Elekit TU-4523 — 45/2A3 Single-Ended Power Amplifier Kit

Tubes are not included. Shipping from late October The Other End of the Triode Family If the TU-8900 is where Elekit lets a 300B and a 2A3 argue over who gets to fill the room, the TU-4523 is where the conversation gets quiet. This is the 45's amplifier: a single-ended, class-A kit built around the most delicate of the classic directly-heated triodes, with a manual switch that lets you drop back to a 2A3 whenever you want a little more scale. The 45 first appeared in 1930s American radio sets, was pushed aside for decades by tubes that could simply make more noise, and has spent the last twenty years being quietly rediscovered by listeners who care more about texture than headroom. It has a well-earned reputation as the sweetest-sounding tube in the 45/2A3/300B family — and the most limited. The TU-4523 is Elekit's purpose-built home for it, sharing its 2A3 socket with the TU-8900 so the two kits meet in the middle, while each pushes off in its own direction: the TU-4523 toward finesse, the TU-8900 toward drive. Why Choose the TU-4523 Over the TU-8900? Both kits share Elekit's now-familiar formula — automatic tube-type detection, DC-heated filaments, MOSFET-regulated B+, and a proper NFB/non-NFB switch for tone-shaping without a soldering iron. Where they part ways: A different pair of tubes entirely. 300B/2A3 versus 45/2A3. The 2A3 is the shared middle ground; the 45 and 300B are the two extremes either kit lets you reach for. Boutique components as standard, not as an upgrade. The TU-4523 ships from the factory with Lundahl output transformers, Takman resistors and an ALPS R27 potentiometer built in — components that are optional upgrades on the base TU-8900. A smaller, lighter, cooler-running amplifier. At roughly 9.8kg and drawing 42W (45) or 65W (2A3), the TU-4523 asks less of your shelf, your power bill and your room in summer than the 11.2kg, up to 95W TU-8900. More headroom to modify the sound yourself. Elekit has deliberately left extra board space for larger coupling capacitors (up to 22mm × 44mm), and added a second selector so speaker impedance can be matched separately for 45 or 2A3 operation. A closer relationship with its most famous historical role. The 45 is a lower-powered, lower-voltage tube than the 300B, so the TU-4523's whole design — voltages, cathode resistors, board layout — is tuned around getting the most out of a tube that was never meant to be loud in the first place. If you already know you want the biggest, most authoritative single-ended sound Elekit builds, stay with the TU-8900. If what drew you to SET amplification in the first place was the promise of the most transparent, most "in the room" midrange going — and you can live with roughly 2.5W to get it — the TU-4523 is built for you. TU-4523 Full Specifications: 45 vs 2A3 Specification With 45 Tubes With 2A3 Tubes Tubes required 2 × 45 + 2 × 12AU7 (ECC82/6189) 2 × 2A3 + 2 × 12AU7 (ECC82/6189) Circuit Class A, single-ended, self-biasing Class A, single-ended, self-biasing Max. output (8Ω, 1kHz, THD10%) 2 × 2.5W 2 × 4.5W Output at 1% THD (8Ω, 1kHz) 2 × 1.5W 2 × 3W Rated input 660mV rms 800mV rms Voltage gain 19dB (NFB) / 27dB (non-NFB) 19dB (NFB) / 26dB (non-NFB) Damping factor (8Ω, 1kHz) 6 8 Residual noise (IHF-A, 8Ω) 12µV rms 15µV rms Recommended speaker impedance 6–16Ω 4–16Ω Frequency response (−3dB) 10Hz – 90,000Hz 10Hz – 90,000Hz Rated power consumption 42W 65W Shared Across Both Tube Types RCA line-level input (≈50kΩ input impedance); gold-plated binding-post speaker outputs (banana-compatible); 3-pole 6.3mm headphone output with adjustable level via a rear shorting pin; universal AC115V/230V power input (set at assembly); dimensions 356 × 214 × 320mm; weight approx. 9.8kg (assembled, excluding tubes and power cord). Specifications per Elekit's official TU-4523 documentation and subject to change without notice. Sourcing 45 Tubes for Your TU-4523 Every Elekit SET kit ships without tubes, and that's usually a minor detail — a matched pair of current-production 2A3s is inexpensive and easy to find. The 45 is a different story, and we'd rather tell you that up front than have you discover it after the kit arrives. The 45 never went back into mass production the way the 2A3 and 300B did. Today it's effectively a specialist tube: the main current-production source is Emission Labs (Czech Republic), whose standard and mesh-plate 45s run roughly £300–£450 a matched pair through UK/European dealers and can be somewhat more through US retailers — noticeably more than an equivalent 2A3 pair, and worth budgeting for separately when you're costing out this kit. Fittingly, it's an Emission Labs 45 pictured in Elekit's own TU-4523 literature. Genuine vintage-original 45s (RCA, Sylvania, National Union and others) can still be found through valve specialists and vintage-radio dealers, but pricing is condition- and rarity-dependent and supply is finite, so we'd generally point first-time 45 owners toward current production. None of this affects the 2A3 side of the amplifier — those tubes remain as affordable and plentiful as they are in the TU-8900. It's only the 45 half of this kit's dual personality that comes at a premium, and we think it's a premium worth knowing about before you buy rather than after. Ask us about tube pairing options — we're happy to help you source a matched set for either tube type.