Archive for September, 2011

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.

Posted in Amp Repair, Amps | Leave a Comment »

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.

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