I put up a pdf drawing for a head cab a while ago, just search through my posts. You can easily adapt it for a 1x12 combo by lengthening the sides.

It appears thepwebsite photos don't match the layout. I've checked my layout and I built to an earlier version which is the same as the photos so I guess he didn't update the website photos when he changed the layout.

It seems yours is correct to the layout.

Switches look wrong to me. Check agains the photos of you armp on the site to make suer you are interpreting the layout drawing correctly.

OK if you are getting sounds but the relays are not working i.e. not clicking at all check that you have 12volts on them. Do you still get sound with the relays removed?

Nik has said many many times that the switch wiring confuses lots of people because the layout is drawn in a particular way and you might have interpreted it incorrectly. Treble check your switch wiring with the photo of your amp on the site.

I think you might have wired your relay switches incorrectly.

Compare yours with this http://www.ceriatone.com/images/completeAmpsPic/Overtone_100/b18B.jpg

JMP50 = Plexi 50 surely.

What about installing the Metroamp FX loop? Considering it myself.

Im' sure you mean EL43's

Microphonic...... Can't get past 3-4 on the dial.

Its easy to confuse the wiring of the rear switches and socket and get them the wrong way round. Check against the pics on the site.

Also check you've got the relays the right way round.

Don't be. Niks build quality is excellent.

Be prepared to find a NOS Mullard EF86 to cure microphonics. Even running mine through a separate cab a few feet away didn't prevent the stock valve been horribly microphonic.

Check whether this problem is pre-amp or power amp related by pluging a line level input to the FX loop return, this will divide the problem by 2, no output then the problem is topside of your FX return jack, full output then it is the preamp.

Dressing of cables correctly wired will only affect the tone of the output not the existence of output. This is a logical circuit so follow it religiously, checking every wire for correct location and connection. I would recommend an A3 print of the layout and a highlighter pen after each wire is installed. The presence of correct voltages on the test points will tell you whether you have half the circuit right, no output will tell you that your signal circuit is broken or you have a bad valve. Nik will send you a voltage chart that will give you a good starting point for checking, get the voltages right and you are almost there. I think you can safely assume that Niks circuit boards are good until proven otherwise.

Or try a line level source into FX return socket.

No you must use the 16 ohm setting on your amp to run a 16 ohm speaker. Any other setting and you risk damaging your amp.