Introducing the KT88se amplifier

the new KT88se amplifer by the Richards Amplifier Company - Australia

the new KT88se amplifer by the Richards Amplifier Company – Australia

Ladies and gentlemen ! Let us proudly introduce you to our very first amplifier designed from the ground up to showcase the mighty KT88 power output valve. There are another two models in the early stages of design and construction, but the prototype KT88se is the first and has been in constant use by owner Christopher Earle since he took delivery Christmas 2013/2014. Chris is a baritone guitar and open-tuning guitar stylist from Sydney, Australia. He has been using the KT88se for creating, previewing  and recording his repertoire.

the KT88se (with FX Loop)

the KT88se (with FX Loop)

The KT88 valve, in the ideal circuit, is capable of creating the most awesomely robust guitar tones you can imagine. They were employed back in the day in a number of Australian and New Zealand built amplifiers, Wasp being the best known example – also in a number of higher powered British amps, famously including the Marshall Major. In the days of rack-mounted power amps and preamps, there was also a very fine sounding KT88 dual 100W power amp from Seymour Duncan. However, during the 80’s and 90’s things looked very bleak for the KT88 – it became impossible to source KT88’s of sufficiently high quality construction to hold up ‘on the road’ (as well as the fact that the original UK manufactured examples became impossibly expensive). All those Wasp amps, and Marshall Majors,  were ‘retired’ from active duty.

KT88se chassis - rear view

KT88se chassis – rear view

Thankfully, that situation has completely turned around in the last decade or so with a number of factories producing very good sounding KT88’s – Genalex/Gold Lion and Electro Harmonix are two brands we can recommend from personal experience in guitar amps. We have yet to try the new Mullard (reissue) KT88’s. In this first amp chassis we have employed a pair of Gold Lion 12AX7’s in the preamp, as well as the single KT88 output valve. The combination is stunning.

KT88se chassis - front view

KT88se chassis – front view

Well, moving on folks: the ‘se’ in KT88se obviously stands for ‘single-ended’. Rather than a ‘push-pull’ power amplifier configuration (the most common arrangement in valve guitar amps), utilising a pair or multiple pairs of output valves for greatest efficiency, in this configuration we utilise a single power valve, driving a very substantial output transformer specifically designed for this application, and biased to operate in pure ‘Class-A’ mode. By employing the KT88 valve, we can achieve an audio output of 15 watts with suitable transformers – ample power to achieve good results with our favourite vintage style guitar speakers. By comparison, most single-ended guitar amp models, whether commercial or boutique, actually only deliver about 4 watts maximum employing a single EL84 or 6V6, with limited bandwidth, regardless of any marketing claims.

the Genalex KT88 (new production)

the Genalex KT88 (new production)

The ‘single-ended’ output stage results in a unique tone, compared to the ‘push-pull’ output stage. Whether one is ‘better’ than the other is purely a question of personal taste, of course. For the guitarist, the ‘single-ended’ amp does not cancel out even order harmonics, so the resulting sound is very rich in the 2nd, 4th and so on harmonics, which are more pleasing to the ear than odd order harmonics, and are heard as a warmer, fatter and more complex tone. The asymmetrical clipping on overloads further emphasises even order harmonics. Power supply hum is rejected with additional filtering, and the inclusion of a filter choke capable of carrying the full high voltage current draw of the amplifier, “upstream” from the output transformer.

(optional) buffered FX Loop with KT88se sitting on Hame 1x12 cab

(optional) buffered FX Loop with KT88se sitting on Hame 1×12 cab

The KT88se has full guitar preamp functionality with a single high impedance input jack, preamp volume control,  three 12AX7 gain stages, three band ‘British’ passive EQ, a buffered FX Loop driven by the spare 1/2 12AX7 stage, metal power and standby switches with power ON indicator. We are also offering the same amp without the FX Loop for those who require the purest possible signal path. Completing the front panel functionality is the unique Drive control, which operates in the power amp circuitry and adjusts the global amp gain or sensitivity by increasing or reducing/bypassing the effectiveness of the global negative feedback loop.

The rear panel also offers full functionality with mains and HV (high voltage) supply fuses, power output jacks for 4, 8 and 16 ohm speaker systems, and a line-level signal output jack. The Bold/Vintage switch reduces power output from 15 watts to 6 watts in ‘Vintage’ mode. Our amp launch held at the Rock God Music School (Wyoming NSW) revealed the completed amp design exceeded all expectations and delivered a monstrous tone. In our next blog, we will publish Chris Earle’s testimonial/review of the KT88se.

Ivan Richards.

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One Response to “Introducing the KT88se amplifier”

  1. Chris Says:

    It is such an awesome amp!!

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