ERO 1837) film worked fine, resulting in a flat line
If it can't be fixed by some magic on Placid itself, like changing some caps for example, then I guess cap across outputs is the way to go since I don't like idea of resistor there.


P.S. Is Placid V1 = Placid HD? I have Placid HD too and it shows same problem (just smaller), but not like yours...

Edited by user Monday, November 9, 2015 6:57:27 PM(UTC)  | Reason: Not specified

Hi AlexanderT,

Do you also have the distortion on the PSU only when the music plays?

Somehow my Placid HD V2 is steady.

The V1 for the Teleporter is not but only when the music plays.
When it plays it shows like next picture and when I stop it (without disconnecting anything) its just a flat line...

!!EUREKA!!

I noticed it was the Teleporter adding noise to it's PSU (with both versions Placid)

Lowering the Shunt Current near to zero, as to the point where the Voltage begins to drop, it stabilized. But only with with music playing. With the music on hold it was steady anyway.

So it must be the signal distorting the PSU.

Measuring the Voltage at the Teleporters VIN it was the same value of the setting of the PCU; 5,25V.

I remembered that the Teleporter requires a Max input Signal voltage of 3.3V
The WaveIO does accept 3.3-5V.

To make a long story a bit shorter I placed a Blue LED in the VIN wire from the Teleporter to the WaveIO and it stabilized at 3.3V exact.

And guess what?!

Clean Power at the Placid!!

AlexanderT check the input voltage of the signal to the WaveIO

(and oh yeah, it also solved my little light switch flipping/ lock loosing issue)




Hm well. In practise the voltage is quite a bit lower but it works.
I tried it with a Red LED which should have a lower treshold value than a blue one bit that did'nt work somehow..

Let's try a green one..
Yep, better 3,23V..

Edited by user Tuesday, November 10, 2015 2:52:15 PM(UTC)  | Reason: Not specified

Yes!

I use a green LED now which lowers it a bit more than 3,3V

Probably you have some of those green LED's as spare from the DAC.

Hm ok...

So one seperate for the WaveIO, one seperate for the Teleporter and one for the Isolator circuit of the WaveIO.

That means an extra transformer.

Any suggestions for a decent supply?
I have two Placid V1's left. Can I modify them to make it suitable for lower voltages?
The Placid stops at 4,6V....

Edited by user Tuesday, November 10, 2015 7:44:13 PM(UTC)  | Reason: Not specified

No not at the side of the WaveIO.
I have a supply for the teleporter and one for the WaveIO on the sender side.
On the receiving side it's shared with a DAC's supply.

Does the Teleporter have LED options? Where exactly?

The Isolator circuit draws 18mA so that's minimal...

Edited by user Tuesday, November 10, 2015 8:58:25 PM(UTC)  | Reason: Not specified