There are three questions that determine which tube amplifier kit is right for you. Most buyers focus on the wrong one.
The question most people start with is: which tube sounds best? That's actually the third question. The first is about your speakers. The second is about how you want to build. Get those two right and the tube question becomes much easier to answer — and more enjoyable to explore.
Question one: do your speakers have enough sensitivity?
Single-ended tube amplifiers produce low output power by solid-state standards. The Elekit TU-8400 delivers up to 9.8 watts. The TU-8900 with 300B tubes delivers around 8 watts. The SpotFire SE5 delivers 5 watts per channel.
This is not a limitation — provided your speakers are efficient enough to work with it.
Speaker sensitivity is measured in decibels at one watt, one metre. A speaker rated at 90dB/W/m will produce 90 decibels from a single watt — enough to fill a typical living room with ease. A 9-watt amplifier driving a 90dB speaker can play loudly with headroom to spare.
The problem arises with low-sensitivity speakers — anything below 88dB. These need substantially more power to reach usable volume levels. A 5-watt amplifier into an 85dB speaker will run out of headroom in a medium-sized room long before the music sounds right.
A practical guide:
93dB and above — any single-ended kit in the range will work well.
89–93dB — TU-8400 or TU-8900 are suitable; SpotFire SE5 is marginal at volume.
Below 88dB — consider the TU-8888 push-pull monoblock (approximately 60 watts per channel), or verify whether your speakers are genuinely as demanding as their specifications suggest.
Speaker sensitivity is listed on the manufacturer's specification sheet — usually under "Sensitivity" or "Efficiency." If you're not sure, it's worth checking before you choose.
Question two: how do you want to build?
There are three ways to own an amplifier from this range, and the right one depends on your confidence, your schedule and how much of the process you want to experience.
DIY kit — all components are supplied with clear English-language instructions and local support from Secret Chord Analogue if you run into difficulty. Most builders complete a kit over a weekend. The TU-8400 is particularly well-suited to first-time builders. Tubes are not included with most kits, which allows you to choose your own from the outset.
Amp Camp — a supervised build workshop held on the third weekend of most months, in a purpose-built, air-conditioned facility in Wentworth Falls in the Blue Mountains, west of Sydney. Your first day begins with a short soldering course — covering technique and the common errors that cause build failures, before a single component is installed. From there, construction proceeds at your own pace with expert guidance available throughout. All tools, materials, lunch and refreshments are provided. You leave with a fully built and tested amplifier.
Amp Camp runs one project per day. Building a preamplifier and power amplifier together means two days — Saturday and Sunday. A residential option is available in partnership with Falls Lodge, next door to the workshop — a full weekend with access to a complete tube hifi system, including turntable and streaming capability, between sessions.
Build service — Secret Chord Analogue will build the amplifier for you. It arrives assembled, tested and ready to play.
Question three: which tubes and which kit?
Once you know your speakers can work with single-ended power levels, the tube question is about character — and the good news is that several kits let you explore this over time rather than commit to a single answer from day one.
The 300B is the most celebrated output tube in the world. It is associated with rich midrange, extended bass for its power class, and a musicality that tends to keep listeners deeply engaged. The TU-8900 is built around the 300B — and uniquely, also accepts the 2A3, a smaller tube with a gentler, more delicate tone. A clever automatic power supply detects which tube is installed and adjusts filament voltage accordingly, making it the only single-ended design that supports both without any manual intervention.
The EL34 is a pentode with a different character: more extended at the top, slightly leaner in the midrange, and particularly well-suited to orchestral music and acoustic recordings. Both the TU-8400 and the SpotFire SE5 accept EL34 tubes.
KT88 through KT170 — the power pentodes. More output, a slightly different tonal signature, and a quality that handles dynamic recordings and higher-volume listening well. The TU-8400 accepts the full range from KT66 to KT170; the TU-8850 is specifically designed around the KT88 family, with three power modes that open the door to an unusually wide range of octal base pentode tubes.
The 6V6 is a smaller, more modest tube — limited output power but a sweet, unassuming character that suits lower-volume listening. The TU-8400 accepts the 6V6 in its LOW mode.
Kit by kit
SpotFire SE5 — from $1,089
Australian-designed single-ended EL34 amplifier. 5 watts per channel, headphone output, Bluetooth, NFB on-off switch. A solderless variant is available for builders who prefer not to solder. The most accessible entry point in the range for listeners with efficient speakers.
Elekit TU-8400 — from $1,119
The most versatile kit in the range. Single-ended, compact, accepting tube types from 6V6 to KT170 with automatic bias adjustment. Triode, Ultra Linear and Pentode modes. Two RCA inputs, a 3.5mm jack, and a headphone output. Pairs naturally with the Elekit TU-8450 preamplifier for a complete tube system with phono capability. The natural choice for a first build.
Elekit TU-8900 — from $1,841
The premium single-ended option. Built for the 300B and 2A3, with automatic tube detection. Optional Lundahl amorphous core output transformers and Mundorf silver-gold oil coupling capacitors for a reference-level result. Three five-star reviews from builders who have lived with it.
Elekit TU-8850 — from $2,033
A tube roller's dream. Three power modes allow an exceptionally wide range of octal base pentode tubes. If experimenting with different tube types over time is part of the appeal, this is the kit that rewards that curiosity most.
Elekit TU-8888 — from $2,363
Elekit's flagship monoblock push-pull design. Two units for a stereo system. Approximately 60 watts per channel through a Lundahl LL3733 output transformer. For listeners with speaker systems that demand real output power without sacrificing tube character.
Where to start
For most first-time kit builders with reasonably efficient speakers, the TU-8400 is the logical starting point. It accepts the widest range of tube types, integrates easily with existing equipment, and leaves room to explore — different output tubes, different operating modes, a preamplifier added later — without committing to a single direction from day one.
If the 300B sound is specifically what you're after, and your speakers are up to it, the TU-8900 rewards that intention directly.
Unsure what's right for your setup? We're happy to talk through speaker sensitivity, room size and what you're connecting before you decide.
Written by Stephen Price, founder of Secret Chord Analogue. Secret Chord Analogue is an authorised Australian dealer for Elekit of Japan and for the SpotFire amplifier range.