Nobsound TUBE-T4C Stereo Vacuum Tube Preamp Review

The Nobsound TUBE-T4C is a stereo vacuum tube preamp priced at $49.99. It sits between your sources and your amplification: stereo RCA input and output let it connect to a PC, phone, tablet or CD player on one side, and to your existing power amplifier or active speakers on the other.

The design uses a Class A tube stage, which the maker says filters out digital harshness and adds warmth, depth and an expansive soundstage, with a circuit layout intended to keep the background silent. The default tubes are 6J5 types in pluggable sockets, and they can be swapped for 6J1, 5654, 6AK5, EF95 and similar models to explore different voicings — a simple way to customize the sound.

Controls are limited to what matters: independent bass and treble knobs for fine-tuning the tone to your gear and taste. The published specs are a 20-30kHz frequency response, 100dB signal-to-noise ratio and 2.5x voltage amplification, all in a 78x82x32mm chassis weighing 230g — small enough for a desktop setup. The unit ships with 2x 6J5 tubes and a DC 5V power adapter.

Two usage notes from the maker: the TUBE-T4C is a preamplifier and must be paired with a power amplifier or active speakers, and it cannot connect directly to passive speakers. It should be used with the supplied DC 5V/2A adapter, or another power supply delivering at least 2A, or it may not function properly.

Specifications

How it compares

The nearest match is the Nobsound NS-10P Vacuum Tube Stereo Preamp review, also $49.99: a small tube preamp with treble and bass knobs and two tubes in the box. The TUBE-T4C page lists RCA in and out, two 6J5 tubes, 2.5x gain, SNR of 100dB and a DC 5V adapter that must give 2A or more, in a 78 x 82 x 32mm body at 230g. The NS-10P page lists 3.5mm in and out, two 6J1 tubes, only 1.5-2.0x gain, SNR of 110dB or better, a volume control and a universal AC adapter (DC 6V 2000mA out), in a 105 x 69 x 32 body at 205g. Pick the T4C for RCA gear, and the NS-10P if you want the higher printed SNR and a 3.5mm chain; neither page prints test conditions.

At the same price, the Douk Audio P6 MINI Bluetooth Tube Preamp review ($49.99) adds Bluetooth 5.0, a U-disk player and an input selector, with distortion of 0.03% or less printed against no THD figure on the T4C page. At the other end, the Douk Audio TUBE-T5C 4-Way Tube Preamp review ($109.99) is $60.00 more for four RCA inputs, two outputs, a headphone amp and a VU meter; its page also puts the tube at a boosted 180V, a figure the T4C page does not give. The T4C is the choice if you have one source and an amplifier and want a tube stage and tone knobs for the least money; it has no input selector and no headphone output.

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.