Service centre for “65 Amps” in Australia

65-amps-p1020689Hello and welcome back to the blog after a long break. We are now offering world-class (non-warranty) service & repairs to the range of valve (tube) amplifiers from 65 Amps guitar amplification of California, USA. We should point out that we have no official relationship with 65 Amps, so we cannot accept any warranty repair claims without their endorsement.

Lil' Elvis chassis - note the high-quality transformers by Mercury Magnetics

Lil’ Elvis chassis – note the high-quality transformers by Mercury Magnetics

Our customer, singer/songwriter Shane Nicholson delivered this “65 Amp” to our workshop for a general service & revalve. This model is called the Lil’ Elvis  and is a 1×12 combo of around 12 to 15 watts output, loaded with the very fine Celestion G12H30 70th Anniversary speaker. The valves (tubes) employed in this design are as follows: 3 x 12AX7 for the preamp, tremolo & PI stages, 2 x EL84 output valves (cathode-bias) for the power amp, plus a 6CA4 rectifier. The latter choice indicates there will be considerable sag/compression (ie similar in effect to the famous Marshall 18 watter).

chassis layout and wiring - not as obsessively neat as you might expect but very serviceable indeed

chassis layout and wiring: not as obsessively neat as you might expect but very serviceable indeed and superior to any PCB based amp in that regard

The circuit design of the Lil’ Elvis appears to incorporate design elements inspired by several vintage American amplifier designs, including the Fender Princeton and the simpler Ampeg models, featuring a single passive tone control. The 2nd 12AX7 stage is unusual – a bit like adding in a cathode-coupled phase-inverter into the signal path, prior to the actual split-load phase-inverter. This stage no doubt contributes to the unique tonal qualities of the Lil’ Elvis. The valve-generated tremolo is very effective. A passive FX Loop (ie a series loop) is incorporated into the design in such a way that it does not degrade the signal path with additional circuitry. However, if your FX device requires to be driven by a low-impedance source, then this loop will not be suitable.

65-amps-p1020685The “65 Amps” Bump circuit gives a significant boost, primarily to the mids and lows. You would probably set this one way or the other prior to playing or recording a song, rather than footswitching, due to the size of the boost and the fact that there is a very obvious “pop”, as the switching appears to be changing DC conditions for one of the gain stages, as well as increasing the gain. The cosmetic appeal of the amp is very distinctive. We are glad to see the cabinet is of sufficient proportions to give a reasonable low frequency response, ie this is not a ‘boxey’ sounding amp like some of the competition.

65-amps-p1020687We gave the amp chassis a good appraisal, with power output test, electrical safety test etc. A full revalve was called for but there were no other issues, all good !  65 Amps are evidently rather precious about which brands of valve (tube) go into each position, but we tried the Tung Sol (current production) versions in each case (except the 6CA4) and it sounded very good with that choice, although that brand might not be the best choice in every amp that is out there – we have to keep an open mind.

NTE2973 mosfet device

NTE2973 mosfet device

Finally, the “master” control, in spite of the hype on the website, is actually a power amp attenuator which works by reducing (attenuating) the high voltage supplied to the preamp and output valves (excepting of course the tremolo oscillator). The design is similar to that used in a number of amps, including our own 10 watt EL34se single-ended model, employing the NTE2973 mosfet device. It works very effectively, but as we have said before, it does inevitably change tone and dynamics at the lower settings. It is still a good feature to have with lower powered amps, which will often be used in home studios, etc.

Thank you again, Shane, for your continued custom. We look forward to providing world-class service and repairs to more 65 Amps models in the future. IR.

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