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Just completed the Legato 3 with Buffer - and have one quick question: Adjusting VR1 and VR2 to provide 0VDC at the balanced output is no problem - however, adjusting VR3 and VR4 doesn't make any difference to the DCV at SE outs - this being 0.02VDC on both sides. In short, the 0.02VDC measurement doesn't move, even winding VR3 and VR4 flat out in both directions. Any thoughts? 
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A follow up - I plugged the DAC in, and get no sound. So, I've done something wrong... 
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Check relay orientation.
Check power supply, what voltage are you supplying.
Check if there's power to the OPAMP.
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Thanks for your assistance here - greatly appreciated.
Checking without power connected (and I'm not sure if the relay switch is coming into play), but the output of buffer is shorting to ground. Consequently, the SE output is shorting to ground on both L + R channels and headphone outs. Balanced out is fine - SE is the only problem. I can send a pic on Saturday (when my camera returns).
I'm using 3 separate power supplies, and when I connect power to the centre section of the board (Ballsie), I get 1.29VDC instead of 12.3VDC at power in on the positive rail. So, a short somewhere? Everything appears okay up to and including the opamp.
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Without power applied the outputs will be shorted to GND. That is what the relay does.
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Without power, the relay does short the SE outputs to GND, so it seems the relay is installed correctly.
Pictures would really help at this point, top and bottom.
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Hi Russ and Brian, Please see attached pics of pcb. The problem appears to lie in the Ballsie section which has its own power supply - 12.3VDC. At power input I measure 12.3VDC negative to ground, yet only 1.47VDC positive to ground. This is the same at opamp - 12.3VDC neg input, 1.47VDC pos input. I've checked for shorts on the board and on the opamp - everything appears okay. The left and right channel sections of the pcb are fine - 12.3VDC at power inputs. Any help is appreciated. narla attached the following image(s):  Legato 3 top view.JPG (191kb) downloaded 407 time(s). Legato 3 rear view.JPG (158kb) downloaded 405 time(s). Legato 3 top view 2.JPG (230kb) downloaded 406 time(s). Legato 3 rear view 2.JPG (184kb) downloaded 407 time(s).You cannot view/download attachments. Try to login or register.
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Why don't you try getting it working with a regular op-amp at IC1. It this point it seems the natural thing to do. Also that extra capacitor you have will not be helpful.
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By your current setup, I guess you're using 3 different power supplies?
Since you did not install J1-J4 you need to power each section independently (you're probably doing this already, just checking...).
Yeah, as Russ pointed out I would test with the included Opamp just to eliminate points of failures.
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Thanks Russ and Pinnocchio - and yes, I'm using three power supplies for the Legato.
OK - I've now replaced the Burson discreet opamp with the standard LM4562 - however, the result is similar. This time I get 1.23VDC pos to ground and 12.3VDC neg to ground. That's exactly ten percent of voltage required on the pos rail!
Any thoughts?
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I have an idea. Test the power supply. Load the power supply with ex. 100 ohm and measure. Can it supply it ?
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Did you first started to test with stock parts to see if everything was working properly then gradually upgraded to PRP and Foil resistors?
On R2 and R3 your currently using 180R instead of stock value 150R
Can you double check each PRP and foil resistors to make sure the right values are at the correct position? Also, foil resistors are much more fragile when soldering, just double check that they're not damaged.
Thanks
Do
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R1 - R4 are 180 Ohm and measure accurately. Likewise the foils - all OK.
The power is supplied via shunt regs, that operated perfectly with Legato V2. I've basically swapped Legato 2 for Legato 3.
I'll double check the power supply, but I believe it's OK.
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What I saw when swapping Legato 1(.5) for 3.1 was an increase in power consumption. I had to up the Placid.
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AVR300 is right. Make sure your Placids are at maximum current then if that fixes the issue, I would leave a 60mA headroom, however, if you don't have enough current available, voltage should automatically drop much lower on the + and - rails.
Just set your Placid at 12V-15V then connect and while it is operating re-measure each rails and see if the voltage has moved. If they drop, then you don't have enough current available to supply your rails.
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Another note... once you do get it working, you will want to drastically shorten the wires running to your discrete op amp (ideally eliminate them). As it is, you have a huge feedback loop, and it will be very prone to oscillations.
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Just to end this thread on a good note. The problem was the power supply. I'm using Paul Hynes Shunt Regulators - that required a lower value resistor, to allow for more current to the Ballsie stage. Once done, it worked a treat and I'm now getting a stable 12.3VDC on both rails. Better news - it sounds great! More detail, space and dynamics. An excellent upgrade and congratulations must go to Russ and Brian. 
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