audio-technica HPA-KG NARU Tube Headphone Amplifier User Manual

audio-technica HPA-KG NARU Tube Headphone Amplifier

Product Information

The NARUKAMI HPA-KG NARU is a tube headphone amplifier and pre-amplifier. It is designed to enhance the audio quality of headphones and other audio devices.

The amplifier measures 50cm x 20cm and weighs 50kg. It operates on AC power and has a power consumption of 1040 watts. The NARUKAMIfeatures a Class amplifier for optimal sound performance.

It has a 3.5mm input jack and an ON/OFF switch with an LED indicator. The amplifier also has built-in Wi-Fi capabilities with a 2m range. The package includes an AC power cable.

Product Usage Instructions

1. Connect the NARUKAMI amplifier to a power source using the provided AC power cable.
2. Turn on the amplifier using the power switch.
3. Choose the desired input source by adjusting the input selector switch.
4. Adjust the volume level using the volume control dial. This will control the volume for both the headphone output and pre-output.
5. Connect your headphones or audio device to the amplifier using the appropriate connectors. The amplifier supports both 6.3mm and XLR4 headphone connectors.
6. If using balanced headphones, connect them to the BALANCED1 or BALANCED2 outputs. For unbalanced headphones, use the LINE1output.
7. For balanced headphones, select the appropriate settings on the amplifier according to the user manual instructions.
8. Enjoy high-quality audio output through your headphones or audio device.

Dear valued customers

We would like to take a moment to express our sincerest gratitude for choosing our product. We are thrilled to have the opportunity to enhance your audio experience and provide you with high-quality sound.
Before using your new amplifier, we kindly remind you to read the user manual carefully before use. The manual contains important information such as basic precautions and guidelines for proper usage. We want to ensure that you have a seamless experience and get the most out of your new device.
At Audio-Technica, we take pride in creating products that exceed expectations and provide exceptional value. We understand that your time is valuable, and we have made every effort to design our amplifier to be user-friendly and intuitive. Again, thank you for choosing our product. We appreciate your business and look forward to serving you in the future. If you have any questions or feedback, please do not hesitate to contact us.

• Best regards,
• Audio-Technica Corporation

Introduction

Thank you for purchasing this Audio-Technica product. Before using the product, read through this user manual to ensure that you will use the product correctly. Please keep this manual for future reference.

• This product can only be used in the country in which it was sold.
• Please confirm that the voltage and power cord plug of the product are suitable for the country in which you live.

Safety precautions

Important information

Warning
To prevent fire or shock hazards, do not expose this apparatus to rain or moisture.

Caution

• Do not expose this apparatus to drips or splashes.
• To avoid electric shock, do not open the cabinet.
• Refer servicing to qualified personnel only.
• Do not expose this apparatus to excessive heat such as that generated by sunshine, fire or other heat sources.
• Do not subject this apparatus to strong impact.
• This apparatus should be located close enough to the AC outlet so that you can easily grasp the power cord plug at any time.
• In case of emergency, disconnect the power cord plug of this apparatus quickly.
• Do not place any objects filled with liquids, such as vases, on this apparatus.
• To prevent fire, do not place any naked flame sources (such as lighted candles) on this apparatus.
• Do not install this apparatus in a confined space such as a bookcase or similar unit.
• Install this apparatus only in the place where ventilation is good.
• To prevent fire, do not cover the ventilation of this apparatus with newspapers, tablecloths, curtains, etc.
• This apparatus with Class I construction shall be connected to the AC outlet with a protective grounding connection.
• This apparatus is not disconnected from the mains as long as it is connected to the AC outlet, even if the unit itself has been turned off.
• In order to maintain proper ventilation, do not place any objects around the rear of this apparatus.
• This apparatus should not be placed near to other electrical apparatuses.
• Keep the top of the apparatus at least 50 cm and the sides and back of the apparatus at least 20 cm away from any other surface if sitting on shelving, such as an audio apparatus rack. Failure to do so may cause this apparatus to overheat, which in turn may cause it or surrounding items to catch fire.
• The operating voltage of this equipment is factory-set and cannot be changed by the user. In order to prevent serious damage and in some cases the risk of fire, do not attempt to change the voltage of this equipment.

Notes on use

• Be sure to read the connected device’s user manual before use.

• Do not subject the product to strong impact to avoid electric shock, malfunction or fire.

• Do not store the product under direct sunlight, near heating devices or in a hot, humid or dusty place to avoid malfunction. Do not allow the product to get wet.

• The headphone output terminals of the product are for the use of stereo headphones only. Never connect devices other than stereo headphones.

• When connecting headphones with 3.5 mm stereo mini-plug, use a conversion plug adapter (sold separately). Note that depending on the shape of the conversion plug adapter, it may not be able to be pulled out of the jack.

• The contact pressure of the jack of the product is designed to be a little stronger in order to improve the sound quality. It may be difficult to remove some plugs (especially small plugs that are hard to grip) from the jack.

• Be sure to minimize the volume when turning the power on and off and when connecting headphones. Sudden loud sounds may have bad effects on hearing. Also, it may cause failure of the headphones.

• Please purchase the appropriate cable for the device to be connected.

• Make sure to insert the cable’s plug into the jack.

• Power off a device before connecting it to (or disconnecting it from) the product.

• This product uses vacuum tubes, so it will get hot, but this is not abnormal.

• Keep this product at least 2 m away from inverter-type fluorescent lamps, LED lamps, and wireless devices such as cell phones and Wi-Fi routers. Using them nearby could cause noise in the product.

• If the AC power supply environment is not suitable, use a commercially available audio power supply. Noise or fluctuations in the AC power supply may prevent this product from performing at its best.

• Whenever this product is transported, a special moving rack is required. Please contact our local Audio-Technica dealer for more information.

• This product uses vacuum tubes. To get sufficient sound quality, make sure to turn on the power and age it before using the product.
  (Before first use: more than 72 hours)
  (Before each use: more than 15 minutes)

• This product is made of natural wood. Since natural wood may deform or change color under hot, humid, dry, or ultraviolet (sunlight, fluorescent) conditions, be careful in these environments.

• The natural wood may scratch or split if subjected to impact. Do not drop the product or allow it to be hit by sharp objects.

Package contents

Before using this product, please make sure that all of the following items are included in the package. If some items are missing or damaged, contact your local Audio-Technica dealer.

1. Amplifier main unit
2. Vacuum tube (TA-300B) (replacement) x 4
3. Function explanation plate

There are no indications on the switches or dials of the amplifier itself. Place this function explanation plate in front of the amplifier main unit.

About the power cable
The product does not come with a power cable. Please check the specifications of the product and purchase a power cable (3-core, 3-pin).

Part names and functions

Front panel

1. Power indicator
   When the power switch is turned ON, the light blinks for about 90 seconds and then turns on. While blinking, it is warming up.

2. Power switch

3. Input selector switch

   • BAL1: Balanced 1
   • BAL2: Balanced 2
   • LINE: LINE 1

4. Output selector switch

   • PRE: Pre-output
   • XLR4: XLR4 balanced headphone output
   • HP: 6.3 mm headphone output

5. Headphone impedance selector switch

   • Select according to the impedance of the headphones.
   • 32: 32 ohms to 80 ohms
   • 150: 80 ohms to 250 ohms
   • 600: 250 ohms to 600 ohms
   • Also, select the impedance position to achieve the desired sound quality according to the type of headphones
   • and the genre of music played.
   • When pre-output is used, it is automatically set to 600 ohms internally.

6. Volume control dial
   Adjusts the volume of the headphone output and pre-output.

7. Left/Right balance adjustment dial
   Adjust the left/right volume balance.

8. XLR4 balanced output jack
   Connect headphones.

9. 6.3 mm headphone output jack
   Connect headphones.

Rear panel

1. Line pre-output terminal
   Connect to a power amplifier or similar device using an RCA audio cable.

2. XLR balanced pre-output terminal
   Connect to a power amplifier or similar device using an XLR-balanced cable.

3. Line input terminal
   Connect to a CD player or other device using an RCA audio cable.

4. Balanced input terminal 2
   XLR 3-pin balanced input.
   Connect to a CD player or other device using an XLR cable.
   For pin assignments, see “About connectors and plugs” (p. 9).

5. Balanced input terminal 1
   XLR 3-pin balanced input.
   Connect to a CD player or other device using an XLR cable.
   For pin assignments, see “About connectors and plugs” (p. 9).

6. Inlet for power cable (to AC IN)
   Connect the power cable. Be sure to check that the indicated AC voltage matches the voltage in the country of use. If the voltage setting is different, the internal voltage setting of the unit must be changed. Please contact our service center or distributor. This product does not come with a power cable. Please check the specifications of this product before purchasing and using the power cable (3-core, 3-pin).

7. Fuse holder

Use the specified fuse.

About connectors and plugs

Balanced pre-output connector

1. SHIELD/GROUND
2. + (HOT)
3. – (COLD

Balanced input connector

1. SHIELD/GROUND
2. + (HOT)
3. – (COLD

XLR4 balanced headphone output connector

1. L (+)
2. L (-)
3. R (+)
4. R (-)

About connectors and plugs

6.3 mm headphone output plug

1. Tip (Lch)
2. Ring (Rch)
3. Sleeve (GND)

Connecting method

Rear panel

• The product offers three inputs of audio signal, including two balanced inputs (Balanced 1 and Balanced 2) and one unbalanced input (LINE 1). Balanced audio, commonly used in professional and high-end consumer audio systems, is transmitted as the voltage difference between the non-inverted and inverted signals over three wires, resulting in a cleaner audio signal with reduced noise and interference. In comparison, unbalanced audio, found in consumer-grade devices, relies on two wires and shielding to protect the audio signal.
• Apart from its headphone amplifier function, the product can also serve as a preamplifier. Its high-quality Lundahl transformers and vacuum tubes provide exceptional audio quality, resulting in an extremely high-performance preamp audio output. The preamp is designed to amplify low-level audio signals from a source component, producing a warm and natural sound character from vacuum tubes, and bringing it to a level suitable for driving a power amplifier. The output terminals of the preamp are compatible with both balanced and unbalanced connections, making it suitable for different power amplifiers

Front panel

• The product features one 6.3 mm stereo headphone output terminal on its front panel and one XLR4 balanced headphone output. The headphone outputs can deliver up to 1600 mW of output power per channel and is compatible with headphones that have an impedance of 32 to 600 ohms.
• The product is a full-balanced headphone amplifier, and when the XLR4 balanced headphone output is selected, the left and right channels are each connected to separately: left +, left -, right +, and right -. By transmitting the audio signal via positive and negative wires, noise and interference are minimized. The positive and negative signals are transmitted in opposite phases, so any noise or interference affecting one positive signal will also affect the negative signal in the same way at the same time, resulting in the cancellation of the noise. Connected headphones require a 4-pin XLR connector with two wires on each side for positive and negative signals.
• Two headphones cannot be used at the same time.
• It’s important to note that the PRE, 6.3 mm, and XLR4 output terminals cannot be used simultaneously.
• The selection between these outputs needs to be made using the switch located on the front panel of the product

Using the product

To start using the product, follow these steps.

1. Connect the audio source to the product using interconnects and attach the headphone cable to the appropriate output terminals securely.
2. Attach the power cable to the rear IEC inlet of the product and plug the other end into a grounded AC power outlet.
3. Turn on the audio source and all other components but mute the audio output.
4. Turn on the power switch on the front panel to start warm-up and the power indicator will blink. Wait until it lights up.
   • The product has an automatic mute circuit that lasts about 90 seconds to allow the product to stabilize voltage before becoming active. Once activated, the power indicator will be lit up.
5. Choose the audio input selector switch based on the connection terminal of the audio source.
6. Choose the audio output selector switch based on the listening method and connection terminal, whether it’s the pre-output, XLR4 balanced headphone or 6.3 mm headphone output.
7. When listening with headphones on the product, choose the appropriate impedance setting for your headphones.
8. After setting the input and output, you can then unmute the audio player output, initiate the source playback, and adjust the volume as required.

To shut down the product, follow these steps.

1. Mute the audio player output.
2. Turn off the power switch on the front panel of the product.
3. Turn off the audio player and any associated input source components.

• It’s important to note that after turning off the product, you should wait at least five minutes before turning it back on. This allows the large bank of power capacitors to drain energy completely. Failing to wait long enough can lead to blown fuses or other damage to the product.

Amplifier circuit block diagram

Cautions for using the product as a preamplifier

Since this product uses vacuum tubes, sufficient sound quality may not be obtained when loud playback is performed through speakers. To ensure optimal performance, consider the following suggested layouts when using the product output with speakers:

If the speaker’s woofer is on the front
It is recommended to avoid placing the product directly facing the sounding position of the speaker. Instead, it’s suggested to place the amplifier in the center of the back of the woofer. This will help to minimize the impact of loud sounds on the vacuum tube and ensure optimal performance and sound quality. By placing the amplifier in this position, you can help to ensure that the sound waves from the speaker do not directly impact the vacuum tube, which can cause distortion and negatively impact the sound quality

If the speaker’s woofer is on the rear or side
It is recommended to position it in front of or to the side of the listener to prevent sound waves from directly impacting the vacuum tube and causing distortion. This positioning allows the sound waves from the speaker’s woofer to reach the listener first, improving sound quality and ensuring optimal performance. It is important to note that the exact positioning of the product will depend on the specific speaker setup and the preferences of the listener. Experimenting with different positions can help to determine the optimal placement for the product in your specific setup.

For even louder playback or better bass
If you are looking for even louder playback or better bass from the product, one option is to install acoustic shielding that matches the environment in which it will be used. Acoustic shielding can help to reduce unwanted noise and vibrations that can negatively impact the performance and sound quality of the preamplifier. Acoustic shielding is typically made from materials such as fiberglass or acoustic panels, and can be installed around the amplifier to absorb or deflect sound waves. When selecting acoustic shielding, it’s important to choose materials that are appropriate for the specific environment in which the preamplifier will be used. For example, if you’re using it in a small room with hard surfaces, you may need more absorbent materials to prevent sound reflections and echoes. On the other hand, if you’re using it in a larger room with soft surfaces, you may need more reflective materials to help distribute the sound throughout the space. By installing acoustic shielding that matches the environment in which it will be used, you can help to ensure optimal preamplification performance and sound quality from the product.

Cleaning

• Get into the habit of regularly cleaning the product to ensure that it will last for a long time.
• Use a dry cloth to clean the product. Do not use alcohol, paint thinners or other solvents for cleaning purposes.

Troubleshooting

In case the equipment is not functioning correctly, please check the following. If the issue persists even after checking the suggested points, be sure to unplug the power cable from the outlet and contact your local Audio- Technica dealer for assistance.

Power is not supplied

Ensure that the power cable connections between the wall outlet and the product power supply are
inserted firmly.

• If the product is plugged into an AC line conditioner, make sure the line conditioner is turned on.
• Check the circuit breaker for the AC circuit that the product is plugged into. If the breaker is tripped, flip it back on. If it does not turn on, there may be a short circuit in the lines or in a device connected to the AC circuit. Check the power cables for your components to make sure none have been damaged.
• If none of these conditions restores power, it’s possible that one of the product’s internal fuses is blown.
• Do not attempt to change the fuse by yourself, as the product requires special high-voltage fuses that are not commonly available. Contact your local Audio-Technica dealer for service.

No sound is heard

• Verify that the audio source is playing.

• Check that the product is turned on and that the headphones are connected correctly according to the
  output selection.

• Ensure that the product volume setting is not too low.

• Ensure that the audio player volume setting is not too low.

• Verify that the correct input selector switch is selected on the product

Sound is faint / Sound is distorted

• Adjust the volume of the audio source to a medium level if the audio signal is too low or too high.
• Increase or decrease the signal level of the audio input if it is adjusted too low or too high.
• Make sure that the appropriate headphone impedance is selected and matches your headphones.

Audio only plays in one ear

• Check that the audio cable is properly connected to the playback device.
• If one tube is defective, replace it or contact Global Support : www.at-globalsupport.com for assistance.

Sound does not start immediately after power-on

• Please wait for about 90 seconds for the sound to start playing once the circuit is stable.

Dimensions

Specifications

1 kHz): 1600 mW + 1600 mW (32-ohm load)

1300 mW + 1300 mW (150-ohm load) 1000 mW + 1000 mW (600-ohm load) Balanced output (10%, 1 kHz):

1600 mW + 1600 mW (32-ohm load) 1300 mW + 1300 mW (150-ohm load) 1000 mW + 1000 mW (600-ohm load)

Maximum output level| Pre-output (10%, 1 kHz): Balanced pre-output: 35 dB Line pre-output: 29 dB
Frequency response| Headphone output: 10 Hz to 60 kHz (±3 dB)

Pre-output: 10 Hz to 90 kHz (±3 dB)

Total harmonic distortion| 0.8% or less (at 10 mW output, 20 Hz to 20 kHz) 0.08% or less (at 10 mW output, 1kHz)
Gain| 6.3 mm (1/4”) headphone output / balanced output: 15 dB (32-ohm load)

17  dB (150-ohm load) 18 dB (600-ohm load) Pre-output:

18  dB (balanced pre-output) 12 dB (line pre-output)

Noise| 6.3 mm (1/4”) headphone output / balanced output:

-98 dBv or less (A-weighted)

Separation between channels| Single-end output: 68 dB (Load: 32 ohms, 1 kHz) XLR4 balanced output: 100 dB (Load: 32 ohms, 1 kHz)
Analog input terminal| RCA jack line input x 1 XLR balanced input × 2
Headphone output terminal| 6.3 mm (1/4”) stereo headphone output × 1 XLR4 balanced stereo headphone output × 1
Input switching| BAL1: Balanced1 BAL2: Balanced2 LINE: LINE1
Output switching| PRE: Pre-output

XLR4: Balanced headphone output HP: 6.3 mm (1/4”) headphone output

Headphone impedance switching| 32: 32 to 80 ohms

150: 80 to 250 ohms

600: 250 to 600 ohms

Power input terminal| IEC Type (Class I)
Power supply| 100 V AC, 50/60 Hz; 110 V AC, 50/60 Hz; 120 V AC, 50/60 Hz

220 V AC, 50/60 Hz; 230 V AC, 50/60 Hz; 240 V AC, 50/60 Hz

115 W

(Switched with jumper wire inside product)

Power transformer| EI core transformer × 2 (L/R separated power supply) R core transformer × 1 (for control)
---|---
Vacuum tube| TA-300B (TAKATSUKI) × 4, ECC83S Gold (JJ-electronic) × 4, GZ34S (JJ-

electronic) × 2

Audio output transformer| LUNDAHL (amorphous core, silver wire) × 4
Dimensions| 493.5 mm (19”) × 409 mm (16”) × 352.5 mm (14”) (W × D × H)
Weight| Approx. 50 kg (110 lbs)
Accessories| Vacuum tube (TA-300B) (replacement) × 4, Function explanation plate

• For product improvement, the product is subject to modification without notice.

Warranty

• The product comes with a three-year warranty against defects in workmanship or materials from the date of purchase. Please note that the warranty is non-transferable.
• The warranty is void if the product has been subject to misuse, or negligence or has been modified, repaired or opened by a non-authorized person without the written authorization of Audio-Technica.
• When returning the product to our premises, please use the original flight case for transport. Please note that we are not responsible for any damages incurred during transport, and any repairs required due to transport damage will be charged. We recommend purchasing transport insurance. If you no longer have the original flight case, please contact your local Audio-Technica dealer.
• To service your product, please reach out to your local Audio-Technica dealer. For additional assistance or globalsupport, please visit www.at-globalsupport.com.

Audio-Technica Corporation

• 2-46-1 Nishi-Naruse, Machida, Tokyo 194-8666, Japan
• www.audio-technica.com.
• ©2023 Audio-Technica Corporation
• Global Support Contact: www.at-globalsupport.com.

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