HA 6AMK2 - Audio Amplifier Cayin - Free user manual and instructions

Brand	Cayin
Model	HA-6A MK2
Product type	Tube headphone amplifier
Configuration	Two chassis: separate power supply and amplifier
Power supply dimensions	160 × 297 × 185 mm
Amplifier dimensions	285 × 297 × 185 mm
Power supply weight	8.2 kg
Amplifier weight	11.2 kg
Power consumption	130 W
Tubes used	2 × JJ 12AU7/ECC82, 2 × Genalex KT88, 2 × JJ GZ34/5AR4
Maximum headphone output power	Up to 4500 mW + 4500 mW (4-pin XLR, ultralinear)
Headphone load impedance	8 to 600 Ω, selectable (L / M / H)
Audio inputs	XLR balanced, RCA unbalanced
Headphone outputs	6.35 mm, 4.4 mm balanced, 4-pin XLR
Preamplifier output	RCA (PRE-OUT)
Operating modes	Triode / Ultralinear, switchable
Soft start	Yes, approximately 60 seconds
Remote control	Yes
Frequency response	10 Hz – 26 kHz ±3 dB
Signal-to-noise ratio	104 dB (A-weighted)
Distortion (THD+N)	≤ 0.3% (1 kHz, 200 mW)
Maintenance	Clean with a dry cloth only
Safety	Do not open the device; risk of electric shock
Spare parts / repairability	Spare tubes and fuses included, replaceable by a qualified technician

Frequently Asked Questions - HA 6AMK2 Cayin

How to choose between Triode and Ultralinear modes?

The Triode mode offers a warmer, richer and more natural sound, ideal for vocals and acoustic music. The Ultralinear mode delivers more power and extension, with a dynamic and authoritative sound, perfect for music that demands punch and control.

How do I select the output impedance for my headphone?

Use the impedance selector according to your headphone's value: L for 8 to 64 Ω, M for 65 to 250 Ω, H for 251 to 600 Ω. An incorrect selection can degrade the sound quality.

What tubes are used in the HA-6A MK2 and how to replace them?

It uses two JJ 12AU7/ECC82, two Genalex KT88, and two JJ GZ34/5AR4. To replace them, turn off and unplug the device, remove the cover, then replace the tubes respecting their position. If you are not comfortable, call a qualified technician.

Why must the protective foams be removed before the first power-on?

The foams protect the tubes during transport. If they are not removed, they can cause overheating or fire. Check the tube cover and remove all foams before connecting the amplifier.

What to do if the amplifier does not turn on?

Check the power cord, the external fuses, and make sure the switch is properly positioned. If the problem persists, consult a technician.

Can I connect my sources in XLR and RCA at the same time?

Yes, but it is recommended to select only one source at a time to avoid interference. Use the SOURCES selector on the front panel to choose XLR or RCA.

Does the remote control allow volume control?

Yes, the included remote control allows you to increase, decrease the volume and put the device on standby. It is convenient for adjusting the level remotely.

What safety precautions should be followed?

Unplug the device if unused for a long time, do not expose it to moisture, ensure good ventilation, and never remove the internal cover. Failure to comply may result in electric shock or fire.

How to clean the amplifier?

Use a dry cloth to dust the chassis. Never use liquid, solvent, or abrasive products that could damage the finish.

What is the function of the soft start?

The soft start of approximately 60 seconds prevents surges at power-on, which protects the tubes and extends their lifespan.

USER MANUAL HA 6AMK2 Cayin

HA-6A MK2

HEADPHONE AMPLIFIER

Thank you for choosing Cayin HA-6A MK2 Headphone Amplifier.

We have inserted protective foam inside the Vacuum Tube Cage in order to protect the vacuum tubes during transportation. Please remove these foams before you connect the amplifier into your sound system. Fail to do so might cause serious damage to the amplifier or disaster such as fire accident.

We have prepared this user manual to help you understand the features and get familiar with the operation of the amplifier. We suggest all customers read through this manual before they start to use the device.

Table of Contents

Table of Contents.... 1

Package Contents.... 2

Safety Precautions.... 2

Product Features.... 3

Specifications.... 4

Precautions.... 5

Front Panel Functional Description.... 6

Rear Panel Functional Description....7

Top Panel Functional Description.... 8

Vacuum Tube Substitution.... 8

System connection.... 10

Connect to Headphones.... 11

Turning on.... 12

Small Tips.... 12

Warranty Service.... 12

Basic Operation.... 13

Troubleshooting.... 14

How to Install Vacuum Tubes.... 15

Follow us.... 16

Package Contents

Please place the box in upright position according to the marking of the package. Please examine the product package before you open it, the package should be free from any physical damage or water stain. You should find the following items when you open the package:

1. Cayin HA-6A MK2 x1
2. User's Manual x1
3. AC Power Cord x1
4. Umbilical Power Cable x1
5. Remote Control x1
6. Spare Fuses:

①.External Main Fuse x2 (\~220V-240V: T1AL250V; \~100V-120V: T2AL250V)
②. External Fuse for High Voltage x2 (T160mA E250V)

Safety Precautions

1. Unplug the power cord if you are not going to use the product for an extended period of time.
2. The machine will become hot after working for a long time. Please keep the unit's ventilation open and install the amplifier at a well-ventilated place to avoid troubles and fire hazard.
3. Forbidden to operate when the output is open or shorted.
4. Do not attempt to service this product yourself. Opening the cover may expose you to dangerous voltage or other hazards.
5. We are not responsible for any problems caused by checking and opening without permission of our company. For service, Please contact a qualified service technician.
6. Do not place any objects filled with liquids such as vases or some others on the top or around.
7. Clean only with dry cloth.
8. Please move the amplifier carefully not to drop the unit or be subject to other strong shocks.

Product Features

◆ Point to point wielding with premium wire. The entire circuitry is handwired by skillful craftsman.
◆ Matched-pair custom build EI output transformers.
◆ In-house Designed Premium Toroid Power Transformer with high inductance and high efficiency.
Split Design for Cleaner Sound: The power supply and audio circuit are placed in separate units to reduce interference and provide cleaner power to the audio section.
◆ Stable and Quiet Power Supply: Different parts of the circuit use their own power supplies. The voltage amplifier gets a low-noise regulated power source for better performance and sound quality.
◆ Pure Single-Ended Amplifier: The amplifier uses a single-ended design to keep the music natural and highlight its warm, rich character.
◆ Two pieces JJ GZ34/5AR4 are applied for power rectification.
◆ JJ 12AU7/ECC82 are used for voltage amplification.
◆ Genalex KT88 are used for power amplification.
◆ High quality Neutrik 6.35mm single-ended headphone, NIPPON DICS 4.4mm balanced headphone, and Neutrik 4-pin balanced headphone are included.
In -house designed output transformers provide three set of impedance matched outputs (High, Mid, Low) from 8Ω to 600Ω at your direction.
◆ Two sets of line input XLR balanced RCA single-ended. One set RCA PRE-OUT connector.
Dual operation mode Triode & Ultralinear. Triode mode is tendering, rich in harmonic, smooth, iush and holography. Ideal for vocal and string music. Ultra-linear mode can improve power and extension. Clean, energetic, and authoritative. Ideal for music requires a lot of punch, dynamic and control.
◆ Strong output power to match with wide range of headphone in the market.
◆ Lock on and quick-release aviation grade copper connectors with silver plated Teflon umbilical cable provides low internal resistance, low dissipation, and more stable transmission for outboard power supply connection.
◆ Soft start function (about 60 seconds).
◆ Equipped with remote control.
◆ Design with an innovative circuit layout and highly effective shielding consideration, the components will function at premium environment to ensure high quality audio performance form the amplifier.
◆ Equipped with easily-installed tube cover for protection.

Specifications

◆ To reduce the risk of electric shock, do not remove the cover.
◆ No user serviceable parts inside. Refer servicing to qualified service personnel.
◆ To reduce the risk of fire or electronic shock, do not expose the unit to rain or moisture.

The lightning flash with arrowhead symbol is intended to alert user to the presence of uninsulated “dangerous voltage” within the product's enclosure that may be of a risk shock to persons.

The exclamation point is intended to alert user to the presence of important operation and maintenance (servicing) instructions accompanying the appliance.

Recommendation: Cayin HA-6A MK2 Headphone Amplifier is designed and manufactured with our original parts and reaching the best results. We are not responsible for problems and damages caused by non-original parts replacement in the amplifier. Please keep all packaging materials for future use as you may need to repackage the amplifier in the future. Please fill in the product warranty card immediately and mail it to authorized dealer to safeguard your after-sales service.

Note: Please make sure local voltage level is matched with the input level of the amplifier, which indicates on the rear panel. Too low or too high voltage may cause problem. Please contact our company or our local agent if you've found improper voltage.

Precautions

1. Connecting the power supply unit and AC socket.

After connecting with the audio source, connect the quick-release power supply cable between the main unit and the outboard power supply unit, then connect with power supply unit to an AC power supply socket with the power cable.

1. Connecting and disconnecting of the quick-release power supply cable.

Connecting: Align the slots (marked with the red dot) of the connector with the slot (marked with the red dot) of the socket of the power input/output on the machine (Figure 1), and plug the power cable to connect.

Disconnecting: Firmly hold the lock ring of the connector and pull it out (Figure 2), the power supply cable would be disconnected.

There should be sufficient space around the power outlet to facilitate plugging and unplugging the power cord.

Front Panel Functional Description

Diagram 1: HA-6A MK2 Front Panel

①. Power On/Off: Turn on and off the amplifier. Press "down" the button to turn on the amplifier, Press again the button will resume to original position and the amplifier will power off.
②. Power Indicator: Indicate the working status: The indicator will remain always on when the amplifier is in regular operation
③. Headphone Output Selector: With the switch you can select the suitable type of headphone output. HA-6A MK2 offers three types output.
④. STANDARD: Output for headphones terminated in 6.35mm TRS connector
⑤. 4. 4 Balance Output: 4. 4 balance output for headphone terminated in 4. 4mm connector.
⑥. 4PIN BALANCE: Output for headphones terminated in 4pins XLR connector
⑦. IMPEDANCE: Select the most desirable: impedance-matched output from the amplifier, three options were offered: (L:8\~64Ω; M:65\~250Ω; H: 251\~600Ω)

⑧. VU meter: monitor output level of the amplifier
⑨. TR/UL: Used to select the operation mode between Triode and Ultralinear.
⑩. SOURCES: select balanced or single-ended input
⑪. Working State Indicator/Mute Indicator

Used to indicate the working state. The indicator will be on when it is working normally. The indicator will flicker for 60 seconds when it delays to work. The indicator will keep flickering when it is at mute state.

⑫. Volume Knob

Used to control volume

⑬. IR Remote Sensor

Used to receive the code of remote control.

Attention:

◆ If you want to connect a 3.5mm terminated headphone to the amplifier, you need a 3.5mm to 6.3mm adapter (not included in the package).
◆ Listening through headphones at a high volume for extended periods of time can result in hearing impairments.
◆ Please do not use mono (TS) phone plug with this amplifier as this might cause serious damage such as short circuit in the amplifier.
◆ Please unplug the power plug from AC power circuit if the amplifier is not used for a long time.

Rear Panel Functional Description

Diagram 2: HA-6A MK2 Rear Panel

①.Balanced input (XLR)

Connect a balanced audio input to the amplifier. Please make sure the left and right channel is connected correctly

②.Single-ended input (RCA)

Connect a single-ended audio input to the amplifier. Please make sure the left and right channel is connected correctly

③.PRE-OUT:

Connect to Amplifiers with Pre-In Input.

④.Output Selection Switch:

Select PRE-OUT or headphone out.

⑤.HV FUSE: (T160mA E250V)

⑥.Power Input for Amplifier Unit.

⑦.Power Output from Power Supply Unit.

⑧. AC Power Input with Fuse Holder:

Please replace fuse with the same specification

Attention:

Please make sure the AC voltage of your local power supply match the voltage of the amplifier. Cayin will not be responsible for the damage or accidents such as fire caused by incorrect input voltage

Top Panel Functional Description

Diagram 3: HA-6A MK2 Top Panel

①. V3、V4: JJ GZ34/5AR4 Vacuum Tube
②. A1、A2: Genalex KT88 Vacuum Tube
③. V1、V2: JJ 12AU7/ECC82 Vacuum Tube

Attention:

◆The vacuum tube will become very hot during operation, please be careful and don't get burned.
◆ Please turn off the amplifier for 20 minutes before replacing the vacuum tube. Hold the base of vacuum tube firmly and to avoid damaging the fragile part of the vacuum tube.
When install vacuum tube to the amplifier, position the vacuum tube correctly according to the alignment pin before push the vacuum tube base into the socket.
◆Only used matched pair KT88 and 12AU7 in the HA-6A MK2 amplifier.

Vacuum Tube Substitution

Vacuum Tube	Acceptable Substitution
Genalex KT88	EL34、KT66、6CA7、6L6、KT77、KT88、6550、KT90、KT120、KT150
JJ GZ34/5AR4	GZ34、GZ37、5AR4、5V4G、5R4G、5U4G、5Y3GT、5DJ4
JJ 12AU7/ECC82	12AU7、ECC82、ECC802S

Remote Control

①. MUTE Button
②. Volume UP and DOWN Button

Effective Distance: about 6 meters.

Installation:

1. Remove the screws from the back cover of the remote.
2. Clean the battery holder thoroughly, ensuring there is no dust or grease.
3. Hold the battery by its edges, align it with the battery compartment, and gently press it in until it is flat and secure.
4. Screw the battery cover back into place.

NOTE:

◆ Please handle the remote control with care and keep it in a dry environment.
◆ The battery has a lifespan of approximately three years. Replace the battery promptly when its capacity is insufficient.
◆ Please use the CR2032 lithium coin cell battery.
When replacing the battery, do not touch both the positive and negative terminals simultaneously. Remove and install the battery by holding it from the edges.

System connection

This section will illustrate how to connect audio equipment to the HA-6A MK2 amplifier.

BALANCE Socket:

1. The BALANCE socket is with XLR input. The functions are following:

◆ Music signal is transferred as balance signal without the outside disturbance.
◆ Professional XLR connectors are used to raise reliability of connection.

1. In the following two systems, professional XLR connectors are used for inside connection.

a. USA System:

①PIN1 : GND;

②PIN2 : HOT;

③PIN3 : COLD

b. European System:

①PIN1 : GND;

②PIN2 : COLD;

③PIN3 : HOT

1. This amplifier uses the USA System.

If the XLR balance connector is used by European system, the restored signal of pre-amplifier or main amplifier will be inverse. Therefore, please setup the correct phase in advance.

Attention to Audio Connection:

1. Please refer to the manual of associated equipment whenever necessary.
2. Do not connect the power cord until all equipment are properly connected
3. "R" indicates the right channel; "L" indicates left channel.
4. Please make sure all connectors are securely installed. Bad connection might cause noise and degrade in audio performance, or even damaging your equipment.
5. Please do not tie the power cord, audio interconnects, and speaker cable together or run them in parallel because this will produce adverse effect on audio performance.
   Note: Please make sure + and -, left and right are connected properly.

Connect to Headphones

Selecting Headphone Connection provided three types of headphone output: 4-pins XLR for balanced, 4.4mm Balanced, 6.35mm for singled-end, we have optimized the headphone amplifier to perform satisfactory for all outputs, user are free to use any headphone output according to their need without worrying one is better than the other.

Single-ended Headphone Connection

• HA-6A MK2 provides one set of 6.35mm headphone input, the pin definition of the headphone connector is as illustra
• Headphones terminated with 3.5mm connector will require a 3.5mm to 6.35mm adapter in order to use it with this headphone amplifier.

4.4mm Balanced Headphone Connection

• HA-6A MK2 provides one set of 4.4mm headphone input, the pin definition of the headphone connector is as illustrated.
• Headphones terminated with 2.5mm connector will require a 2.5mm to 4.4mm adapter in order to use it with this headphone amplifier.

XLR Balance Headphone Connections

• HA-6A MK2 provide one set of 4-pin XLR headphone input, the pin definition of the XLR connector is as illustrated.
• Headphones terminated with dual XLR (3-pins), 4.4mm or 2.5mm balanced headphone connectors will require corresponding XLR4 adapter in order to use it with this headphone amplifier.

IMPEDANCE matched output

• Headphones are currently available from 8 to 600, in view of this wide range of impedance rating, HA-6A MK2 provides three sets of impedance matched outputs (L:8\~64; M:65\~250; H: 251\~600) to ensure the headphone amplifier can handle vast variety of headphones satisfactory.
• We recommend users to start with the output setting that match the impedance rating of your headphone.
• It is technically safe to select any impedance setting for your headphone. You can try other impedance setting without worrying causing any damage to your headphone.

Attention:

◆Balanced headphones can convert into single-ended headphone with appropriate converter and use the 6.35mm headphone output.
◆ Single-ended headphone cannot use an adapter to plug into the XLR4 balanced headphone output of the HA-6A MK2, it can cause damage to your headphone and/or headphone amplifier.
◆Turning the volume to the minimum when you exchange the Headphone.

Turning On

Before turning on the amplifier please make sure all connections are right and power supply is stable.

◆ Turn on the amplifier, the power indicator will be on and the working indicator will keep flickering.
◆ The working indicator will be on after 60 seconds. It means that the amplifier is working normally. If the working indicator is off, please turn off the power and contact with our local agent or our company.
◆ Select the right audio source channel, adjust the volume to a certain position and then you can enjoy the music you prefer.

NOTE: 1. When the audio system is under working state, don't unplug the signal cable or speaker cables, or it will cause damage to the amplifier and other equipments.

1. It should at least takes 2 minutes before you turn on the power again, or it will cause damage to the vacuum tubes.

Small Tips

Read the Manual —— Please read the user's manual carefully before installation and operation.

Keep the Manual —— Please keep the manual for future reference.

Warning Signs —— Don't tear off or rub off the serial number.

Operation —— Do the operations as you are instructed in the Manual.

Parts —— If you are going to use parts not supplied by our company like power cord, fuses etc please make sure that parts you used are compatible with the safety requirements. Or it will cause fire or electric shock.

Placement —— Put the amplifier on a level place. Make sure that it doesn't bring damage to the children, adults and the amplifier itself.

Power —— Please make sure the local voltage is the same level as indicated on the rear panel.

Overload —— If the power socket is overloaded with other equipment, it will cause fire or electric shock.

Warranty Service — Do not open the product and change the components inside yourself. Opening the cover may expose you to dangerous voltage or other hazards. The warranty doesn't extend to any product that has been opened by you without permission of our company.

Troubleshooting ——If you encounter any abnormal behavior during setup or playback, please refer to the advice in next pages of this manual to recover your amplifier back to normal operation. If you fail to rectify the problems after that, please contact your authorized dealer for technical support.

Warranty Service

1. The Product is warranted for a period of twelve (12) months from the date of original purchase (the “Warranty Period”). Replacement Products are warranted for the remainder of the original twelve (12) month warranty period. Six-month warranty on stock vacuum tubes.
2. The defective product must be returned to your dealer or our company for repairing when your dealer or our company accepts your requirement.
3. The warranty doesn't extend to any product that has been opened by you without permission of our company.

NOTE: The information in this manual is subject to change without further notice.

Basic Operation

Please make sure all connections are correct and power supply voltage is stable before turn on the amplifier.

1. Turn on the amplifier, the power indicator will light up.
2. When the power indicator remains lighted up steadily, the amplifier is ready for operation. If the power indicator will become steady (always ON). It means that the amplifier is ready for operation. If the power indicator did not light up, the amplifier is malfunction, please turn off the power and contact your local dealer for service support.
3. The tubes regulated power supply might require around 30-60 seconds to ramp up the voltage gradually, it is normal if you heard ting-ting noise from your headphone or speaker during this time.
4. The vacuum tube might require 10 minutes of warm up before they reach optimum performance.
5. Select your input source: XLR for balanced input, RCA for single-ended input.
6. If you are using single-ended headphone, insert the 6.35mm connector of your headphone into the STANDARD headphone output on the front panel. Switch the headphone output selector (PHONES) to STA.
7. If you are using a 4.4mm balanced headphone, insert the 4.4 connector of your headphone into the 4.4 BALANCE headphone output on the front panel. Switch the headphone output selector (PHONES) to 4.4 BAL.
8. If you are using a 4pin XLR balanced headphone, insert the XLR4 connector of your headphone into the 4 PIN BALANCE headphone output on the front panel. Switch the headphone output selector (PHONES) to 4 PIN BAL.
9. Select the appropriate output (L, M, or H) on the IMPEDANCE switch according to the specification of your headphone for optimized performance.
10. Adjust Volume to appropriate level and enjoy your music.

Attention:

◆Please do not disconnect your interconnect when the amplifier is operating, this might cause damage to the amplifier or associated equipment

◆You can swap headphones during playback, but to avoid damaging your sensitive headphone and protect your hearing, please turn the volume down to 0 when you unplug or plug in another pair of headphone.

◆If you have turn off the amplifier, please wait 2 minutes before you turn in on again, ot it might cause damage to the vacuum tubes.

Troubleshooting

Please follow the instruction in the manual in order to keep the amplifier work in its best state. If wrongly operated and you thought that would be troubles please check according to following tips to look for the exact reasons.

Problem		Cause	Solution
No Sound after power on	Power Indicator is OFF.	Power is not connected	Connect power cord securely Check main power supply
		Main fuse is out.	Replace fuse with same specification
	Power Indicator is ON.	NO input signal .	Check source equipment is working Select input source correctly
		Volume at minimum position	Turn up volume
		Interconnect not properly connected	Connect all cables securely
		Headphone cable not properly connected	Connect headphone cable properly
		Headphone output not specified correctly	Select headphone output correctly
		Selected the wrong output	Select headphone or speaker output correctly
		Umbilical Power cable not properly connected	Reconnect the umbilical power cable, position the alignment groove correctly before tighten up the screw-threaded connector
	Working State Indicator is OFF.	Control circuit power failure	Contact authorized dealer for technical support
	Working State Indicator is ON.	External Fuse for high voltage is out.	Replace fuse with same specification
Excessive noise		Input source badly connected	Install interconnect properly
		Equipment malfunction	Contact authorized dealer for technical support
Soundstage and imaging not focused		Left and right channel of source equipment reversed	Reinstall related cabled correctly
		Headphone cable polarity reversed
Malfunction of Remote Control.		Be disturbed.Low Battery.Obstacles between the amplifier and remote.	Keep away from the source of disturbance. Turn off and restore.Replace with new batteries.Remove the obstacles.

NOTE: Rayin® is the registered trademark of Zhuhai Spark Electronic Equipment Co., Ltd.

How to Install Vacuum Tubes

How to Install 9-Pin Vacuum Tubes

Applicable vacuum tube:

Instructions to Change and Install the vacuum tubes:

To install a nine-pin vacuum tube, align the pins of the vacuum tube with the holes of the tube socket and insert the tube vertically up and down (as shown in the figure above).

▲ Please note that when installing the nine-pin vacuum tube, pay attention to the alignment of the vacuum tube pins with the holes of the tube socket. Otherwise wrong insertion will cause damage to the vacuum tube and prevent the amplifier from working properly, which may lead to failure of the amplifier.

How to Install 8-Pin Vacuum Tubes

Applicable vacuum tube:

Instructions to Change and Install the vacuum tubes:

To install an eight-pin vacuum tube, align the positioning pin of the tube with the grooves in the positioning holes of the tube socket, and install the tube by pulling up and down vertically (as shown in the figure above).

▲Please note that when installing the eight-pin vacuum tube, pay attention to the alignment of the vacuum tube positioning pin with the positioning hole of the tube socket. Otherwise wrong insertion will cause damage to the vacuum tube and prevent the amplifier from working properly, which may lead to failure of the amplifier.

How to Install 4-Pin Vacuum Tubes

Applicable vacuum tube:

300B、2A3 etc. 4-pin vacuum tubes.

Instructions to Change and Install the vacuum tubes:

To install a four-pin vacuum tube, please pay attention to the thickness of different pins of the vacuum tube and the size of the tube socket hole. Thick pin should be aligned with the big hole, and the thin pin should be aligned with the small hole. Install the tube vertically up and down (as shown in the figure above).

▲ Please note that when installing the four-pin vacuum tube, pay attention to the thickness of differnet pins of the vacuum tube and the size of the tube socket holes. Otherwise wrong insertion will cause damage to the vacuum tube and prevent the amplifier from working properly, which may lead to failure of the amplifier.

How to Install Big 4-Pin Vacuum Tubes

Applicable vacuum tube:

845、805、211 etc. 4-pin vacuum tubes.

Instructions to Change and Install the vacuum tubes:

To install the big four-pin vacuum tube, align the vacuum tube positioning pin with positioning pin slot of the tube socket and then rotate 45° clockwise to tighten. (As shown in the picture above). To take out the big four-pin vacuum tube, turn the tube 45° counterclockwise and take it out upward after loosening.

▲ Please note that when installing the big four-pin vacuum tube, pay attention to the alignment of the vacuum tube positioning pin with positioning pin slot of the tube socket and then rotate 45° clockwise to tighten. It is strictly forbidden to install the vacuum tube when the positioning pin is off or missing. Otherwise wrong insertion will cause damage to the vacuum tube and prevent the amplifier from working properly, which may lead to failure of the amplifier.

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Zhuhai Spark Electronic Equipment Co., LTD

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