Invader User's Manual Aiken Amplification 1225 Montague Avenue Greenwood, SC 29646 Tel: 864-993-8383 http://www.aikenamps.
Contents Contents...............................................................................................................2 Getting Started.....................................................................................................3 Front Panel Controls and Switches...................................................................5 Rear Panel Controls and Switches....................................................................8 Tube layout and replacement.................................
Getting Started Congratulations on purchasing your new Aiken Invader amplifier! The Invader is an all-tube amplifier, available in 18 or 30 watt versions. This amplifier is truly touch-sensitive, going from clean to crunch to singing leads by just adjusting the volume control on the guitar. The 4-input design allows jumpering of the two channels, which are independently voiced, to provide a wide range of tones from any guitar, using single-coil or humbucking pickups.
Massive, custom-wound, high-interleave transformers, rated for over twice the maximum amplifier output power, allowing the amplifier to be run full power into an attenuator continuously, without failures. Output power (at onset of clipping): 18W (or 30W for 4-EL84 models) into 4, 8, or 16 ohms resistive load. Built-in power attenuator with 0dB, -3dB, -6dB, -9dB, -12dB positions, as well as a REC (15dB) position for low volume recording, or apartment/bedroom volume practicing.
Front Panel Controls and Switches Input jacks: Channel 1 is voiced bright, channel 2 is voiced much darker. The upper inputs are higher gain than the lower inputs for each channel. You can jumper the channels by plugging into channel 1 upper input and connecting a patch cord from channel 1 lower input to channel 2 upper input. This allows you to mix the two volume controls for the desired balance of bright/dark tones, and is very useful for tailoring the tone to your needs.
Bass: The bass control adjusts the low frequency equalization. Dwell: The dwell control adjusts the drive to the reverb tank. Higher dwell levels result in an apparently "longer" decay time of the reverb. The dwell control also allows adjustment of the proper drive level when playing clean or distorted. Distorted settings typically require a much lower dwell level than clean settings, as there is more drive to the reverb tank when the volume control is increased.
Pilot lamp: The pilot lamp lights when power is applied to the amplifier and the power switch is on. Standby switch: The standby switch allows muting of the amplifier output when not in use. When the switch is in the up position, the amplifier is on, and when it is in the down position, the amplifier is on standby. The tube filaments remain on and warmed up, so the amplifier is ready to play as soon as it is taken off standby.
Rear Panel Controls and Switches AC Mains: Plug the supplied IEC mains cord into this outlet to provide power to the amplifier. Mains Fuse: 18W amplifiers: 2A slo-blo 30W amplifiers: 3A slo-blo Note: the silkscreen on the back of the amplifiers reflects the original 1A designation and should be ignored – use the above recommended fuses to prevent “nuisance” fuse blowing from turn on surges.
speaker emulator usually sounds best at louder settings on the attenuator, because of the interaction between the speaker and the amplifier, which results in a more natural tone. A bit of equalization may be required on the board, typically a midrange cut or bass boost, for the most natural tone, especially at lower attenuation settings. It may also be necessary to cut frequencies above 4kHz –5kHz to tailor the high frequencies to your liking.
Tube layout and replacement The Invader uses four ECC83/12AX7 tubes, one ECC81/12AT7 tube, and two 6BQ5/EL84 output tubes (four EL84s in the 30W version). It also uses a single 5AR4/GZ34 rectifier tube. The preamp tubes are housed in removable "bayonet" metal shields. The shields can be removed by pushing down on them and rotating the shield to the left, then pulling it upwards off the tube. The tube can then be pulled out of the socket.
Biasing Biasing is very easy, and doesn't require removing the chassis from the cabinet. You simply use a voltmeter (any inexpensive digital multimeter will do), set it for the smallest DC voltage range (typically 200mV). Then: (1) Unplug any guitar cords going into the four input jacks. Turn the two volume controls all the way down (other control positions don’t matter). Unscrew the lock nuts on the bias and balance pots on the rear panel, and turn the bias control all the way down (counterclockwise).
Speakers Changing speakers is like getting a whole new amp. Every model sounds completely different, some sounding quite good and some amazingly bad. The amplifier is particularly suited for use with Celestion loudspeakers, which give the characteristic "British" sound this amplifier is designed to create. Celestion Greenbacks have less volume and a dip in the mids, which makes them nice and smooth.
Troubleshooting Pilot lamp not lit: Is the amplifier plugged into a functional outlet of the appropriate voltage? Is the mains fuse blown? If so, replace with the appropriately rated fuse. If the fuse again blows, the amplifier may have a shorted output tube or rectifier tube. Replace the tubes and fuse, and power the amplifier up again. If the fuse still blows, the amplifier will need to be serviced.
Humming or buzzing noise: Unplug the guitar cord from the input and unplug any cable used for jumpering the two inputs. If the buzzing stops, try replacing the cord. Be sure to use only guitar cables, not unshielded speaker cables! If in doubt, unscrew the connector and look to see if there is a shield around the center connector. Some smaller speaker cables are easily mistaken for guitar cables. Fluorescent lights and light dimmers can be a source of hum/buzz, as can computer monitors.
Ringing noise or feedback that occurs with no guitar plugged in: If the amplifier exhibits a "ringing" noise, especially when tapping on the chassis, or if it makes a howling or whistling feedback noise when the volume is turned up but no guitar is plugged in, there is probably a microphonic tube in the amplifier, likely in the first position (the small tube closest to the input jacks), or in the reverb recovery position. Remove the shield and lightly tap on the tube with the volume turned up.
Specifications Output Power: 18W (or 30W for 4-EL84 model) at onset of clipping into resistive load at rated impedance. Input Impedance: 1Megohm (upper inputs on channel 1 or 2) or 136K ohms (lower inputs on channel 1 or 2, not jumpered) Input sensitivity: 10mV for output clipping, all volume/tone controls fully up, ali mode.
