Nobsound AV-525 Bluetooth Vacuum Tube Amplifier Review

The Nobsound AV-525 is a hybrid integrated amplifier priced at $459.99 on Douk Audio's site. It combines a vacuum tube preamp stage with a transistor power stage inside a vintage-styled chassis that the product page and its linked user manual list at 330 x 315 x 160mm and 7.16kg net, 9.0kg boxed. Douk Audio's product page rates output at 100W+100W into 4 ohm speakers and 70W+70W into 8 ohm, aimed at buyers who want tube coloration up front without giving up the power to drive real speakers at real volume.

For the tube side, Douk Audio's listing names EL84, 6K4 and 5726 tubes for preamplification with a WY2P tube for rectification, handing power duties to four Toshiba 5200 and four 1943 transistors fed by dual toroidal transformers. The product page lists total harmonic distortion at 0.1% at 1kHz and signal-to-noise ratio at 88dB or better, with treble and bass controls rated at plus or minus 9dB. Worth flagging: the user manual linked from the product page (a PDF) lists a different rated output, 200W+200W, and a 64GB U-disk storage limit rather than the product page's 128GB. We rely on the current product page's figures here since they describe the exact listing being sold today.

Connectivity spans Bluetooth 5.0, a U-disk USB input for MP3, WAV, APE, FLAC and WMA files up to 16-bit/48kHz, plus coaxial and optical digital inputs and two groups of stereo RCA. Speaker output runs through banana jacks rated for 4 to 16 ohm loads, and a dedicated low-frequency output is built in for connecting an active subwoofer, making a 2.1-channel setup straightforward without a separate preamp. The manual adds a detail not in the main listing: a HiFi IN/OUT jumper pair on the back lets an owner insert an equalizer or preamp between source and amplifier, but warns that removing both connection straps without plugging something into that loop will cut all sound from the speaker outputs.

The box includes the amplifier, a Bluetooth antenna, a power cord and a remote control, though Douk Audio's own listing notes the remote ships without batteries. Douk Audio also describes the dual VU meters as reactive only to loud, bass-heavy passages rather than constant motion, so buyers expecting meters that move on every track should adjust expectations accordingly.

Independent commentary on this specific model is thin: the owner threads we found could not be opened to check, so this review rests on the store's page and the maker's manual.

For comparison, Douk Audio's own T6PRO sells for $139.99 and takes a different approach: a JAN5725 tube preamp stage feeding a TPA3255 Class D amplifier chip rated up to 300W into 4 ohm per channel, with newer Bluetooth 5.1 and aptX-HD/LDAC codec support, but no coaxial or optical digital inputs, no USB U-disk playback and no dedicated subwoofer output. The AV-525 costs roughly three times as much but adds those digital inputs, file playback and subwoofer support, along with a hybrid tube-and-discrete-transistor output stage instead of a single switching amplifier chip.

On policy, Douk Audio's current shipping page states duties, taxes and customs fees are included in the checkout price for international orders, which typically arrive within 2 to 8 business days. Returns need pre-approval within 30 days of delivery and must ship back within 7 days of that approval, and the company separately lists a 24-month warranty against manufacturing defects, excluding accidental damage, unauthorized modification and misuse.

Specifications

How it compares

The Nobsound DA3 Bluetooth Tube Amplifier review ($189.99) is the closest on features at less than half the price, $270.00 less: Bluetooth, optical, coaxial, U-disk and two RCA inputs, a pre-out for active subwoofers and a headphone jack, with 35W x 2 into 4Ω and 25W x 2 into 8Ω and two 6J1 tubes in the preamp stage. The AV-525 page lists 100W+100W into 4Ω and 70W+70W into 8Ω from a Class AB output stage, a dedicated subwoofer output, VU meters and a 7.16kg chassis, with THD of 0.1% at 1kHz and SNR of 88dB or better, against THD of 1% and SNR of 70dB on the DA3 page. The AV-525 page lists no headphone output; the DA3 page does. Both pages print their figures without test conditions.

The Nobsound DA7 Vacuum Tube Power Amplifier review ($349.99 for US, UK and EU destinations, $110.00 less) is a pure tube design: 12W x 2 into 4Ω, Bluetooth 5.3/5.0, USB and RCA inputs and twin VU meters, on AC 220V only, with banana speaker jacks and a stereo RCA output rather than a dedicated subwoofer output. The Douk Audio ST-02 Integrated Tube Amplifier review ($239.99, pre-sale, $220.00 less) also takes digital inputs: Bluetooth 5.4, PC-USB, optical and coaxial inputs, two headphone outputs and a power table giving 107W+107W into 4Ω with its boxed adapter, from a TPA3255 chip instead of the AV-525's transistor Class AB stage. The AV-525 suits a living-room system that needs a subwoofer output and a heavier amplifier; the DA7 suits listeners who want tubes in the power stage; the ST-02 suits a desk with headphones. The AV-525 page gives no mains voltage, so confirm it before ordering.

Shipping, returns and warranty

• Shipping: Douk Audio's current shipping page says orders are generally processed no later than the next business day and arrive in 2-8 business days, with duties, taxes and customs fees included in the checkout price unless noted otherwise.
• Older shipping terms are still online: airmail at 10-25 days for parcels under 2 kg, DHL, UPS or FedEx at 5-8 days above that, and a line saying the store is not responsible for import duties. Check the delivery estimate and any duties at checkout.
• Returns: ask within 30 days of delivery and wait for approval before sending anything; an approved return has to ship within 7 days. Items need all packaging and accessories and no excessive wear, or the store can refuse them or refund part of the price. Refunds go to the original payment method after inspection.
• Not refunded: original and expedited shipping, duties, taxes and customs charges, unless the law requires it or the store made the error. The return page does not say who pays return postage, and the older refund page excludes mistaken orders and change-of-mind returns from free after-sale service.
• Warranty: 24 months from purchase for manufacturing defects, with free repair, a replacement unit and free shipping both ways for covered repairs. Drops, liquid, DIY repairs, lightning, extreme temperatures and misuse are excluded (partial fees may apply), and damage from weak packing on the way back may not be covered. The older refund page still says 1 year.
• Seller: the site is run by Shenzhen Anba Technology Co., Ltd (Shenzhen, China) and HONGKONG LONGSHENG Import and Export Trading Co., Limited (Hong Kong); support is by email at [email protected]. These terms cover orders placed on doukaudio.com; other sellers apply their own.

For this product, the page has a 'Shipping to' selector (US, UK, EU, AU, Other) and shows Free Shipping, 2-8 Days Arrival, 30-Day Return and 2-Year Warranty badges near the price.