ROLA JTM-45 Handwired Amplifier Head

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• published: 26 Feb 2015
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http://www.guitaraust.com.au/accessories/amps.html The Rola JTM-45 is without a doubt one of the finest handbuilt amps I've ever had the pleasure to play. While the amp is clearly a tip 'o the hat to Marshall's own 1962 JTM-45, Graham Dicker's meticulous work and choice of original but vintage components is simply mind-blowing and separate this version of the JTM-45 from most others. There is absolutely no compromise on components or quality. More from Graham: "Here it is my latest creation the famous JTM45 KT66 version limited edition, all hand wired point to point on turret boards as shown in the photos. Unlike modern mass produced amps full of dry joints and mechanical reliability issues, this amp is built using traditional 50's wiring - not a printed circuit board in sight, hand laced wiring, every component tied off on the turret board before being soldered. Dynamic matched and demagnetised valves, lots of NOS valve options for customers to audition before purchase and more. Each one of these amps takes 40 hours to build. I will never get rich building them but it sure is rewarding and after 50 years of building valve amps I still get a kick out of every one I build going to a good home. The output transformer is custom wound and uses 20% radiometal core material so it naturally compresses instead of clipping like modern ones, this is the way 1950's output transformers behaved. You can't go out and buy radiometal as it has not been produced for nearly 60 years, it can only be recycled from 1940's and 1950's transformers and then new GOSS core hydrocut to the same dimensions, the net result is an output transformer about twice the size of modern ones (just look at the photos - most 30w output transformers are 1/2 to 1/3rd this size. Each output transformer weighs around 5.5 pounds (2.5kg). Like the original it uses a 5AR4 rectifier and a quality filter choke in the power supply. Output impedance is selectable for 4,8,16 ohms and if you want to use a couple of odd impedance cabs let me know as I custom make the output transformers and can wire speaker sockets to suit any weird combination you may have. Amps are built using RF grade Semco silver mica 70's capacitors made from now totally unavailable Ruby Mica, each one silver dipped and epoxy coated, each capacitor installed with care ensuring the orientation to minimise noise and circuit coupling. IRH Australia vintage 50's carbon composition resistors (precision German made Byscfhlag or Rhoderstein metal film where IRH values are not available), Gold plated input sockets (plated here in Australia with 10 microns gold), Bakelite knobs with allen head grub screws, hand made turret boards, solid silver Teflon (Aviation grade Tefzel) hookup wire, Plexi front and rear panels reverse silk screened and reverse coated in gold paint, not a low cost laser engraved panel. Unlike todays production amps using PCBs designed to last only 3 years, these amps are hand built to last 50 years. All amps are wired as they were made in the 50's and 60's, on a solid punched aluminium chassis with TIG welded corners. The amp cab is made from ply, with a high quality non covered version using Australian solid timbers an option. The head comes complete with a full 12 month RTB (Adelaide) warranty, and after warranty support. the amp includes 3 x Mullard ECC81's made at Philips Hendon South Australia, Semco silver mica plate coupling caps." Today's tools: Guitar: Fender CS '56 RI with Brierley Sweet-tone Pickups (See: http://www.brierleyguitarpickups.com.au); Gibson CS '61 SG RI with Sin PAF's Amp: ROLA JTM-45 with Palmer 1x12 Cabinet (Greenbacks) (See: http://www.sonicfrog.com.au/p/75/palmer-1-x-12-cabinet-celestion-g12m-greenback. Extra effects: Dr Scientist The Elements and Empress Tape Delay Cables: Providence Mic: Violet Design The Amethyst (amp) Samson Airline77 (me) Camera : Canon 60D (me) and Sony HDR CX150 (pedal) Soundcard: AVID Mbox Pro 3 Computer: Apple iMac 27" i7 3.4 GHz 16 GB RAM Software: Pro Tools 11, Waves CLA Guitars (slight comp over input track), Waves L3-16 Limiter (to keep levels in check at output), Apple Final Cut Pro X (video editing and Youtube compression).