Archive for the ‘Amps’ Category

MODs to the Fender ‘Super Twin’ amplifier

May 22, 2016

Super Twin P1020234Howdy there folks – welcome back to the world of valve (tube) amps. This week we look at servicing and especially modding a (relatively) rare Fender amp introduced in the mid-1970’s: the 180 watt (!) Super Twin 2×12 combo. The marketing people at Fender must have decided that higher power amplifiers were the way of the future as several models were redesigned for an increased power output during this time, including the “Twin Reverb” and the “Bassman”.  The Super Twin employs a sextet of 6L6GC output valves, with a HT voltage of over 500V DC, in ultra-linear configuration, to achieve the rated 180 watts output. This amp is not recommended for anyone with a bad back – it is seriously heavy !

Super Twin P1020236The design of the Super Twin features an elaborate EQ system that includes the conventional Fender 3-band passive EQ located between two 12AX7 preamp stages as per the Twin Reverb, plus a 5-band graphic EQ and a presence control, both active, driven by a 12AU7 valve. This is not a parametric EQ as is sometimes suggested on user forums.  The EQ is also footswitchable. The power amplifier is driven by a conventional long-tailed pair 12AX7 phase-inverter stage, followed by a 12AT7 cathode-follower stage to provide a low impedance drive to the sextet of 6L6GC output valves. There is also a distortion control which uses both halves of a 12AX7 valve, which is so awful that nobody ever uses it.

Super Twin P1020232Unfortunately, this amp is just too loud to be of any practical use for most guitarists. It would make a great bass amp if it was a bit more powerful. The amp stays clean until you reach the rated power and the overall tonality is rather glassy. BUT, we have a solution to offer which halves the output power and warms up the tone somewhat. Our standard MOD for these amps is to rewire 4 out of the 6 output valve sockets to reconfigure 2 pairs of 6L6GC to triode mode of operation. The remaining pair stay wired as tetrodes. At 90 watts this amp will still be very loud, but useable with a warmer, more musical sound.

We have implemented this MOD recently for Heath Crawley of Aussie indie bands Children Collide and Vanuatu Scalps, and for Nash Chambers, well known as a music producer and artist manager. In both cases there were numerous other issues to be addressed, as might be expected in a 40 year old guitar amp. General servicing includes replacing the high voltage electrolytic filter capacitors, replacing noisy and microphonic preamp valves, cleaning of pots, jacks and valve sockets, electrical safety compliance, and noisy or leaking capacitors in the signal path, including the graphic EQ which employs inductors and capacitors in five series resonant circuits.

It has been suggested on some user forums that the Super Twin was designed by Paul Rivera, but this is definitely not the case. Thanks for checking in to the blog, and we offer world-class service, repairs, restorations and upgrades to most Fender musical instrument amplifiers. I.R.

MODs to the Fender ‘Super 60’ amplifier

May 14, 2016

Super 60 016Hello again. The Fender Super 60 was introduced in the late 1980’s as one of the dreaded ‘red knob’ series of amps, which weren’t always favourably received. This model caused some confusion for people who purchased one, as it sounds nothing like the traditional Fender amplifier models. It has a few admirers, to be sure, but the model was eventually deleted. On the plus side, this is a 60 watt 1×12 amp in a compact combo (although quite heavy as a result), with ‘clean’ and ‘overdrive’ modes plus reverb (solid-state driven, not valve/tube). The ‘clean’ tonality is good, it’s just not quite the same as a ‘blackface’ Fender.

Super 60 011On the minus side, the ‘overdrive’ mode is not that great, and the clean/overdrive tonalities and levels really don’t match up. This is due to the amount of shared circuitry, which is re-configured using opto-couplers. The bias supply voltage is not adjustable, leading to complications when installing a fresh pair of 6L6GC output valves. So, the service tech has to change resistor values as required to achieve the desired result. This is really tedious ! However, the PCB can be modified to accept a bias trimpot.

Super 60 012Which leads us to serviceability issues with these amps. As you can see from the 2nd and 3rd photos, all components (apart from transformers) are mounted to either the large main board (PCB), or the smaller front panel board. Unfortunately for the service tech, these boards are kind of ‘back-to-front’ with the solder side of the board facing upwards, and the component side facing downwards, so they cannot be inspected without stripping out the boards. The valve sockets are mounted direct to the main board.  The three preamp valves are not especially a problem, but the heat from the pair of output valves will to some extent end up being absorbed into the chassis and the main board.

Super 60 013This customer’s amp was delivered to us with low output level, a couple of badly damaged pots, and broken jacks. The input and footswitch jacks on this model are the very brittle and easy to break PCB mounting types from the 80’s and 90’s. The pots have a solid shaft with a flat section, and the original knobs naturally match this shape. The ‘clean’ mode level was considerably lower then the ‘overdrive’. We would have to completely strip out the boards anyway, so this was the perfect opportunity to implement some MODs to try and improve the ‘overdrive’ qualities plus balance up the two modes a bit better. This ‘balancing act’ doesn’t achieve absolute perfection, but is a definite improvement over the stock amp. We would suggest leaving the 3-band EQ as it is, to maintain the ‘clean’ tonality, even though the EQ is less than ideal for the ‘overdrive’ mode.

Super 60 015For those of you who have access to a schematic we modded the following components: R167 to 82K, C102/C105 to 0.01uF, R103 to 100K and R158 is the resistor to be changed for different bias levels, or else remove altogether if a trimpot is to be installed. We rebiased for 2 x 35ma Ik at B+ of 487V DC. Biasing this amp to run much hotter would be a mistake, as per the preceding paragraphs. The end result is still a compromise, but the changes will result in a fuller signal range and also more saturation available for a more modern ‘lead’ sound. Upgrading the preamp valves will improve the tone of the amp in both ‘clean’ and ‘overdrive’, and will smooth out the spiky distortion characteristic and reduce hum/noise. We have more Fender MODs to be published soon. IR.

Super 60 017p.s. the previous owner of this amp discarded the red knobs, but installed some really cheapo looking ones in their place; we ended up matching up some Fender vintage reissue black knobs, which look much better.

p.p.s. some comments on the web forums mistakenly attribute this amp to the Paul Rivera era at Fender – this is not the case, this design is dated 1988 – well after Rivera moved on to manufacture his own products. IR.

Warning !

Valves [vacuum tubes], transformers, capacitors, amplification circuits found within a guitar amplifier operate at high voltages that can cause permanent injury, disability or death. Valves [vacuum tubes] operate at high temperatures that can cause severe burns. Never attempt to repair, modify, test, work on or touch electronic equipment unless you are trained or otherwise qualified to do so. Likewise, never remove a protective cover from electronic equipment unless you are trained or otherwise qualified to do so.

Warning !

Do not remove the amplifier rear panel, the amplifier chassis, the amplifier fuses, the valves [vacuum tubes], or any other part of the amplifier with the 240V AC mains supply connected.

6L6GC conversion for the DeLuxe Reverb Reissue (DRRI)

April 24, 2016

DRRI Project P1020347Welcome back ! Hopefully we are now back into a routine of publishing a fresh blog every week. In this week’s blog, we discuss a major upgrade project recently completed for the (Fender) ’65 Deluxe Reverb Reissue, which we will refer to as the DRRI. The guitarist in one of Sydney’s best loved and longest surviving blues bands has been playing through a Twin Reverb for decades, but decided to downsize to a lighter amp for the smaller rooms, which makes complete sense, and invested in a new (2015) DRRI.

DRRI Project P1020345As you can see from the photos, this particular Limited Edition DRRI looks very smart indeed, with the early ’60s Brownface amps cosmetics. Also included in the Limited Edition package was a Jensen (new production) speaker. All other aspects of this amp were identical to the standard edition DRRI.

DRRI Project P1020346Unfortunately, the tonality presented by this amp was very thin and rather shrill. Overdrive characteristics when the amp was turned up (no pedals) were actually pretty awful. We attribute a lot of this to the choice of speaker. Just as critically for our customer, the lack of headroom with this amp and speaker combination defeated the whole purpose of investing in this particular amp, as it was virtually unuseable even for the smaller gigs.

DRRI Project P1020343The first step in this project was to upgrade the speaker, as is so often the case with combo amps. Choosing a speaker is not as easy as it sounds – there are a bewildering number of specialist guitar speaker options out there now. WGS offer some excellent choices at very reasonable prices, and we ended up choosing the G12C from their American Vintage range. We could just as easily have chosen the G12C/S for a smoother, softer top-end, but this model does seem to complement the DRRI voicing and adds a couple of dB in efficiency which will help with the headroom problem. Most importantly, the G12C fills out the missing lows and mids of the DRRI and behaves itself very well under overdrive conditions. The 75 watt rating of this speaker allows a healthy overload margin.

DRRI project P1020322Having restored the basic tonality of the amp with our new speaker, in consultation with the customer we devised a major upgrade project to increase the headroom available by implementing a conversion from the existing 6V6GT output valves to the larger 6L6GC output valves. To take full advantage of the larger valves we also replaced the existing transformer set.

DRRI project P1020320The available space and the need to allow clearance for the 12-inch speaker restricts our choices somewhat, but by re-orientating the output transformer and choke just slightly, we could install the power transformer, filter choke and output transformer set as per the 60’s Vibrolux/Tremolux series 6L6 amps. Such a reproduction transformer set was available at very reasonable pricing from Magnetic Components of Chicago, USA, although the cost of shipping adds quite a bit these days.

DRRI Project P1020337Such an upgrade will increase the power output of the amp to between 30 and 40 watts, as per the original amps of the abovementioned series, without a huge increase in the weight of the DRRI. It will be necessary to modify the bias circuitry slightly (one resistor) to increase the range of the bias adjustment to accomodate the 6L6 output valves. We also upgraded the main high-voltage filter capacitor to the good quality F&T brand.

DRRI project P1020321This was not an inexpensive project by any stretch of the imagination, but much, much cheaper than selling the amp on and reinvesting in a more suitable amp. We have replaced the shrill and brittle tonality, as presented by this example, with a very warm, full sound, still characteristic of the best examples of the Fender Deluxe Reverb, and increased the headroom significantly. This is now a fine performance amplifier which will serve our customer well !

DRRI Project P1020344

Correcting electrical safety issues in a Bad Cat ‘Classic Cat’

April 9, 2016

Bad Cat 0159Hello again. In this week’s blog we look at correcting some electrical safety issues in a Classic Cat 1×12 combo from Bad Cat amplifers, of the USA. This particular Bad Cat would appear to be a limited edition, maybe even a one-off custom order, and we could find no reference to it at all on their website.

Bad Cat 0163Most Bad Cat and Matchless amplifiers are derived in some way from (or inspired by) vintage 1960’s made-in-UK VOX amplifier circuits. This model is completely different, and is obviously derived from 1950’s Tweed/Fender and Valco/Supro amplifier designs. Classic Cat controls and functions are really sparse – just a pair of input jacks plus volume and tone controls. That’s it ! The design follows the classic Supro pattern of a pair of 5881 or 6L6 output valves, cathode-bias, for a nominal output of 24 watts rms at the onset of clipping.

Bad Cat 0164There is a single 12AX7 gain stage followed by interactive volume control and single (“tweed”) tone control. The effectiveness of the tone control depends on the position of the volume control and also offers no control at all over bass or lower midrange frequencies. This stage is followed by a 12AX7 valve employed as a “paraphase” (self-balancing) phase-inverter, very similar to some mid-1950’s Fender (“tweed”) designs. However, this type of phase-inverter is not known for achieving perfect balance or low distortion, and so adds to the raw vintage character of the amp’s performance.

Bad Cat 0154Our good customer Danny brought this amp into the workshop to resolve some electrical safety issues. The most obvious sign of trouble is the broken IEC 240V power inlet. Further investigation revealed a lost earth connection, plus a loose mains fuseholder which could not be tightened. This latter component was also not compliant for 240V in the first place. We replaced the IEC inlet and installed a dedicated chassis earth point. We replaced the dodgy fuseholder with a compliant component and installed a T1A fuse.

Bad Cat 0155The amp now passed the Workcover NSW electrical safety test with flying colours, meaning that we achieve an earth test of less than 2 ohms from the earth pin of the 240V plug to any exposed metal part on the amp. You can see from the next photo the IEC inlet and fuseholder wired correctly, plus the dedicated earth connection to the chassis. The final photo shows the internal layout of the chassis, and hand-wiring Bad Cat/Matchless style.

Bad Cat 0158We would like to thank Danny for his continued custom, and for supplying us with the subject matter for this blog. We offer world-class service, restoration, repairs and advice re most boutique level valve (tube) musical instrument amplification.  It HAS been a lifetime obsession.


Bad Cat 0156Please check out our earlier blogs re amplifiers by Matchless, DR-Z, Landry, Jackson, Morgan, Matamp and others, plus our own Richards custom design amplifiers.

Repairs to the Peavey Classic 50 in Australia

April 4, 2016

Classic 50 P1020263Welcome back to the blog, everyone. We have been servicing the Peavey Classic Series 30 watt and 50 watt combo’s since their introduction back in the 1990’s and we are in fact still the A.M.I. authorised Peavey warranty repairer (valve/tube amps only) for NSW. Since the 1990’s the 30 watt 1×12 combo has overtaken the 50 watt models in terms of popularity as they provide reasonable performance in a compact package. Reliability has been questionable at times – we have had to repair printed circuit boards (PCB’s), replace transformers, valves and 9-pin valve sockets, and so on. Bias for the EL84 output valves is non-adjustable, which means some amps run rather hot.

Classic 50 P1020262The subject of this blog is a more recent 2×12 model delivered to us by a local music shop, reported as losing output and nil reverb level. It may not be immediately obvious from the photo, but the speaker connection tagstrip, normally pop-riveted to the speaker basket, has come adrift, causing unreliable operation. This is a problem we have witnessed many times with the cheaper OEM speakers supplied by Eminence of the USA to various amp manufacturers. The only reliable solution is to carefully drill out the remaining body of the pop-rivet and refasten the tagstrip by other means.

Classic 50 P1020264In the meantime we isolated the ‘nil reverb’ problem to the reverb tank itself, which is mounted in a vinyl bag at the bottom of the cab. The only way to gain unrestricted access to both the problem speaker and the non-functional reverb tank is to remove the speaker baffle completely from the cab. This is what is known as a ‘floating baffle’, with mounting screws along the top and bottom front of the cab, which must be removed. The amp chassis has to be removed before this can happen, of course.

Classic 50 P1020267Once the baffle is removed and placed face down on the workbench, we can repair the speaker. We choose to refasten the tagstrip with nut/bolt/lockwasher rather than another pop-rivet. It takes longer but will survive the demands of rock’n’roll guitar. The other speaker on this 2×12 baffle is checked OK.

Classic 50 P1020269Before we re-install the baffle into the cab, we will repair the reverb tank. One of the transducers tests open-circuit (O/C) and is not repairable, so we will replace the unit altogether. This is not a bad thing as we will upgrade the reverb with one of the ‘MOD’ tanks, The reverb will sound much better than it did previously.

Classic 50 P1020270Reverb tanks are available in various combinations of impedances and delay times, so it is important to select the correct unit for the individual amp. In the Peavey Classic Series, the reverb tank is driven by an IC, requiring a different input impedance than for example a Fender ‘Deluxe Reverb’. The replacement tank is placed within the vinyl bag, which provides some degree of isolation from vibration, which in turn is screwed into the bottom of the cab. The baffle and amp chassis are each reinstalled into the cab, and the reverb cable reconnected within the amp.

Classic 50 P1020272We had previously tested all the valves (tubes), external to the amp, and also carried out a power output test and electrical safety test. The final play test revealed a huge improvement, and the amp was returned to the music shop. Thanks for checking out the blog and we are located here in Gosford (Wyoming) NSW for all your valve (tube) amp service needs, including custom design. IR.

Greg’s custom amplifier build progress

March 19, 2015
18W 'British Lead' chassis

18W ‘British Lead’ chassis

Welcome back to the blog after a long break of 3 months. We have been busy !Here is another in our occasional series of blogs where we publish a visual report of a custom-order amp build, in progress. This example shows a Richards Amplifier Company British Lead Series chassis underway for our good customer Greg, of Sydney. Greg has previously purchased our Expressionist and Blue Mood model amps, with matching Tone Cabinets.

18W 'British Lead' chassis

18W ‘British Lead’ chassis

Greg has developed an appetite for vintage ‘British’ tones, but with the output scaled down to a more manageable 18 watts at full power, by employing a pair of 6V6GT output valves (tubes), in lieu of the more obvious choices, such as EL34’s, KT66’s or KT88’s. Rectification of the high voltage supply on this model is handled by a GZ34/5AR4 valve (tube), with excellent current production valves now also available from Tung Sol and Mullard.

18W 'British Lead' chassis

18W ‘British Lead’ chassis

With this project, we are looking to create the broadest range of classic, vintage British tones possible – including those tones recorded by (for example) artists as stylistically diverse as Mark Knopfler (JTM45) or ZZ Top’s Billy Gibbons (JTM45/Plexi/JMP). To that end, we have included a trio of mini toggle switches on the front control panel to reconfigure both the ‘front end’ circuitry and the 3-band passive EQ as required to achieve ‘JTM45’, ‘Plexi’ or ‘Metalface’ voicings. The 2nd mini toggle switch actually switches an additional 12AX7 valve (tube) into the signal path to achieve the more aggressive ‘JMP’ or ‘JCM800’ voicing and gain structure.

18W 'British Lead' chassis

18W ‘British Lead’ chassis

The control panel starts on the right hand side with the traditional 4 inputs, arranged as a pair of inputs for each preamp channel – ‘Brilliant’ and ‘Normal’. The preferred method of operation is to plug into the 1st channel, then use a short, high-quality jack-jack patch lead to cross connect to the 2nd channel. The ‘Brilliant’ and ‘Normal’ channels are now connected in parallel. The player then sets the desired balance between the two tonalities with the preamp volume controls. This is probably best done with the EQ set fairly flat (ie, 12 o’clock), then having balanced the volume controls – fine tune the amp’s voicing using 3-band passive EQ and the ‘active’ presence control.

18W 'British Lead' chassis

18W ‘British Lead’ chassis

A mini toggle switch configures the 3-band passive EQ as per the early ‘blues’ JTM45 voicing, or the later (post 1968) ‘crunch’ voicing. The presence control functions as part of the power amplifier circuitry and adds emphasis to the upper-midrange and high frequencies. A good starting point is to set this control to the 12 o’clock position, then fine tune from there according to the acoustics of your playing environment.

18W 'British Lead' chassis

18W ‘British Lead’ chassis

You could consider the balancing of the two channels as your ‘primary’ equalisation, and the tuning of the 3-band treble/middle/bass controls as your ‘secondary’ equalisation. Then the presence control adds further brilliance as required – in effect the amplifier’s ‘final’ equalisation. We think that a master volume control is absolutely essential on an amp like this, even though it was not provided on the original amps that inspired us all.

18W 'British Lead' chassis

18W ‘British Lead’ chassis

Once you have found your ‘sweet spot’, mixing the preamp volumes and refining the EQ and voicing options available on this amp (as discussed in the paragraphs above), there is a reasonable chance that you will be playing at a volume that is considered excessive under the prevailing circumstances, hence the inclusion of our master volume to keep it all under control. The guitarist who prefers to play with the amp running wide open will appreciate the transparency of our master volume design when set to maximum clockwise rotation.

The master volume (MV) control actually functions as part of the power amplifer circuitry – ie, it is located post phase-inverter stage (PPI) in the signal path. The primary function is to manage the output levels as required, but when used specifically to generate distortion, its location means that every preamp valve (tube), including the 12AX7/ECC83 phase-inverter stage, is contributing to the end result. There are other benefits to this design approach as well. With the MV set to maximum clockwise, the amp (up to the point of power amp clipping) is delivering its cleanest, brightest and tightest tones. On the other hand, as the MV is rotated anti-clockwise, the effect of the global negative feedback loop is progressively minimised, and the amp loosens up and behaves much more like a vintage amp design, with a sound full of fat, warm ‘valvey’ character.

The remaining front panel controls include high-quality metal toggle switches for power on/off and standby/play functions, plus a power-on indicator. The rear panel controls/functions include mains and high voltage supply fuses, full-power/half-power switch (once again a high-quality metal toggle switch), output jacks for 16, 8 and 4 ohms, plus an earth-lifted output jack for line/recording, ie DI.

We will now be offering this amplifier model as a permanent fixture in our range of designs, with power output options of 18 watts (6V6’s), 30 watts (KT66’s), 40 watt club amp (EL34’s), 50 or 100 watts (EL34’s), 60 watts (KT88’s).

Thank you Greg, for your continued custom and enthusiasm for our amplifiers !  IR.

a testimonial to the Richards KT88se amplifier

October 28, 2014
the mighty KT88

the mighty KT88

Here is a testimonial to the KT88se model amplifier, rated at 15 watts into 4, 8 or 16 ohms, designed and hand-wired, one at a time, by the Richards Amplifier Company – Australia.

The testimonial was written by Chris Earle, Sydney based baritone guitar and open-tuning guitar stylist and is reproduced in it’s entirety without any editing. Chris commisioned the development of this unique design and ordered the first two amps to be completed.

Please see our previous blog for an introduction to the KT88se and a detailed background to the development of this model. Many thanks to our good customer Chris for these words……….

“This amplifier is unique and highly innovative – during my research I’ve not come across a dedicated KT88 single ended amplifier built to such a high specification – there may be some ‘home brew’ ones out there – but none with the same impeccable build quality, application of years of hard won intellectual property, and unquestionable tone.

The oversize Mercury Magnetics transformers and choke certainly play their part – but it’s Ivan’s skill and insight with amplifier design that makes this the best amplifier I’ve heard or played by a country mile.

It has a truly rich beautiful sound – the notes decay with a chunky well defined solidity that I’ve never heard before – the 2nd harmonic is sublime with this amp – it provides an extra depth that is unforgettable.

The use of a Richards modified Hiwatt style preamp is a master stroke by Ivan. It allows the clean signal to be uncluttered by any form of fizz or fuzz and translate every subtlety and nuance from the fretboard.

This means it sounds amazing with modulation, be it Uni-Vibe, Chorus, Phaser or Flanger as well as long, full delay trails. But the piece de resistance is the driven sound – a richer, fuller sound is not humanly possible !

Yet it still retains astonishing clarity with my oversize guitars, be it open-tuned chords, slide or blazing single note runs and vibrato – no mean feat given the shortcomings of a single ended design that I’d experienced previously: lack of headroom and a compressed, cluttered sound.

Once the sound was dialed in – EQ flat, no adjustments necessary (though there was extensive experimentation), I was shocked to discover I had the guitar tone I’d craved all my life – you encounter that only once and I’m glad I did and get to play it !”


Thanks Ivan.


Chris Earle,

Sydney, Australia. October 2014.

Introducing the KT88se amplifier

October 22, 2014
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.

Jonothan takes delivery of his ‘Expressionist’ 15W amplifier

September 30, 2014
Expressionist 15W head in vintage red tolex with checkerboard grille

Expressionist 15W head in vintage red tolex with checkerboard grille

Welcome Back. This blog showcases once again the Expressionist Series amplifier, designed and built by the Richards Amplifier Company – Australia. This latest example is a custom order for Sydney-based guitarist Jonothan Holmes, in stunning vintage red tolex covering, with a contrasting ‘checkerboard’ front grille cloth. We previously presented the Expressionist amp in blogs dated 01May2012, 24July2011 & 10July2011, including photographs and a testimonial written by Aria Award winning producer, Jonathan Burnside.

the Expressionist 15W model

the Expressionist 15W model

We have been building the Expressionist models for well over 10 years now, with 15 watts currently the most popular power rating. The Studio Expressionist option, as pictured in this blog, enables the user to select either the standard (for this model) EL84/6BQ5 output valves or the alternative 6V6GT output valves, offering the broadest possible range of tones for your recording projects.


rear view Expressionist 15W

rear view Expressionist 15W

The EL84 output valves, which are employed throughout the Expressionist Series amps, are famous for their chimey tops, complex midrange and lively dynamic response. By contrast, the 6V6 output valves are noted for sounding smooth and sweet, ie they were the valves typically used in the smaller Gibson and Fender amps back in the day. This is actually the first time we have employed the new Mullard (reissue) 6V6GT valves, as well as the new Tung Sol (reissue) GZ34/5AR4 rectifier valve. EL84/6BQ5 valves by JJ, Electro-Harmonix and Tung Sol (reissue) have all proved themselves to be reliable performers in cathode-bias/Class-A amplifiers in the 15 to 30 watts range.

Expressionist 15W chassis - top/front view

Expressionist 15W chassis  top/front view

The intention of the Expressionist Series model is to offer the classic vintage Brit tones from 1959 to 1965, and well beyond. The preamp offers two discrete channels, ie each channel has it’s own unique signal path and equalisation. There is no shared circuitry until the two preamp signals are combined in the phase inverter stage of the power amplifier. The two channels are mixed together in such a way that they are back in phase with each other, conveniently enabling the channels to be patched together in the traditional way, or combined with an A/B/Y pedal (supplied with each Expressionist).

Expressionist 15W chassis top/rear view

Expressionist 15W chassis
top/rear view

Channel 1 is built around the EF86 pentode preamp valve, recently reissued by Tung Sol, but also still available on the n.o.s. market. This channel is voiced with a (relatively) flat midrange response, as opposed to the more usual ‘scooped’ midrange response of iconic valve guitar amp designs since the 1960’s. The deceptively simple 6-way Colour tone switch enables the perfect midrange to low frequency balance for your performance. Here’s our tip: patch CH-1 and CH-2 together for a blend of ‘scooped’ and ‘non-scooped’ EQ – it’s a huge and powerful tone. Always use a short, high-quality jack/jack patch lead for this purpose.

Expressionist 15W chassis

Expressionist 15W chassis

Channel 2 employs a pair of 12AX7/ECC83 twin triode valves to provide two sequential gain stages and a cathode-follower ‘tone stack’ driver stage. Obviously this channel was inspired by the famous  ‘top boost’ channel in the mid 1960’s British Invasion amps. We have spent the last decade tweaking this channel to achieve a tonality that equals the very best examples of the vintage era (quite unlike the various ‘reissues’ from the last couple of decades, including both UK and Chinese manufacture).

EF86 with added dampening

EF86 with added dampening

Finally, the power amplifier section has recently been upgraded with an over-spec’d power transformer that runs cool at full power. We have also upgraded the filter choke, which is an over-spec’d clone of an original mid-60’s Brit choke. This component is an important contributing factor to the ‘feel’ of playing through this amp, while filtering the rectified high voltage (HV) DC to a more significant degree. This means there is less power supply hash in your signal, ie less non-musically related harmonics. Our intention always is to build amps that just sound so damn good that you don’t want to put down that guitar !!

The power amp section is where we have situated the master ‘tone cut’, which is like a passive presence control, and a key ingredient in the tone of these amps, plus the master volume. The design of the master volume enables the preamp to be overdriven at conversation levels, but at full clockwise rotation has no effect on your tone. However, for that chimey clean Brit-pop tonality we recommend setting the master volume to max, and running the amp ‘wide open’. Set the ‘tone cut’ control to personal taste – it is very useful for controlling the spikey high end of some single coil pickups.

All our amps, regardless of which model, are designed from the outset to work well with your pedals. The pedals are intended to be patched between guitar and amp. We obviously cannot comment on every one of the thousands of overdrives/fuzzes/etc out there on the world market, but most of our customers are using various combinations of pedals/pedalboards very successfully with our amps. Each and every one of our amps is individually hand-built, one at a time, by one person, from beginning to end. It takes a lot longer this way, but it’s worth it !

Ivan Richards.

the Landry 100 watt amplifier in our workshop

August 3, 2014
the Landry amplifier

the Landry amplifier

Hello again. We are now offering world-class (non-warranty) service and repairs to Landry amplifiers of St. Louis, Missouri USA. We should point out that we have no official relationship with Landry amplifiers, so we cannot accept any warranty repair claims without the endorsement of Landry or their Australian sales representative. The Landry amp is a relative newcomer to the boutique guitar amp scene. We endorse the fact that these amps are totally valve (tube) circuitry (apart from solid-state rectifier), and are completely hand-wired and assembled, presumably by one person.

the Landry amplifier

the Landry amplifier

Landry are producing only one or two models, very obviously voicing their amps towards the classic British/Marshall sounds (in both channels), but with a number of enhancements and more modern high gain sounds available as well. There are two independent preamp channels, each with its own 3-band passive EQ. The ‘clean’ channel is voiced similar to a JTM45/Bassman style amp, and the ‘distortion’ channel is voiced similar to a JMP series amp, but with additional gain available via a footswitch. After the channel switching takes place the signal is routed via a valve-driven series FX Loop.

the Landry amplifier

the Landry amplifier

The master volume is of completely conventional design, following after the FX Loop, but works very effectively in this amp design. The big surprise in a Marshall inspired amp such as this, is the inclusion of a valve (tube) driven reverb of very acceptable sound quality. Certainly much better than the reverbs ever were in Marshall amps over the years ! The phase inverter, power amp and power supply stages are very similar to what you would find in a 100 watt JMP Marshall.

Landry turret board and hand wiring

Landry turret board and hand wiring

The power and audio output transformers are in fact the very excellent 100 watt JMP style models by Classic Tone/Magnetic Components of Chicago USA. The claim on the Landry website that the ‘clean’ channel delivers sparkling blackface tones is of course an exaggeration. This channel delivers the fatter JTM45/plexi/’59 Bassman type tones, and there is absolutely nothing wrong with that at all.

setting the bias on this amp is very easy

setting the bias on this amp is very easy

Our good customer, Steve Edmonds brought this 100 watt head into the workshop last week, stating that the amp had lost some of its magic. Please see our post of 25/2/2014 re the Steve Edmonds band, and new project Mescalero. Inspection of the chassis revealed no apparent problems, but testing all the valves (tubes) separately from the amp did reveal most of them were in a degraded state, suffering from microphony, low gain, etc. Apart from a Tung Sol (reissue) 12AX7 in position V1, all other valves (tubes) were Chinese 12AX7B and EL34B. Now this amp is really only a few months old, but Steve is currently the hardest working guitarist we know, generally playing four gigs per week.

Landry chassis: six preamp valves in total

Landry chassis: six preamp valves in total

As a sweeping generalisation, Chinese manufactured valves (tubes) can quite often sound very good indeed when brand new, but can also lose their quality relatively quickly. Their 12AX7’s especially seem to become not only microphonic but also rather harsh and brittle. No doubt they will improve their quality of manufacture over time, the Russians certainly have. We installed a mixture of JJ, Electro-Harmonix and Tung Sol (reissue) valves, pre-tested and graded in our workshop, making an effort to select the ideal valve for each position. For the output stage we installed a matched quartet of Tung Sol EL34B, which have been certainly the most reliable of current production EL34’s (in our experience), although they do sound different to other EL34’s – therefore the customer’s personal tastes have to be taken into account in these situations.

the Landry chassis

the Landry chassis

Rebiasing the Landry for new output valves is easy and convenient – I wish the major manufacturers would take note ! All four EL34 cathodes are connected together to ground via a 1 ohm/10 watt resistor, which in turn is connected to external DVM test points. Simple ! The amp passed its power output and burn-in testing with flying colours, and it seems that Steve is very happy with what he was hearing at last week’s rehearsal. Many thanks to Steve Edmonds for his continued support and for supplying us with the subject matter for this blog. IR.