Nobsound F2 Single-Ended Class A Tube Amplifier Review

The Nobsound F2 is a single-ended Class A tube amplifier priced at $349.99. It brings the rich, smooth tone of a single-ended vacuum tube design to a home setup, with lifelike detail and natural dynamics aimed at relaxed, immersive listening with matched speakers.

The tube complement is designed for rolling: all tubes are pluggable. The default set is a 5U4G rectifier, a 6SN7GT preamp tube and 6CA7 power tubes, with compatible alternatives including 274B, 5Z3P and 5Z3PA rectifiers, 6SN7, CV181, 6H8C and 6N8P preamp tubes, and EL34 power tubes - enough combinations to personalize tone and texture. Around the tubes sit audiophile-grade parts: a robust 160W transformer with a Japan Z11 steel core, an ALPS precision potentiometer and gold-plated terminals, chosen to reduce noise and elevate musical detail.

Power output is about 9W x 2 into 8 ohm in Class A operation, which Nobsound says can drive a wide range of bookshelf and floor-standing speakers - specifically passive models rated around 10-100W with sensitivity of 88dB or higher, in a desktop or living room setup. Compatible speaker impedance spans 4-8 ohm; 6-ohm speakers can connect to either the 4 or 8 ohm terminals, with the 8 ohm terminals usually recommended for better dynamics. Dual RCA inputs with a front selector let a DAC, network streamer or CD player stay connected for instant switching. Listed performance is THD under 1% at 1kHz, an 88dB SNR and a 20Hz-20kHz response, and the unit weighs 8.6kg.

Specifications

How it compares

The Douk Audio F3 Single-Ended Class A Amplifier review ($299.99) and the Douk Audio F5 Single-Ended Class A Amplifier review ($459.99) are the other single-ended Class A amplifiers here. The F2 sits between them on price but has the highest power rating: 9W x 2 into 8Ω against 3.2W x 2 for the F3 and 6W+6W for the F5. It is also the heaviest of the three, 8.60kg against 2.5kg and 6.57kg, and the only one whose page lists a 5U4G tube rectifier and names replacements for all three of its tube types. The F3 page says other tube types may damage it. The F5 page lists replacements for its 6L6 and 6N1 tubes and marks its 110V version as unavailable, while the F2 page lists AC 110V-120V and 220V-240V ranges. The F2's printed THD is under 1% at 1kHz, against up to 7% at rated power for the F3, and the F5 page gives none.

The Nobsound DA7 Vacuum Tube Power Amplifier review ($349.99 for US, UK and EU destinations; the store's option data prices AU and Other at $469.99) costs the same for those destinations and is a pure tube amplifier too, but a different one: 4x 6P1 power tubes and 3x 6N1, 12W x 2 into 4Ω and 8W x 2 into 8Ω, Bluetooth 5.3/5.0, USB and dual RCA inputs, twin VU meters, 7.6kg, and AC 220V only on its page. Its THD is listed as 1% at 1kHz and its SNR as 85dB, against under 1% and 88dB on the F2 page. Choose the F2 for a plain analog chain and tube rolling, if you can confirm which mains version ships to you; choose the DA7 for Bluetooth and a USB source, if you can confirm the 220V version.

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 lists shipping from US, UK, EU, AU and China warehouses and shows Free Shipping, 2-8 Days Arrival, 30-Day Return and 2-Year Warranty badges near the price.