First, what DOA is it? A pre-built or a DIY? If it's a kit, swap the opamps and see if the problem follows. Also, have you seen the DOA install page http://classicapi.com/catalog/DOA_Install.php I highly recommend never testing a new preamp build with a new opamp build. There are too many variables and you may never know what the issue is. If it's a pre-built opamp from me, chances are, it is not bad. Gary and Scott both run them in for many hours before sending them to me.
Have you completed the pre-start tests at the end of the old VP2x Assembly Guide? If you are building a VP312, the C to O DCR value will be about 8.5 ohms. Make sure all voltage readings are correct.
Double check all component values and make sure caps are facing the right way. Resistors cannot be measured once both ends are soldered to the PCB. You will get many odd readings. Either use the color codes to verify or one end must be desoldered to get an accurate DCR reading.
Double check the lead colors/pads for the output transformer. Take your time and be sure. Countless times I have heard back from folks who checked and checked and then a few days later realized that some of the leads were placed incorrectly.
Next, reflow the solder on the 3 Toneluck pushbutton switches.
If it's the Grayhill stepped gain option, do you have 25k when measuring between the to outside pins of the switch? If not, check with a magnifying glass as there probably is a short between some solder pads. These can be checked end to end by probing between adjacent pins. You should get the resistance of each of the R's on the pdf as you work from one end to the other.
Scan the board and check all solder pads with a magnifying glass of some kind. The biggest issue, besides what I mentioned above are cold solder joints. Sometimes they can look fine but not be good.
