The 18 Watters
These volume friendly amps have really gotten popular in the last few years. No doubt because fewer home players need a raging 50 or 100 watt Marshall amp driving the family and neighbors crazy.
The original Marshall 18 watt amp was the 1974 model (the model number has nothing to do with the year of manufacture or circuit design date, its just how Marshall numbers their amp models) and it was produced only for a very short period of a few years in the 60's. It was recently reissued by Marshall as a boutique "hand wired" version in the last few years at close to Two Grand! for a head version.
These amps are characterized by a great clean tone- actually kind of bright. And the EL84 power tubes distort in a Marshall crunch manner just great for Rock and Blues. They are very pedal friendly as well.
The original amps had two separate channels- a normal with a volume and tone control and a second channel with volume, tone and tremolo. Modern variations have included the 18 watt Lite which is just the normal channel mated with the power section, the TMB version which has the second channel minus the tremolo but adding a full Treble, Middle and Bass control (hence TMB). Also modifications include adding a Master volume to either of these versions for overdrive at lower volumes, several tone stack switching options, having an EF86 first preamp tube rather than the classic 12ax7 tube for more of a Vox vibe. I have built all of these variations and then some.
Here is a hot rodded 18 watt dual channel amp set up with the normal channel- on the right- and the Second channel as a TMB style. I also added a master volume in one of the input jack spots for the second channel. This top view shows the row of the rectifier tube, 2 el84 power tubes all with wire tube retainers and the red colored tube shields for the preamp tubes. Also, the blue can capacitor you can see on the end is typical of how Marshall builds their power supply capacitor setups. Fender mounted the caps under a "doghouse" on the topside of the chassis and used individual capacitors. Marshall used multiple caps built into a stacked "can" instead. The result is the same. This amp was built into a Marshall reproduction chassis with gold "plexi" faceplates.
Here is a picture of the typical Marshall style turret board. They use raised posts or turrets rather than eyelets to solder components to. I hand build these and they are a pain but make a very secure amp. I also drilled holes by each turret to pass the socket connection wires through. This makes any debugging of the connections after the board is mounted easier as you can see the wire and make sure its well soldered. Sometimes I pass the wire from under the board through the top of the turret. Either way works, I just like to mix things up when I build. You can also see the central grounding buss on the right side of the board for all the grounds. This makes a quiet amp with little hum. There is a small toggle switch in blue on the left side of the picture- this is an added gain switch I added for the customer. He wanted a switchable gain option for more overdrive. Its cathode biased .Notice the tightly wound tone and volume control wires leading to the pots. I like to minimize noise and this technique takes more work but sounds better.
Here is a variation of the 1974 Marshall Circuit. Take just the TMB channel with its full tone stack then tweak it for more gain and you get a Superlite amp. Its like the Lite IIb concept of dividing the Marshall 1974 amp into two separate amps both sharing the same power output section but having the preamp tweaked for certain characteristics.
Mate an 18 watt power section to a Cascaded preamp front end with a full tone stack and you get hi gain supreme. Well, OK that is a little hyperbole, but you do get a huge amount of gain when you hit the boost switch. The preamp section can be run in a classic plexi style Marshall front end or when the switch is engaged, it "cascades" the preamps sections together for a lot more gain. Similar to how Mesa and other makers add gain to their designs. True to its 18 watt roots, its cathode biased but when the boost switch kicks in, there is a separate gain control pot that lets you tailor the gain "cascading" into the rest of the preamp section. When that circuit is in normal mode, that pot does not get used. Its a great circuit but easy to get out of control and I had to tweak the values to get it sounding smooth. It does sound great.
The original Marshall 18 watt amp was the 1974 model (the model number has nothing to do with the year of manufacture or circuit design date, its just how Marshall numbers their amp models) and it was produced only for a very short period of a few years in the 60's. It was recently reissued by Marshall as a boutique "hand wired" version in the last few years at close to Two Grand! for a head version.
These amps are characterized by a great clean tone- actually kind of bright. And the EL84 power tubes distort in a Marshall crunch manner just great for Rock and Blues. They are very pedal friendly as well.
The original amps had two separate channels- a normal with a volume and tone control and a second channel with volume, tone and tremolo. Modern variations have included the 18 watt Lite which is just the normal channel mated with the power section, the TMB version which has the second channel minus the tremolo but adding a full Treble, Middle and Bass control (hence TMB). Also modifications include adding a Master volume to either of these versions for overdrive at lower volumes, several tone stack switching options, having an EF86 first preamp tube rather than the classic 12ax7 tube for more of a Vox vibe. I have built all of these variations and then some.
Here is a hot rodded 18 watt dual channel amp set up with the normal channel- on the right- and the Second channel as a TMB style. I also added a master volume in one of the input jack spots for the second channel. This top view shows the row of the rectifier tube, 2 el84 power tubes all with wire tube retainers and the red colored tube shields for the preamp tubes. Also, the blue can capacitor you can see on the end is typical of how Marshall builds their power supply capacitor setups. Fender mounted the caps under a "doghouse" on the topside of the chassis and used individual capacitors. Marshall used multiple caps built into a stacked "can" instead. The result is the same. This amp was built into a Marshall reproduction chassis with gold "plexi" faceplates.
Here is a picture of the typical Marshall style turret board. They use raised posts or turrets rather than eyelets to solder components to. I hand build these and they are a pain but make a very secure amp. I also drilled holes by each turret to pass the socket connection wires through. This makes any debugging of the connections after the board is mounted easier as you can see the wire and make sure its well soldered. Sometimes I pass the wire from under the board through the top of the turret. Either way works, I just like to mix things up when I build. You can also see the central grounding buss on the right side of the board for all the grounds. This makes a quiet amp with little hum. There is a small toggle switch in blue on the left side of the picture- this is an added gain switch I added for the customer. He wanted a switchable gain option for more overdrive. Its cathode biased .Notice the tightly wound tone and volume control wires leading to the pots. I like to minimize noise and this technique takes more work but sounds better.
Here is a variation of the 1974 Marshall Circuit. Take just the TMB channel with its full tone stack then tweak it for more gain and you get a Superlite amp. Its like the Lite IIb concept of dividing the Marshall 1974 amp into two separate amps both sharing the same power output section but having the preamp tweaked for certain characteristics.
Mate an 18 watt power section to a Cascaded preamp front end with a full tone stack and you get hi gain supreme. Well, OK that is a little hyperbole, but you do get a huge amount of gain when you hit the boost switch. The preamp section can be run in a classic plexi style Marshall front end or when the switch is engaged, it "cascades" the preamps sections together for a lot more gain. Similar to how Mesa and other makers add gain to their designs. True to its 18 watt roots, its cathode biased but when the boost switch kicks in, there is a separate gain control pot that lets you tailor the gain "cascading" into the rest of the preamp section. When that circuit is in normal mode, that pot does not get used. Its a great circuit but easy to get out of control and I had to tweak the values to get it sounding smooth. It does sound great.