Double glazing

Two panes of Optilam Phon hanging out in front of the harmonium

Today the glazing turned up – two 1m x 1.5m panes of Pilkington Optilam Phon, a name reminiscent of a Thai noodle dish. One is 10.8mm thick and the other is 8.8mm. They’re both made of two glass sheets bonded to an extra thick (0.8mm) laminate layer. I hope my calcs for matching the wall they will be sat in are about right; if not I shall be inserting a third panel between them in the frame (I am planning the frames to have a gap for such an event – nothing worse than having to take the whole lot out.

Optilam Phon – 10.8mm and 8.8mm



Whilst waiting for the glaziers to turn up this morning I continued the kind of obsessive task that makes building a studio suicidally long-winded for someone like me: drawing out the schematic for a distribution amp module. Years ago a friend and I bought two 3U racks of eight amps that drive 10 balanced outputs (600Ω) from one balanced input. I have decided to put one rack of them to use as the drivers for the eight channel headphone monitor mixers I shall be making for the live space – these suckers will be able to send to 10, which is 5 more than I think necessary for the space here. I can’t take any circuit for granted and have an Abbey Road approach to gear as I must know how it works and thus how to fix it. There aren’t any schematics available for these so I shall draw them out myself, which means lots of holding it up, flipping it over, prodding with hte multimeter and scrawling on a notepad. I’m most of the way there and will no doubt come up with a modification or two to make for a slightly better signal path (they’re a little lacking at the top and bottom, or a little midrange heavy depending on how you look at it). Here’s one now…

1×10 balanced distribution amp module

The large black box is a mains transformer as each module is self contained, thus no overall PSU problems, and having spare modules means I can swap them out mid-session if any futt-out. The input transformer is a cute little Beyerdynamic number. The UA727 dual op-amp that follows this is not a great delight on paper so I shall do some tests to see if (a) it sucks and (b) how to swap it out if it does.

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