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Trouble running Buffalo DAC/IVY directly to power amp
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Joined: 11/11/2014(UTC) Posts: 5  Location: Gothenburg
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Hi,
I have the first generation Buffalo DAC with the IVY linestage and it has performed very well indeed for several years now. Now I want to get rid of my preamp so I got a Volumite to control the DAC volume. That part works nicely.
However, when I connect the DAC & IVY (SE outputs) directly to my power amp I get a distinctive humming noise in one channel only. When I connect the preamp inbetween there is no audiable noise what so ever. The humming noise stays in the same channel even when I switch channel output from the DAC. A guess this would suggest a problem with the power amp but that power amp seems to be doing just fine with several other inputs.
I have searched but not found a good place to start identifying this problem. Any ideas on how to find this problem?
Can DC offset cause anything like this?
Regards,
Mac
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It sounds like a grounding issue.
My first guess is signal and ground are reversed on that channel.
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Rank: Member
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Joined: 11/11/2014(UTC) Posts: 5 Location: Gothenburg
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Originally Posted by: Brian Donegan  It sounds like a grounding issue.
My first guess is signal and ground are reversed on that channel. Thanks, will have another go at looking over the entire signal path. /Mac
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Rank: Member
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Joined: 11/11/2014(UTC) Posts: 5 Location: Gothenburg
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Just finished going over the entire signal path from the DAC and through the power amp, the polarity seems to be ok all the way as far as I can tell
I noticed that even though the Volumite pot is turn down (counter clockwize) to its end position I can still hear music at a low level through the system. Is this normal or should it be completely quiet when the Volumite is turn down to its lowest seeting?
/Mac
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Originally Posted by: Maccie Just finished going over the entire signal path from the DAC and through the power amp, the polarity seems to be ok all the way as far as I can tell
I noticed that even though the Volumite pot is turn down (counter clockwize) to its end position I can still hear music at a low level through the system. Is this normal or should it be completely quiet when the Volumite is turn down to its lowest seeting?
/Mac Its by design. It allright.
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Rank: Administration
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Joined: 10/24/2006(UTC)
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Can you post a picture of your setup?
Are the RCA outputs both isolated from the chassis? I assume your chassis is connected to mains Ground...
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Rank: Member
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Joined: 11/11/2014(UTC) Posts: 5 Location: Gothenburg
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Opened up everything I built a few years back when the first Buffalo DAC was released - believe I just found a grounding problem.
I may have more than one grounding problem. One thingbis that in my previous appartment there was no ground available in the wall outlets so I probably didn't pay enough attention to the issue. Now I have grounded outlets everywhere but not all the components in my setup are in fact grounded ... Will be back with details.
Thanks for your help so far.
Regards,
Mac
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Rank: Member
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Joined: 11/11/2014(UTC) Posts: 5 Location: Gothenburg
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Little bit ashamed here, newbie misstake - my DAC is in fact not connected to mains ground. In short this is the situation:
- Beacause of the form factor I have a separate PSU case with two toroid transformers, one toroid for the analog power supply and one for the digital. Only the toroids are in the PSU case, the power supply boards are in the DAC case with the rest of the DAC and the IVY.
- Mains ground is not connected at all, I will have to build a new cable connecting the PSU case with the rest of the DAC to route mains ground to the DAC case
- The output RCAs from the IVY are isolated from the chassis
Question:
Would it be feasible to connect the ground on each of the output RCAs to each other and to the ground output on the analog supply board even though mains ground is not yet connected? Is this worth trying?
If I understand this mains ground should be connected to the ground on both output RCAs and output ground on the analog supply board in a star ground type configuration?
Regards,
Mac
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Rank: Administration
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Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA
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Was thanked: 141 time(s) in 134 post(s)
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Personally, for low-voltage situations like this, I connect the Mains Ground to the chassis, but leave the analog ground isolated (floating), and not connected to the Mains Ground at all. If it does get connected, it is through a "ground breaker" circuit, to prevent current flowing from/to it unless there is sufficient voltage (a fault). Here is a good article by Rod Elliot: http://sound.westhost.com/earthing.htm
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Trouble running Buffalo DAC/IVY directly to power amp
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