Frequently Asked Questions find more here

More questions?

1. What is your warranty and return policy?

Exchanges and returns must be requested and approved within 20 calendar days upon order delivery. Promotional items must accompany the return/exchange or the item(s) will be deducted from the credit/refund at full retail value. Customer is responsible for shipping the item(s) to us. Orders with upgrade parts, custom components, and special order items cannot be exchanged or returned. Shipping cost is not refundable.

Approved return is subject to a 10% restocking fee on Woo Audio products. A 15% restocking fee on vacuum tubes, headphones, cables, accessories, and all non Woo Audio branded products. Confirmed defective products are not subject to restocking fee.

Only confirmed defective products can be exchanged for the same item or another product. Cost differences are adjusted accordingly by Woo Audio. A credit or a refund will be applied if the replacement item cost less than the item for exchange. Customer is responsible for paying the difference if the replacement item cost more than the item for exchange. Customer pays shipping on all exchanges.


2. How long do vacuum tubes last?

Vacuum tubes used in our products last between 5000 - 9000 hours depending on where they are used. Drive tubes (the smaller tubes) are generally last up to 9000 hours, and power output tubes (the larger tubes in our amplifiers) about 5000 hours. They do not usually completely fail after this time, but gradually deteriorate as the cathode begins to lose its coating and cannot emit electronics at the maximum rate. The sound usually becomes less focused and 2D like lacking HF response.


3. What shipping methods do you offer?

Typically, we use FedEx Ground for Continental United States address, or FedEx Economy for Alaska, Hawaii, and International. Additional fee may apply if other shipping method or insurance is specified.

We will secure your package in the best possible way to avoid damage during shipping.


4. What tubes should I buy?

Consult with us whenever in doubt. In general, you are looking for tubes with the same model number. However, there are many different models number can be substitute directly.

Some tubes have two different types of numbers on them. For instance, a 12AU7A that also has ECC82 printed on the tube.

The ECC82 is the European numbering system and the 12AU7A is the US system. There are quite a few tubes that have both numbers printed on them, but many will only have one or the other number. They are the same tubes, no matter what numbering system is used.

6922=E88CC=6DJ8, 6080=6AS7, 12AU7=ECC82, 12AX7=ECC83, 5AR4=GZ34


5. Do you ship outside of the U.S.?

Yes. we do. Please contact us for rate quote.


WA3: 11 pounds or 5kg WA3+: 12 pounds or 5.5 kg WA2: 19 pounds or 8.6 kg WA4: 31 pounds or 14 kg
WA5/LE: 51 lbs or 24 kg per pkg WA6: 15 pounds or 6.8 kg WA6-SE: 24 pounds or 11 kg WA-GES: 22 pounds or 10 kg



6. Do I need to adjust voltage bias?

Our current amplifiers are self-adjusted. A matched pair of tubes is what you need.


7. Is there any unit available for immediate delivery?

Typically, we do not build amplifier to stock but build per order.

Build time is normally within 1 to 2 weeks. However, delivery date can be delayed due to outstanding orders.


8. How to modify my amplifier?

Please do not perform this task unless you are experienced in electronics. In this forum, "Woo3 Modified", you will find abundant information on unit modifications, tuberollings, and many interesting discussions. Have fun!


9. How do you ensure the highest quality for my order?

All units are handcrafted with high precision. We test and tune each amp with professional equipment. Each unit must pass hours of stress test against several different output devices before packaging.


10. What are indirect and direct heating tubes?

Inside an indirect heating tube, the filament is used to heat a separate electrode called the cathode, and to use the cathode as the source of electron flow in the tube rather than the filament itself. This minimized the introduction of hum when the filament was energized with alternating current. In such tubes, the filament is called a heater to distinguish it as an inactive element.

On the other hand, direct heating tube is to use the filament as the source of electron flow.

For example, 6080, 6922, and 5AR4 are indirect heating tubes while 300B and 5U4G are directs.


11. Can I change the amp voltage for AC220?

Yes, all products have a AC110 and AC220V voltage selector built-in. There is no modification required. You have to make certain the voltage setting is correct for your region before switching on the amp. AC220V setting is usable for AC220V to AC240V 50/60Hz.


12. Why is a tube glowing blue?

It could mean that the tube is defected as air gets trapped inside the glass, but a small amount air would not cause noticeable degrade in sonic. You can hardly find a tube that is completely vacuumed.


13. Do you custom-made amplifier?

We do build your own amplifier depending on the complexity of the modifications. Please let us know your idea and we will provide you a solution.


14. How long do tubes take to warm up?

A tube reaches operating temperature within a minute; however, you will notice the amp sound better after approx 20 minutes warm-up.


15. How to install a vacuum tube in the socket?

Hold the body of the tube securely with your fingers, and then align the tube pins to the socket. Nudge (do not twist) the tube slowly but firmly until the base of the tube reaches the socket or the tube cannot goes in any further.


16. Should I leave the units on permanently?

There is no real reason to leave the units switched on permanently. The advice is that if the units are left switched on permanently then the tube life and other components will deteriorate at a faster rate.


17. Can I leave the amp on whole day long?

Never and never leave your amp on unattended. Due to various reasons such as power supply over-heating or tube failure, your amplifier can cause serious damage. For the safest use, please do NOT exceed maximum 10 hours of play time. Let the amplifier cool down completely for next listening session.


18. What to do when my amplifier developed a light hum/noise?

This could a typical issue due to tube deterioration or it could be introduced from your input sources or surroundings. There are several simple test procedures you may use.

1. Remove all input sources from the amp and listen to any different. If the hum/noise goes away, the noise is coming from your sources.

2. Keep your amp away from frequency emitting devices such as cell phones, radios, PDAs, ect. Noise can be picked up by tubes, especially in high gain design amp.

3. Clean tube pins with cleaning alcohol. Oxidized pins can cause mal-connection.

4. Swap the drive or power tubes from left to right channel. If the hum travels, one of the tubes may be deteriorated.

5. Replace "good" drive, power or rectifier tubes.

6. Try a different AC wallet. Noise can be easily introduced from a poorly grounded wallet. You may also try a "cheater" plug (plug that do not have a ground) to see result.


19. What payment method do you accept?

We accept PayPal, Money Order/Certified Check, or Personal Check which would take 3 to 5 business day to clear bank. If you'd like to send a personal check, it is more convenience and simpler to send a eCheck from PayPal. Our PayPal email address is
Note that International payment with PayPal or Credit Card will incur a 3% fee in addition to the total amount.


20. Can you expedite my order?

We will try the best we can. The build sequence is the order of purchase date; therefore, the earlier you place an order the sooner you will receive it. A fee may be required if you absolutely need to receive your order sooner.


21. Is it normal to hear noises/hum when switching on the amp.

Absolutely normal because tube's heater is warming up as to stablize voltage. Noise will go away gradually as the tube warms up.


22. Can I change headphones when the amp is on?

It is safe as long as you minimize the volume.


23. What are the compatible tubes I can use?

See the Tube Compatible Chart here. You can also submit a tube here.


24. What are the differences among the amps?

See the Amplifier Comparisons Chart here.


25. Where can I register my order?

Please fill out the form here.