ivanrichards

More about Rivera amps: the ‘Ninja Boost’ MOD

December 16, 2011

Those of you who are regular readers of our blogs will know that we have visited the subject of providing quality service to Rivera amplifiers (USA) in a couple of previous blogs. This time, we are not discussing a fault as such, but addressing a design limitation with a (relatively) simple MOD.

As we have discussed previously, the classic Rivera amp models have two discrete preamp channels, one with ‘British’ voicing, and one with ‘California’ voicing, plus master reverb, FX loop and prescence controls. Both channels have gain boosts, activated from ‘pull-on’ functions on the front panel controls. On the USA (green LED) channel this is known as ‘Ninja Boost’.

The Ninja Boost feature when activated provides a substantial gain boost. In a live performance situation, activated from the footswitch unit, this gain boost is actually unmanageable, which is the whole point of this blog. We were recently approached by a local Central Coast (NSW) rock guitarist, Mr Greg Taylor, to provide a MOD so that the level of boost can be preset to a more appropriate level from a suitably located additional control.

The gain boost in the USA channel takes place between the 2nd & 3rd gain stages, where an interstage attenuator is partially bypassed by a fixed resistor when the boost is activated. Each gain stage uses one half of a 12AX7 twin-triode valve (tube). This attenuator and associated switching circuitry is located on the main board.

Inspection of the chassis and board revealed that we could snip one end of the abovementioned fixed resistor, close to the input grid of the 12AX7 gain stage. Having done this, we could run a pair of shielded cables to a pot located in a spare position on the rear panel. The pot is wired up as a variable resistance in series with the existing fixed resistor, meaning that only 2 of the 3 lugs are connected. Thus we control the amount of boost by varying the insertion loss of the attenuator circuit. Because this is a series attenautor, as opposed to a volume control, a pot with a linear or reverse-logarithmic taper is more suitable than a logarithmic taper, giving a smoother sweep.

We use a high quality shielded cable (eg, Canare), rather than ordinary hook-up wire, so as not to introduce any additional hum & noise when the boost is activated. The shields of both cables are earthed (grounded) at one end only, in this case to the body of the pot, to avoid creating an earth-loop (ground-loop). Heatshrink is used at both ends to prevent accidental short circuits, and also to create a stable connection to the resistor that we snipped at one end – the other end of this resistor is still connected to the board. The whole job is neatly routed into the existing wiring and held in place with nylon cable ties. Although we have performed an intrusive modification, the amp has not been degraded in any way, from the perspective of reliability or additional noise.

So how did the MOD perform in the final play test ?? The amount of boost is now variable from a just perceptable boost at minimum (anti-clockwise) setting, to the original level of Ninja Boost at the maximum (fully clockwise) setting, all in a smooth, linear sweep preset from the rear panel. Thanks to Greg Taylor for his continued custom and for the many challenges he has provided us over the years ! Coming soon we have a blog about the legendary Wasp amplifiers, modding current Fender amps for blues-harp players, and mods to the Fender Blues Junior amps.

Posted in Amp Repair, Amps | 20 Comments »

Rivera Bonehead amp powers up but nil output !

November 4, 2011

Hello guitar amplifier enthusiasts ! This week’s blog could easily be given an alternative title the lights are on but nobody’s home, as those were the classic symptoms we were confronted with when powering up the Bonehead for the first time. This is a relatively complex repair example to describe and photograph for a blog, which is why it’s taken us over two weeks to get it together.

The Paul Rivera Bonehead amp is a huge, rather heavy, 100 watt 4xEL34 valve (tube) head with three discrete pre-amp channels, and incorporating the Los Lobottom woofer output to drive a separate low-frequency amp/speaker system. The Bonehead can be (and normally would be in this case) operated without the Los Lobottom feature connected to anything. The design concept is attributed to guitarist Steve Lukather, formerly of the U.S. band Toto.

This Bonehead was shipped up to us some time back by Bondi Intermusic (Sydney), on behalf of one of their customers. At first appraisal, we had no idea what was going on – the amp powered up OK, and all the circuit conditions looked normal, power supply voltage readings were in the ball-park of what you’d expect in such an amp, both high-voltage and low-voltage supplies, and yet there was zero output from any of the three channels, and none of the front-panel status LED’s were active.

Discussion of the amp’s history with the customer, Paul, revealed that this same fault had occured a number of times in the past, with the fault condition returning almost immediately after the customer received the amp back from repairs (previous repair attempts undertaken by a Sydney based tech not personally known to me). This is a pretty rare amp in Australia and the first time we have ever seen an example of this model, so the first thing was to try to track down some official service info/schematics from Rivera USA, via their Australian distributor. This took quite a while and finally we received a faxed copy of the schematic, which was a little lacking in resolution compared to a soft copy, however much better than nothing at all !

All the switching in the Bonehead, including for LED status indication, originates in a complex circuit of seven CMOS logic IC’s, mounted in 14-pin and 16-pin IC sockets. There is other discrete circuitry as well, to drive the LED’s and the opto-couplers. It would be very difficult to service this amp without a schematic diagram. Thankfully, Rivera chose to install the IC’s in sockets. BUT, the quality of the sockets they used was NOT professional user standard. I remember from my earlier career in the Telecommunications industry, when Telecom circuits went from electro-mechanical to 1st generation digital/solid-state, we had endless faults caused by the fact that IC’s weren’t seated properly in cheapo sockets.

It was now obvious that the fault causing nil output was not in the valve (tube) cicuitry at all, but was the result of a non-functioning switching circuit. Due in part to my history of bad experiences with cheapo IC sockets, and also due in part to the complete lack of voltage and logic test points on the schematic diagram, it also was now obvious that I should replace all seven IC’s and most importantly, the IC sockets, using only industrial quality machined pins sockets. Interestingly, the previous service “tech” had chosen to carry out a quick fix, basically just trying to hold the IC’s in their sockets with some kind of goop, rather than actually cure the problem once and for all.

The main board now had to be stripped out of the amp chassis, which involved removing all control knobs and pot nuts, etc, as all pots are p.c.b. mounted in Rivera amps. The IC’s were removed then the old IC sockets were removed from the board – this required desoldering the socket pins on a double-sided, plated through hole board. Rather laborious and tedious and a task requiring a great deal of care so as not to damage any of the pads and through plating, otherwise we would be up shit-creek, basically. Having cleaned up all excess solder the next task was to install these new, industrial quality 14-pin and 16-pin sockets. Once again, applying enough heat to make sure the solder ran through to both sides of the board, but not so much heat that we damage the board.

You can see in the previous three photos the underside of the board with the soldering of the IC sockets in the foreground, and two views of the component side of the board with the new sockets installed successfully. The next two photos show views of the board with IC’s installed in the new sockets, with the complete switching circuitry in the foreground.

But now we hit a snag ! Look at the photo on the left. The IC’s designated IC306 and IC307 are positioned too close together on the board, which means that the two IC’s cannot be inserted fully into their respective sockets. HUH ?? No wonder the previous tech resorted to using goop to hold the whole thing together – trouble is, it only worked for about 5 minutes that way. I had to use secret Aussie male ex-Telecom Australia technical workforce service techniques to get both IC’s into their sockets. But seriously folks, this kind of design boo-boo should not be happening in this level of equipment.

The repair job was finished with some routine tasks, including rebias of the EL34 output valves, and cleaning of jacks with DeOxit and pots with FaderLube. Power output test and electrical safety test were both fine. The Bonehead is probably the least successful amp from the Paul Rivera range, judging by Rivera user forums. How did it shape up in the final play test ? The three channels, clean, crunch and full-on distortion for want of a better description worked well, allowing fine control adjustments as each channel has its own independent level and EQ, as well as “Ninja” boost and other features. The robust FS8 footswitching unit works well – the use of CMOS logic IC’s to control the switching enables Rivera to use simple momentary footswitches to activate channels and FX Loop. The only criticism we have here is the continued use of DIN plugs and sockets, which on the road are a constant source of problems – they are just too flimsy, resulting in intermittent connections. This criticism applies to many commercial manufacturers, not just Rivera.

Rivera amps usually have a “Fender” voiced channel and a “Marshall” voiced channel. I usually much prefer the “Fender” voicing on these amps, and that applies to the Bonehead model as well. The “Marshall” channels are just not that convincing to my ears, but it’s very much a personal thing. Paul Rivera is well known as having redesigned some of the Fender amps in the early 1980’s and turned that company’s fortunes around in the amp business. The Super Champ is my favourite model from that era. Bondi Intermusic’s customer was most pleased to have his amp back again after so long, working properly at last !!

In coming weeks we will have another major 1970’s Musicman refurbishment, this time a 4×10 combo (rare around these parts), an overhaul of a very rare early 1970’s Marshall 1×12 tremolo combo, a transformer replacement in a mid-1960’s made in Sydney Galaxie, by Vadis, ie Soundcraft Industries, went out of business back in the early 1970’s. We also have more amps and cabs from the Richards Amplifier Company nearing completion. Don’t hesitate to email me re any of this stuff – regards, Ivan.

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An Afternoon of Speaker Comparisons

October 24, 2011

In this week’s blog we get together with some members of the Sydney Shadows Club, ie guitar playing enthusiasts who love the guitar instrumental music popularised by the Shadows (UK) and many others, in the late 1950’s/early to mid 1960’s.

The local NSW Central Coast enthusiasts get together for an all day jam session every 2nd Thursday by invitation only at a private residence on a small acreage (so no complaints from neighbours !).

I make a point of attending this jam session whenever possible, at least for an hour or so. You will notice there are always a couple of Expressionist series amps from the Richards Amplifier Company – Australia in attendance.

On this particular day, I turned up with a newly completed 1×12 tone cabinet, which was a custom order for Chet Romero, an Aussie slide guitar specialist, loaded with the Weber 30W Blue Dog speaker. We have supplied this specific Weber model on previous occasions with our Expressionist amps, always with great results.

Part of the afternoon was devoted to conducting comparison tests between the Weber loaded 1×12 cab and a well played in 1×12 cab loaded with the mighty Celestion 15W Blue Alnico model. The cabs are of identical proportions, athough the older Celestion loaded cab was a TV front style, and had a brown basketweave grille, as distinct from the checkerboard grille of the (red) Weber loaded cab. The different grilles do have an impact on tone. We will explore this issue in a forthcoming blog.

Well, both speakers sounded great in their own right, but there were unexpected differences. In all comparisons, a 1963 Fender Strat in original condition was played through a 7.5W Richards Studio Expressionist amp.

This amp was designed from the ground up for home studios and/or home jamming, and sounds just as good as the 15W and 30W models, its just that it breaks up earlier. The ’63 Strat played through such an amp easily replicates the classic Hank Marvin tones from the Shadows golden era.

The majority opinion after numerous Shadows instrumentals was that the Celestion Blue was a bit brighter (but not in a bad way) and quite noticeably louder, and broke up later ! The Weber lacked the characteristic growl in the lower midrange of the Celestion, in fact if anything it was the more refined of the two.

However, we all agreed the Weber sounded great, in spite of the earlier break up. We were intrigued by the fact that the Weber imparted this delicious kind of midrange gronking quality on the wound strings of the Strat. Actually, I don’t have the appropriate words to describe it, but it was definitely there !

The chrome plated stand you see in some photos was one of a number custom made for members of the Sydney Shadows Club by an enterprising fellow. These stands replicate the look of the original stands used by groups such as The Shadows and The Beatles with their Vox amps back in the day.

The Shadows, and Hank Marvin in particular, had their own signature model Burns guitars back in the day. Some of these models have been reissued by Burns of London in recent years, although no longer made in the UK. They do capture the tone from that period quite convincingly, and the well-engineered tremolo (vibrato) design works well for this style of music (but probably not for dive-bombing styles).

In our final two photos we have the ’63 Strat with the 7.5W Studio Expressionist amp and 1×12 tone cabinet loaded with the Celestion Blue, as used in our comparisons. On top of the amp is a Rich Switch A/B to switch between the two distinct channels, and a tape-echo simulator that probably very few of you have seen – the Amtech Age One.

The Amtech is manufactured by a small Swedish company I believe, possibly their main products are in the medical equipment industry. But whatever it is they do, they are obviously serious Hank Marvin fans, as they designed a completely analogue circuitry tape-echo simulator, built in a 1RU high rack-mount enclosure, that comes closer to anything else I’ve ever heard to specifically reproducing the tape-echoes that played such a major role in recording the Shadows sound.

The other cool characteristic of the Amtech is that the preamp sounds very good on its own, with the echoes bypassed. A very warm and musical analogue sound. The pictured amp was one of the very first in our Expressionist series of models. These amps, as per all our current range, were designed and built directly as a result of customer requests and/or suggestions. This example is the Studio Expressionist model, meaning that the output stage can be switched from a pair of EL84 output valves, operating in class-A/push-pull, to a pair of 6V6 output valves operating under similar conditions, but with different bias conditions. In either mode the amp is self-biasing. The unused pair of output valves remains at full temperature for instant operation, but is only drawing a trickle of current, extending valve life.

In EL84 mode, naturally the amp sounds distinctly British, with either CH-1 (EF86 pentode), or CH-2 (12AX7 “top boost”), although Hank Marvin enthusiasts would automatically choose CH-1 for the most authentic tones possible from any amps we’ve heard thus far. In 6V6 mode with either channel, the amp delivers tones that would only be possible from some of the more obscure 50’s/60’s USA manufactured amps. For example, the combination of CH-1’s pentode preamp with cathode-biased 6V6’s would suggest vintage Gibson amp tones. Perfect for rock-a-billy, jazz, swing, blues, rhythm&blues, etc. CH-1 and CH-2 can be patched together in-phase (or combined with an A/B/Y pedal) for a huge tone.

Well – thanks to the Shadows enthusiasts for their input into this week’s blog. Please see earlier blogs describing how the Expressionist series amps have been used for recording and performing by very demanding contemporary guitar stylists. For those who might be interested, I believe that Amtech have an Australian distributor. Please tune in again next week ! Regards – Ivan.

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Chet Romero takes delivery of his new 1X12 tone cabinet in red tolex with checkerboard grille

October 16, 2011

Chet Romero is pictured here proudly displaying his brand new 1×12 tone cabinet in stunning red tolex & checkerboard grille, built by the Richards Amplifier Company – Australia. This tone cabinet is loaded with the Weber Blue Dog 30W alnico instrument speaker, specifically intended to be matched with Chet’s most recent amp acquisition – the Orange Tiny Terror 15W head. As you may have read in previous blogs, we have been servicing Orange amps for many years now, for the musicians of Central Coast NSW, and also for Bondi Intermusic of Sydney.

You can see that our standard Richards Amplifier Company logo is missing from this cab, instead Chet has supplied us with his own personal logo which is basically a truckers symbol of a very shapely and unclad female reclining on the bonnet of a truck. We are happy to indulge our customers requirements and personalise our cabs in this way, so bring it on ! Easy to see that Chet is a staunch St George supporter, by the way.

Having played with Men at Work, the Foreday Riders, and many more, plus composed music for film, television and live theatre productions, Australia’s wildest blues guitarist is about to launch his latest band Chomp Incorporated in November 2011, so watch out for more news about that ! Chet played that delicious little slide guitar solo on Men at Work‘s last single, Everything I Need (from the Two Hearts album).

This Weber-loaded tone cabinet sounded phenomenal either with the Tiny Terror or our own Richards Expressionist Series amps. In next week’s blog we get together with some members of the Sydney Shadows Club and compare the Weber against the Celestion 15W alnico Blue speaker. They both sounded great, but there were unexpected differences ! Thanks to Chet Romero for his news and his continued interest in our products and services. Regards – Ivan.

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A pair of problem solving pedals

October 7, 2011

Hello ! In this week’s blog we’ll draw attention to a pair of problem solving pedals hand-wired by Ivan Richards Audio fx right here in Gosford, New South Wales. These pedals don’t have the glamour and appeal of distortion and/or modulation models, that’s for sure, and we don’t build them in large numbers either, but for a number of performing musicians out there this type of pedal can make life a lot easier.

Our first example, in the photo above, is called the Double A/B Pedal, and is one of our ongoing Rich Switch series of signal routing pedals. This design is a passive, bi-directional, 100% hand-wired selector intended to switch two pairs of instruments. Four LED status indicators alert the player as to which instruments have been selected. The true hard-wired bypass design prevents signal loss or colouration, plus prevents phase problems being introduced. 9V battery or pedalboard power supply operation is required for the LED status indication only. This pedal is not intended to be used on powered speaker connections.

This unique pedal was originally created a few years back when we were contacted by Australia’s Mark Lizotte, who was at the time preparing to go on tour with two pairs of instruments, one pair of electrics and one pair of acoustic guitars. The intention was to use wireless transmitter/receivers for mobility, so this would have resulted in four wireless packs. By introducing the Double A/B Pedal, the number of wireless packs could be halved, and the whole rig streamlined. This is why the two pairs of A/B are labelled electric and acoustic, however customers can label the top panel in any way they find appropriate to their individual circumstances. Dymo labelling works fine in this situation, and can be removed without damage.

To prevent an earth loop being introduced (a.k.a. ground loop in the USA), the signal earths for the electric instruments selector and the acoustic instruments selector are isolated from each other. The Hammond die-cast aluminium enclosure is earthed via the electric instruments circuit. The electric instruments output jack also switches on the internal 9V battery, when installed.

Our second example, pictured to the right, is called (as you might expect) the FX Looper pedal. Guitarists who use stompboxes (and who doesn’t ?) often have to resort to costly loop-switching systems to solve signal-degradation problems introduced when bypassed fx are not switched completely out of the signal chain. The reason for this is that most fx devices do not provide a true, hard-wired bypass when the effect is switched out (even in some cases where the manufacturer implies the device is true bypass). When this happens, your clean guitar signal can lose definition and clarity due to the bypassed device’s tone-sucking circuitry. The more pedals/devices you string together, the worse the problem becomes.

The FX Looper pedal allows you to place a preset combination of fx pedals or devices in each of its two loops, and switch the chain in or out of the signal path with the loop bypass footswitch. Because it’s a true hard-wired bypass, your clean signal remains obsolutely free of stompbox interaction and/or signal degradation. In other words, the FX Looper gives you the purest possible connection between your guitar and your amp when in bypass mode of operation.

Our V1.3 Looper offers two independent loops which are wired for series operation (ie, loop #1 output feeds loop #2 input), and each loop has its own dedicated LED status indicator. The input jack is placed on the right-hand side of the enclosure, as per accepted tradition, but the output jack is parallel-wired to both the left hand and right hand side of the enclosure, facilitating placement in different positions on a pedalboard, for example. 9V battery or pedalboard power supply operation is required for LED status indication only.

So, to summarise, there are many advantages to using an FX Looper in your setup. There is no additional active circuitry in the signal path, ie the Looper adds no noise. There is no load on the guitar pickups when in bypass mode, ie no tone-sucking. The high-impedance send to fx pedals provides correct interaction with vintage stompbox input circuitry. To some extent the Looper is able to mute switching pops and clicks – this minimises a typical vintage fx pedal design problem.

Please join us again next week for another (hopefully) informative and entertaining blog. In coming blogs we will look at a new tone cabinet in stunning red tolex for Aussie slide-guitar specialist Phil B Colson. Philby played that delicious little slide solo on the last Men At Work single, back in the 80’s. We will also conduct a speaker comparison with some older guys from the Sydney Shadows club. We also hope to check in with Ilya, the guitarist with Continental Robert Susz, and Marcus from NSW band Sparrows.

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Approved service centre for Orange amplifiers

October 3, 2011

Hello everybody ! Welcome to this week’s blog. It’s been a busy October long weekend 2011, with gigs for the 5-piece band plus the duo, so this will be one of the less detailed blogs, but hopefully still of interest.

Actually, we have been repairing Orange Amplifiers for years, but not the warranty claims. Bondi Intermusic (Sydney) have sent us quite a few over the years for servicing. With the possible exception of the made-in-China Tiny Terror series, the Orange amps have been consistently well made and have presented very few servicing issues. The modern Orange amp has a particular sound, which is quite different to the original amps from the 60’s/70’s, which had a huge clean sound, and baxandall EQ, which is not everybody’s cup-of-tea. The recent amps have more conventional passive/interactive EQ and a contemporary “British” sound that is more appropriate for grungier styles ( to our ears anyway).

If you are the lucky owner of an original Orange or Matamp from the 60’s/70’s (and most definitely the current Matamps, which are an excellent boutique-grade amp from the UK), and you want your amp serviced/overhauled/restored by someone who knows what they’re doing and has a genuine passion for this kind of work, then please contact Ivan Richards Audio.

Orange amplifiers are distributed in Australia by the same people who distribute Gibson & Epiphone guitars. If you have a warranty service claim there is a procedure to be followed. First thing is to contact the dealer who sold you the product. They will book it in with the distributor. A repairer to resolve the warranty claim will be nominated by the distributor on the basis of both competency and geographical location.

The AD30TC 2×12 combo amplifier in the photos belongs to a regular customer of ours, a working muso (with a day gig), based on the Central Coast of NSW. The almost brand new amp just “stopped”, and the warranty repair was referred to us via Turramurra Music (Sydney). The reason soon became clear after removing the chassis from the cab (not a quick job, by the way) – one of the internal fuses was “blown”. The fuse protecting the 6.3V AC heater supply to the valves (tubes), to be precise. However, in this case the blown fuse was not indicative of a bigger problem, it was just one of those things that happen, usually at the most inconvenient time. We replaced the fuse and subjected the chassis to a power output test, burn-in test, electrical safety test, and final play test/functionality test. All OK !

In the final photo, it may not be very clear from our crap photography in workshop lighting conditions – but we are observing a sine wave on the oscilloscope, as part of the power output test for this amp. This is one procedure for checking for abnormal amplifier behavior under load and also accurately measuring the audio power actually delivered to a nominated load, for example – 8 ohms.

By the way, just a suggestion – if you have a bad back – don’t invest in one of these 2×12 combo’s ! They are seriously heavy. More next week – Ivan R.

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Major overhaul for a 1970’s MusicMan 130W amp

September 25, 2011

This week’s blog examines a major repair completed this week to a MusicMan 130W 2×12 combo, purchased brand new from Harry Landis Music in Sydney (Australia), and still owned by this customer. These 1970’s manufactured MusicMan amps were among the best of the American amps of that time, and were certainly built to last the distance. They were built to a very high standard by people who knew what they were doing. Probably the most popular and most collectable model was the 65W 2×10 combo.

The highly reliable and great sounding MusicMan chassis was let down to some extent by pretty average speakers, especially in the bass guitar models. You will often see that the original speakers have been replaced, sometimes quite early in the working life of the amp, or in the case of the amp heads you will almost always see them hooked up with a different brand of speaker cab. Not surprisingly, the MusicMan amps strongest appeal was their great “clean” tone, reminiscent of the very best of the Fender tones. When it comes to overdriven sounds………..forget it ! You will need your pedals for that.

What style of guitarists love their MusicMans ? Most probably those playing country rock, rockabilly, old-school rock and blues and any traditional roots music styles. The 130W model is clean enough for keyboards, too. This particular example was damaged some years back at the Goulburn (NSW) Blues Festival. It was quickly patched up to get through the gig, but this amp as is would never pass an electrical safety inspection that meets Workcover NSW compliance.

You can see from the thumbnails there are quite a number of outstanding service issues to be resolved. Firstly, there was some doubt as to whether the power transformer itself was 100% functional, as it had temporarily been rewired for half-power only. The wiring and general internal appearance of the transformer looked pretty crusty. I had to suss out the colour code for the primary connections in order to make any sense out of the situation.

Having achieved that, the first step was to replace the damaged 3-core 240V flex and 3-pin plug, and to make a new chassis earth connection which would achieve compliance testing. This involved rewiring the fuseholder as well. Beware: the fuseholders in some older amps are not wired in a way that meets electrical safety standards, ie they are wired so that the outer part of the fuse remains active, even if the fuse is blown. If this is the case, the wiring should be reversed. The fuse should also be wired in series with the 240V active (brown), NOT the neutral (blue). Refer all such issues to an experienced and trusted technician !

The next step was installing a new power switch on the front panel. This is actually a 3-way SPDT toggle switch with a centre-off position, labelled HI/OFF/LO. What is actually happening is the incoming 240V AC can be switched to either one of two primary voltage taps, which gives higher or lower internal DC voltages to power the EL34 output valves (tubes). In all cases we insulate the high voltage connections with heatshrink.

The unusual design feature of these amps, apart from a completely solid-state preamp, is the fact that on the HI power setting, the EL34 output valves have +700V DC on their anodes, and +350V DC on their screen grids. You cannot install cheapo valves in this amp and expect them to last very long ! Stick with brands that have a proven track record in reliability, for example JJ are a good choice for this amp. The next step was to replace a number of electrolytic capacitors in the high voltage (HV) and low voltage (LV) power supplies, all of which were still original and starting to look very crusty indeed.

The HV supply requires a pair of 100uF/500V capacitors in a voltage-doubler configuration for the 700V supply, and a pair of 22uF/500V capacitors after the filter choke for the screen grid and phase-splitter supplies. For the bias voltage supply we needed some 100uF/100V capacitors. The HV supply caps are mounted in their own “can” on the top side of the chassis.

All the capacitors were bedded down in some silicone to keep them secure and to take the strain off the leads. For DIY people out there, always make sure that you use “neutral cure” silicone, ie non-corrosive, or you might be in for a nasty surprise in the long-term.

Equally as important as the HV supply capacitors, is the replacement of the LV supply caps, which in the case of the MusicMan amps, shares some common circuitry with the bias voltage supply for the EL34 output valves (tubes). Rock-solid biasing of the output valves will depend on the quality of the bias voltage supply.

Well, to wrap it all up, I cleaned up the input and output jacks with DeOxit, and installed a JJ 12AX7-S in the phase splitter valve position, and installed a matched and burned-in quad of JJ EL34 valves in the power amp sockets. I set the bias for the EL34’s for 25ma cathode current each at 700V HT, as per the original spec. This is quite adequate at 700V. A power output test and burn-in test is then carried out – the amp is hooked up to an 8 ohm dummy load and a signal generator connected to the input jack. Observation of the sine wave output into 8 ohms reveals a clean signal and a power amp that reaches the onset of clipping at approx 120 watts rms. The power amp drops into “class-B” as we get closer to maximum power output, as expected.

The final play test was fine – the reverb and tremolo both work OK, although the solid-state reverb is not comparable to the valve-driven reverb on a Fender Twin, of course. You may notice the customer had removed the MusicMan logo (which was a bit toy-town looking), and the top strap handle, which he didn’t trust to carry the weight. The original speakers were replaced long, long ago with a pair of Etone 12-inch speakers, manufactured in Sydney. As a proud Aussie, I would like to say that the Etones sound great, but the reality is these speakers do absolutely nothing for this amp. They sound rather flat and overly bright. In order to demonstrate this to my customer, I played a TELE through the amp as is, then hooked up my workshop speaker cab, which is loaded with a 100W 12-inch Jensen NEO, and the difference in tone, complexity, and sheer volume was quite obvious. Perhaps this will be the subject of a future amp/speaker upgrade ?? See you next week – Ivan.

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Bob’s “Lil’ Buddy” amp returns to HQ for a complete overhaul

September 17, 2011

This is actually the very first amp I designed and built for Bob Spencer, a much loved and admired Aussie rock guitarist formerly of such bands as Finch, Skyhooks, The Angels, etc, and more recently RAW BRIT, as well as facilitator/coach on the Weekend Warriors programme in Melbourne. This amp was built back in 1997. We actually met in 1995, when Bob was recording the Temple Gods album, in a studio somewhere on the Hawkesbury River. He showed up at my house in Gosford at about 11 o’clock at night, to get a modification done to his AC30 clone amp (built by Ross Nichol in Melbourne, I think ?). This is how you meet guys like Bob !!

This was at the time when I was working from the kitchen/family room of our house in Wyoming (NSW) – there were amps waiting repair from one end of the house to the other, and amp parts stored in every room of the house – even under the kids’ beds, etc etc. Not the ideal way to live, and eventually I rented my current workshop space. Anyway, Bob made himself at home in the kitchen, my wife made us cups of tea, and I got on with the job. Bob obviously liked what he saw and heard, and kept making the trip up to the Central Coast whenever he needed something done to his amps and pedals.

Bob was living in Katoomba (NSW) at the time, in a charming house built 100 years ago or so. Once he discovered I built amps/pedals/power supplies, he started getting stuff custom-built. First up, he ordered two rack-mounting preamps – the first enabled him to switch between a Hiwatt voiced preamp and an Ampeg voiced preamp. The second one enabled him to switch between two AC30 voiced preamps. Bob was the first customer to purchase my first two successful pedal designs in 1997 – the Rich Drive and the Rich Fuzz. We kind of agreed on what we were looking for in a pedal, as well as what was missing from commercial pedals, and a lot of collaboration went into those two pedal designs, especially the Rich Fuzz. I love that kind of stuff ! Both pedals are still available today (2011), and the designs have not been altered in any way, although the cosmetics continue to change.

Bob was building a home-studio in the house at Katoomba, and ordered a low powered amp (6V6 output valves) to drive a 1×10 cab housed in an isolation box. I originally built a switchable 8W/4W push-pull amp, based on the designs I was using at that time. This was well before the current craze for low powered amps. We soon realised, however, that a mere 8 watts wasn’t driving the chosen 10-inch speaker hard enough to achieve the optimal recording results when mic’d up ! There is definitely a lesson there for everyone. The power output was increased to 12 watts, and then 15 watts, substituting different transformers. The circuitry itself stayed the same. Why is the amp called the Lil’ Buddy amp ? It’s because at that time I was calling everybody my little buddy – regardless of how tall they were. Something to do with a 70’s TV situation comedy called Gilligan’s Island. Thankfully, I have stopped doing that.

This amp was used for recording of course, but also gigs, rehearsals and teaching. I recall seeing Bob’s blues band in a pub at Crow’s Nest (Sydney) years ago, using the Lil’ Buddy driving a Wasp 250 watt/4 x KT88 amp used as a slave, into a pair of 2×12 cabs, loaded with Etone speakers (from Peakhust/Sydney, no longer manufactured). What a sound ! Some noise complaints, though. How rude ! At the beginning of this millenium, Bob & missus relocated to Melbourne and also ordered firstly an 85 watt/4 x KT66 amp which is currently Bob’s stage amp, and secondly a 28 watt KT66 amp. Both amps were custom designs employing baxandall EQ, and other features unique to Bob. The Lil’ Buddy amp fell into disuse for many years.

So where do we stand right now ? Well, Bob and Paulene are in their new residence in Melbourne, and Bob is setting up a new home studio and is preparing to do some recording, so there is a valid reason to refurbish this amp and bring it into line with the current Richards amp range. Although this is still a custom amp, it will be somewhat similar to our Blue Mood models. As you can see from the photos, new component panels have been pre-wired to install in the chassis. The amp also has received a new output transformer (a critical component in any valve amplifier), new pots/jacks/capacitors, and so on, plus a bit more attention to electrical safety issues, in line with today’s compliance environment. The power transformer on the chassis was the third such unit, this one giving us slightly over 15 watts rms.

Some of you will have noticed a Headphones switch on the rear panel – unusual in a valve amp – this switches the ouput to a resistive load and attenuator, so the amp can be operated safely but at headphone levels. The Headphone jack can still be connected to a speaker in this mode of operation. So who is the guy playing the Craig Upfold custom Tele in the first photo ? This is Jonny Gardiner, creator of the Rock God Music School here in Wyoming, and also the singer/guitarist with successful Sydney-based band The Nevilles.

Jonny was kind enough to give us his review of this amp after the update was completed. These are his impressions:-

“this amp has the warmth of a Vox but with more clarity (and also more gain), ie the individual notes really ring through ! this amp’s forte is those delicious sounds inbetween clean and dirty, ie the crunch sounds ! a satisfying aspect of the amp’s performance is that you can control your dynamics with pick attack ! (ie the amp has great touch sensitivity)”

To finish off the blog, we have a photo of Bob playing with RAW BRIT in Melbourne with his Richards 85W/4 x KT66 amp head. Some great live videos of RAW BRIT in action have been uploaded to youtube.com, so you can check out these great players doing their thing.

Posted in Amp Repair, Amps, Friends of Ivan Richards Audio, History | Leave a Comment »

Do we cater for the metal head ?

September 11, 2011

Yes ! We offer our repair services and custom-design/custom-build services to every type of musician who is reliant on musical-instrument amplification, and in particular amplification that is based on vacuum-tube (thermionic-valve) technology. As it happens, there is also a breed of amplifiers out there, marketed at the heavy-metal guitarist, that is primarily solid-state in design. We will also service many of these products. Check with us first, if in doubt.

As you can see from the photos, the inspiration for today’s blog is a recent repair to an Engl 50 watt (all-valve) head. My general impression of the Engl amps is that the standard of construction is a bit cheap and there have been some reliability issues along the way. This is all the more surprising considering they are designed and manufactured in Germany. Every Engl repair we get seems to require a mod to the power supply and/or the bias supply, in the latter case this is because usually you can’t get a wide enough range of adjustment to bias up an amp with new output valves properly (normally Engl’s are loaded with 6L6GC valves, or equivalent). I have found the JJ 6L6GC to be the ideal replacement output valve for these amps. If you have more money to spend, a great sounding alternative is the Winged-C 6L6GC (formerly SED), from St Petersburg, Russia.

The single biggest problem impacting on long-term reliability is the fact that the power output valves are printed circuit board mounted. Given that the Engl chassis is top-mounted in the cab, and the power output valves hang down from the chassis, then the heat from the valves naturally goes up into the chassis, and in particular into the printed circuit board. The output valve board can get so hot that critical components actually desolder themselves ! This was a common fault when these amps were first introduced into Australia a few years back – the screen grid resistors would desolder themselves, possibly even falling off the board, and the affected valves would stop working. The good news is we can do our best to bullet-proof your amp to improve reliability.

Some other brands of amps that we have serviced that are appropriate to this genre of music woud include (in no particular order):- MESA, Blackstar, Laney, Hughes & Kettner, Randall, Crate Blue Voodoo (serious reliability issues), Bugera (serious reliability issues), Egnater (serious reliability issues), Cornford, Marshall JCM800, JCM900, JCM2000 (some models of JCM2000 reliability issues), and also the JCM600 (serious reliability issues). There are others, this list was just off the top of my head.

No discussion of amps for the metal player would be complete without the mention of the Peavey EVH120, known variously as the 5150, 5150 II, 6505, 6505+ amps. The 5150 II model seems to have got the thumbs up from any of my customers that own this amp. In response to customer demand, from young metal bands recording their own material and wanting to achieve the best recorded performance from these amps, we have been offering a range of mods and upgrades to these models.

Any upgrade would obviously include valves (tubes). There is such an excess of gain in these amps that valve (tube) microphony becomes a major issue. Therefore we have put the replacement 12AX7 valves through our own selection test. On the short list of valves are the JJ 12AX7 and 6L6GC, also the Winged-C 6L6GC, the Tung Sol reissue 12AX7, and we are about to trial a new 12AX7 valve (tube) released by TAD, specifically intended for such demanding applications.

Other requested upgrades include power supply capacitors, bias circuit modification for greater range of bias adjustment, and the installation of a Mercury Magnetics MC10 power choke in the power supply, in lieu of the standard resistor. One last upgrade for those of you resident in the land of Australia who have purchased their amp via the internet – we can install the factory supplied 240V AC mains transformer, so you don’t have to lug around that heavy and inconvenient step-down transformer.

That’s it for tonight’s blog – please feel free to submit suggestions re other amps that you feel should have been mentioned, and/or contact us re your specific amp problemos. Perhaps we can make a big difference. By the way, for those of you who are into 70’s and 80’s metal, we do build amps to special order which are inspired by the great Marshall JMP amps of the mid 1970’s. We can nail that sound plus no more reliability issues.

Posted in Amp Repair, Amps, Discussion | Leave a Comment »

Barry takes delivery of his new 2X12 Tone Cabinet in white tolex

September 8, 2011

Barry Wellard, one of our local rock’n’rollers here on the New South Wales Central Coast, today took delivery of his 2nd 2×12 Tone Cabinet. This cab features vintage white tolex covering, nicely contrasted with a black & gold speaker grille, top strap-handle at Barry’s request (we also offer heavy-duty metal side-handles from Penn), and is presented in the TV Front style. Various other options are available.

The cab is loaded with a pair of the wonderfully musical Celestion G12 “Blue” Alnico speakers, resulting in a cab power rating of 30 watts total, and a cab impedance of 8 ohms (parallel-wired 16 ohm speakers). The rear panel heavy-duty metal jack plate features a pair of parallel-wired jacks to facilitate connecting an additional cab. These speakers will enhance the tone of just about any amp !

The dimensions of this cab were optimised to suit the chrome-plated speaker stands made for members of The Shadows club in Sydney. These stands replicate the look of the stands used by groups such as The Shadows & The Beatles with their Vox amplifiers back in the 60’s.

Barry currently owns two Richards amplifiers: a 30 watt Expressionist (4 x EL84) head with EF86 and 12AX7 channels, plus the custom addition of reverb, as well as a custom-design variation on the Blue Mood series amps loaded with a quartet of 6L6GC output valves for a very conservative 60 watts output. This latter amp was specifically design for Barry’s rhythm guitar playing style to facilitate huge chord sounds with lots of clean headroom.

Every purchase of a Tone Cabinet from the Richards Amplifier Company Australia includes a complementary speaker lead. Heavy-duty lined covers are available as an optional upgrade. Cabinets are available in 1×10, 2×10, 1×12, 2×12 and 1×15 semi-open-back format, constructed either from furniture-grade ply with a choice of tolex coverings or exotic Australian natural timbers as an optional upgrade.

Barry is a founding member of The Rebel Rousers, a 50’s/60’s rock’n’roll band, and has recently acquired celebrity status by appearing in the pages of The Australian Women’s Weekly Magazine, see page 257 of the September 2011 issue. Barry has become famous not for his guitar playing, but for his dahlias, a variety of flower as supplied to Saskia Havekes, a prominent Sydney florist.