UralTone Stereo HiFi PP-EL84 (v2.0) Tube amp kit

Our first vacuum tube hi-fi amplifier kit is now updated with the new case and mechanical structure. We maintained the best features of the old but improved it in many places. The kit is now easier to build and we think it looks lot better than the previous version.

Features

We kept the circuit the same as the predecessor - it is pointless to change a good concept. Simplicity is a winner in all sound reproduction. Rarely, a complex structure and thousands of components in the signal path improve sound quality. Distortion can be made very small and the measurement results very impressive, but in our experience, sound quality does not always meet with the measurement results. Tube amplifiers have evolved little in decades: many classic 50s devices are still considered unbeatable for their sound quality.

Circuit

For the size and output power, we wanted about 2x10W because this is enough for most speakers and listening rooms. A higher power rating would increase the cost of components without improving sound quality. The EL84 power tube, which is currently one of the most sensible hi-fi tubes, also fit well into that power class. EL84 is a classic tube that has not retained its position in vain.

The amplifier is designed for 8-16 ohm speakers, but the power transformer can also be connected for 2-4 ohms.

Distortion values ​​and frequency response are measured excellent. THD is 0.01% at 1W and 0.3% at 10W, which is a good value for a tube amplifier with only 10dB feedback. Increasing the feedback makes the distortion even less but the input sensitivity goes down requiring preamp. For preamp and phase inverter, we chose a common ECC83 tube because it provides good input sensitivity, allowing the entire driver and phase reversal to be implemented with a single ECC83 tube: so the amplifier has only 3 tubes per channel!

Structure

The primary goal of the upgrade was to make the amplifier easier to build. The input selector switch and its wiring have often caused a headache. We ended up using a relay selection at the input. This way, the incoming signal is selected immediately after the RCA connectors, and there is no need for eight individual wires from the back to the front panel switch. The amplifier is built on a highest quality circuit board with the entire circuit except for input selection.

Components

We have selected the best possible reasonably priced parts for the kit. Even if the parts were replaced at considerably more expensive ones, the benefit obtained in terms of sound quality or durability would remain very small or even non-existent. The components included in the construction kit correspond to the quality of the components of the best commercial tube hi-fi amplifiers.

As a result, we get a very high-quality amplifier for a reasonable amount of money.

Perhaps the most important single part of a tube amplifier is the output transformer. PP-EL84 uses super high-quality toroidal core output transformers designed and manufactured in Finland.

Chassis

Powder coater black chassis is also made in Finland. The dimensions of the case are slightly smaller than the previous version. The width of the new amplifier is 21.5 cm, which is half of the traditional stereo components. The same case type will be used in our other future Hi-Fi series.

Wooden side panels and potentiometer knobs shown in product pictures are not included in the kit.

Technical features

• 4xEL84 and 2x ECC83
• Output Power 10W @ 8 ohm, with 0.4-0.9V input (0dB-10dB with feedback)
• 3 x RCA stereo and 1x 3.5mm inputs
• Controls: on-off, feedback 0, 6, 10dB, volume, input selector
• Very high sound quality
• Frequency response min. 6.2Hz-60kHz +/- 0.5dB (without cutting up to 100kHz)
• THD 0.01% at 1W, 0.3% at 10W
• Feedback selectable with switch: 0, 6 or 10dB. 6-10dB is considered by many hi-fiers to be the optimal value for tube amplifiers. The effect of the feedback on the sound is very speaker-specific.
• The construction set is also suitable for beginners. You need basic tools, soldering skills and some patience.
• Pre-machined and painted chassis, so no metalworking tools are needed.
• External dimensions approx. 360x215x130mm (with tubes and protective housing).
• Weight approx. 4.7kg.
• Unlimited email support.

The kit comes with a layout picture, schematics, and a bill of materials. A series of pictures of the construction of the amplifier will be published soon in our info section.

Stock 1	UralTone Helsinki, 00530 FI	17 units available