Twisted Pear Audio Support
»
Product Support
»
General Questions
»
Nasty 'plopping' noise when autoswitching DSD -> I2S
Rank: Member
Groups: Member
Joined: 4/13/2010(UTC)
Posts: 19
Location: The Netherlands
|
Hello all,
I have modified my Denon 2200 player to directly output DSD. This works like a charm and I'm using a homemade OTTO-like switch to automatically switch between DSD and I2S (switch signal comes from the Denon | DSD; signal = high). So far so good. However, when I switch from SACD to Redbook CD, the switching off of the relay causes a nasty 'plopping' noise (some spike on the digital input).
Any ideas how to cure this issue? (and if nobody has a simple solution: Russ / Brian, could this harm my Buffalo?)
Thank you for your thoughts.
Maarten
|
|
|
|
|
|
Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
|
You might want to mute the DAC while switching.
Also some AC coupling caps prior to the relay may help.
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 4/13/2010(UTC)
Posts: 19
Location: The Netherlands
|
Russ,
Thank you for the reply. I am however a relative newbie (especially with digital circuitry), so could you explain yourself a bit more?
-Do you mean muting the analog outputs of the Buffalo or muting it with the mute function?
-Do you mean AC coupling of the digital signals? If so, do I just place a 0.1uf capacitor in series with DCK, LRCK, DATA and with DCK, D1 and D2?
Thank you,
Cheers Maarten
|
|
|
|
|
|
Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA
Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
|
Can you explain how you are powering the relay and the rest of the circuit?
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 4/13/2010(UTC)
Posts: 19
Location: The Netherlands
|
The relay is a 5V OMRON relay, powered by a TP LCDPS. The switching signal comes from the Denon 2200 (DSD select signal, DC ~3,3V, high when a SACD is in the player). Because of the common ground plane of the DSD select signal and the digital signals, they share the same ground. This ground is also shared with the LCDPS ground, due to the circuit. Other then the shared ground, the circuit is comparable to the OTTO switch.
I also tried using the 5V line from the Denon (from the main board), this line has however a voltage drop, resulting in a too low voltage to keep the coil closed. I could try to take 5V from the power supply board of the Denon, if you think this would help.
|
|
|
|
|
|
Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
|
Do you have a diode accross the relay coil?
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 4/13/2010(UTC)
Posts: 19
Location: The Netherlands
|
Yes there's a diode, cathode side connected to the +5V side and anode connected to the -side and collector of the transistor. I just took it out and did a diode test with my multimeter, seems to be ok..
|
|
|
|
|
|
Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
|
It is always going to take the DAC a little while to detect and switch formats. During that transition your likely to get noise.
To fix this you can send I2C command to the DAC to enter MUTE state. And then send I2C command to go back to playing.
|
|
|
|
|
|
Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA
Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
|
How are you powering the DAC? What is shared with the relay circuit, if anything?
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 4/13/2010(UTC)
Posts: 19
Location: The Netherlands
|
The relay driver shares its LCDPS with the MUX. The DAC itself is powered by its own Placid, as is the IVY.
Because of my extended knowledge of I2C programming (read=none), and the need for the Buffalo datasheet. Would it be possible to program the Volumite in such a way, using one of the I/O ports, that when the 'switch signal' goes from 3.3V to 0, it sends the mute command and after a certain amount of time, it sends the command for playing? If possible, would you be willing to implement this (if this cannot be solved in an simpler way)?
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 4/13/2010(UTC)
Posts: 19
Location: The Netherlands
|
Brian, thanks,
Changing the MUX from the LCDPS to the Buffalo's placid did the trick. Still have to check some other configuration but for now no plops anymore.
Maarten
|
|
|
|
|
|
Twisted Pear Audio Support
»
Product Support
»
General Questions
»
Nasty 'plopping' noise when autoswitching DSD -> I2S
Forum Jump
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.
