I have built a Legato 3, but haven't installed it yet, in part because I am having difficulty understanding and researching if common mode DC will damage my system.
I have active loudspeakers made by ADAM, and I have emailed them to inquire if common mode DC will work with their equipment. I think that I failed in explaining the situation to them, as they answered as if I was inquiring about offset. I would bet that it would be ok to use the Legato with my setup, but I want to ask the manufacturer to be certain.
Here is what I am thinking of writing to them in response, please let me know if I have made any errors, or if I should add anything.
The DAC I want to use has common mode DC at the balanced output, but no differential DC. At the balanced output of the DAC, there is no DC between + and -, but 7-9 volts of DC between + and Ground and - and Ground. Will the DC between + and Ground, and - and Ground cause problems for the amplifiers, or will it work since the DC between + and - cancels itself out?
Thank you for your time and assistance.
Aaron.
I have active loudspeakers made by ADAM, and I have emailed them to inquire if common mode DC will work with their equipment. I think that I failed in explaining the situation to them, as they answered as if I was inquiring about offset. I would bet that it would be ok to use the Legato with my setup, but I want to ask the manufacturer to be certain.
Here is what I am thinking of writing to them in response, please let me know if I have made any errors, or if I should add anything.
The DAC I want to use has common mode DC at the balanced output, but no differential DC. At the balanced output of the DAC, there is no DC between + and -, but 7-9 volts of DC between + and Ground and - and Ground. Will the DC between + and Ground, and - and Ground cause problems for the amplifiers, or will it work since the DC between + and - cancels itself out?
Thank you for your time and assistance.
Aaron.
I would add, "Or can I omit the signal ground all together?" As this would eliminate the DC all together. It is often not needed.
May I ask a question regarding removing ground on balanced outputs? A balanced output works by keeping the signal that is equal and opposite in polarity respecting to ground, and discarding the signals that are equal in polarity and voltage.
How can you remove ground with no issues, where is your common reference?
Regards,
Regi
How can you remove ground with no issues, where is your common reference?
Regards,
Regi
Finished my legato 3.1
Playing through some cheap headphones atm. Have never heard them sound this good though
Tried using no ground connection to my icepower 1000asp modules (with attenuator for testing purposes). I had a little background noice through the speakers. Are yours completely silent?
At start up the + - outputs measure 2mV dc but settles down to 0,0 and I was wondering what your numbers are? Do you see the same during warm up?
I had the output at 0mV initially but noticed that after a while I had aprox -2mV so I adjusted it too keep it as close to 0 as possible when warm.
Playing through some cheap headphones atm. Have never heard them sound this good though
Tried using no ground connection to my icepower 1000asp modules (with attenuator for testing purposes). I had a little background noice through the speakers. Are yours completely silent?
At start up the + - outputs measure 2mV dc but settles down to 0,0 and I was wondering what your numbers are? Do you see the same during warm up?
I had the output at 0mV initially but noticed that after a while I had aprox -2mV so I adjusted it too keep it as close to 0 as possible when warm.
Ok,
Thank you.
Playing through my T1`s atm. Next step is to set up my Placid HD BP. Just need to finish it up by cleaning the board and inspecting the solder joints. Too bad the tridents are close to impossible to get a hold of. Lots of exiting plans and designs, but hard to plan out a complete solution atm. But hey, thats diy
Thank you.
Playing through my T1`s atm. Next step is to set up my Placid HD BP. Just need to finish it up by cleaning the board and inspecting the solder joints. Too bad the tridents are close to impossible to get a hold of. Lots of exiting plans and designs, but hard to plan out a complete solution atm. But hey, thats diy
Hey Guys,
Just read through the forum. I'll be outputing to a home theater preamp processor from Legato 3.1 balanced outputs with a dual mono buff II config. What I got for the thread is that for this config the SE/Balsie buffers are not required and no output caps are required...
Then essentially you just wire it as shown for dual mono buff II under the IVY-III section of the TPA site.
Do I understand correctly?
Just read through the forum. I'll be outputing to a home theater preamp processor from Legato 3.1 balanced outputs with a dual mono buff II config. What I got for the thread is that for this config the SE/Balsie buffers are not required and no output caps are required...
Then essentially you just wire it as shown for dual mono buff II under the IVY-III section of the TPA site.
Do I understand correctly?
It is unlikely that it'll work.
1. If you mean 2 BII's into 1 Legato: it won't work if you wire the outputs as in the classic dual mono setup. Because in that case, obviously your wiring should be the same as a single IVY3/Legato board.
2. If you mean 2 BII's into 2 Legato's: it won't work since the dual mono wiring uses the SE outputs, and those outputs won't work without the SE stage.
I'd skip that part if possible. Simply use a volumite to control the volume, it's extremely unlikely the preamp will be an improvement.
Lenov,
I'm not using the preamp cause I think it will be an improvement but my preamp processor controls my whole system and therefore i need to use it for the convenience factor of not having to unplug stuff.
I was not asking if I could forgo the Ballsie/SE stage...I was asking if I can safely omit the buffers on Legato 3.1. I believe in a previous post Russ mentioned that a dual mono x 2 Legato was a situation in which the buffers provided no benefit.
Second I was asking if I needed some film caps at the balanced output to take care of the common mode DC...but I believe in this case that it is not needed as well as it is canceled out in this configuration.
Russ...can you confirm? Also I looked for the wiring diagram for dual mono and I couldn't find it on the TPA site any more...you think you could include it as part of the Legato Manual before you take it out of draft status.
Best Regards,
Theo
I'm not using the preamp cause I think it will be an improvement but my preamp processor controls my whole system and therefore i need to use it for the convenience factor of not having to unplug stuff.
I was not asking if I could forgo the Ballsie/SE stage...I was asking if I can safely omit the buffers on Legato 3.1. I believe in a previous post Russ mentioned that a dual mono x 2 Legato was a situation in which the buffers provided no benefit.
Second I was asking if I needed some film caps at the balanced output to take care of the common mode DC...but I believe in this case that it is not needed as well as it is canceled out in this configuration.
Russ...can you confirm? Also I looked for the wiring diagram for dual mono and I couldn't find it on the TPA site any more...you think you could include it as part of the Legato Manual before you take it out of draft status.
Best Regards,
Theo
Ah, you think you'll unplug it...
Russ repeatedly said the buffers do no harm. I'd include them, if you on one day want to feed a HP directly they'll be handy.
DC offset in a balanced configuration should be cancelled out. It would be a rare occasion if you need caps in such a setup. But without specifing the circuit the signal goes into I doubt anyone is willing to say with 100% certainty you don't need caps.
I think you were looking in the wrong section for the diagram:
http://www.twistedpearaudio.com/docs/digital/dualmono_BII+IVYIII.pdf
Russ repeatedly said the buffers do no harm. I'd include them, if you on one day want to feed a HP directly they'll be handy.
DC offset in a balanced configuration should be cancelled out. It would be a rare occasion if you need caps in such a setup. But without specifing the circuit the signal goes into I doubt anyone is willing to say with 100% certainty you don't need caps.
I think you were looking in the wrong section for the diagram:
http://www.twistedpearaudio.com/docs/digital/dualmono_BII+IVYIII.pdf
I'm using 3 separate power supplies, and when I connect power to the centre section of the board (Ballsie), I get 1.3VDC instead of 15VDC at power in on the positive rail.
Legato If not connected, everything is ok.
We 15V everywhere.
I current set to all sources for the 150mA.
Can someone help?
Thank you!
Legato If not connected, everything is ok.
We 15V everywhere.
I current set to all sources for the 150mA.
Can someone help?
Thank you!
It sounds like you have something installed backwards (relay, opamp, etc). Can you post a picture?
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