Repair log – December 14th, 2006 Gibson ES335 thin-line double cutaway archtop guitar SN: xxxxxxxx made in the Nashville Plant, TN, USA
Copyright retained by Terry Relph-Knight 20/06/18
Current value range estimate – £ 1,500 to 2,000
Weight = kg. lbs.
Delivered with Gibson branded hard case
Strung with – 0.008, 0.010, 0.015, 0.024, 0.033, 0.046 ????
This guitar is an extremely well made, double cut away, thin line archtop electric. A classic Gibson dot neck, 19 frets to the body in cherry finished flame maple. In pristine condition.
Gibson ES335 thin-line double cutaway archtop
Body – Thin-line double cutaway arch-top semi-acoustic of laminated flamed maple ply with a maple centre block and two F holes. Finished in cherry nitro with cream plastic binding back and front.
Neck – A one piece mahogany neck with a medium U’ profile and cream binding. 22 medium frets on a rosewood fretboard, 12 inch fret radius. Dot mother of pearl fret markers above the 3, 5, 7, 9, 12, 15, 19 and 21st frets. Truss rod adjustable from the headstock, 5/16 brass hex nut. The neck tenon extends half way under the neck pickup. 24 3/8inch scale length.
Hardware – The 2 Gibson humbuckers are ‘57 Classic’s (I unscrewed the pickups and checked the labels on the back). They have a replica black and gold Patent Applied For sticker (which is kinda funny) and a label – ‘57 Classic 1212060303 on the neck and ‘57 Classic 1212060237 on the bridge (made on the 12th of December 2006). They have nickel plated nickel silver bases and covers. So the two pickups appear to be the same. Gibson also make the ‘57 Classic Plus which has a few more turns on the coils for a higher output and you might expect to find it in the bridge position. That doesn’t appear to be the case here. The ‘57 Classic pickups, like the Burstbucker, are intended to mimic the best of the old 1957 PAF pickups. They have the lower strength Alnico II magnets and, unlike the Burstbucker, the two coils are balanced, which offers maximum hum rejection, but a slightly warmer tone than the Burstbuckers. In this guitar the ‘57 Classics do sound great, warm and smooth with great definition.
According to Jim DiCola, master luthier at Gibson USA, the ’57 Classic is made to Seth Lover’s original specifications, to the exact letter, in particular the two coils are very closely matched, while the Burstbucker is a consistent version of how the production PAF pickups were actually made, with an imbalance between the two coils. The Burstbucker version 1,2 and 3 also has Alnico II magnets. The legendary pickup maker Tom Holmes apparently worked for Gibson on the design of the ‘57 Classic. Holmes has built guitars for Billy Gibbons and is perhaps the first person to produce an accurate reproduction of the original Gibson PAF pickups.
In the original production PAFs the coils were used as they came off the winding machine, with no attempt at matching and the magnets used might be Alnico II, IV or V, depending on what Gibson happened to have purchased for each inventory period.
The controls on this guitar are the usual Gibson two volumes, two tones and three way toggle switch. I don’t know if the volumes are 300K linear or 500K log. The controls are fitted with Gibson small black witch hat knobs and metal pointers. Floating three-ply black pick guard. Nickel plated zinc alloy Gibson ABR-1 Tune-O-Matic bridge and stop bar.
Grover three on a side sealed nickel plated tuners with metal kidney buttons.
Bridge height – guitar top to top of the thumbwheel – 8mm on the bass 8mm on the treble
Stop bar height – guitar top to underside of the bar – 6.5mm on the bass 3mm on the treble
I’m not sure why anyone would choose to tilt the stop bar like that. The two threaded bridge supports are screwed quite far into the body. Their tops are around 3mm below the top of the holes in the bridge.
The threaded bridge support posts are UNC 6-32 thread by 1 inch (25.4mm) long. Around 7/16 (12mm) of an inch is driven in to the top of the guitar. This leaves very little of the post within the post holes in the bridge.
Delivered strung with – Ernie Ball Nickel wound Super Slinky’s 0.009, 0.011, 0.016, 0.024, 0.032, 0.042.
Problems – In for a general check and setup. Needs a good clean and polish. Exhibits the usual tuning instability of nut stick for a Gibson instrument with 3 on a side tuners. Customer also wanted to try a vibrato on the guitar. Originally a Bigsby, but by the time the necessary modifications were added to avoid drilling holes in the guitar and to stabilise the Bigsby tuning problems, this would have been a very expensive option. I suggested a Duesenberg Les Trem II vibrato.
Work done –
Guitar cleaned and polished. Frets level checked with a fret rocker. Frets and neck cleaned and polished. Polished the corian nut with metal polish on a toothbrush, including flossing the the string slots with string offcuts, to reduce friction through the strings slots as much as possible. Also sprayed on a coat of beeswax and buffed the nut to a high gloss. Tuning still wasn’t stable so I also fitted a String Butler (later upgraded to a String Butler Tremolo model).
Fitted the Duesenberg Les Trem II vibrato in place of the stop bar.
The Gibson 6-32 bridge posts are an acceptable fit in the Goldo bridge post holes so I stayed with them rather than removing them and drilling to fit the Goldo inserts and posts. I stabilised the Gibson posts by fitting 6 washers underneath the thumb wheels, drilled and tapped the Goldo for M3 locking screws and then locked the bridge in place. I had to fit the Goldo bridge with the locking screws and intonation screws facing towards the bridge pickup otherwise access to the screws is blocked by the Duesenberg vibrato. The bridge pickup height can be dropped down to improve access to the intonation screws while intonation is set.
Re-strung and set up the action and intonation. I tried winding the strings with one turn below the string through the post hole then two turns above the hole. I wanted to lock the strings and minimise the break angle over the nut to help tuning stability by reducing friction over the nut. In practice this didn’t work very well because the coils of the string didn’t settle smoothly around the post. The easiest way by far to get a tidy string wind around the post is to allow the right amount of slack for two or three winds around the post and then to feed the string on from the bottom.
This guitar suffers from the same problem that all recent Gibson’s with a corian nut suffer from – the strings do not slide smoothly through the nut. As a result any string bends result in the string going slack when the bend is released and the tuning goes flat by around 10 cents on every string.
Adding a vibrato system of course just makes things a lot worse! One difficulty is that with the vibrato the string tension of all six strings interacts because they are coupled together by the vibrato balancing spring. If even one string jams in the nut then this change in net tension affects the tuning of all six strings. When using a fixed stop bar, rather than the vibrato, any nut jamming problems with each string are confined just to that string.
Rather than replace the unpolished Plek cut Gibson corian nut straight away I wanted to try to get the existing nut to work. Extreme care is needed when making any adjustments to a Gibson nut because Gibson choose to set the Plek to cut the slots as low as they will go before buzzing on the first fret. Added to that the nut is shaped to a sharp edge to minimise the amount of cutting the Plek machine has to do. Unlike many other guitars, there just isn’t much leeway in the Gibson nut slots.
First I tried polishing the nut with metal polish on a toothbrush. Although this did a fine job of polishing the surface of the nut, it seems it did not get right down into the string slots. Next I tried flossing the slots with offcuts of guitar string coated in a few dabs of metal polish. To my vast surprise this actually seems to have worked!
Intonation as received
This test consists of first accurately tuning each string to pitch, depressing each string behind the nut until it touches the headstock, then releasing it. The pitch is then measured (and recorded). If the string is sticking in the nut the string will go sharp.
If any problems are found the nut slots are filed and lubricated and the test is repeated.
The second set of numbers are from tuning up to pitch then applying a whole step bend to each string.
Behind nut bendWhole step bend Bend – After all modifications
E +10 -10 0
A +11 -10 0
D +22 -3 0
G 0 -10 0
B +15 0 0
E +10 -3 0
Note – There is still some tuning instability for extreme use of the vibrato.
The Duesenburg Les Trem II
The Duesenburg Les Trem II won’t fit this guitar without modification because the inserts for the stop bar fixing studs are on 82.5mm centres. The DLTII requires the fixing centres of the stop bar mounting studs to be 81.5mm apart.
The nickel plated stop bar from this guitar looks like a standard Gibson part, but has no identifying marks. The distance between the inside faces of the two stud hooks is 73.6mm and the hooks are 7.9mm wide. So the fixing centres should be 81.5mm. Unlike the Les Trem II there is enough clearance left in the Gibson stop bar for it still to fit with the studs at 82.5mm.
Drawings of the Wilkinson stop bar show the centres as 82mm, Allparts shows it as 82mm and AxesRus Gotoh as 82mm, AxesRus aluminium as 82.5mm and AxesRus zinc as 82.5mm.
So the only way to fit the DLTII is to file or drill out the holes in its base plate to gain the clearance for the two bolts. Seems dumb that Duesenberg didn’t elongate the holes to allow for variations in the insert spacing.
I had thought perhaps that the guitar wouldn’t fit in the hard case with the DLTII installed, but I have done a test fit with it attached by only one of the stop bar bolts and there seems to be plenty of clearance.
Eventually I filed the outsides of both fixing holes just a little and managed to get the DLTII to fit the stop bar insert spacing on this guitar. I fitted just one washer under each end which was enough to clear the top curve of the guitar. The entire assembly with the arm fitted seems to go inside the case just fine, even without any string tension pulling it down.
Another possible drawback of the Les Trem II is that the spring and bar pivot are quite close to the bridge and some players may find that this protrusion gets in the way, depending on playing style.
The Goldo roller bridge
The Goldo bridge has 4mm holes at either end (the holes in the ABR-1 are close to that) and is supplied with solid posts with integral thumb wheel that screw in to press fit inserts. The guitar has an ABR-1 bridge with two threaded posts screwed in to the top of the guitar. So the option is either remove the two posts and re-drill the top of the guitar for the Goldo inserts, or keep the threaded posts and fit the Goldo to those.
With lock screws fitted to either end of the Goldo bridge, once those are tightened, the bridge will no longer be adjustable for height through turning the thumb wheels. I decided to stabilise the bridge and stop the thumb wheels coming loose and rattling, by fitting a stack of washers under each thumb wheel. The Gibson ABR-1 measures 12.1mm and the Goldo roller 13.3mm from the curved base to the top of the centre two saddles. So the Goldo is 1.2mm higher than the Gibson. To fit the Goldo subtract that 1.2mm from the previously measured 8mm thumb wheel heights and set them at 6.8mm to arrive at around the same action. Which is 6 x 0.63 mm thick washers = 3.15 under the 2.72mm thumb wheel.
Re-stringing – Three wraps of the strings around the Grover tuner posts requires 52mm of string. This is more than enough for the wound E, A and D strings. The lighter strings can be allowed a few more wraps. Unstable loops of string around the tuner post will contribute to tuning instability.
I experimented with different methods of stringing such as winding the string upwards above the string through the tuner post (to reduce the angle over the nut) and one turn under the string through the rest above to help lock the string in the post. Eventually decided that winding the string onto the post neatly for two or three turns below the hole is the easiest, most efficient and most stable way to do it.
Note also that the brass ball on bridge end of the strings is attached with a simple twist. This can and does, act like slip knot and settling in this twist is one of the main causes of tuning drift when new strings are fitted. At worst slipping in the ball end twist can be a long term cause of tuning problems. The more expensive strings tend to have more reliable twists. D’Addarrio NYXL for example have solder bonded twists for the plain strings.
With this guitar it is very important to guide the strings in to the centre of the bridge rollers and rollers on the String Butler.
The String Butler
The String Butler is device that is intended to stabilise tuning for guitars which have 3 on a side tuner headstock’s, such as Gibson, by deflecting the strings into a straight path over the nut. It is attached using the barrel nuts on two tuners. It consists of a metal plate with an attachment forks on either side that clamp under the two tuner nuts. The plate carries four rollers on short vertical posts. The A, D, G and B stings are passed around the rollers, pulling them into a straight path across the nut. This helps to reduce friction in the nut slots, particularly on the D and the G strings which normally angle both downward and to either side and almost always exhibit tuning problems due to nut stick.
On the standard version of the String Butler the rollers have perhaps 2mm of vertical movement. This in itself can be a source of tuning problems. The ‘tremolo’ version has small rubber O rings fitted above the rollers to reduce vertical movement. Sven Dietrich at Sting Butler sent me a String Butler Tremolo version, which I ordered to replace the butler I borrowed from my Les Paul and a packet of eight 4.5mm outside diameter, 2.5mm inside diameter O rings. The String Butler Tremolo version ships with a single O ring fitted above each string roller, limiting the slack vertical space on the roller posts.
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Alternate tuning DADGAD
As a teenager I was so cool that most of the music I listened to was recommended to me by my dad. This was often in the shape of classic British and American singer songwriters such as James Taylor and Steve Earle, and while I have since diversified somewhat, the influence that this sound had on my development and style have been really important to me as a musician. I found there to be something soulful and joyful about this acoustic sound that seemed to have depth in antiquity as well as feeling effortlessly contemporary, even decades after release. I would spend a lot of time carefully listening through particular tracks so I could then attempt to work out the pieces on my guitar, trying wherever I could to replicate certain stylistic riffs and movements. Whilst I usually had little trouble working out faithfully accurate recreations, there were a few guitarists that would more often than not leave me stumped, and totally unable to recapture the mood and tone of their songs. This was made all the more annoying by the fact that I almost invariably had this issue with the guitarists whose style I most admired. They were, at the time, Stephen Stills, John Martyn and Richard Thompson. What I heard when listening to them was to me rich and engaging, and despite being able to find the correct structure and chord sequences, I just could not make my guitar sing in the same way.
Around this time, and during a family get together at the home of an uncle of mine who is an excellent guitarist himself, I did the done thing for a teenager and eventually sloped off for a bit of space away from the people I love. It was then that I found a guitar magazine and came across an article about the alternate tuning DADGAD. I followed the instructions, tuning both the low and high E strings down by a whole tone to D, along with the B string also down a tone to A, then picked through a couple of the riffs that were tabbed out in the piece. Suddenly something clicked, and I found there to be something familiar to me about this sound. Over the next few weeks I spent my practice time discovering more about this tuning, using my ear to find chords and patterns within these new parameters. I found it very exciting to be exploring this new way of playing, as there now seemed to be a new and greater depth and tone to almost everything that I tried. I then had the idea of going back to many of the songs that I had before struggled to learn, as now I was able to try them from a new angle, and with much more success. Suddenly I could emulate the dry twang of a Stills song, or the rhythmic strut and swing of John Martyn’s playing, all while keeping the sound rich and full.
It is almost limitless what you can already achieve on a guitar in standard tuning, but when you discover the use of alternate tunings it is almost like being introduced to several new instruments. The quality and timbre of each string can be manipulated in many ways, to help you to discover a plethora of new voices within your guitar. When I first started experimenting with DADGAD, I initially placed my first finger on the second fret of the 3rd string, and strummed all 6 of the strings, giving me a D5 chord. All I had with this chord was a D in three different octaves, and an A in two octaves, but what enticed me about this sound was a deep hum and buzz in the strings; there was something much more alive about this simple D5 chord. From there I began to explore songs in the key of D, and found that the richness and simplicity of the chord shapes gave me much more freedom to play around with the rest of the fretboard, generally finding more ‘diddly’ bits on the higher strings, while still allowing low tones to ring out and mingle underneath.
Music is so often about exploration and discovery, and I find that many guitarists can lose much of their interest once they feel that they are repeatedly playing the same pieces and running down the same dead ends. While it is very important to be meticulous in practice, and to perfect anything that you begin to work on, musical motivation can often falter with the loss of discovery and excitement. This is where alternate tunings can become invaluable. Changing the voicing and tones available to you is a great chance to start again, and to experiment purely through what you hear as opposed to what you know. Whenever I am faced with a tuning that is entirely new to me, I frequently begin by trying to forget what I know about scales, progressions and intervals, and simply begin by picking out various strings and placing my hands along the fretboard, attempting to follow feelings and voices, and seeing where it leads me. This can be a massively liberating way of learning, as pleasing moods and patterns will begin to emerge through your own, totally independent discovery, and the sound that you create will feel unique and personal.
So next time you find yourself falling out of love with your guitar, look up some new tunings, and find one that sits well in your ear. Take your time then to discover it, and you may find yourself to be captivated by a whole new set of voices, and then to be compelled to spend more time with your guitar, not working through a tab or following a YouTube tutorial, but instead just getting to know it all over again. The use of alternate tunings has since become integral to the development of my style and ability, and I often find myself returning to where it all began with the DADGAD tuning. Even now after all this time, it still has so much for me to discover.
Repair Log: 1998 Martin D28 rosewood back and sides, figured spruce top dreadnought SN: xxxxxx
23/06/18 Copyright retained Terry Relph-Knight
New D28s list at $3,299
Current value – £1,089 to £1,479
Supplied with a Martin ABS hard case.
Serial number is on the inside face of the heel block.
A classic Martin D28 14 frets to the body, with one piece mahogany fake bridal joint dart neck, with rosewood headstock veneer, rosewood fret board (20 narrow frets, mother of pearl dots) and bridge, bone nut and saddle and Indian rosewood back and sides. The guitar has had a headstock repair at some point. A small crack is visible just below the volute and the area has been over sprayed in a dark brown. Top is of highly figured spruce with a black scratch plate. I contacted Martin and they confirmed the date of the guitar, but said they had no special notes on its construction and that the highly figured top must just be luck of the draw. 6 ply binding/purfling back and front of the body. The two piece rosewood back has a dash pattern centre stripe. The Martin name and est. in 1833 is stamped on the top of the headstock in gold ink.
The 6 white bridge pins look fancy with a central abalone dot, but they are in fact soft plastic.
Bone nut and saddle. The saddle may have been replaced since it does stand quite high and contributes to the high action. Removing the saddle from the bridge reveals a pencil line 2mm above the bottom, so it looks as though it was marked to be cut down, but the cut was never made.
The guitar has a high action due to a combination of a belly bulge and the high saddle. If, as suspected, the high saddle is a replacement that was never cut down then this itself will put extra tension on the top and be contributing to the degree of belly bulge.
The bridge has been drilled at either end for an under saddle pickup and the body is fitted with a wooden end pin with circumferential scratches in the finish, well below the waist of the pin. This may indicate that the guitar was at one time fitted with an under saddle pickup and an end pin jack which have now been removed. This would explain why the saddle had perhaps been replaced and never properly fitted.
Martin D28 rosewood back and sides Repair Log
A tap test on the body shows it is very lively and resonant. As you might expect the back has higher, harder pitch than the boomier front.
Stamped onto the liner strip that spans the join between the two halves of the back is the instruction – USE MEDIUM GAUGE STRINGS OR LIGHTER ONLY
Small sealed chrome plated tuners branded Martin, probably made by Ping.
The truss rod adjusts inside the body at the end of the fret board, accessed via a cut out in the top brace just inside the soundhole. A large L Martin 3/16 inch hex key is usually required (supplied in the case). Owner says this is jammed – he is right, it won’t move.
Problems – High action. Needs a good clean. Is missing the heel cap. The guitar has a fair bit of belly lift. We agreed the first thing to try would be to lower the saddle by 2mm (fit a new saddle and keep the old one just in case). Owner likes ease of play and a bright punchy sound so agreed to fit a set of Elixir 11 to 52 bronze. These are light gauge for acoustic so they will put less stress on the top and feel easier and slicker to play. The brass wound strings gives them a brighter sound.
Work done – Replaced the original bone saddle with a Graph Tech saddle shaved to produce the 2mm height reduction and lower action. Fitted a set of brass bridge pins replacing the old plastic pins. Brass pins are harder wearing and add a little mass, improving sustain. Soft plastic pins damp some of the string vibration. Cut and glued on a new rosewood heel cap. Cleaned and polished the body and neck. Checked the fretboard for high frets, buffed the frets and cleaned and oiled the fretboard. Loosened the jammed truss rod, lubricated the truss rod nut and re-adjusted for a little forward bow. Fitted a set of 10 to 47 Elixir (bronze) brass winding on the wound strings.
Straightened the bend out of the case lid, cleaned the outside of the case and vacuumed dust and grit out of the inside.
This guitar does seem to have a particularly flexible top and it may at some point have been fitted with heavy strings, which Martin warns against with the internal stamp – USE MEDIUM GAUGE STRINGS OR LIGHTER ONLY. This may account for the belly bulge (see below).
Rosewood back and sides 1998 Martin D28
Evidence suggests that at some point it may have been fitted with an under-saddle pickup, with the original saddle shortened. If so the pickup has been removed and the saddle has probably been replaced with a new saddle that was never trimmed to height for the correct action.
The guitar has a fairly pronounced belly bulge and the bridge noticeably tilts forwards. With the strings off and therefore tension off the guitar most the bulge relaxes and the bridge and top flattens out. None of the bracing seems loose. A JLD Bridge Doctor could be fitted to completely remove the bulge.
Even without the belly bulge the action seems a little high. With only the low E string replaced and measured ‘open string’ there is 7/64s of an inch between the top of the twelfth fret and the bottom of the string.
Apparently the Martin guitar factory considers the action to be within specification if the distance from the 12th fret to the bottom of the low E string is between 2.38 mm (3/32″) minimum, to 2.78 mm (7/64″) maximum. So without the belly bulge this guitar would meet that spec.
The high ‘e’ treble string should measure between 1.59 mm (1/16″) and 1.98 mm (5/64″) at the maximum.
Fitted with the 10 to 47 Elixir and with the new saddle lowered, the guitar meets the Martin specification, Low E is at 7/64 and the high E is at 1/16.
The truss rod was adjusted so the neck was dead flat, there may even have been a little back bow. The owner says he has tried adjusting the truss rod, but it seems jammed and won’t move. Eventually managed to unscrew it (anti-clockwise). It had been turned clockwise as tight as it could go, probably in an effort to reduce the high action. Seems to be a single action rod and the adjustment nut feels like it will come off altogether. It does – hex tube or rod nut 9mm diam by 30mm long. I lubricated it with a little grease in the threads and replaced it. Tightened it by 2/3rds of a turn from slack.
Martin Acoustic strings run from 10 to 47 extra light, through 11 to 52 custom light and 12 to 54 light, up to 13 to 56 medium. String makers seem to have stopped using the description ‘heavy’ for strings, so ‘medium’ is now the old ‘heavy’.
As delivered the guitar was fitted with a set of
0.011, 0.016, 0.025, 0.032, 0.042, 0.054
Re-strung with Elixir 80/20 Bronze Nanoweb
0.010, 0.014, 0.023, 0.030, 0.039, 0.047
It will have less bulge and be easier to play with the set of 10 to 47 as detailed above.
Repair Log: 1981 MusicMan 75 Head 2100 – 75 EX SN: xxxxxxx
23/06/18 Copyright retained Terry Relph-Knight
RRP in 1980 $445 Value today – £ 200
Supplied with a 1M Fender speaker jack cable.
This MusicMan head is a hybrid transistor / valve design, rated at 75 Watts r.m.s. !! from a pair of 6L6GC output valves (it currently has a pair of JJ’s).
The B+ voltage must be very high (yup it’s 700Volts, the JJ 6L6GC is rated at 500Volts maximum).
This would seem to be pushing what can be achieved from a push-pull pair of 6L6GC, which are rated at 30Watts maximum anode dissipation each, to almost insane levels. It is set for 220Volt mains, which probably means it is over-volting even further. Power rectification is of course solid state.
Like apparently all Music Man amplifiers this amp can be switched to low power or (75 Watts) high power on the three way Standby switch, which is standby in the middle, up for Hi power and down for Lo power. This is done by switching between two voltages for B+. Hi power is 700volts and Lo is 350volts. Actual measurements into an 8 ohm resistive load show 63Watts and 30.25Watts, so no you can’t squeeze 75Watts out of a pair of 6L6GCs and Lo power is half the high power output
The pre-amp is entirely solid state. It has two channels – Normal and Bass. Each channel has two inputs – 1 and 2 with 2 being -6dB quieter than 1. Both channels have a Bright/Normal rocker switch and Volume, Treble, Middle and Bass controls. The Bass channel has in addition a Master volume and a Deep/Normal rocker switch.
1981 MusicMan 75 Head 2100 – 75 EX Repair Log
According to the dscription on the Reverb site this design is intended to provide good clean tones with a little added warmth from the push-pull valve output stage. However the circuit shows it has a master volume mixing stage that has back to back transistor / diode pairs in the feedback loop of an op-amp, which looks very much like a distortion circuit to me. This model was manufactured from 1980 to 1984. It uses a mix of op-amps (LF353 or TL072 in the pre-amp) and transistors right up to the the output valves. The push-pull output circuit has a pair of identical JE1692 transistors driving signal into the cathodes of the output valves, preceded by two op amps (dual op-amp LM1458) one of which provides signal to drive one transistor, and the other a phase inverted version to drive the other transistor. There is an internal adjustable bias control which sets the output valve idle current via the two cathode drive transistors. All four op-amps are fitted in sockets.
The inputs to this amp are quite low impedance, around 300K, rather than the ‘standard’ for guitar amplifiers of 1Megohm. Each channel uses one half of a dual op-amp as a pre-amp before a ‘classic’ passive tone stack. The second half of the op-amp buffers the tone stack. A dual gang channel volume has one half in the feedback loop of the input amp, controlling it’s gain and the second half as a passive volume on the output of the tone stack buffer with the buffer driving the wiper of the passive volume.
The outputs from the tops of the two passive channel volumes drive the input of a single op-amp stage that appears to be configured as some kind of distortion stage with transistor / diode pairs in its feedback loop. The output from this drives the top of a master volume and the wiper drives the input of a two op-amp phase splitter for the power amp. The two outputs from the splitter drive common emitter NPN transistor stages, each of which drives the cathode of an output valve. The suppressor grids of the pair of 6L6 pentodes are both connected to the 350 volt rail via 470 ohm resistors and the control grids are both connected to a +22 volt rail via 220 ohm resistors. The anodes drive either side of the centre tapped primary of the output transformer.
Problems – The output valves have been replaced with new JJs without re-biasing. The Bass channel hardly passes any signal (it’s possible that corrosion on the op-amp pins and socket has caused loss of contact). Amp is quite dirty and has some rusty bits. Looks like it was left standing in a shallow pool of water for a while.
Output stage biasing checked and re-set. Replaced the dead TL072 dual op-amp in the Bass channel. Cleaned the cabinet, knobs and the amplifier front panel. Much of the original knob numbering had worn away so I rubbed white wax into the knob engraving to improve the visibility of the numbers. Tightened several loose nuts on the controls. Measured the output into a resistive load while observing the output on an oscilloscope for power measurement, purity and clipping point.
The cabinet of this amp is quite dirty and various metal parts are quite rusty, with some rust on the transformer laminations! It looks as though the amp may have been left sitting in a shallow puddle for a while. The chassis is a welded steel tray with an angled front for the controls, suspended upside down in the cabinet from four long bolts in the four corners in the fashion of all the old Fender amplifiers. Getting the fourth nut, which is tucked behind the power transformer, into place on the thread of the bolt is an absolute PIA!!
Hand written on the pre-amp PCB is – BC 1/12/81. Assuming the American convention of month/day/year this probably means the amplifier was assembled or final tested on the 12th of January 1981. The chassis has a paper self adhesive label 81-4.
Since the dead ‘Bass’ channel has a dual TL072 op-amp as the main active component and the op-amps are socketed, the easiest thing to do, rather than poke around measuring things, was to try replacing the op-amp. Seems to have worked.
An online source says this about bias
Section I DRIVER TRANSISTOR BIAS CALIBRATION PROCEDURE
A. This applies to all models containing the following circuit boards:
DB-2, DB-3, DB-4, GP-1, GP-2, GP-3, GP-3A,GD-1,GD-2 AND GD-2A.
B. Adjustment is as follows:
1. Turn the amplifier to “ON” with the HI / LO Standby switch in the HI
position. No Signal.
2. Using a voltmeter measure the voltage from emitter to ground on each of
of the two driver transistors. Across the 3.9 OHM emitter resistors is a
convenient measuring point.
3. Adjust the bias trimpot (TR-1) until you read 25mv DC across the 3.9
OHM emitter resistors. If there is a difference in voltage between the
emitters of the two driver transistors, set the lower of the two to 25mv.
The higher of the two should not exceed 55mv DC.
Voltage across the 390 ohm nearest the back panel is 16.4mV and 14.4mV across the in-board (which at some point had burnt out and has been replaced by two 680 ohm).
Reset to 25.7mV and 24.3mV. Remeasured 28.9mV and 28.1mV.
Voltage on either side of the Standby / output power switch is 242.5V and 362.2, basically the voltage is the same on either side and it changes as the switch is flipped ???? Hmm, seems there is some odd voltage doubling circuitry. The actual B+ to the red wire on the output transformer does what it is supposed to. Pin 3 (anode) on the output valves flips between 483volts and 722volts as the switch is thrown.
The amplifier is set for 220V mains so yes the B+ will be even higher than the specified 700V.
Output transformer primary has a red wire to B+ a blue to the anode of V2 and a brown to the anode of V1 (V1 is the valve nearest the end of the chassis, anodes of 6L6GC are pin 3).
Red to Blue = 212.4 ohms, 1.207 on Hi Red to brown = 191.0 ohms, 0.99volts on Hi
Red to ground = 726volts Hi, 485 Lo
Anode current V1 = 1.207/212.4 = 0.005682674 amps = 4.1Watts dissipation !? doesn’t seem right
Anode current V2 = 0.99/191 = 0.005183246 amps = 3.758 Watts dissipation
Output power tests
Standby switch up Hi power measured output into 8 ohms = 63 volts p-p = 63 Watts r.m.s.
Standby switch down Lo power measured output into 8 ohms = 44 volts p-p = 30.25 Watts r.m.s.
Guitar Lessons in Whetstone
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Mastering the Pentatonic
Article 4 – Mark Knopfler; “Sultans of Swing”, adding the 2nd, and flirting with Harmonic Minor.
The Pentatonic Scale is the holy grail for guitarists. It’s easy to play and it sounds amazing.
This series will show you how to get the most out of our favourite scale, and how making small modifications will get you sounding like the pros and their signature sound.
With any scale, it is important to learn the shape starting on the E string (like in previous articles) but also starting on the A string. This article will be using the D minor pentatonic at fret 5 on the A string (see right).
You will notice an extra note added in blue, this is the 2nd, a note Knopfler often uses in a trill with the minor 3rd (see in the licks below).
Achieving the signature Knopfler sound isn’t just about note section but also articulation and phrasing. You will very rarely (if ever) see Knopfler using a pick. He employs a “claw” technique between his thumb, first and second finger. This means he plays lines that you might not think up with a pick. This also leads to the heavy use of double stops; playing two notes at the same time, and rakes.
“Sultans of Swing” licks: 1. Intro
This opening lick perfectly shows the 3 main ingredients to Knopfler’s playing; the pentatonic scale, finger- style, and the use of the 2nd.
Bar 1 & 2 is made up of a classic pentatonic lick with lots of vibrato. Bar 3 has a “rake” in it from the G string to the E string, quintessentially Knopfler – assign a finger to each string and make it snappy! It’s also worth noting that these notes make up a D minor arpeggio and highlight the chord underneath perfectly, another Knopfler move. Finally we have a hammer-on-pull-off between the 2nd and m3 on the B string.
2. Verse double stops
Here we see how Knopfler uses double stops. They reinforce the harmony but also act as a rhythmic device. The syncopated pattern help push these couples bars along. Play these using your 1st and 2nd finger, with the final triad being played with thumb, 1st and 2nd finger.
Below is a lick that is made up of all the ideas we have discussed so far.
3. Verse Harmonic Minor use.
Although very much in D minor, “Sultans of Swing” throws in an A dominant 7 chord every now and again, a chord “outside” the key. If you were to play a D minor pentatonic over the A7, the C (m7) of the D minor pentatonic would clash with the C# (3rd) of the A7 chord. To get around this, Knopfler dips into a D Harmonic Minor scale, which is a D minor scale with a major 7th:
Repair Log: 1988 Black Gibson 335 semi-hollow electric guitar SN
Repair Log: 1988 Black Gibson 335 semi-hollow electric guitar SN: xxxxxxxx
23/06/18 Copyright retained Terry Relph-Knight
Supplied in a tan Gibson hard case.
Made in the Gibson Nashville Tennessee plant, completed on February 24th of 1988, this is a classic Gibson 335 thin line semi-hollow electric guitar in gloss black nitro-cellulose lacquer with nickel plated hardware. From the condition of the nickel plating and scuffing on the finish, the guitar shows signs of a fair amount of use, but considering its age it is in good condition and has been well cared for.
From 1969 to 1986 Gibson was owned by the Norlin Corporation, so this is a post Norlin guitar from the early period of Juszkiewicz management. From 1986 Gibson has been a privately held company, owned by its chief executive officer Henry Juszkiewicz and its president David H. Berryman. In May 2018 the company filed for Chapter 11 bankruptcy protection.
Body of pressed maple/poplar/maple plywood with a maple centre block and a one piece mahogany neck with a 22 fret rosewood fretboard. Pearl dot fret markers. Fretboard shows some fingernail gouges in the first position and the medium frets appear to have recently been fret dressed, as there is little fret wear, the tops of the frets are quite flat and the fretboard is very clean for a guitar of this age.
Black Gibson 335
Hardware – Two humbucking pickups (should be old Classic ‘57s) with nickel plated shells. Now checked – externally these pickups look very similar, even the pole spacing is the same at 49.2mm. The pickups have nickel silver shells and base plates – stamped PAT. 2,737,842, no other markings. The serial is a known Gibson quirk. It isn’t the patent number for humbuckers, but actually the patent number for the old combined bridge and tailpiece found on the very earliest Les Paul goldtops. Since the pole spacing is the same, one has a coil tap and the embossed Pat. No. only marking was not introduced until 1990 (maybe), these may not be the original pickups. Perhaps a pair of 490Rs, with one modified with a coil tap.
Open bottom nickel plated cast zinc alloy Nashville bridge with metal saddles. The bridge has sagged in the middle by 0.8mm due to string pressure. Probably a zinc alloy stop bar. Grover 3-on-a-side nickel plated tuners.
The Volume control for the bridge pickup has been modified with a built-in pull-push switch, to switch a coil tap on the bridge pickup. This pot has an Asian 16 spline shaft. The other three pots are American and have 24 spline shafts. All four knobs are the original American 24 spline.
Gibson 335 semi-hollow electric guitar
As delivered, fitted with flat wound strings, gauges – 0.009, 0.014, 0.017, 0.023, 0.034, 0.046
Problems – Needs cleaning and a general check over. The pick guard threaded support rod is missing the outer nut and the plastic block the rod runs through, is no longer glued to the back of the pick guard. The retaining nut on the output jack is loose. Pickup selector switch nut is loose. Pot nuts are loose. Truss rod cover is broken at the nut end (52mm fixing centres). Two of the black UFO knobs are cracked and one does not fit the pull/push bridge Volume pot. Bridge is corroded and has some sag.
Work done – Guitar cleaned and polished. Polished all the metalwork. Repaired and reattached the pick guard and its mounting bracket. Tightened the loose output jack and pickup selector switch and painted clear nail varnish onto the fixing nuts and threads to lock them. Tightened various loose nuts and screws on the tuners. Fitted a Faber locking kit with spacers to the stop bar and fitted a Tone Pros locking bridge. Dug lumps of nitro- cellulose lacquer out of the truss rod route so there is clear access to the truss rod nut. Removed the truss rod nut, cleaned off blobs of nitro-cellulose lacquer and filed off burrs from previous attempts to adjust it. Put some lubricating grease on the threads and replaced the nut on the truss rod. Replaced the broken truss rod cover, the cracked control knobs and the broken pickup rings. Cleaned, waxed and buffed the fretboard and frets. Fitted a new set of 10 to 47 round wound strings, adjusted the set up and intonation.
The floating pick guard support is missing the acorn nut and the threaded plastic block the support rod threads into has come unglued from the pick guard. The outer diameter of the threaded portion of the pick guard support rod is 0.12 inches. This is equivalent to a number 5 thread. If it is a UNC thread then there will be 40 threads per inch as against 44 tpi for UNF. Most likely it is a 5-40 thread. So I need a 5-40 Acorn or blind nut. Replacement UNC 5-40 acorn nuts or even 5-40 nuts are almost impossible to source. Eventually I took a 4 B.A. nut, which was a loose screw fit on the rod, and soldered it onto the end of the rod.
As it turns out this pick guard would never have fitted properly with this old style threaded rod support. When the vertical post is screwed to the outer rim of the guitar the pick guard rides up on the inner nut of the threaded rod. As a result the pick guard has to bend for the threaded plastic block that is glued to the back of the pick guard to thread on to the rod. This puts unnecessary pressure on the glue joint between the plastic block and the pick guard and eventually the joint fails.
There are two solutions – re-shape the outer edge of the pick guard so it clears the nut, or cut a notch in the edge of the guard to clear the nut. Re-shaping by hand would be a lot of work so I opted to notch the guard. Refitted the guard and re-glued the guard to the plastic block with super glue. This may not hold on the back of the vinyl guard, but it seems fairly solid so far.
Intonation as delivered with the flatwounds
Set up as delivered – The stop bar is screwed all the way down and the two E strings are touching the back of the bridge.
The bridge from the top of the guitar to the top of the thumb wheel is at 7.5 mm on the bass side and at 5.75mm on the treble.
Open string height at the twelfth fret – top of fret to bottom of string – is 2mm on the bass, 1.6mm treble. Relief with low E fretted at 1 and 12 is around 0.5mm.
All the electronics seem to be functioning correctly. Unscrewed the two pickups for cleaning and to check the back. The bridge pickup has been rewired for the coil tap with a grey cable. Neck pickup ring is broken – top high E corner.
From the front with the strings on all six tuners seemed secure and the front collar nuts seemed tight, however with the strings off and holding each of the tuner buttons I could waggle the tuners on the low E and the D, G and B strings. Either the tuners move back and forth on their rear screws or the button tension screws are loose and therefore the gear trains are loose, or both. The D and G had particularly loose gears. Any movement in the tuners will affect the tuning stability of the guitar.
Removed the truss rod nut to lubricate it. Looks like an attempt has been made to adjust it with the wrong tool. There is some damage on the flats of the hex nut.
Why middle C?
By Terry Relph-Knight, copyright retained 03/06/18
Most people will have heard of middle C, but apart from knowing it is a musical note somewhere around the middle of the piano keyboard, won’t know it’s significance. Why C? Why middle?
Guido the Monk
The existence of western musical notation and consequently middle C, is due to the Catholic Church seeking uniformity in church worship. The church leaders were concerned about heresy, they wanted to be sure that wherever Christianity was practised, everyone followed the same dogma; they believed the same things and all worshipped in the same way. In the 10th century, plainsong or plain chant – unaccompanied singing performed by monks and boys – was a part of religious services. The problem was there was no accurate system of writing music. All they had was a series of marks or neumes above the written words of the chant. This did little more than indicate that the next note went up or down in pitch and provided some idea of the articulation. Chants had to be memorized and could only be taught directly from one person to another. There was always the possibility for mistakes to creep in, or for music to be lost altogether.
A musical theorist, a monk known as Guido of Arrezo https://en.wikipedia.org/wiki/Guido_of_Arezzo or sometime just Guido Monaco (the monk), solved the church’s problem by inventing the basis of western musical notation.
He took the neumatic notation and extended it into a five line staff or stave. Five lines are a small, easily drawn and read number. Notes are written either between, or on the lines, and by placing the bottom note in a sequence just above the bottom line, then counting all the spaces and lines and ending immediately above the fourth line, you get seven notes. The eighth note in the sequence is of course the octave, so a five line staff can comfortably cover one octave. To cover wider ranges of pitch, further sets of five staff lines can be used and short extension ledger lines can be drawn above or below the five line staff. Each staff is separated by at least a single ledger line which isn’t drawn as a continuous line, leaving space between staves for the purpose of legibility.
Guido based his system on the pitch range of the male human voice. The overall pitch of a five line staff is indicated by a clef sign (clef from the French, meaning key) at the beginning and Guido started with two pitch ranges of bass and treble. He used the letters of the Roman alphabet to name the notes and he chose to start with A in the gap between the bottom line of the bass clef and the next line up. He then carried on naming the seven notes of the major scale in alphabetic order, as B, C, D and so on, ending on the seventh as G just below the top line. The next note is the octave A, the same as the starting note only twice the frequency, and the seven letter sequence repeats.
So, despite the modern practice of referring to a C to C octave, the note sequence originally started logically with the letter A, not C. For tuning purposes the reference note is usually an A. The frequency of this reference note has varied over time. Only relatively recently in the early 1900’s has orchestral pitch settled (more or less) on an A of 440Hz which puts ‘middle’ C at 261.63Hz (Hertz or Hz is cycles per second in old money).
Guido was creating musical theory in the 10th century to suite the church music of the time. This was modal music based on six note hexachords. Now a thousand years later musical complexity and musical taste have changed and the C major scale, the only major scale with no sharps or flats, is central to Western music. The C to C major scale organisation of the white keys on the piano, an instrument not even thought about in Guido’s time, along with the five black keys, is an easily recognised pattern and the piano keyboard is often used as a reference. If we were to re-write musical theory and the method of musical notation today, we might choose to re-label the notes.
The Grand Stave
The Grand Stave covers a span of three octaves, with the treble clef above the bass clef, divided by the single ledger line occupied by Middle C
If you stack a treble stave above a bass stave you get two sets of five lines separated, for clarity, by a single ledger line (and a space above and below it). Although never used in written music this is known as a grand stave or staff. Following the Guido system, starting with A in the bass clef you will find the note letter that sits on that central ledger line is a C. This is where middle C comes from, for the grand stave it is the central note between the bass and the treble staves.
The bass clef symbol is a stylised letter F with the two dots split by the stave line for the note labelled F and the treble clef symbol is a stylised letter G with the centre curl of the letter on the stave line for G.
The Grand Stave covers a range of three octaves. A good fit for the range of the average human voice, which is around three and a third octaves. The range of many instruments doesn’t extend much further, although their overall pitch may be higher or lower.
In written music with treble and bass staves the two are written spaced apart and high notes in the bass or low notes in the treble are given their own short ledger lines, rather than migrating across from one stave to the other. Multiple ledger lines are often used, but beyond four or five ledger lines the notation becomes hard to read and at this point the notation may switch staves. The assumption is that the treble and bass parts will be performed on different instruments and music is more easily read if the parts are separated. Instruments such as the piano, that can span across the bass and treble, still have the parts written on separated staves because the left hand plays the bass and the right the treble.
Written guitar music
It is a curious fact that the modern guitars pitch range places it in the bass clef, but guitar music is usually written an octave higher in the treble stave. This can cause problems for session guitarists expected to play from a score written by a composer that doesn’t know the real pitch of the guitar. The F of the bass clef is normally pitched at 174.61Hz. The low E of the guitar is the second E below that, at 82.41Hz, located on the first ledger line below the bass stave.
There are other clef symbols than the treble and bass G and F clef’s. For example the alto clef, which is well suited for the pitch range of cello music and as it happens, guitar. And the tenor clef. In total there are ten clefs that have been used in musical notation. However these ‘specialist’ clef’s are rarely used, it’s just simpler to use the treble and bass clef’s and transpose parts to fit.
The reason for this pitching oddity is that early guitars, like many string instruments even today, had only four strings (or more accurately – four courses of two strings each). The name “guitar” derives from the Old Persian “chartar”, which literally means “four strings”. Many four string instruments, like the violin, are often played in ensemble and rather than having strings added to expand the range, are part of a family of instruments. For the viol family we have, roughly speaking, the violin, the viola, the cello and the double bass. Both the Cremonese old masters – Amati, Stradivari and Guarneri del Gesu – and modern makers have supplemented this range with other sizes of instrument. Traditionally the viol family is used classical orchestras and the frequency range is expanded by the use of different sizes of the basic instrument design. In comparison the guitar is not considered an orchestral instrument, rather it is an instrument that is often played on its own, or in small groups. Although we do have the bass guitar and the rarely seen, short scale Terz guitar. The four string tenor guitar doesn’t really count as part of the guitar ‘family’ because it is really a banjo with a guitar body.
Over the years, just as with the lute, which started life as a four string instrument, composers and players sought to extend the range of the guitar and it acquired a fifth bass string and then a sixth. This is one of the things which makes the guitar a special instrument, these extra strings make it possible to play a bass line, rhythmic chord patterns and melody lines all at the same time. Altered tunings extend these possibilities even further. It is quite natural to down tune the two bass strings and play a bass line on those, with the top four strings for chords and melody.
As to why western music uses seven notes for a major scale and eleven notes including sharps and flats (or 8 notes and 12 notes if you include the octave) is a question for a another time.
Mixolydian and the minor Pentatonic
When faced with improvising over a dominant seventh chord or a progression of dom7’s, many guitar players tend to resort to the minor or the Blues pentatonic as their default tonal material. Especially in a “bluesy” context, such as a standard Blues progression, this works very well and the straight forward structure of the pentatonic allows plenty of room to think about phrasing, timing, tone and all the other musical parameters that go beyond harmonic material.
However, integrating the Mixolydian scale into your harmonic repertoire will add a whole new musical component to your solo playing and, especially in combination with the minor pentatonic, can make your solos sound a lot more exciting and engaging to the listener!
Constructing the Mixolydian scale
Mixolydian is the fifth mode of the Ionian system. This means that if you’ll play the Ionian (major) scale from its fifth note onwards – thinking of that fifth note as the new root – you will end up with a Mixolydian scale.
Take for example C Ionian ( C D E F G A B C ) and play it from its fifth note G onwards, up to the next G – this will give you G Mixolydian ( G A B C D E F G). The numbers above the tab below tell you which degree of the scale each note represents:
If you’d like to read more about the Ionian System and its modes, have a look here: https://www.londonguitaracademy.com/seven-modes-of-the-ionian-system
For the most part, the Mixolydian scale is identical to the Ionian scale, except for one crucial detail: While Ionian has a major 7, Mixolydian has a minor 7, making it the perfect scale for Dom7 chords, which – just as the Mixolydian scale – contain a major third and minor seventh.
So, another easy way of constructing Mixolydian scales is taking a major scale and simply lowering its seventh note by a semitone. In the following examples, we’ll expand the scales over several octaves covering all six strings to give you a practically useful pattern for each scale.
Note that the difference between C Ionian and C Mixolydian is their seventh note (B and Bb).
Combining Mixolydian and the minor pentatonic
As mentioned earlier on, a strong way of incorporating the Mixolydian scale into your solo is combining it with the minor pentatonic, as this brings out the characteristics of each scale. Let’s have a look at which notes the two scales have in common and which notes make up the differences:
C minor pentatonic
C Eb F G Bb C
C D E F G A Bb C
The main difference – apart from the obviously different amount of notes that each scale is made up off – is the major third in Mixolydian opposed to the minor third in the minor pentatonic. This minor third played on a Dom7 chord (which itself inherently has a major third) is what makes it sound “bluesy” and somewhat wailing, and is an important stylistic device in Blues improvisation. Using the major third of Mixolydian will give you a brighter sound, bringing out a different shade of the Dom7 chord you’re improvising on. The major second and sixth of Mixolydian further add to that brighter sound, the rest of the notes (1 4 5 7) are identical to the pentatonic. In the following example on a C7 chord we’ll combine the two scales – note how the feel gets brighter once we switch to Mixolydian in bar 3 (not counting the pick up bar)!
Every Dom7 chord has its own respective Mixolydian scale. When the chord changes from C7 to F7 in our Blues progression, the Mixolydian scale of the moment would now change to F Mixolydian as well.
A strong way of navigating through those chord changes without “merely” jumping from one Mixolydian to the next, is to alternate between the minor pentatonic of the key (C min pent) and the Mixolydian scale of the moment (C, F or G Mixolydian).
A great exercise to practise this is to write out the chord progression your are improvising on and to mark in which tonal material you’ll use in your solo at what point. An example could look like this:
As you can see, there are almost endless possibilities of when to use which scale and it is great practice and a lot of fun to experiment with different combination of those scales and to listen to how the sound and feel of your solo changes!
The Mixolydian Pentatonic
At the end of this article, I’d like to show you hybrid between the minor pentatonic and the Mixolydian scale: The Mixolydian Pentatonic, which just as the minor pentatonic (and every other pentatonic for that matter – that’s why they call it pentatonic) consists of five notes. We can easily construct that scale by simply turning the minor third of the minor pentatonic into a major third:
This scale contains the “essence” of the Mixolydian sound and, due to its structural similarity to the minor pentatonic, is a great gateway from the minor pentatonic towards the Mixolydian scale!