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#703
From previous posts it looks like the NTD1 board on the spreadsheet includes the PS board, see the first page of this thread. But we still do not have info on the resistors Owen says he is ordering, or built boards... I expect we just have to be a little patient for the wiki page to come up.
 
#705
I modified(improved?) a friends AudioNet SAM V2 that was defect (DC-failure) with the Wire Amp!
As Audionet didn't agree on anything but sending the whole amp to them for repair ($$$) I didn't have much choice🙂.

Do you think there any problem to have just 5V difference between LME and Fet voltage?
In the SAM the regulated voltage is 54V and with 200mA disspation the Fet supply drops to 49V. I measure about 50 degrees on the rather small cooling fin.

Everything went really smooth building it and it works like charm! - thanks again OPC!

An externally hosted image should be here but it was not working when we last tested it.
 
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#706
Deerhunt:

Awesome implementation! That's a little more elaborate than a standard repair job, but you're much better off now anyhow!

No worries at all about the 5V delta between the LME and the fet rails. That's actually about perfect as the FET rails will probably sag another few volts at full power which is where you really need the LME to he higher.

Having the sinks at 50C at idle is probably fine, but if they're small it doesn't leave you a lot of thermal overhead. Again, probably not a problem, but something to be mindful of if you ever drive it hard for prolonged periods of time. What bias current are you running at?

Congrats on a great build, and glad to hear it all come together without a hitch!

Regards,
Owen
 
#708
Stammheim said:
Hi guys,

my 49830-boards run well, but I have a problem with the signal...
When I short the signal-in (+-) the amp is deadly quiet, but when I connect any kind of source (smartphone, laptop, cd-player, standalone soundcard) there is a quiet hum audible (like dzdzdzdz...). When I open the signal-in the hum is a little louder.
I checked any grounding possibilities, tried only one and two amps per power supply, one power supply per amp (including the LME49830) and a separate ps, but always with the same result.
Does anybody have any idea, what I can try?

I tried a ps consisting only of capacitors and also a stabilized ps, no differences. In same environment other amps are not having this problems...
Click to expand...


Hi,

I got exactly the same problem. That's weird. Tried al lot of things but still this little hum. Anybody? For decoupling caps LME and Latfets I used 1uF instead of 0,1 uF but I don't think that would be the problem.
 
#711
Hi Andrew,

The last (right) schematic, SE, AC coupled. I only changed the value of the decoupling caps on the pcb. 0,1 uF to 1 uF and the 0,33 uF to 1 uF. (couldn't get 0,1 uF/100V easy) The 20 pF (C79) is a high quality 22 pF rf cap, but not the one from the BOM. Put a zobel on the PCB. (3,9 ohm with 0,22 uF) Rest of the values are the same. I can't think of a reason for this hum in both channels. Tried different PSU, groundings, etc.
 
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