Oldfield 5918 User manual

Oldfield Amplifiers User Guide
Model&5918

Oldfield Amplifiers User Guide
Important Safety Instructions
• For your safety read, retain, and follow all instructions. Heed all warnings.
• Only connect the power supply cord to an earth-grounded AC receptacle. This amplifier is designed to
operate on standard North American 115V AC and should only be plugged in to a receptacle meeting
those specifications.
• WARNING: To prevent damage, fire or shock hazard, do not expose this unit to rain or moisture.
• Unplug the power supply cord before cleaning the unit exterior (use a damp cloth only). Wait until the
unit is completely dry before reconnecting it to power.
• Maintain at least 6 inches (15.25 cm) of unobstructed air space behind the unit to allow for proper
ventilation and cooling of the unit.
• This product should be located away from heat sources such as radiators, heat registers, or other
products that produce heat.
• This product may be equipped with a polarized plug (one blade wider than the other) or a three-prong
grounded plug. This is a safety feature. If you are unable to insert the plug into the outlet, contact an
electrician to replace your obsolete outlet. Do not defeat the safety purpose of this plug.
• Protect the power supply cord from being pinched or abraded.
• This product should only be used with a cart or stand that is recommended by the manufacturer.
• The power supply cord of this product should be unplugged from the outlet when left unused for a long
period of time, or during electrical storms.
• This product should be serviced by qualified service personnel when: the power supply cord or the plug
has been damaged; objects have fallen, or liquid has been spilled onto the product; the product has
been exposed to rain; the product does not appear to operate normally or exhibits a marked change in
performance; the product has been dropped, or the enclosure damaged.
• Do not drip or splash liquids, nor place liquid filled containers on the unit.

Important Safety Instructions - Continued
• CAUTION: No user serviceable parts inside, refer servicing to qualified personnel only. Do not expose
the circuit of the amplifier under any circumstances.
• CAUTION: By nature vacuum tubes get very hot during operation. Do not touch vacuum tubes until they
have sufficiently cooled.
• Oldfield amplifiers are capable of producing very high sound pressure levels. Use care when setting and
adjusting volume levels during use to protect your hearing from possible damage.
• Failure to comply with any of these safety precautions could result in damage to the amplifier and in
worst cases bodily harm. Non-compliance with any safety precaution may void any stated warranties.
Oldfield Amplifiers User Guide

Oldfield Amplifiers User Guide
Overview
Congratulations on your purchase of a new Oldfield 5918 amplifier. The Oldfield 5918 gets it roots
from the legends of the late 1950’s and is well suited for Country, Jazz, Blues and Rock players.
This amplifier is all tube and hand-wired using the best quality components available for guitar
amplification. It is built to last a lifetime and give the owner countless hours of enjoyment whether
on stage, in the studio, or in the home.
Feature summary:
- Two channels, each with input jacks for normal and high gain instruments
- 20 watts output power into 8Ω
- All tube, hand-wired circuitry
- 6V6 Power amp tubes
- 5751 Preamp, 12AX7 phase inverter
- 5V4 Rectifier tube
- Finger–jointed pine cabinet

Oldfield Amplifiers User Guide
Operation
Front Controls
Reference the front panel viewing left to right
Channel 1 Lo Input / Hi Input - Instrument inputs for channel 1. The Lo input has less gain than
the Hi input.
Channel 2 Lo Input / Hi Input - Instrument inputs for channel 2. The Lo input has less gain than
the Hi input.
(NOTE - Channel 2 is brighter than channel 1)
Channel 1 Volume - Volume control for instruments plugged into the channel 1 input. Rotating the
control clockwise will make the channel 1 volume louder and increase overall gain and harmonics.
Channel 2 Volume - Volume control for instruments plugged into the channel 2 input. Rotating the
control clockwise will make the channel 2 volume louder and increase overall gain and harmonics.
Tone - Rotating the control clockwise will increase the high end frequencies output by the amplifier.
This control affects channel 1 and channel 2.
Indicator Light - Lit when the mains switch is on.
Standby - Move to the up position for play and down to put the amplifier in standby mode. The
standby switch should only be moved to the play position after the Mains switch has been in the on
position for at least one minute to give the tubes time to arm up.
Mains - Move to the up position for play and down to shut the amplifier completely off.

Oldfield Amplifiers User Guide
Operation - Continued
Rear Controls
FUSE - Replace only with a 2.0 Amp slo-blo fuse. Never install a larger fuse than specified. Have the
amplifier tested by a qualified technician if it repeatedly blows fuses.
Rectifier Selection Switch - Your amplifier is capable of using a tube or solid state rectifier. Each
type will yield a slightly different tone. Make sure the amplifier is in standby before changing the
position of this switch.
Power Level - The power level control is a variable voltage control for the amplifier. At 100% the
amplifier will produce the maximum output and be the loudest. Turning this control
counterclockwise will reduce the overall volume.
Impedance Selector - Use the Impedance Selector to match the amplifier output impedance to the
attached speaker. The amplifier is capable of handling a 4, 8, or 16 ohm load.
MAIN SPEAKER - Connection for the primary speaker (internal or external).
EXTERNAL SPEAKER - Use this connection when using more than one speaker cabinet.
Note - Do not exceed a 4 ohm load.

Oldfield Amplifiers User Guide
Tubes
Looking at the back of the amplifier and reading left to right the tube compliment is as follows:
Rectifier - Your amplifier comes shipped with a 5V4 tube rectifier.
Power - Your amplifier uses (2) 6V6 power tubes. When replacing power tubes use only a matched pair
from the same manufacturer. Your amp does not need to be re-biased when changing power tubes.
Phase Inverter - Your amplifier uses a 12AX7 dual triode for the phase inverter.
Preamp - Your amplifier uses (2) 5751’s as preamp tubes.

Oldfield Amplifiers User Guide
Performance Notes:
• For a more “tweed” type tone try replacing the preamp tubes with a high quality 12AY7’s and the
rectifier tube with a 5Y3. If you are unfamiliar with replacing tubes this should be done by a qualified
service technician.
• For a little higher gain try replacing the preamp tubee with a 12AX7’s.
•To blend the two channels run a jumper between the low gain input of channel one and
the high gain input of channel 2. Plug your instrument into the high gain input of channel
1. Adjust volumes to taste.

Oldfield Amplifiers User Guide
Warranty
The following warranties apply to the original owner of the amplifier. All warranty work must be
performed by Oldfield for the warranty to be in effect. Warranties do not cover normal wear and tear
or abuse. Failure to comply with the safety precautions outlined earlier in the owner’s manual will
void all warranties.
Rectifier and Power Tubes – Guaranteed for thirty days after date of purchase. If a failure occurs
Oldfield will replace any rectifier or power tube during this period free of charge. Power tubes can
only be replaced by a qualified service technician since a re-bias will be necessary.
Preamp Tubes - Guaranteed for ninety days after date of purchase. If a failure occurs Oldfield will
replace any preamp tube during this period free of charge.
Power Transformer, Output Transformer, Reverb Transformer, And Choke - These items are
guaranteed for ten years after date of purchase against manufacturer’s defects. If a failure occurs
due a defect in manufacturing Oldfield will replace any of these items during this period free of
charge. Warranties on these items are void if the owner uses any type of power soak or
attenuator in conjunction with the operation of the amplifier.
Defects Due To Workmanship – Oldfield guarantees the amplifier to be free from workmanship
defects for 5 years after date of purchase.
Circuit Components – Any failed circuit component will be replaced at Oldfield’s discretion. Some
circuit components have a limited life such as filter and bypass capacitors and Oldfield must use
judgment to determine if the component was at end of life or failed prematurely.
In every case Oldfield guarantees to work with the customer to remedy any situation in a
timely manner and to the satisfaction of the amplifier owner.