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Oldfield Amplifiers
User Guide
Model&6440-OD
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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&lifier&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¬&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; or objects have fallen, or liquid has been spilled onto the product;
or the product has been exposed to rain; or the product does not appear to operate normally or
exhibits a marked change in performance; or the product has been dropped, or the enclosure
damaged.
• Do not drip or splash liquids, nor place liquid filled containers on the unit.
• CAUTION:&No&user&serviceable&parts&inside,&refer&servicing&to&qualified&personnel&
only.&Do¬&expose&the&circuit&of&the&lifier&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 which may cause
temporary or permanent hearing damage. Use care when setting and adjusting volume levels
during use.
• Failure to comply with any of these safety precautions could result in damage to the amplifier
and in worst cases bodily harm. Noncompliance with any safety precaution may void any
stated warranties.
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Oldfield Amplifiers
User Guide
1"•"Inputs"-"Hi"/"Lo:"This&is&the&input&for&musical&instruments.&Use&the&Hi&Input&for&the&highest&gain&and&the&Lo&
Input&for&less&volume&or&higher&gain&instruments.
2,•"Boost"Switches:
"Switch&the&Mid-Boost&Switch&to&the&on&position&to&give&the&lifier&more&mid&range&bite.&When&this&switch&is&in&
the&on&position&the&lifier&will&obtain&distortion&slightly&faster&than&when&the&switch&is&in&the&off&position.&&&
The&Mid-boost&switch&must&be&in&the&on&position&when&controlling&the&function&with&the&foot&switch.
Move&the&Bright&Switch&to&the&on&position&to&give&the&lifier&more&top&end&bite.&&This&function&is&front&panel&
selectable&only&and&can¬&be&controlled&by&the&foot&switch.
3•"Volume:"This&control&determines&the&overall&amount&of&gain&for&the&clean&channel&of&the&lifier.&As&the&
volume&control&is&rotated&towards&max&the&&will&become¬&only&louder&but&rich&harmonic&overtones&will&
mix&with&the&tone&as&well.
4"•"Treble:"This&control&determines&the&amount&of&treble&frequencies&present&in&the&lifier&tone.&At&the&max&
setting&the&lifier&is&at&it’s&brightest.&This&control&also&adds&a&bit&of&bite&to&the&lifier&as&it&is&turned&towards&
max.
5•"Middle:"This&control&determines&the&amount&of&mid&frequencies&present&in&the&lifier&tone.&The&mid&
control&effects&are&less&dramatic&than&the&treble&and&bass&controls&and&tend&to&soften&the&overall&&tone&as&
the&control&is&turned&towards&the&maximum&setting.&It&should&also&be¬ed&that&as&the&middle&control&is&turned&
towards&the&maximum&setting&the&player&will¬ice&that&the&treble&and&bass&controls&have&less&effect&on&the&
overall&tone.
6"•"Bass:"The&bass&control&determines&the&amount&of&bass&frequencies&present&in&the&tone.&Turning&this&control&
too&far&towards&maximum&could&result&in&causing&the&overall&tone&to&seem&too&muddy.
towards&max&the&tone&will&become&more&compressed&and&distorted.&
7"•"OD"Gain:"The&OD&Gain&control&determines&the&amount&of&Overdrive&signal&that&is&fed&from&the&first&overdrive&
gain&stage&to&the&second&overdrive&gain&stage.&As&this&control&is&turned&towards&max&the&tone&will&become&more&
compressed&and&distorted.&
8"•"OD"Level:"The&OD&Level&control&determines&the&amount&of&Overdrive&signal&that&is&fed&from&the&Second&
Front Panel: Controls And Features
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Oldfield Amplifiers
User Guide
9"•"Master:"The&Master&control&determines&the&overall&loudness&of&the&lifier.
10"•"Reverb"Dwell:"This&control&determines&the&gain&(strength)&of&the&lifier&reverb.
11"•"Reverb"Mix:"This&control&mixes&the&reverb&and&the&dry&signal.&
Note"-"Use&the&Dwell&and&the&Mix&control&together&to&find&the&reverb&sound&that&works
best&for&you.
12"•"Speed:"This&controls&the&speed&of&the&lifier&tremolo.&As&the&speed&control&is&rotated&towards&maximum&
the&lifiers&tremolo&will&speed&up.&
13"•"Intensity:"This&control&determines&the&amount&tremolo&in&the&lifier&signal.&
14"•"Pilot"Light:"Illuminated&when&the&lifier&is&on.
15"•"Standby:"Switch&to&On&to&play&through&the&lifier.&Do¬&take&the&lifier&out&of&Standby&for&at&least&
30&seconds&after&turning&the&Mains&On&to&give&the&tubes&time&to&warm&up&to&operating&temperature.
16"•"Mains:"Switch&to&On&to&power&on&the&lifier.
Front Panel: Controls And Features - Continued
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Oldfield Amplifiers
User Guide
Rear Panel: Controls And Features
1"•"Fuse:"Slo&Blo&fuse.&Replace&only&with&recommended&value&stamped&on&the&back&of&your&lifier.&Failure&to&
comply&with&the&recommended&value&could&seriously&damage&the&unit.
2"•"Rectifier"Selector:"The&switch&will&allow&you&to&go&between&a&tube&rectifier&and&a&solid&state&rectifier.&The&solid&
state&rectifier&will&give&the&tone&a&slightly&tighter&feel&than&the&tube&rectifier.&Do¬&change&rectifier&settings&
unless&the&lifier&is&in&Standby&Mode.
3"•"Pentode"/"Triode":"Allows&user&to&select&between&full&and&half&power&output.&Do¬&change&power&settings&
unless&the&lifier&is&in&Standby&Mode.
4&•"Bias"Adjust:"Allows&a&technician&to&adjust&power&output&tube&bias.
5"•"Impedance"Selector:"Set&the&impedance&selector&to&match&the&impedance&of&the&attached&speakers.
6"•"Main"Speaker"Jack:"Connect&the&main&lifier&speaker&to&this&jack.&
7"•"External"Speaker"Jack:"An&external&speaker&can&be&connected&to&this&jack.
Note"-"A&speaker&must&be&connected&to&one&of&the&speaker&jacks&at&all×.&Failure&to&do&so&will&result&in&serious&
damage&to&the&unit.&
8•"Line"Out:"The&line&out&jack&provides&a&speaker&emulated&signal&that&can&be&send&to&an&external&lifier&or&PA.
9"•"OD"Trim:"The&OD&Trim&control&determines&the&amount&of&Clean&signal&that&is&fed&from&the&output&of&the&clean&
channel&to&the&first&overdrive&gain&stage.&As&this&control&is&turned&towards&max&the&tone&will&become&more&
compressed&and&distorted.&
10"•"Reverb"Out:"Connect&the&output&lead&from&the&reverb&tank&to&this&jack.
11"•"Reverb"In:"Connect&the&input&lead&from&the&reverb&tank&to&this&jack.
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Oldfield Amplifiers
User Guide
Rear Panel: Controls And Features - Continued
12"•"Clean"/"OD"Switch:"This&switch&selects&the&clean&or&overdrive&channel.&When&using&the&foot&pedal&this&
switch&should&be&in&the&OD&position.
13•"Footswitch:"Connect&the&input&1/4”&jack&on&the&foot&pedal&to&this&jack&to&control&switching&from&clean&to&
overdrive&using&the&foot&pedal.
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Oldfield Amplifiers
User Guide
Tubes
Tube layout as viewed left to right:
• Rectifier - 5R4 or GZ34
• Power Tubes - (2) 6L6
• Phase Inverter - 12AX7
• Tremolo Driver - 12AX7 or 12AY7
• Reverb Driver - 12AX7
• Overdrive - 12AX7
• 1st and 2nd Gain Stage - 12AX7 or 5751
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Oldfield Amplifiers
User Guide
Notes"About"Setting"Up"The"Overdrive
When&setting&up&the&overdrive&channel&the&player&needs&to&be&aware&how&the&audio&signal&flows&through&the&
amplifier.&Keep&the&following&items&in&mind&when&dialing&in&the&overdrive&channel.
1.&Start&with&getting&the&clean&tone&that&you&want&from&the&&using&the&volume,&tone&and&master&volume&
controls.
2.&The&output&from&the&clean&channel&feeds&the&input&of&the&overdrive&channel&after&all&the&tone&control&
settings&have&been&applied&to&the&audio&signal.&The&strength&of&the&signal&that&gets&sent&to&the&overdrive&
channel&is&determined&by&the&OD&Trim&control&setting&on&the&back&of&the&.&Turning&the&OD&Trim&up&will&also&
add&some&depth&to&the&overdrive&tone.&
3.&The&OD&Gain&control&receives&the&audio&signal&after&the&first&overdrive&gain&stage&and&determines&how&much&
of&that&signal&is&sent&to&the&second&overdrive&gain&stage.&Too&much&OD&Gain&and&the&tone&can&become&fizzy.
4.&The&OD&Level&control&receives&the&audio&signal&from&the&second&gain&stage&and&determines&how&much&of&that&
signal&is&sent&to&the&master&volume.&This&control&is&very&useful&in&matching&the&clean&channel&volume&with&the&
OD&channel&volume.&
Using&these&four&gain&controls&together&will&allow&the&player&to&dial&in&the&type&of&overdrive&tone&they&are&
looking&for.&Keep&in&mind&that&this&is&a&complex&gain&structure&and&it&may&take&the&player&a&little&time&to&
understand&how&each&control&affects&the&overall&tone.&
Page 9
Oldfield Amplifiers
Warranty
User Guide
The&following&warranties&apply&to&the&original&owner&of&the&lifier.&
All&warranty&work&must&be&performed&by&Oldfield&for&the&warranty&to&be&in&effect.
&Warranties&do¬&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&may&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&lifier.
Defects&Due&To&Workmanship&–&Oldfield&guarantees&the&lifier&to&be&free&from&workmanship&defects&for&5&
years&from&the&purchase&date.
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&lifier&owner.
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