"Hello everybody and welcome to the first article on my return from a few weeks break in Australia, with my friend Mervin….Doctor Valve."
Right…..this one was great fun! This is how it looked when first received - but, the story really starts with another tech-guy friend of mine, John Beer of Amp-Fix. Having a clearout, John offered to send this to me as a present for my friend Mervin to take back to Australia. On receipt of the amp and checking to see if it was actually going to work….the output transformer was faulty so……Merv & I decided to strip it completely and re-build it….our way!
The chassis & cage both needed some welding attention; and of course a re-spray. We also added the necessary holes for an impedance selector & output jack sockets (shown further down).
I feel pretty sure that this is a Northcourt/Linear kit form unit; as the front panel says “Linear” in the middle at the top, whereas the factory built Conchord 30 has a slightly longer panel (to the front-right) and the name is usually there…at the right of the controls.
Typical Linear Spaghetti-Junction wiring again! After ripping the whole thing apart, we had the welding done (compliments again of my metalwork man/friend…..Steve) and then fully Powder-Coated with a colour that Mervin choose…..Antique Silver.
Now that’s better! All the hardware in place and ready to start the re-wire.
A few tubes plonked-in to get an idea how she’s going to look….especially with one of my Champ “Partridged” look-a-like transformers! This transformer is far superior to the originals that were fitted to these!
As above and also showing the impedance selector and the jack output sockets….not normally fitted to these.
And with the cage laid-over…just to get the idea of looks again. At this point we are still in the UK, and it is two days before Merv goes back to Oz… along with me too for a few weeks holiday. It was intended that we take the Linear to Oz with us and finish her off over there. Merv also had a Watkins Copycat to take back too, and I’m not quite sure how he wangled this but I ended-up with the reasonably heavy Linear in my case and him with the little Watkins in his! Crafty!
Now here we are in Oz and on Mervin’s workbench. We did the wiring between us and didn’t intend to make it “ultra-neat”. We decided that we would do the wiring in a similar fashion to the original Linear’s but with a complete change of circuit and design. We used both my “tried & trusted” phase splitter and tone circuit. Merv wanted to stick with an EF86 for the higher gain channel and I then used one half of an ECC83 (12AX7) for the other channel. The two channels are then mixed in a conventional way from the two volume controls and then through the other half of the ECC83, the tone stack, and finally to another ECC83 for the splitter. The amp is also now in fixed-bias using two 20-turn pots….one for each output tube. When I have time I’ll draw the schematic and post it here.
Finished and looking really cool now. I bought a big stock of these large-blue pilot lamps……I think they really look the part!
Very pleasing result all round.
And with the cage now fitted plus…..that’s Mervin’s (Doctor Valve) sticker on the back….not one of mine; but I’ll let him off this time!
And now down to the million-dollar-question….what does it sound like? I can tell you all now that it sounds absolutely phenomenal; she is doing 54 watts RMS with no effort at all! This is all down to the re-design circuit and the output transformer - as everything else is pretty much the same and (or) as original. This, without doubt is the most powerful and best sounding Linear Conchord out there! All the best, John & Merv.
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