Rambler 15 & 40 Owner s Manual DC Developments Musical Equipment Design & Development Unit 13 Rosshill Industrial Park, Southend-on-Sea, Essex SS2 5PZ, England Tel/Fax +44 (0)1702 610964 www.dc-developments.com 1995-2007 CORNELL Musical Equipment Design & Development 1
CONTENTS Introduction 3 Construction and Design 3 Technical Design 4 The Pre-amplifier The Output Stage Controls 5 Specifications 6 Valve Replacement 7 Please read all instructions before operating the amp! WARNING To prevent damage, fire or shock hazard, do not expose this unit to rain or moisture. No user serviceable parts inside. Refer servicing to qualified personnel only. This unit must be earthed. Use the correct mains cord. If you require any further information regarding the Rambler amplifier, or any other CORNELL products, please do not hesitate in contacting us (details on front page). 1995-2007 CORNELL Musical Equipment Design & Development 2
Introduction Thank you for choosing a Cornell Rambler 15 / Rambler 40 amplifier. Your amplifier employs valve technology, and is hand built to the highest standards. Only top quality components are used in our amplifiers, so that you can enjoy years of trouble-free use. Please take time to read this manual, to ensure that you get the best from your Rambler 15 / Rambler 40 amplifier. Construction and Design Virtually all modern amplifiers are built using printed circuit boards, which helps to speed up production and keep down costs. There is, however, one major drawback with printed circuits - conductor tracks that connect components together often run very close to one another, creating a small capacitance. The result of this in a guitar amplifier is a substantial loss in both high frequency response and harmonic richness. Cornell amplifiers are designed to avoid this by having point-to-point wiring throughout. Components are mounted onto a specially designed component board which is then sealed, using a conformal coating to prevent noise and the reduction of component life caused by moisture penetration. The hand wiring, carried out by our highly-trained staff, takes time but ensures that each of our amplifiers performs to the highest standards of reliability and sound. The stainless steel chassis holds our specially-designed transformers, and chassismounted (rather than circuit-board mounted) valves (tubes). Such attention to detail ensures a very close reproduction of the full harmonic spectrum of your guitar s pick-ups, resulting in a pure, natural sound that will turn heads at any venue and/or that records superbly. 1995-2007 CORNELL Musical Equipment Design & Development 3
Technical Design The Pre-amplifier The Cornell Rambler is designed to be simple in use and yet produce the wide range of sounds that the musician expects from a professional amplifier, with the superb tones that you can only get with valves. Channel 1: The Bass and Treble controls work over the entire frequency range of your guitar, allowing increased amounts of low and high frequency adjustment. Channel 2: Has a core tone set to the mid-frequency range of the guitar. Gain and Volume controls adjust the amount of overdrive; the Tone controls adjust the upper and lower frequency range of the overdrive setting. Reverb: Adjusts the amount of reverb signal. The reverb design on the Cornell Rambler is such that it is independent of the dry signal. The two signals are mixed together at the output stage, thus the reverb control is also the reverb volume. This enables you to blend the amount of reverb you require; 100% can be achieved by simply reducing the dry signal, i.e. the Master Volume. The Output Stage The Cornell Rambler 15 has a Class A output design achieved by means of fixed bias resistors. The resistance values are selected to complement exactly the characteristics of the output valve. Cathode bias resistors help to stabilise current flow throughout the lifetime of the valve. The voltage across each bias resistor will vary with the valve s characteristics. When these voltages are equal, each valve is drawing the same amount of current and the valve set is matched resulting in maximum output and long life. Our Class A design has less cross-over distortion, resulting in a smoother output sound when the output stage is driven beyond its output level. Cornell Cream Box Part of the Cornell Rambler 15 sound is due to our little cream box. We can t tell you what s inside - it s our little secret. We think it makes our Rambler 15 sound rather special. But take a listen and judge for yourself. The Cornell Rambler 40 uses a Class AB output design. This configuration allows greater output to be achieved without increasing the temperature of the output valves unduly. The sound of the Rambler 40 ranges from crystal clean to singing lead tones. 1995-2007 CORNELL Musical Equipment Design & Development 4
Controls 1. Input - Hi & Lo Both inputs offer high impedance connections for instruments. The Hi input provides 6dB more gain than the Lo input. 2. Volume - Adjusts the overall volume of the amplifier. 3. Bass - Adjusts the amount of low frequency boost. 4. Treble - Adjusts the amount of high frequency boost. 5. Gain - Adjusts the gain/overdrive of channel 2. 6. Reverb - Adjusts the amount of reverb (works on both channels) 7. Master - Adjusts the overall volume of the amplifier. 8. Mains Indicator When illuminated, this shows that the valve heaters are on, and that there is power to the amplifier. 9. Standby Connects power to the valves for operation, use Standby mode for breaks in usage (eg, between performance sets). 10. Valve/Diode Switch - Selects the rectifier type. 11. Output Switch The three-position output switch selects full power (position A ), 1/5 power (position B ), and 1/15 power (position C ) [these figures are approximate] 12. Impedance Switch The switch at the rear of the chassis next to the external speaker jack is an impedance switch. This switch should be pointing downward for normal use (with 8 Ohms internal speakers only, or 8 Ohms external speakers with the internal speakers disconnected); and should be switched to point upwards for use when an 8 Ohms extension cabinet is used in parallel with the internal speakers (or some other combination totalling 4 Ohms). Using the correct impedance selection enables the amp to deliver maximum power to the speakers. 13. Mains Fuse The fuse holder, next to the mains switch on the back panel, contains the mains fuse for the amplifier. The mains fuse protects the amplifier from electrical faults. Replace a failed fuse only with the same type and rating. Do not operate the mains switch without a 30 second delay between operations. There is an internal thermistor to reduce mains surges. This protects the amp and helps to ensure a long life for the components. The thermistor works by introducing a resistance in the circuit when the power is switched on. Within a few seconds the thermistor heats up and its resistance reduces, allowing the full current to flow into the mains transformer. After switching off the amp, it takes a few seconds for the thermistor to cool down and to return to its initial, protective resistance value. 1995-2007 CORNELL Musical Equipment Design & Development 5
Specifications POWER Rambler 15... 230 Volt AC, 50Hz, 120 Watts Rambler 40... 230 Volt AC, 50Hz, 280 Watts FUSES Rambler 15... 500mA, 240v Slo-blow 250mA Slo-blow HT Fuse Rambler 40... 1Amp, 240v Slo-blow 500mA Slo-blow HT Fuse INPUT IMPEDANCE... Hi - 2.2 MegOhm: Lo - 47 kohm CONTROLS... Volume, Bass, Treble [Channel 1] Gain, Volume, Bass, Treble [Channel 2] Reverb, Master OUTPUT Rambler 15... 15/3/1 Watts Rambler 40... 40/8/2 Watts SPEAKERS... 1 x 12 (Celestion/Jensen/Tone Tubby) 2 x 10 (Celestion/Jensen) with 8 / 4 Ohms impedance selector switch CABINET... Pine shell & plywood baffle. Leather handle. Rubber feet. SIZE... Height: 19in (490mm) Width: 24in (600mm); Depth: 9in (230mm) WEIGHT... 51 lbs / 23 Kg OPTIONS (on request)... Choice of speakers, covering material and colours, grille cloth material/colours 1995-2007 CORNELL Musical Equipment Design & Development 6
Valve Replacement Valve life varies, depending upon playing style and application. Power valves have a much shorter life than pre-amp valves, which can last for years. In order to maintain the optimum performance of your amplifier, the valves should only be replaced with the same types of valve, as specified below. Your Cornell Rambler amplifier has eight valves: three pre-amp valves (12AX7/ ECC83), two 12AT7/ECC81 valves for the reverb, two power valves (EL84 for the Rambler 15, and EL34 or 6L6 for the Rambler 40), and a rectifier valve (GZ34). Warning When changing valves, ALWAYS unplug the amplifier, and remember that the VALVES ARE HOT! Wait for the valves to cool, or replace the valves when the amplifier has not been used for several hours. Valve Line-up Front panel Mains Transformer Output Transformer Rambler 15 GZ 34 EL84 EL84 ECC81 ECC81 ECC83 ECC83 ECC83 6L6 or EL34 6L6 or EL34 Rambler 40 1995-2007 CORNELL Musical Equipment Design & Development 7