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.

the Marshall Class 5 in 2015

December 14, 2014
the C5 head after VVR mod

the C5 head after VVR mod

Hello and welcome back to the blog. Only a couple more weeks now and the year 2014 will be history. Our most popular amp mod’s during 2014, apart from the perennial Fender Blues Junior and Pro Junior mod’s, would have to be to the Marshall Class 5, aka C5. We have completed mod’s/upgrades to a number of these amps now with consistently good results for our customers.

 

the C5 head after VVR mod

the C5 head after VVR mod

Basic mod’s to the C5 start at $200 inclusive (Australia), and include installation of the VVR module and upgrade of signal path and tone control capacitors. For those who really love their C5, we suggest looking at upgrading to the Mercury Magnetics transformer and filter choke set. For a more detailed description of our C5 mod’s, see our December 2013 blog.

However, to summarise – the capacitor upgrades result in more effective EQ and a tonality more like the favourite old-school Marshalls, for example the “Plexi” series amps. The VVR module works as a power attenuator, reducing the output of the amp to quiet conversational levels. Very handy for apartment dwellers. The most suitable location for the VVR module, both electronically speaking and for user convenience, is directly behind the Class 5 logo. But, at least now we have located a source of traditional looking Marshall style control knobs with set screws, to suit the solid shaft of the VVR control. Many thanks to all our customers from 2014 !!

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.

Ivan’s Belman ‘Albatross’

August 2, 2014
Belman Albatross

Belman Albatross

Thanks for checking in to our blog. From time to time we like to share our experiences in upgrading our own instruments, as distinct from customer repair work. This week we discuss an Australian made instrument – the Belman Albatross (standard). The most recent similar blog was published November 24 2013, regarding a ’52 Tele (reissue) upgraded with the marvellous  Pete Biltoft pickups, plus an upgrade of an ESP Tele. We purchased the Belman at the beginning of this millenium from East Gosford Music (NSW). The proprietor, Trent Crawford, was one of the first stockists in NSW (as far as we were aware) of the Belman guitar and was a Belman player himself.

Belman Albatross

Belman Albatross

Trent enthusiastically promoted the Belman, and quite a number of local Central Coast players (including myself) purchased the Albatross and subsequent models such as the double-cutaway. The thing that struck us all was the consistent quality of construction and assembly of these instruments, especially when making direct comparisons to the leading imported brand (at that time), selling for twice the price or more. Another unique aspect of the Belman was the use of exotic Australian tone woods.

 

Belman headstock & logo

Belman headstock & logo

Belman guitars were hand-made in Melbourne, Australia from 1994 to 2007. I recall visiting their factory in Thomastown (Victoria) in the company of Bob Spencer, who was in the process of ordering a customised model. Belman was only ever a small operation, involving just a handful of people. Like many such small businesses in a highly competitive industry, they were under-capitalised and had no choice but to stop production in early 2007. For a more in depth discussion of the Belman models – see the Jedistar Belman Page. East Gosford Music also closed their doors a few years back, due to the shift in musical instrument retailing from bricks and mortar to on line. Trent, however is still very much involved in the music industry – see Trent Crawford Music.

location of the serial number

location of the serial number

With the Belman Albatross – I always thought that the electronics let the guitar itself down very badly. The pots, 3-way switch and jack socket were all just a bit cheapo, and were upgraded to Switchcraft and CTS components a.s.a.p. All the other Belman hardware was excellent. We don’t understand the reasoning behind these choices, as the RRP of the Albatross at that time was $2,399 ! Please note: when replacing cheapo guitar pots, the mounting holes will usually have to be carefully enlarged to 3/8″ diameter with a suitable reamer.

rear view with EGM sticker still in place

rear view with EGM sticker still in place

I was never happy with the high output pickups either, and didn’t feel that they were bringing out the best in this instrument at all. This particular issue of course applies to thousands of guitars out there, a fact which supports a whole after-market guitar pickup industry. Next, I installed a set of Lindy Fralin humbuckers which also were too hot and therefore too muddy. I probably should have researched my requirements a lot more, as Lindy Fralin offer many choices from underwound to overwound. I went through a P90 obsession phase, and installed a set of Seymour Duncan Phat Cats, which are P90 pickups modified to install in a standard humbucker mounting.

new Seymour Duncan neck humbucker

new Seymour Duncan neck humbucker

I still wasn’t getting the combination of warmth/sweetness/clarity/articulation that I was craving so badly by now. I knew the problem wasn’t the guitar itself – the solution could only be achieved by matching up the right choice of pickups. Last year I upgraded the neck pickup in my ESP Ronnie Wood Telecaster (also purchased from EGM), with a Seymour Duncan ‘Seth Lover’ humbucker, with the best results so far in that guitar, paired up with the ‘Jerry Donahue’ bridge pickup (both Alnico II). I ordered a set of Seymour Duncan ‘Seth Lover’ pickups, SH-55b (8.07K) and SH-55n (7.33K), from a dependable supplier Darren Riley, for around $100 ea USD.

I could have spent well over $400 AUD acquiring the new Joe Bonamassa signature pickups, or some other more exotic boutique models, but exercised some restraint and I’m pleased I did, because these pickups have worked wonders for my Belman which now has mucho warmth without compromising on clarity, and the amp can be easily cleaned up from the guitar volume control, which is always a good thing. The tone is vintage PAF to be sure, but these pickups can still supply enough boldness and punch for most applications short of heavy rock and metal. IR.

 

another Laney AOR Series ‘Pro Tube Lead’ amp in our workshop

July 20, 2014
the Pro Tube lead 100 head

the Pro Tube lead 100 head

Hello and welcome to the blog. Once again we have completed major repairs to a Laney (UK) “AOR Series” amplifier – model name Pro Tube Lead, this time a 100 watt head for customer Ben Rabey. We previously published blogs on 14/5/2013 and 10/7/2012 describing repairs and MODs to Laney amps in detail, including the AOR Series 50 watt combo, and also the LC30-II combo.

 

Pro Tube Lead 100 head sitting on a Hame speaker cab

Pro Tube Lead 100 head sitting on a Hame speaker cab

The fault description from our customer was that the amp plays OK for a while, and then the output drops markedly ! Upon removing the chassis from its sleeve, the first things we noticed were that the mains fuseholder was loose and could not be tightened satisfactorily, plus the amp was seriously under-biased resulting in a much higher than normal current draw by the quartet of EL34 output valves (tubes).

 

removing and reinstalling the board is quite a task, but has to be done !

removing and reinstalling the board is quite a task, but has to be done !

We replaced the fuseholder altogether with a current production unit that complies with contemporary electrical safety standards. We also installed the correct value HT fuse – T1A. Following this, the amp passed electrical safety testing to Workcover NSW standards. This is all important stuff, and should never be overlooked. We tested the quartet of EL34 valves and all the 12AX7 preamp valves externally to the amp with no apparent problems revealed.

access to much of the wiring is under the board, but available space is very tight !

access to much of the wiring is under the board, but available space is very tight !

After re-installing the valves (tubes), we rebiased the EL34’s to a sensible current draw. The amp tested both very low and very distorted output signal into a dummy load. We observed a good drive signal to the EL34’s from the phase-inverter stage, with a signal injected at the FX Loop ‘return’ jack, so we had every reason to suspect that the output transformer had broken down internally. We quoted Ben on replacing the output transformer plus other tasks, and the project proceeded.

 

the new output transformer installed on the Laney chassis

the new output transformer installed on the Laney chassis

As we are an authorised repairer for Marshall amplification, we therefore have access to the full stock of Marshall spares for current and vintage models. It just so happens that the 100W output transformer for the JCM800 series, designated C2668 (by Dagnall Electronics), is a perfect match and perfect fit for the 100W Laney. This is hardly a surprise, as the Laney is very obviously based on the JCM800 design, but with additional gain and additional features.

repairs completed and board reinstalled

repairs completed and board reinstalled

Getting access to the wiring to carry out this task is not easy, as much of the wiring passes underneath the single large printed circuit board (PCB). Definitely not mil-spec wiring, but the JCM 800 amps are exactly the same (although their wiring is somewhat tidier). Removing the board requires removing a number of fasteners, plus also removing all the front panel controls, as all these controls are hard-wired to the board, as you would expect.

new 'touch proof' mains fuse installed

new ‘touch proof’ mains fuse installed

The replacement C2668 transformer wiring of course has a completely different colour code to the original Laney unit, which required some additional investigation to complete the installation successfully. While we had both sides of the board exposed, this was the perfect opportunity to replace the bias supply filter caps, plus some of the low-voltage supply components (as per the previous Pro Tube Lead repair job). You can see a burn mark on the component side of the board under a power resistor in the low-voltage supply, so this appears to be a common problem in these amps.

rear view Laney 100W head

rear view Laney 100W head

For those interested in technical matters, this amp was serial # 2685, and appears to have been built in 1988. After installation of the new transformer and rebias of output valves (tubes), we had a high-tension voltage supply of just under +470V, and a bias voltage of -38V. The amp delivered 43V into 16 ohms @ the onset of clipping = 115 watts. Was the blown audio output transformer a direct result of the under-biased output valves ? We will never know – sometimes these are just random events. Many thanks to Ben for his continued custom. As always with these models – once set up and running properly the amp sounded huge !   IR.

Servicing the Carr ‘Sportsman’ amp in Australia

July 5, 2014
the Sportsman logo

the Sportsman logo

We have had a relationship with Carr amplifiers of North Carolina, USA, going back several years to when the former Bondi Intermusic Australia began importing these amps. Of course Bondi is long gone, so therefore we are no longer the national warranty service agent as the brand has been taken over by another distributor. However, with the full approval & support of Carr USA, we are still providing post-warranty after-sales-service to the entire range.

the Carr Sportsman 1x12 combo

the Carr Sportsman 1×12 combo

We have previously published blogs re the Carr Artemus and other models in the range. The Sportsman model is a relative newcomer to Australia, and this is our first servicing experience with this model, for new customer Matt. The design of the Sportsman follows on from Carr’s most successful models, being somewhat like a hot-rodded “blackface” Princeton Reverb amp. That’s the best way we can describe it, although there are some differences, particularly in the phase-inverter and power amplifier circuits.

the Sportsman front panel

the Sportsman front panel

The power amplifier is designed around a pair of 6V6 output valves, employing a form of compound bias – combining both fixed bias & cathode bias, with a power output @ the onset of clipping of about 16 watts into a 16 ohm load. This arrangement seems to work well in practice, although when Fender (as a division of CBS) tried something similar in the late 1960’s the results sounded so bad they had to implement a redesign of the “Silverface” models.

the Sportsman from the rear

the Sportsman from the rear

The power supply uses solid-state rectification, as opposed to valve (tube). The “headroom” control is actually a master volume with some tone shaping, following on from the final preamp gain stage. As per the Two-Rock amp discussed in the previous blog, this control is intended to manage the gain structure of the amp, rather than introduce distortion, hence the “headroom” label.

Sportsman chassis & speaker

Sportsman chassis & speaker

The reverb on this amp is exemplary, which is a real contrast with the many current production guitar amps offering really poor reverb !! There is no tremolo on this model. The chassis is completely hand-wired. Matt reported that although the amp was still functioning, the sound of the amp had deteriorated markedly. We examined the interior of the chassis looking for any signs of component failure or drift, but chassis checked out A-OK.

Sportsman 006We carried out a full re-valve and once more the Sportsman was delivering the kind of attitude that Matt was missing. The one and only concern we might have with this amp is the minimal ventilation for the horizontally mounted 6V6 output valves, which are biased to run quite hot. We have to thank new customer Matt for providing us with the subject matter for this blog. I think the only remaining question for Australian guitar players would be – could you buy an amp with a duck on the front panel ??    IR.

Sportsman 008

Service centre for Two-Rock amplification in Australia

July 5, 2014
Two Rock 001

Two-Rock EXO15

Hello 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 Two-Rock guitar amplification of California, USA. We should point out that we have no official relationship with Two-Rock Amplifiers, so we cannot accept any warranty repair claims without the endorsement of their Australian distributor.

Two-Rock EXO15

Two-Rock EXO15

We recently serviced the Two-Rock EXO15 head (serial # 62) for Sam, one of our regular customers – the amp is featured in the accompanying photos. Sam advised us that the amp ‘just stopped’, which is a fairly common amp fault description, and in most cases would suggest a valve (tube) or other component failure, or at least a blown fuse.

 

 

6V6 powered EXO15

6V6 powered EXO15

The EXO15 is a single-channel, 15 watt 6V6 powered and valve (tube) rectified class AB amp, designed in an all-metal enclosure,  with a pair of 12AX7 preamp valves (tubes), one of which functions as the phase-inverter. The preamp design is somewhat similar to the “clean” channel in a Dumble guitar amp, as per the Two-Rock heritage, and the 3-band passive EQ is also voiced along similar lines.

5AR4/GZ34 rectifier

5AR4/GZ34 rectifier

The master-volume is placed directly after the 2nd gain stage, and is therefore intended more for managing the gain structure than generating massive amounts of distortion (a design approach which we endorse). The master feeds a passive FX Loop, for time-based FX devices that can accomodate line levels. In spite of the name & description, the “contour” control is in this case a simple passive high frequency roll-off, as per the vintage VOX AC15/AC30 amps. We heartily endorse the inclusion of a GZ34/5AR4 valve (tube) rectifier in an amp of this power rating.

under the chassis view from the front

under the chassis view from the rear

Anecdotal evidence from the customer suggests this hasn’t been a particularly reliable amp. As this is our first service job on this particular amp, we are not familiar with its previous service history. Assembly is a combination of circuit boards and hand-wiring. All connections to valve sockets, jacks/pots/etc are hand-wired which of course we endorse. Components are of commercial standard but not “boutique” standard, with no apparent design problems.

under the chassis view from the front

under the chassis view from the front

We replaced the blown mains fuse, and also the output valves & rectifier valve just to be on the safe side. Our initial choice of JJ 6V6 output valves was not a success, as they are too tall for the cover to fit back on !! We ended up installing a matched pair of 6V6GT by Electro-Harmonix, which have been pretty reliable at the voltages within this amp (+440V DC in our Wyoming NSW workshop). We rebiased for a sensible current draw with the 6V6’s (this may have been the problem all along ??), and measured the power output @ the onset of clipping = 22 watts.

ventilation grille at the top of the reassembled enclosure

ventilation grille at the top of the reassembled enclosure

We were looking for any other factors which may have contributed to the unreliability factor, at Sam’s request. When we looked at the speaker output jacks (4, 8 & 16 ohms), we were really disappointed at the nondescript quality of the jacks installed, and their current condition. We installed a trio of the very fine Switchcraft jacks, which grip the speaker plug very firmly for a positive connection. H/R (high resistance) or O/C (open circuit) speaker connections can cost you not only your output valves, but potentially also your output transformer. Always use the best available jacks & plugs for such critical connections.

Thankfully, no further problems have been reported with this amp. Many thanks to Sam for his continued custom, and for supplying us with the subject for this week’s blog !   IR.