My KAT-DG HIWATT 50 Special

I have long been a big fan of David Gilmour and his undeniably sublime tone! For years now I have been surrounded by AC30's and the like, mainly because on my work but also because I do love Brian's sound. But, trying to get DG tones from an AC30 or any of its derivatives is just not going to happen. For starters, it simply doesn't have the headroom and thereafter it's lack of negative feedback just adds too many harmonics to the sound. Great for BM tones, not so for DG. So for a number of years now I have slowly been chipping away at a DG Special, both in my head and on paper. Twice I have been offered a DR103 head and 4 x 12 cab and twice I was tempted, but these are very loud amps, and a 100W HIWATT in the small studio I have is just not going to work, so I needed something a little more bespoke.

A couple of years ago I was fortunate to be able to buy a HIWATT Hi-Gain 50 combo for a few quid. It didn't work, but I didn't need the amp or speakers. just the cabinet, the steel chassis and the two transformers. The rest was put on eBay.. The non-working parts actually sold for twice the price I bought the combo for! :-)

Once I had the cabinet and chassis, I had the impetus to get on the with the design of it. Like my AC30/15 amp, this was to be a 50W version of the DR103, not a DR504. There are differences, believe me! Slowly and surely, the designs came together and when I got a spare moment, I would order in parts and put them in a box. I slowly, over a number of months, ammassed all the bits ready for the build. I had also decided to include a reverb pan within the design as I quite like the warmth they add especially in DG mode.

I had been searching for years to find a good condition pair of Fane Crescendo speakers (Rocking-Horse doodoo is easier to obtain!) and last year, a company I know had been removing some old column speakers from a church only to find they were loaded with four of the wee beasties. You can just imagine how much stress and strain they been subjected to over the years.. exactly...none!.. they were immaculate, and two of them were now mine... My parts haul for the project was effectively complete. I just needed to find the time to build it!

Roll forward to March 2020. A global pandemic requireing us to remain at home and not leave untill told to do so hit us like a brick! Difficult, yes. Worrying, sure.. Time to open that box and build the 50W special, ABSOLUTELY!! 

So, here's the tale of the KAT-DG HIWATT 50 Special... Hope you enjoy!..

The Hi-Gain 50 chassis was a great platform to build from. For starters, whilst it required new appertures for the additional valve bases and drop-through caps (they're all mounted to the PCB on the Hi-Gain 50), it had very few holes I didn't need, so also looked the part when it was finished. The chassis is welded steel, so once all the machining had been done, It was re-sprayed with primer, then with a satin black top-coat. Originally, I had intended to have it acid-stripped and re-powder-coated, but this was the start of lock-down, so it got sprayed with whatever I had in the garage!

Thankfully, I had designed and had new front and rear control panel facias fabricated, powder-coated and silk-screened before lock-down, so these were ready to roll.

The electronics were to be mounted on and between turret-tag strips in a similar way to the original DR103. These were re-designed to accommodate my version of the amp including the reverb circuits so were not direct facsimilies of the originals, but they looked like they were! I also built boards to allow me to interface with the existing mains transformer and cathode fusing facilities.

The amp came together really quickly. I had inteneded to take my time and enjoy the process as this was not a customer amplifier, but my own and whilst I did take my time and enjoy the process, it still got built in four days! I had been so meticulous with the design stage that everything slotted together without question. Nothing needed tweaking or modification and even more gratifyingly, worked beautifully on initial power-up. 

Once tested, the amp was furnished with a brand new set of Mike Hill valves, and all the aluminium screening cans fitted. Running it up on the load box, it was pushing out 58 Watts RMS undistorted. It has a serious amount of headroom and sounds fantastic.

The finished amp!

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