Many Big Muff users and collectors will tell you that pretty much every Big Muff sounds different, even comparing examples from the same version and/or year of manufacture. We tend to agree with this, based on our experiences servicing these pedals. Apart from normal component variations over time, different component values were often substituted, whether this was intentional or simply a case of running out of certain components, we do not know. We have also noticed different pots fitted to otherwise identical models, which would result in a different sweep altogether !

When considering the reasons for such wide variations in tone & performance with the Big Muff & other E-H pedals, one factor cannot be overlooked. At different times over the four decades of production of E-H pedals, the quality of assembly and in fact quality control in general was pretty poor ! The pedals often looked like they were wired up by someone in a hurry, with soldering that wasn’t going to hold up on the road. This applies to both USA & Russian manufacture.

To give credit where it’s due, however, E-H have come up with some of the most extraordinary pedals over the years. Our personal favourite has to be the Electric Mistress (flanger), for those classic early 80′s guitar sounds, a la The Police, The Pretenders, etc. Once again, there are several versions of the Electric Mistress, and restoring this pedal to full operation can sometimes create challenges for the service tech, depending on the problem.

Recently, a pair of barely functional Big Muff (IC/op-amp) pedals from the late 70′s arrived in our workshop for attention. The two pedals had quite different printed circuit boards, different pots, but almost exactly the same circuit (which we reverse-engineered as the schematics available on the internet often have errors). Even if working properly, these two apparently exactly the same pedals would have sounded very different to each other. You can see from the photo above that the older pedal of the two has been the subject of numerous attempts at rewiring & modification. We ended up correcting & rewiring much of this in order to get the performance on par with the newer of the two pedals.

Amazingly, the pots in both of these pedals work OK, just requiring a squirt of Faderlube to clean & lubricate. The main issues tend to be jacks & switches. The original jacks are cheapo – the best solution is to replace them with Switchcraft jacks. The EQ bypass slide switches are particularly prone to causing loss of signal and should automatically be replaced. Luckily there is an exact size replacement out there. In one of the pedals there was a blown IC and very cheapo IC sockets which just weren’t doing the job, so they were all replaced. Tidy up the wiring & rework any dodgy soldering and we have a pair of working Muff’s, still not quite the same as each other, but much closer than before.

Please contact us by email re any service enquiries for E-H pedals in general, and the Big Muff in particular. In most cases we will be able to assist. We can also supply custom linear power supplies for pedals that require different voltages from the usual 9V DC, ie 18V & 24V DC are sometimes specified by E-H (see previous blog re Rich Split & 18V PSU for example).

For a more detailed appraisal of the issues arising from recording &/or performing with multiple amps &/or signal paths please read our previous blogs on the subject: Rich Switch A/B/Y, Bob’s Rich Split & More About Signal Splitting. These can be found in the Pedals archive.

Here is what Tye had to say:  Hi Ivan, just wanted to quickly say how much I love your pedals, I am the proud owner of the Rich Fuzz & the Class-A Distortion, and they have a permanent home on my pedalboard. Anyway, I was interested in the Rich Split for a studio project where we will be splitting to at least four guitar amplifiers simultaneously. I think the Rich Split will be perfect for the task, but I am also interested in using the pedal at live gigs. My question is would it be possible to have the pedal modified with fooswitches to engage/disengage the sends (outputs) ? Cheers !

So, we set about designing a 4-way Rich Split, with three transformer isolated splits, one direct split, plus four individual mute switches and LED status indicators. An external regulated +18V DC power supply is required, although the pedal will run off +9V DC at reduced headroom. Power consumption is quite low, even with all LEDs illuminated. The electronics, footswitches & Harbuch broadcast quality line transfromers all fit neatly inside a Hammond die-cast aluminium enclosure, which also provides superior shielding from external noise sources. The Rich Split pedal is currently available with up to five splits, although the majority of customer orders have been for the 2-way & 3-way splitters.

A high-quality regulated power supply is a critical component for an active splitter & other similar gear. Although this pedal will happily run off +9V DC, +18V DC is the recommended supply voltage to achieve reasonable headroom. Some commercial pedalboard power supplies will provide regulated +18V DC. We have experimented with some of the switch-mode power suplies (SMPSU) on the market, and have found them to be unsatisfactory for powering the Rich Split & Rich Switch  pedals, ie under some circumstances they have introduced noise into the signal chain. The best solution is still the linear (ie, analogue) power supply.

For customers like Tye, who require an external +18V DC regulated power supply, we can supply the model FX-18 Rich Power pedal at reasonable cost. We are not a commercial manufacturer of power supplies, but have always offered individually custom-built pedalboard power supplies for guitarists in a variety of configurations. These units are relatively indestructable, housed in a robust Hammond die-cast aluminium enclosure, and protected from normal guitarist type abuses & incidents.

Thanks agin to Tye, for his enthusiasm for our products and we hope to hear soon the results of his recording project. Future blogs now being prepared will include the extremely rare Marshall JMP 10 watt Lead/Tremolo combo, and other major overhauls of vintage amps.

Vadis amplifiers were manufactured in a small factory unit in Brookvale, a northern beaches suburb of Sydney, Australia. The business name of the manufacturer was Soundcraft Industries, Pty Ltd. The name of the proprietor was Jerry Dewey, although I can’t be sure of the correct spelling. Production started in the early 1960′s and continued through to the early 1970′s, but those dates are just approximate. Vadis amps were distributed exclusively through Dynamic Music, who were located in the same general area of Sydney. No doubt this arrangement would have limited the profitability of Soundcraft Industries, but it also gave them a broad penetration of the musical instrument marketplace, as it existed at that time.

Believe it or not, we actually have a family connection to the Vadis amp. My father, Jack Richards, a guitarist and arranger on the Sydney pro music scene back in the day, lived in the North Narrabeen/Elanora area of Sydney, as did Jerry Dewey. Knowing that Jerry was in the electronics industry, my father suggested to him repeatedly that it would be a shrewd move to start manufacturing guitar amplifiers, as at that point in time there were only two serious competitors, Moody in Lidcombe (Sydney), and Goldentone in Melbourne. By the time Jerry actually started production, however, there were several new competitors starting up in Sydney, Melbourne and Brisbane. Nevertheless, the enterprise was successful.

My father also claims to have suggested the name Vadis, from the name of a Sydney nightclub, Quo Vadis (also the title of a movie). We have no idea what became of Jerry Dewey after Soundcraft Industries closed its doors.

The classic Vadis 40 watt and 60 watt heads and combos typically employed a pair of 6CA7/EL34 output valves, originally with a 5AR4/GZ34 rectifier, but later replaced with solid-state rectification. A resistor (eg 1000 ohms, wire-wound) was normally used rather than a filter choke. These models had two preamp channels, one brighter than the other, and very effective all-valve reverb and tremolo. The reverb design is very similar to that of the 60′s Ampeg amps, but using a 12AU7/ECC82 driver valve. The tremolo employs direct modulation of the 2nd 12AX7/ECC83 gain stage cathode bias, in the 2nd (reverb) channel, resulting in that classic valve amp tremolo, unobtainable any other way. The 2-band passive EQ in each channel, was sometimes as per the Vox “Top Boost” channel, but driven from the anode of the preceding stage, rather than by a cathode-follower buffer stage, sometimes a very simple “tweed amp” style, but most often used a modified Baxandall EQ, optimised for guitar, and obviously a design unique to the Vadis amp. The more expensive amps used Ferguson transformers, manufactured in Chatswood (Sydney), with cheaper alternatives used in other amps.

There were numerous other lower-powered models employing different output valves, and were generally single channel. Most of the lower powered amps employed the 6GW8/ECL86 dual function triode – pentode valves, which could deliver up to approx 12 watts output in push-pull. These valves were very common in Australian-made guitar amps and record players, etc, in the 1960′s, but are long out of production.

The speakers used in the Vadis amp were primarily MSP (Manufacturers Special Products), a division of AWA in Sydney, or Rola (later Plessey Rola), also manufactured in Sydney. The Rola 12PEG (15 watts) and 12UEG (20 watts) alnico magnet guitar speakers sounded very fine indeed and are quite collectable today. Later, Plessey Rola introduced the updated ceramic magnet versions, the 12U50 and 12P30. The 12UX50 twin-cone model was widely used in PA systems at the time (late 60′s through early 70′s).

Well, by the late 60′s live performance of rock’n'roll music was changing in a big way, with ever more powerful amps appearing on the scene, and we can imagine that Soundcraft Industries, with their mid-60′s style amps, would have been under a lot of pressure from their distributors, and from retail, to reduce costs to stay competitive. By the beginning of the 70′s the Vadis amp was still a valve (tube) power amp, but with a solid-state preamp. Tone and performance suffered compared to the older models, but the writing was really on the wall when the entire range went completely solid-state. Thus, the Vadis story came to an end.

Getting back to Dave’s amp – both the transformers in this amp had previously been replaced by the writer, installing custom wound replacements from Special Transformers, of Sydney (no longer in business). This amp has had a hard working life and has been used in live performance until quite recently. The power transformer was replaced a 2nd time by a tech not known to us, this was possibly a Mojo unit, but was unfortunately underpowered for this application and developed a short circuit, blowing the fuse of course, and leading Dave to bring the amp down to our workshop. We selected a Mojo Tweed Bassman replacement unit, as having closest to the desired current & voltage ratings, ie able to support EL34 output valves plus a GZ34 rectifier, and importantly it would fit in the available space with some additional metalwork to enlarge the rectangular chassis opening.

Apart from replacing the transformer, there were numerous other issues to sort out, as you would expect in a 45 year old amp. I’m sure the designer would be amazed that these amps are still in use, and even more amazed at the alternative styles of music being performed !! In this amp the GZ34 and its octal socket required replacement, and the 240V wiring tidied up with emphasis on a good earth connection, as per compliance with Workcover NSW standards. All these amps will require replacement of 40+ year old electrolytic capacitors, we recommend a good quality cap such as Sprague Atom (USA) or F&T (W. Germany). Some caps will need to be bedded down in silicone to keep them secure. The bias supply voltage is adjusted by means of paralleling up resistors as required, so is not at all convenient. Jacks & pots will need cleaning or replacing as required. One problem will be the condition of the 9-pin preamp valve sockets. In many cases they will be so damaged and/or corroded that replacement is the only option, which is labour intensive as the Vadis amp is wired true point-to-point, with all components mounted directly between tagstrips and valve socket pins.

The tremolo function in Dave’s amp hadn’t been working for some time, but replacement of the 9-pin socket and a couple of resistors & capacitors restored it to full working order. It sounds fabulous !! In spite of the seemingly random earthing employed in the chassis wiring, the amp is amazingly quiet, and sounds pretty damn sweet. The reverb is a bit surf’s up for our tastes, but is definitely useable – just turned down a tad. We think that Mr Jerry Dewey probably knew a thing or two about electronic design, 60′s style.

Thanks again to Dave for his continued custom, and for supplying us with such rare & unusual items to discuss here in the blog.

http://soundslikesunset.com.au

Once again – if anybody can shed any light on any of the missing pieces of the Vadis jigsaw puzzle, please make contact via email and we will publish an update as appropriate.

Regards, Ivan.

Typically, harp players will plug into a Fender Pro Junior, Blues Junior or in this example a Blues Deluxe 1×12 40 watt combo amp, made in the 1990′s and finished in tweed covering. Well, it’s all about personal taste, but my ears tell me that the original Blues Deluxe and Blues DeVille amps had a sweeter tone than the current Hot Rod series of Deluxes and DeVilles. One customer of ours was playing an archtop guitar through this model, plugged into the #2 input jack for the cleanest possible sound, ie for a strict jazz stylist.

So, why would we need to modify these amps in any way ?? Basically, most guitar amps have way too much gain and way too much emphasis on the “treble” end of the spectrum, for amplifying a blues harp. The harp player will experience endless problems getting adequate level before feedback sets in, and also achieving the desired authentic blues tone. A proven approach is to substitute preamp valves (tubes) to reduce gain to manageable levels, which can also have the additional benefit of giving a smoother, more HI-FI response. Substituting the 12AU7/ECC82 valve in lieu of the 12AX7/ECC83 in positions V2 & V3 will make a huge difference. In position V1, we need to work with the individual player to select the most appropriate valve, quite possibly the 12AX7/ECC83, the 12AT7/ECC81 or the 5751 might work well here. The amp will now sound pretty bland if you plug a guitar into it !!

To correct the EQ bias towards the treble end of the frequency range, the harp player is advised to set the bass control much higher than usual for a guitar, and to cut back on the treble & middle controls. The prescence control could be left at 12 o’clock, while the other controls are being adjusted, and then set according to taste. Other amp upgrade options could include replacing the speaker with a more harmonica-friendly unit – I have never been that impressed with the stock speakers in most Fender amps anyway. I believe Weber (USA) offer some speakers with an H (ie harmonica) dust cap, but have not tried such an option personally.

A recommended modification for users of microphones that give their best response into a very high input impedance, is to increase the amp’s input impedance to say around 5 megohms. This MOD will require removal of the printed circuit board (p.c.b.) in any of the amps discussed today, and the replacement of a single resistor, so it’s not like brain surgery, but it is a skilled job strictly for those people with a temperature-controlled soldering tool plus soldering expertise, otherwise you will damage the board.

Thanks for visiting our site – this will probably be our final blog for 2011, but we will be back in 2012 with plenty more amp & pedal material currently in various stages of preparation. Have a great New Year !!

Ian Johnstone has stated on a forum that Wasp in Australia was started in 1967, and that they manufactured amps employing KT88, 6550 and EL34 power output valves.  I can remember from years back some references to people visiting the Wasp operation in Sydney’s inner-west, perhaps it was Leichhardt, perhaps it was Marrickville ? They stated seeing speaker cabs being assembled there. All the Wasp amps that I have ever seen were most likely manufactured during the 1970′s golden-era of rock, and were originally loaded with and biased for the great KT88 English-manufactured valves. This even applies to an obscure made-in-NZ Holden 75 watt amp with an excellent valve-driven tremolo (ie output valve bias modulation).

Of course, by the end of the 70′s the KT88 valve was becoming difficult to find and prohibitively expensive, so people starting substituting 6550 valves, which is OK with appropriate changes to the bias supply, and EL34/6CA7 valves, which  is really living on the edge, and in fact asking for a lot of trouble. Not everyone who serviced these amps from the 80′s onwards really knew what they were doing, and the Wasp amp became a liability in terms of on-the-road reliability, through no fault of its own. This design uses very high internal DC voltages, over 600V in fact on the KT88 anodes, and over 300V on the screen grids. This is how 100 watts output is achieved from a single pair of output valves, and 200 watts from a quad. So setting the bias at optimum for each change of valves is obviously important, and also the original value of screen grid resistors of 270 ohms is inadequate for modern valves, this should be increased to 1K (in my opinion). The Welwyn 7W W22 series ceramic body resistor is perfect for this application in such harsh conditions as exist in a high-power valve (tube) amp.

Ideally the screen grid supply should be regulated, and clamped at 300V maximum. With higher value screen grid resistors this would improve output valve longevity quite considerably. In recent times valve (tube) factories in Russia, Slovak Republic and China have been producing a KT88, so we now have more choices than ever before. Recommended brands include JJ, Sovtek/Electro-Harmonix, and Winged-C (formerly Svetlana). You can see in the photos an example 200 watt Wasp amp where I have installed a matched pair of KT88-EH with good results. 200 watts is way too much power, unless you’re the bass player, so the age-old trick is to install only a single pair of KT88 (6550) and then adjust the impedance the output valves are working into upwards by plugging your 8 ohm cab into the 4 ohm jack on the rear panel. This works a treat and delivers exactly 100 watts ! Still pretty damn loud, actually.

Unfortunately, the Holden/Wasp people saw fit to only provide a non-adjustable fixed-bias supply set to some arbitrary theoretical ideal value. Not a great idea ! Even in the golden age of valves (tubes), the parameters from valve to valve could vary quite significantly, so only a proportion of amps leaving the factory would have been correctly biased. HUH ?? In order to raise or lower the bias volts, we have to resort to this technique: add an appropriate value resistor across the series bias supply dropping resistor (470R) to increase the bias volts (decrease KT88 current draw), or add an appropriate value resistor across the 8.2K resistor that goes from the bias supply to ground, to lower the bias volts (increase KT88 current draw). The other alternative is to install a pot somewhere convenient on the chassis.

Any amp this old will need a lot of work in addition to new output valves, with particular attention paid to electrical safety issues. The 240V 3-pin plug will be pretty trashed and should definitely be replaced. The earth must be tested according to Australian Standards as specified by Workcover NSW, typically using a PAT (portable appliance tester). From the earth pin on the 3-pin plug to any exposed metalwork on the amplifier should read less than 2 ohms, otherwise we are not complying with the standard. Most of the electrolytic capacitors will be at the end of their working life and will need replacement/upgrade. This particularly includes the 4 x 100uF/350V can mounting capacitors you can see in the photos. The condition of the pots and jacks, including the wiring, in the preamp section at the front is always very poor. Asian sourced jacks were used, rather than Switchcraft. I definitely recommend replacement with Switchcraft jacks for improved connectivity. The toggle switches have often been replaced with cheapo units, and one of the neon indicators is usually smashed – this is a bit of a problem finding a suitable replacement that is an exact fit. At the very least, the jacks need to be cleaned with DeOxit, and the pots given a blast with FaderLube, which both cleans & lubricates.

All the Wasp amps that I can remember seeing had two discrete preamps, a British voiced channel and a California voiced channel, with a 12AX7 valve (tube) each. There is an active prescence control in the power amp circuit as well. The preamps are in-phase so they can be patched together for a bigger sound. All circuitry is on p.c.b.’s. The preamp board is mounted vertically on a shield between the preamp and the transformers. Not a bad idea except that the shield is not very rigid. The valves are nearly always microphonic and well past their prime. The 9-pin sockets will benefit from a clean as well. The phase-inverter and driver stage valves are on p.c.b. mounted sockets as well, but closer to the output valves. A quartet of KT88′s benefits from being driven from a lower impedance. The Wasp amp used two valves to implement the phase-inverter and cathode-follower driver stages. Some amps used a pair of 12AX7 valves for this, and the later amps used a 12AT7/ECC81 phase-inverter, followed by a 12AU7/ECC82 cathode-follower. This is good engineering practice – 12AT7′s and 12AU7′s in particular are superior to the 12AX7 as a driver. Unfortunately, the chassis is NOT labelled to indicate which valve goes where, and just about every single amp I have ever seen has these valve positions accidentally reversed ! You can see what I mean about taking your amp to a tech who has the knowledge and experience to deal with the idiosyncrasies of your particular model. This particularly applies to VOX AC30′s/AC50′s down through the years, and all the vintage Aust/NZ valve amps.

The owner of the amp you see in the photos was on a rather tight budget, so we just took care of the most important things, and left capacitors/jacks/pots for another time. The work carried out included clean chassis and valve sockets, new 240V 3-pin plug, electrical safety testing, 1 very microphonic 12AX7 valve, replace pair of screen grid resistors with 1K w.w. ceramic, install matched pair KT88 valves & rebias amp, power output test 100W, burn-in test, final play test OK. Thanks to Jacob for providing us with today’s blog. Apparently Jacob inherited this amp from his dad, who must have been using it back in the roaring 70′s !

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.

Bill provided the original inspiration and design spec for the Richards Amplifier Company Studio Expressionist model, and is the owner of a 7.5 watt head and matching 1×12 cab loaded with the Celestion Blue speaker. A ’63 Strat and an Amtech tape echo simulator and you’re ready to do the business !

Bill decided he wanted some mid-Atlantic tones to complement his decidedly Brit tones and ordered a 2×10 cab loaded with a pair of Weber alnico magnet speakers. We chose the 10A125/30W model as being most appropriate for this application, which turned out to be the perfect choice. The are so many options and alternatives these days, that choosing the ideal model for you can be a daunting task.

To match up with the rest of Bill’s rig, cosmetically speaking, the cab was built as a TV front style with “British” Emerald Green tolex covering, blackened metal corner protectors, and brown basketweave speaker grille material. We have found that this green levant style tolex to be among the hardest wearing coverings, and is excellent to work with. The 2×10 speakers are diagonally offset to facilitate installation in a cab that is actually not much bigger than our 1×12 cab. The part open back design delivers a full, balanced sound, without a boomy bass response, and with the ambience that open back cabs are known for.

All our cabs come standard with blackened metal hardware, including a recessed speaker jack dish with a pair of parallel wired jacks to facilitate various amp to speaker connections. A mono/stereo wired speaker jack dish can be supplied on request (with three jacks: left, right & mono). All our cabs come standard with a complementary jack-to-jack speaker lead.

So, in conclusion – how does the 2×10 cab with the 10A125/30W speakers sound ? It struck me that this combination achieved a great balance between low, mids and highs and delivered a big, punchy sound. Touch sensitivity was enhanced. The mids were slightly scooped, as you would expect with 10-inch speakers, but not excessively so, hence the balanced tone across the whole guitar spectrum. The bottom end was way beyond expectations. In a direct A/B comparison with a pair of Jensen P10R 10-inch alnico speakers, the Webers ate the Jensens for breakfast ! Highly recommended !

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.

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.

Located just around the corner from us, in Brooks Avenue Wyoming (NSW), in what used to be the Mad Cow Theatre (?) is the Rockgod Music School. This is the brainchild of Jonny Gardiner, originally from Sydney and now resident in Wyoming, a veteran of many years in rock bands.

The school teaches students guitar, vocals, drums, bass and keyboards and incorporates a number themed teaching rooms (eg the Hendrix Room), as well as a large sound stage area for rehearsals and performances, including in-house PA and recording equipment.

What is different about this music school compared to other alternatives ?

Jonny devoted about 3 years to putting together a curriculum of rock which creates a structured approach to enable the students to learn the sort of music they want to play, backed up by appropriate and timely coaching in technique and music theory.

The second major difference is that unlike most music schools, that have the occasional or even yearly concert, the Rockgod Music School students gig at the end of every term. Jonny reckons this is the single most important part of the curriculum – the gigs are great fun and are the best possible motivation to keep students playing and practicing for the next big gig !

Jonny is the vocalist/guitarist with one of Sydney’s most successful covers/corporate functions bands – The Nevilles, as well as maintaining a solo career. The Nevilles came to prominence when regularly appearing on Channel 9′s “The Footy Show”, and receive bookings from as far away as Hawaii, Singapore and Hong Kong.

Jonny has quite a collection of guitars, amps and FX pedals. The amps are all valve (tube) models (of course), including Marshalls, Fenders and Vox’s. We are still working on upgrading him to a Richards KT66 amp. We are pleased to say that we are the service centre for all Jonny’s valve amps, guitar electronics, pickup upgrades, etc, analogue FX, plus students amps. Robert Fyfe is providing service to the music school PA sytem and providing custom-made leads/interconnects.

Finally, and best of all from my caffeine-addicted perspective – the music school has opened the Central Coast’s best new coffee bar, the Rockgod Cafe. Located only 5 minutes from the Gosford CBD. I’ll meet you down there !!

www.rockgodmusicschool.com.au