Weird problem with DIT4192 SPDI/AES/EBU Transmitter - diyAudio
Go Back   Home > Forums > Source & Line > Digital Line Level
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 16th January 2009, 12:26 PM   #1
Salar is offline Salar  Germany
diyAudio Member
Join Date: Feb 2006
Location: Germany
Default Weird problem with DIT4192 SPDI/AES/EBU Transmitter

3 years after installing a digital transmitter DIT4192 in my Nakamichi OMS-5EII,
see this

I found out, that the circuit radiates heavily.
(i.e the image on my analog TV was noisy, when the Nak was switched on)
To make a long story short, (besides the fact that the circuit was not properly grounded), I installed a switch, to interrupt power, both +5V and ground.
The DIT4192 is ALWAYS working, nevertheless when being switched on or off!

With ground and +5V Voltage disconnected and only the signal inputs connected, I can always measure around 3 V between the +5V input of the DIT4192 circuit and chassis ground. Even connecting the DIT4192 circuit ground to chassis/player ground will still give +3V in in the DIT4192 +5V input.
When chassis ground is diconnected, I also have some small voltage on the DIT4192 circuit ground.
So, this thing works (no audible distortions), even without being

The only explanation I have is that voltage from the DIT4192 signal inputs (Oscillator Inputs, Bit Clock, Word Clock/L-RClock, they are about 2V) is leaking through the circuit.
I checked the circuit several times, but it seems to be O.K, no leakage because of shorting wires and connections.
The tentlabs oscillator and the DIT4192 have their own power supplies, but their grounds are connected to the player´s power supply ground. So I guess no problems there

So, is this a normal behaviour that the DIT4192 could run from
signal voltage only? Or did I blow the DIT4192 to some unstable state?
All the best,
  Reply With Quote
Old 17th January 2009, 02:10 AM   #2
dmills is offline dmills  United Kingdom
diyAudio Member
Join Date: Aug 2008
Location: High Wycombe
That sort of thing is certainly not unheard of, I had a entire cmos logic board do that to me once, dozens of 4000 series chips and it would work 'most of the time....', eventually I found that there was a condition that occured about once a week or so where there would be insufficient inputs at logic one and some of the logic would reset.

Mr muppet here had forgotten to hook the 5V rail up to the board!

I would solve your RFI problem rather then adding a switch (may be board layout, decoupling or grounding).

Regards, Dan.
  Reply With Quote
Old 17th January 2009, 07:34 AM   #3
Salar is offline Salar  Germany
diyAudio Member
Join Date: Feb 2006
Location: Germany
Hello Dan!
Thank you very much for the reply!
I will rebuild the board with the DIT4192 only + output transfomer, using a SSOP to
DIP converter board. I could build/glue it in a sandwich-like style,the board with chip, one isolated thin copper plane for positive voltage connections, one plane for negative voltage.
But are planes better for RFI? Or should i keep the common connections for supply voltage and GND as physically as small as possible?
All the best,
  Reply With Quote
Old 17th January 2009, 08:09 AM   #4
jahonen is offline jahonen  Finland
diyAudio Member
jahonen's Avatar
Join Date: Jan 2002
Location: Kuopio, Finland
Originally posted by Salar
But are planes better for RFI? Or should i keep the common connections for supply voltage and GND as physically as small as possible?
All the best,

I'd say that plane is a necessity if you are targetting to low EMI. Basic rule to robust and clean digital circuit is basically to use tons of ground. It is the ground/signal inductance that matters above all.

But, you'll also need to ensure that the trace is close enough to the plane for image currents to effectively cancel the trace currents. This means that trace distance through dielectric must not be larger than width of the trace (this makes about 75 ohms impedance traces). For digital circuits this means that you'll need to use very thin PCB or (more practical) use at least 4 layer PCB (not so expensive nowadays anymore).

Also, where you hook digital signals around, always ensure that each signal has current return path (ground) very close to signal itself. Otherwise, it is an invitation for EMI failure.

  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
weird problem sberube Solid State 15 22nd October 2008 06:27 PM
weird hum problem audiopro Tubes / Valves 4 31st August 2008 08:16 AM
Problem with hobbie FM Radio transmitter bmattias Everything Else 4 19th August 2008 05:51 PM
Weird Amp Problem Stewart8989 Car Audio 3 6th April 2007 06:54 AM
Weird PSU problem phn Power Supplies 8 6th February 2007 02:42 AM

New To Site? Need Help?

All times are GMT. The time now is 01:46 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2