Jad Freer Volta Bass Amp

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Specifications

• Product Name: VOLTA all-tube bass head

• Made in: Italy

• Power Rating: 200W

• Tubes: 3x ECC83/12XA7 in the preamp section, 4x KT88 tubes in
  the power amp section

• Warranty: Lifetime warranty against defects in materials and
  workmanship; external parts have a 24-month warranty

Product Usage Instructions

Front Panel Controls & Features

Details on the front panel controls and features…

Rear Panel Controls & Features

• MAINS IN: Connect the power cable provided.
  Use a high-quality cable if needed.

• SPEAKER OUT: Connect speakers using combo
  outputs (1/4 jack or Speakon). Ensure proper ventilation.

• OHM: Select the total minimum impedance of
  connected cabs. Do not adjust while powered on.

• PREAMP OUT: Driven by a dedicated triode for
  signal readiness for pedals or effects.

• POWER AMP IN: Connects to another triode for
  signal enhancement.

• GND/LIFT: Eliminates unwanted hum in the DI
  signal by interrupting ground loops.

• POWER TUBE OPERATION LEDS: Indicate fuse
  failure for power tubes and high voltage sections.

The VOLTA is a hand-made product designed for music enthusiasts.
Connect a mono source to the INPUT jack to start using the amp.

FAQ

Q: What should I do if my product gets damaged?

A: Contact JF Audio for repair instructions. The product comes
with a lifetime warranty against defects.

Q: How do I connect my speakers to the amp?

A: Use the combo outputs (1/4 jack or Speakon) on the SPEAKER
OUT port. Ensure proper ventilation around the amp.

Q: Can I use different impedance cabs with this amp?

A: Use the OHM switch to select the total minimum impedance of
connected cabs. Avoid mixing different impedance cabs while the amp
is powered on.

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MANUAL
Latest update May 2024
Thank you for purchasing a JF Audio product! Your amp has been carefully hand- made in Italy, using only the best parts available. It is our hope that this amp will become a mainstay of your rig for many years to come.
With this document, JF Audio ensures you a life-time warranty against defects in materials and workmanship; external parts like pots, jacks and switches have a 24 months warranty. In the event that your product becomes damaged, contact JF Audio and you will receive instructions on how to go about having your amp repaired.
VOLTA
all-tube bass head
Named after the Italian physicist genius Alessandro Volta (ever heard of Voltage? That’s after him), the VOLTA all-tube bass head is the pinnacle of JF sound and philosophy, embracing the best of old school sound and modern technology and construction. The VOLTA features the best of both heritages of classic tube amplification: an “American” style tube bass preamp with a classic and organic “James” style passive tone stack paired with a “British” style all-tube 200W power amp with four KT88s. Thanks to our proprietary switching power supply the response is quicker and fuller, keeping dimensions compact and a super-light weight. The VOLTA is a powerful, rugged and compact bass amp featuring a traditional voiced tube preamp and passive tone stack, paired with a tube power amp fed by our proprietary switching power supply. The VOLTA merges the very best heritage of American and British all tube designs with modern technology and features. Our proprietary switching power supply is the key factor for a bigger tone, faster transient response and better damping factor, international dual voltage operation (115/230V) and a light weight. Floor noise is close to zero, as also transformer-related noise. Low running internal fans keep the custom vented chassis cool. A good amount of custom internal and external parts, including custom aluminum knobs, are the icing on the cake of one of the very best and unique amplifiers on the market.
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FRONT PANEL CONTROLS & FEATURES
INPUT This 1/4″(6,3mm) jack is the mono instrument INPUT, connect your bass (or mono source) here! The signal will be processed by the preamp and will be present at DI out, PREAMP OUT and SPEAKER OUT. Input impedance is 3.3 MOhm. BYPASS This switch bypasses the passive tone stack and changes the feedback circuit; you’ll experience a higher gain and a more hi-fi, open sound with less “tube-compression” flavour. GAIN This logarithmic pot controls how much of the first tube stage goes into the second tube stage. You can start around noon and turn counter-clockwise for a clean and fast sound or clockwise for a more fat sound. High gain settings result in a pleasant overdriven sound. The tube (1x12AX7) preamp circuit is fed by our switching power supply and it’s based on the iconic design of the B15, modded to our taste. BASS & TREBLE We choose to use an old school passive design for the bass and treble eq; this is traditionally referred to a baxandall or James style eq. and it’s a popular style found in American tube amps. You can experience a “flat” curve when controls are around noon and then boost or cut frequencies. These controls operate on a very broad frequency range and sound very organic and musical. Use them without fear of messing with your tone. MASTER This logarithmic pot controls the overall volume of the SPEAKER OUT. We tailored it to be useful in all its curve but beware: the VOLTA can be a very loud amp so start with a low setting. STBY / POWER Before plugging in the VOLTA check that the STANDBY and POWER switches are in the off (down) position. Start turning on (up) the POWER lever switch, you’ll see a blue led light over the POWER switch and a red led light over the STANDBY switch. In this setting the preamp is 100% working and the power amp is shut off, this makes silent recording operation possible because DI (pre and post) and PREAMP OUT are working.
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When the STANDBY switch is in the ON (up) position, the red led light becomes green and power is slowly given to the power amp section to fully operate the head. While the VOLTA by itself can be safely fully on (green and blue lights on) without any cab connected, it’s important to have a cab connected when playing and raising master volume so we suggest always checking for a connected cab before turning on the amplifier. Any damage to the output transformer due to mishandling is not warranty covered.
REAR PANEL CONTROLS & FEATURES
VOLTAGE SELECTOR This switch allows the amp to be used with international voltages (115-230VAC). The amp is shipped to the new owner with the switch set correctly, according to the Country indicated in the address. It’s very important to NOT mess with this control. If you travel the world with your VOLTA please remember to set the switch to the right voltage BEFORE turning it on. The VOLTA is internally protected by a series of circuits designed for a safe operation, even from an event of voltage mismatch, but permanent damage – not warranty covered – could occur.
MAINS IN Connect here the power cable provided. If your Country needs a different outlet plug use a high quality cable (1mm2 or 0.75mm2 core).
SPEAKER OUT Connect your speakers here, using these combo outputs (1/4″ jackSpeakon). Always provide open ventilation around the amp. Power rating is 200W.
OHM Use this switch to select the TOTAL minimum impedance of the cabs connected to the amp. Do not mess with this control while the amp is powered in and sounding. (If you mix 8 and 4 Ohm cabs you get 2,6 Ohm so use the 2 Ohm setting)
PREAMP OUT It’s driven from a dedicated triode (tube) that set the signal to be ready for pedals, effects units or a slave output to another amp or power amplifier
POWER AMP IN Goes into another triode (tube) that raises the signal adding natural tube overtones.
D.I. OUT (transformer balanced) This XLR output is fully balanced and it’s made by a solid state buffer driving a linear transformer. The kind of DI signal can be selected with a three position switch: PRE it’s the signal taken after the very first tube stage so it’s not affected by GAIN or other controls, in POST the signal it’s taken after the GAIN and EQ stages, before MASTER control while AMP setting is for the signal taken after the output transformer so it carries the full sound of the amp. DI volume can be fine tuned with a dedicated LEVEL pot on the back.
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GND/LIFT This switch eliminates or reduces unwanted hum or noise in the DI signal by interrupting the ground loops between equipment.
POWER TUBE OPERATION LEDS Each led is connected to a dedicated fuse and, if ON, indicates a fuse failure. There are four fuses, one for each power tube and two more for the high voltage sections of the amp.
TUBES The VOLTA uses 3x ECC83/12XA7 in the preamp section and 4x KT88 tubes in the power amp section.
REPLACING TUBES / SERVICE please refer to a professional technician to replace tubes (or any operation that requires opening the chassis). There are two connectors in the back that should be used to measure tube values. All the info for servicing the head and tuning bias are written on the PCB. The head has been made to be easy to service and maintain, without any old stock or obscure component, internal PCBs are made to be exchanged without soldering and every component or function is clearly understandable.

The VOLTA is a work of love and dedication, conceived and hand-made by the JF AUDIO team for you to make music (and make your life easier). Now connect a mono source to the INPUT jack and enjoy the amp!
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