OK here goes. I'm not an electronic engineer and until 3 years ago knew absolutely nothing about valve electronics but thanks to the people here, the internet in general and some good books I have learnt enough to know that the bias control is not just to compensate for unmatched valves.

The bias control on the OTS sets the current flow in the valve at idle (so all controls should be set to 0 and nothing plugged in) by varying the bias voltage on the grid. It changes the bias voltage of both valves together thats why you need matched sets. You could mod it to have individual bias supplies but thats not what we're talking about here.

The bias controls how the valve behaves under load and it is generally recommended that the bias be set such that at idle the current flow is not greater than 70% of maximum plate dissipation. Some people do go higher but this will shorten the life of the tubes, but if this is the tone you want and are prepared to pay, then so be it. However if you set it so high that the valves start to 'redplate' then you will do serious damage and not just to the tubes.

70% plate dissipation equates to around 35-38mA depending on the valve make which because of the bias test system equates to 35-38mV across the test points. A lot of people prefer the tone at around 28-32mV and you should experiement within that range.

You should let the amp warm up fully before doing the measurements. Please make sure you have a load connected to the output 

You're welcome. Enjoy the amp.

Take a piece of good quality, thick paper. Tape it to the top (bottom, but you've got the amp upside down on the bench) of the amp with masking tape, in at least 6 places pulling it tight. Take a childs crayon and rub along the edges to mark the outline. Then find the mounting holes and mark them with a felt pen (use a big  + and o superimposed).  Do this just before actually drilling the holes, paper stretches quite a lot in damp weather (not that you'd get much of that this time of year in Spain.....) so don't leave it lying around.

Cut round the outline and tape it to the top of the amp (you might need to remove the handle) and use it to drill the holes. Personally I would drill smaller pilot hole first to prevent damage to the tolex, then use a modelling knife to cut the tolex before drilling the correct size holes.

Hi Doc, just got my Plexi 50 back from Shane having had the Powerscaling fitted. Mine has got the MM trannies in it and he was saying he thought it sounded very nice indeed. Not had chance to play it yet and I guess I'll never know unless I can A/B it with another built with Niks trannies, but you've now got one with MM's and one with Niks. I know ones a 50 and the new one is a 100watter but what do you think the MM trannies contribute to the tone?

I'm gassing for a Bluesmaster but I've got no band now so no excuse for another amp, plus I've got a parts-o-tele to finish off

Nik, the comments you might have read on other forums about the parts you use are very likely put there by builders or their friends who are very envious of your reputation and are losing business to you. They now seek to tarnish your record by sowing doubt in potential buyers minds.

You should be pleased, no really, you have made them resort to underhand tactics and they will fail. BUT if you do change your parts to lower 'quality' cheaper versions and it gets out, then you will suffer. At the moment we all know these comments are unfounded and will defend you when we see them, please don't change your build philosophy.

Maybe, just maybe Nik isn't your normal businessman. In my dealings with him (3 kits so far and gassing for a fourth) he has been anything but...... I get replies within an HOUR often, he goes above and beyond each and EVERY time I have a question, problem or order. I can truthfully say I have never had customer service better than Nik, he is the model every 'businessman' should follow as it creates happy customers who come back time after time.

And consider this.... possibly Nik realises that the customer type that he has most problems with are those who won't go and find information for themselves, so he constructs his site so that those are discouraged, given that he is running at full capacity anyway he probably does not want more customers who need nannying.

If you are doing that by hand you are a true masochist. Get a router and a jig 

Looks fine to me. All I do different is I use, in addition, a smaller heat shrink to cover the soldered joint aswell.

Tell him I sent you! Ha Ha.....

8 gigs in California coming up in 3 weeks time http://www.mattschofield.net/shows.html

Spread the word, I hope he gets a good crowd.

Yes I think this will be the year he really breaks into the big arena. He deserves it and Ishall always cherish the times I've seen him in a small intimate venue. Next time round he'll be in much bigger venues I'm sure. I urge anyone who who has any interest in guitar playing to go and see him, the passion in his playing is something else.

Matt is certainly not fickle and whilst he got a good deal I imagine, he paid his onw hard earned for his EZG-50. The reason for the change was mostly for simplicity but also to get away from the comparisons with RF and the Dumble clone hype. I have to say I think he sounds better through his new rig, but its only a 1% thing, he always has had a phenomenal tone.

And don't forget those George L's cables could be bad, mine would go bad regularly

My AB763 clone needs have now been satisfied with a DrZ EZG-50 head. It is a clone of the Tremolo circuit of a Super Reverb it appears

Ha Ha..... Preserved in Formaldehyde maybe?

I actually made a new footswitch, with a 5 pin XLR socket on it aswell, so I could have more than one length of cable.

 I then modded my original footswitch as per Pickmasters drawing to take a stereo jack socket, and made a short adapter cable from stereo jack socket ro XLR 5pin.