UralTone Jr (3.5-20w) Tube Amplifier Kit (version 3.1)

The UralTone Jr kit is Finland’s best-selling tube amplifier kit. And for good reason—many current professionals have started their journey into the addictive world of tube amp building with it. Sound-wise, the Jr represents the American tradition of the 1950s–60s. It is not directly based on any existing amplifier but is UralTone’s own design.

Features:

• Preamp with volume and tone controls, ECC83/12AX7 (or 12AU7, 12AT7, 12AY7, 5751...)
• "Double Single Ended" (DSE) power stage
• Separate master volume controls for both power tubes (shared output transformer)
• Accepts e.g. 6V6, 6L6, 5881, EL34, KT66, 6P3C, KT88, 6550 series tubes
• Power stage operates in Class A
• Power output approx. 3.5–20W depending on tubes (at full distortion)
• Headroom control (included) – allows continuous power adjustment (note: normal position is fully clockwise!!)
• Reverb (optional extra) – traditional transformer and tube-driven spring reverb.
• Tube rectified – a true all-tube amplifier
• Works best with 2–8 ohm speakers. Ideal impedance depends on tubes used. Not very load-sensitive.
• Adjustable line out and internal dummy load (no speaker required)
• Front panel rotary switch affects preamp gain and frequency response. Positions: 1. normal, 2. mild bass cut / treble boost, 3. stronger bass cut / treble boost, 4. bass cut / treble boost (preamp) + presence boost (feedback), 5. full-range boost (preamp) + presence boost (feedback), 6. full-range boost.
• High-quality pre-machined Finnish 2 mm aluminum chassis. All holes pre-drilled for easy assembly.
• Durable eyelet fiberglass board like boutique amps
• Easy to assemble, mod, and very durable construction.
• Only very high-quality components!
• Unlimited technical support via email in Finnish or English.

Link to instructions?

The build instructions can be found here:

https://en.uraltone.com/blog/uraltone-jr/

The page also includes layout diagrams, parts list, and other documents. Schematics may be delivered separately in some cases.

Browse the instructions in advance to understand the building process and available guidance. No printed instructions are included.

Links to related products

Additional options:
Reverb add-on:

https://en.uraltone.com/kits/uraltone-jr-sr-kit/uraltone-jr-3-1-reverb-add-on.html

Head or combo cabinets:
https://en.uraltone.com/uraltone-jr-headcab-1.html

Speakers
https://en.uraltone.com/speakers.html

Power tubes

The UralTone Jr power stage accepts 1–2 tubes: one can be 6V6, 6L6GC, KT66, 5881, 6P3C-E, 6P3C (not EL34, 6550 etc.), the other can be EL34, 6550, KT88, KT66, 6L6GC, 5881, 6P3C-E, 6P3C etc. Tubes can be mixed and blended with separate volume controls. Tubes are not selectable; the kit includes quality tubes from ECC83, EL34, 6L6GC, 6V6GC.

What does the kit include?

The price includes all necessary parts to build the amplifier. Does not include speaker or wooden cabinet.

Who is this kit for?

Anyone interested in tube amp building and classic guitar tones. Suitable also for beginners. Important to reserve enough focused time. A cup of coffee/tea helps.

Build time?

An experienced builder can complete it in a day. Hobbyists in 2–3 days.

What tools do you need?

Basic tools are sufficient, but beginners should invest in reasonable quality.

A good soldering station and solder are essential for quality joints.

Always buy a soldering station from a knowledgeable electronics store.

We have compiled a beginner tool kit to make building easier:

BEGINNER SOLDERING TOOL KIT

You will also need screwdrivers. If unsure about your current soldering station, contact us.

How to get support?

A properly built device works—follow instructions carefully. For troubleshooting:

DIY tube amp troubleshooting

If needed, contact us via email. Unlimited support is included. No phone or in-store support available.

What if I still can’t fix it?

We aim for builders to solve issues independently with our help. If not, then

End result?

You will get a great-sounding boutique amplifier that lasts at least 100 years! Skills learned help in future projects.

WARNING: Building guitar gear is highly addictive!