ST-01 PRO Bluetooth Tube Amplifier Review

Douk Audio (also sold under the Nobsound name in some markets) makes a line of tube and hybrid amplifiers, preamps, and DACs aimed at desktop and small-room hi-fi setups, and the ST-01 PRO is one of its best-known models.

The ST-01 PRO pairs two GE 4BZ6 vacuum tubes with a solid-state power stage, and Douk Audio rates it at 100W+100W into a 4-ohm load, with compatibility for speakers rated between 3 and 8 ohms.

Inputs cover Bluetooth 5.0, PC-USB (for lossless playback from a computer), optical, coaxial, RCA, and a USB-drive slot for playing files directly without a source device. Outputs are banana-style speaker jacks plus a 3.5mm AUX pre-out that can feed a subwoofer or a second amplifier.

An independent listening review on HomeTheaterHiFi (November 30, 2023) found the ST-01 Pro handled louder volumes with ease and kept excellent left/right balance on a pair of Jamo S 803 speakers. Even after setting the EQ, the reviewer found the sound cooler than expected for a tube amp, with strong, forward but slightly sharp-edged vocals. That review measured no output power; the only wattage it gives is the maker's 100W+100W (4Ω) rating.

Controls are compact: a single front dial handles power, input switching, and volume, which the HomeTheaterHiFi reviewer found confusing, though the amp ships with a remote that the same review says solves it.

The unit is priced from $109.99 and comes with a 24-month warranty, a 30-day return window, and free shipping with a stated 2-8 day delivery estimate.

Compared with other entry-level tube hybrids in this price range, the ST-01 PRO's main draw is its input flexibility and the VU-meter aesthetic rather than raw power; buyers wanting to drive larger or less-efficient speakers, or chasing a classic warm tube signature out of the box, may want to look at higher-powered or pure Class A models in the Douk Audio lineup instead.

It's best thought of as a desktop or near-field amplifier for small to medium bookshelf speakers rather than a full living-room system driver.

Specifications

How it compares

The nearest alternatives are the other hybrids at a similar price. The Douk Audio T6PRO TPA3255 Tube Amplifier review ($139.99) lists a TPA3255 chip and JAN5725 tubes, up to 300W per channel into 4Ω as a maximum, Bluetooth 5.1 with aptX-HD and LDAC, two RCA inputs and a 3.5mm AUX input, but no USB, optical or coaxial input and no U-disk player. Its power table gives 78W+78W into 4Ω with the 32V/5A supply, 120W+120W with 48V/5A and 250W+250W with 48V/10A, so no listed supply reaches 300W. The ST-01 PRO page rates 100W+100W into 4Ω without saying which supply voltage that needs (a 24V adapter is in the box), costs $30.00 less (the T6PRO's price is for the option without an adapter), and adds PC-USB, optical, coaxial and U-disk inputs, with Bluetooth 5.0.

The Nobsound DA3 Bluetooth Tube Amplifier review ($189.99) costs $80.00 more and is a different amplifier: two 6J1 tubes in the preamp stage, 35W x 2 into 4Ω and 25W x 2 into 8Ω, Bluetooth, optical, coaxial, U-disk and two RCA inputs, a headphone jack and a pre-out; its page prints THD of 1% and SNR of 70dB against 0.07% and 98dB or better here. The Douk Audio X1 Bluetooth Tube Amplifier 160W review ($139.99) adds an MM phono input and a dedicated subwoofer output (the ST-01 PRO has a 3.5mm AUX pre-out that can feed one too) and quotes 160W+160W into 4Ω with THD of 0.5%, but has no USB, optical or coaxial input. For a desk with a computer, a TV and a phone, the ST-01 PRO is the only one of the three with a PC-USB input and it is the cheapest; for vinyl, the X1; for a headphone output and a 6J1 preamp stage, the DA3.

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.