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A M P
N5X
Construction guide
This build guide describes how to build the
N5X guitar amplifier kit from Amp Maker.
The N5X is the successor to the very
popular SE-5a 'British Overdrive' amplifier
kit. The circuit is almost identical, but
with some of the most popular
modifications added as standard:
1.
VCB for getting power valve
distortion at lower room volumes
2. Switchable boost: None/Bright/Fat
3. Bypassable tone stack for more gain
4. More power valve options:
EL84/6V6/6L6/EL34/etc
5. All popular speaker impedances
covered: 4/8/16 ohms
This build guide assumes you have
an N5X kit from Amp Maker (above), but
M A K E R
you can also follow the instructions if you
want to build the amp with parts that you
have sourced yourself. If so, you'll have to
adjust the build to cater for differences in
the parts you have (transformer taps,
etc). If you're building with your own
chassis, or a donor chassis, I strongly
suggest you follow the general parts
layout shown in the guide to help avoid
noise/hum/etc issues from a sub-
optimal layout.
easy as possible to follow and that means
that it contains a lot of detail, tips and
practical advice to help things go
smoothly. If you have any feedback -
please let me know.
ww w. am pm ake r.c om
I've tried to make this build guide as
1
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Related Manuals for AMP MAKER N5X
Summary of Contents for AMP MAKER N5X
- Page 1 N5X guitar amplifier kit from Amp Maker. have sourced yourself. If so, you'll have to The N5X is the successor to the very adjust the build to cater for differences in popular SE-5a 'British Overdrive' amplifier kit.
- Page 2 Kit contents Your N5X amplifier kit contains all of the electronics and hardware parts needed to make a great- sounding valve amplifier. Before jumping in, clear a space on your workbench and unpack all of the components. Start by checking the Kit contents listing below. Look through the electronic components 1M/0.5W...
- Page 3 If you're in any doubt, get in touch with Amp Maker.) w w w. a m p m a ker.c o m...
- Page 4 - perhaps 2V at most. So any rating of 25V or more is fine (I usually supply 100V as they are far more readily available, and still quite small). Capacitors may have voltage ratings higher than specified above (depending on supplies). N5X Construction guide...
- Page 5 Some capacitors have a polarity - a positive terminal and a negative terminal. In this amplifier kit, the blue/black electrolytic capacitors are all polarised. Look closely at the printing and you will see that one of the leads on each of these capacitors is marked by a minus sign (-). This is often contained within an arrow printed on the side of the capacitor, where the direction shows the negative terminal.
- Page 6 For now, just check that it's present in your kit. Turret boards The N5X uses two turret boards, the smaller one is for the power supply and the larger one for the amplifier's signal path. Most of the smaller components will be mounted to the turrets on these boards.
- Page 7 The rest of the kit contents list spells out the sockets, switches, etc you use to make up the rest of the circuit. Check the contents against the list and let Amp Maker know of any problems or missing parts.
- Page 8 N5X schematic The page opposite shows the N5X's full-size schematic. This diagram shows all of the component values added and with numbered lugs for all off-board components. All components are numbered on the schematic (R1, C3, D4, etc), so that you can relate this schematic to your Kit contents listing and the turret board layouts.
- Page 9 www. ampmaker.co m...
- Page 10 The N5X includes a 'noval' socket for EL84 valves (like the SE-5a), but also has an octal power valve socket, V3. So you can plug in a 6V6/6L6/EL34/etc instead of the EL84. These bigger...
- Page 11 (shown by the red triangles). In the N5X, there's a Variable Voltage Regulator (VCB) circuit - shown here as the darker blue block. You can use the VCB pot to dial down the voltage supplied to the power stage. There's just one good...
- Page 12 In each case, use an M4 screw from the outside of the chassis, then the ground lug inside the chassis, then a shakeproof washer and then the M4 nut to secure it. N5X Construction guide...
- Page 13 w w w. a m p m a ker.c o m...
- Page 14 Here's the simpler stuff, in no particular order: * V1 valve socket using M2.5 hardware * V2 valve socket and retaining clip using M2.5 hardware * V3 valve socket and retaining clip using M3 hardware (6mm screw) * 3-way tagstrip using M4 hardware N5X Construction guide...
- Page 15 Front panel and controls The N5X's front panel is held in place by the main amplifier controls: six pots, three switches, one lamp and one socket. However, for now, install only the six pots to allow easy access for other parts later.
- Page 16 M6 bolt to pass through the hole in the chassis. Then rotate the toroid so that the wires are in roughly the correct positions. For the N5X amplifier layout, the thicker green wires of the heater supply go through the rubber grommet that's closest to the centre of the chassis, with the brown + yellow + brown wires of the high-voltage supply going the centre grommet and the six wires of the mains-side primary going through the grommet closest to the edge of the chassis.
- Page 17 Building the power supply In the N5X, we build and test the power supply (including the smaller turret board and the VCB circuit) before building the rest of the amplifier. Start by gathering up the turret board and the following...
- Page 18 Solder lugs 2 and 3, but leave lug 1 unsoldered for the moment. As usual with hand-wired amplifier layouts - in general it's best to keep wires as short as possible and routed directly. Avoid unnecessarily long wires. N5X Construction guide...
- Page 19 Mains-side wiring With the turret board properly installed, you can add the On/Off switch (S3) and the neon indicator (L1) to the front panel. (For clarity, the front and back panels are shown here as if they have been folded down, although in reality they are at the usual 90 degrees to the bottom of the chassis.) The first job is to add three wires to the IEC socket: a short green wire to connect the Earth lug directly to the grounding lug next to the IEC socket, and a brown and blue wire to the Live and Neutral...
- Page 20 MOSFET to clear the power supply board and orientate the MOSFET so that the 'lugs' are closest to the board. Do not overtighten the nut. Finally, add the three connecting wires between the MOSFET and the board and Power level pot. N5X Construction guide...
- Page 21 Ground the power supply board There's just one more wire to add, to ground the relevant components on the power supply board. Take a piece of black wire and connect it from the turret at the negative lug of C16 and connect it to the centre lug of the tag-strip. Now that the power supply is completed, it should look like this (below).
- Page 22 Use the DMM to carefully confirm that you have your mains voltage at the Live and Neutral lugs of the IEC socket. Record this figure in the first column in the voltage chart. Now turn the amplifier on. The neon should glow. N5X Construction guide...
- Page 23 The N5X has two bleed resistors - R22 and R26 - that allow this charge to drain away safely and quickly.
- Page 24 Depending on the valves you are using, you should have a figure of about 6.1-6.5V. Now unplug the amplifier from the mains. Remove the valves from the sockets and put them safely on one side while you complete the rest of the amp build. N5X Construction guide...
- Page 25 Building the main turret board The first step in building the main turret board is to fit the board in the chassis. Use five M3 shakeproof washers and nuts to do this, but for the two mounting points at the bottom-left and bottom-right add the M3 solder lugs.
- Page 26 Now trim and solder R2 and R8 in place, connecting the board to the V1 valve socket (pins 2 and 7, respectively). See below. For resistors R15 and R18, trim them to length and solder them at the turret board end only. (You will add an extra wire and solder them to the V2 valve socket later.) N5X Construction guide...
- Page 27 Turret board wiring The next step is to add wires to connect the turret board with the valve sockets and front panel controls. In each case, keep it as neat and direct as possible. When soldering to valve socket pins, make sure that you avoid wire 'whiskers' where one strand of wire misses its hole and shorts against a neighbouring pin or the chassis.
- Page 28 (this ensures that it cannot short against any other part of the circuit). Connect and solder the inner conductor to the turret that's connected to R2. N5X Construction guide...
- Page 29 Front panel controls II Now it's time to do wire up the pots. Take a deep breath before diving in. :) The first diagram shows the pot wiring with all other wires temporarily hidden from view so you can concentrate on the steps you have to take.
- Page 30 Connect the other ends of these four wires to the turrets shown here. The orange ones connect to the 1uF capacitors and the brown ones connect to the 47uF capacitors. N5X Construction guide...
- Page 31 Output transformer connections Your final connections will complete the signal path of the amplifier. At the moment, the signal path to the power valves is all in place, so all that remains is to connect the power valves to the output transformer and the output transformer to the speaker sockets.
- Page 32 Your finished amplifier Now that it's completed, the inside of your N5X chassis should look something like the diagram opposite. It pays to relax a bit and check off the connections. Look for missing wires, wrong connections and out of position components.
- Page 33 w w w. a m p m a ker.c o m...
- Page 34 'X' marks should show continuity to ground, but the two points shown by the blue 'X' marks should not. Change the switch to the Down position and the amp is in 'Fat' mode. Now the opposite should be true. N5X Construction guide...
- Page 35 If you read anything other than good continuity for any of these tests, go back and check your wiring. Contact Amp Maker if you cannot locate the problem. Your amp is NOT safe to switch on until this is fixed.
- Page 36 If you hear a loud hum or buzz, or if the fuse blows, switch off immediately and contact Amp Maker. Print off this voltage chart, ready to write down the results of your tests.
- Page 37 That last set of measurements lets us know that the power supply board works properly under the load of the circuit. The remaining measurements let us check the DC state of the rest of the N5X amplifier circuit at idle. From this we do a few simple calculations to check everything's within spec and then we're ready to play.
- Page 38 _________mA 3 - EL84 plate current: Subtract the screen current (2, above) from the cathode current (1, above) to get the valve's plate current. A typical result is 36-40mA. Contact Amp Maker if your result is more than 45mA. _________mA 4 - EL84 plate dissipation: Multiply the N-M figure by the EL84 plate current you've just calculated (3, above).
- Page 39 _________mA 3 - Octal plate current: Subtract the screen current (2, above) from the cathode current (1, above) to get the valve's plate current. A typical result is 36-40mA. Contact Amp Maker if your result is more than 45mA. _________mA 4 - Octal plate dissipation: Multiply the J-M figure by the octal plate current you've just calculated (3, above).
- Page 40 The Power level control is a linear pot, which means that the audible effect you hear from turning it down is more pronounced at the bottom end of the dial than it is at the top. This is normal. N5X Construction guide...
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