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DIY Vacuum Tube (Valve) Amplifier Projects

DIY Vacuum Tube Amplifier Projects

Do-It-Yourself (DIY) vacuum tube (valve) amplifier and tube preamplifier projects. Please be aware that most of these vacuum tube projects use potentially lethal voltages that can kill you so do not attempt them if you are not familiar with high voltage safety! Some of the projects use low voltage and if you are new to tubes and high voltage safety you should start with these. For books on the subject of vacuum tubes, see our DIY Audio Book recommendations. If you have some experience with high voltage electronics, the S-5 Electronics tube amplifier kits make a good and inexpensive first tube amplifier project. Questions and discussion about tubes and hi-fi audio is always welcome in the DIY Vacuum Tubes forum.

Last update: 24 March 2014

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DIY Vacuum Tube Amplifier Projects

Chronological list of our DIY vacuum tube Hi-Fi audio projects.

DIY 300B Single-Ended-Triode (SET) Hi-Fi Amplifier DIY 300B Single-Ended-Triode (SET) Hi-Fi Amplifier - 24 March 2014  Greek Flag    NEW 
This DIY 300B triode amplifier project was completed by Stamou Tasos who is from Greece. As a thank you for the 300B amplifier schematics, Stamou has shared his implementation of the 300B single-ended tube amplifier schematic by J.C. Morrison. The 300B SET amp uses a 6SN7 direct coupled driver stage and an all low mu triode array. The power supply filtering sections have been duplicated for each channel for this 300B triode amplifier and premium parts are used throughout. The audio output transformers are Lundahl LL1623. This is a great sounding 300B triode amplifier that I am sure DIYers will find very rewarding.

4S Universal Preamplifier for 12A*7 Tubes 4S Universal Preamplifier for 12A*7 Tubes - 15 December 2013  USA Flag    NEW 
The 4S Universal preamp is a Super Simple Single Stage (4S) line level Hi-Fi preamplifier that works well with the entire range of 12A*7 tubes - 12AU7, 12AV7, 12AY7, 12AT7, 12AZ7, and 12AX7. You can change the tube type to vary the sound and gain considerably. The preamp uses a 6CA4 tube rectified power supply which is very quiet. The Universal preamp is fun as it allows tube rolling to compare various tubes in your stash. This is a great simple preamplifier unit to bring out the most in your power amps.

DIY 6DJ8 (ECC88) Tube Headphone Amplifier DIY 6DJ8 (ECC88) Tube Headphone Amplifier - 24 November 2012  USA Flag
This low power tube headphone amplifier project comes from Bruce Heran. The simple tube headamp uses one 6DJ8 (ECC88) tube per channel. The amplifier circuit is push-pull and biased into class-A operation with a CCS. Gain is sufficient that no driver stage is required for the tube amp. The 6DJ8 tube headphone amplifier is suitable for use with many Hi-Fi headphones. Output power is over 100 mW between 32 ohms to 300 ohms. The response is 20 Hz to 28 kHz within 0.5 dB and the wide band signal-to-noise is -84 dB.

Mini Block Ultra-Linear Class-A Push-Pull EL84 (6BQ5) Valve (Tube) Amplifier DIY EL84 Push-Pull (Class-A, Ultra-Linear) Amplifier - 30 September 2012  USA Flag
Bruce Heran of OddWatt Audio outlines the design and construction of monoblock Push-Pull EL84 (6BQ5) valve amplifiers. The Mini Block tube amps use a 5751 twin triode to drive the EL84 push-pull output stage which is biased into class-A operation, ultra-linear mode. Output power is 5.8 W @ 2% (0.25% @ 1 W) and the response is 10 Hz to 44 kHz within 0.2 dB. Bruce reports that the Mini Blocks are more powerful than the Poddwatts and seem to have more detail while retaining all the good characteristics of the Poddwatt amps.

DIY (12AX7 / 12AT7) Tube RIAA Phono Preamp DIY (12AX7 / 12AT7) Tube RIAA Phono Preamplifier - 1 November 2011  USA Flag
The latest project from Bruce's workbench is the Groovewatt, a tube RIAA phonograph preamplifier design. The preamp uses a solid state HT power supply and DC for the heaters. Gain is 45 dB, sufficient for use with a high output MC cartridge. The design uses two 12AX7 SRPP gain stages, passive RIAA equalization and a 12AT7 cathode follower.

DIY parallel push-pull 300B tube monoblock amplifers Parallel Push-Pull 300B Tube Monoblock Amps - 29 September 2010  Netherlands Flag - [External Link]

Rudolf Moers shares with us his parallel push-pull 300B tube amplifier design. The large 25 kg (55 lbs) monoblock amplifiers were built over a period of 14 months and cost about 1300 Euro. The input stage of the amplifiers consist of a preamplifier and cathode phase splitter using a ECC82, a driver stage using a ECC99 and cathode followers using a ECC82 tubes. The output stage uses four 300B directly heated power triodes in a parallel push-pull configuration. The output power is about 25W. An AX50 tube rectifier is used for the HT supply and all heaters are operated using DC.

DIY ECC802S (12AU7 / ECC82) Vacuum Tube SRPP Preamplifier DIY ECC802S (12AU7 / ECC82) Vacuum Tube SRPP Preamplifier - 23 August 2010  USA Flag
Bruce of OddWatt Audio shares with us his ECC802S tube SRPP preamplifier design. The preamplifier uses a solid state power supply and DC is used for the heaters. The gain of the preamp can be set at 7 or 11. 12AU7 and ECC82 tubes can also be used. The tube preamplifier measures well performance wise and Bruce reports very clean and detailed sound with that typical warm lush tube sound.

DIY 12AU7 / IRF510 Headphone Amplifier DIY 12AU7 (ECC82) / IRF510 Headphone Amplifier - 12 April 2010  USA Flag    Low Voltage 

Rogers has built an improved version of his popular and simple low voltage 12AU7 / IRF612 Headphone Amplifier (5 Aug 2008). The new version allows novice builders to experience assembling and listening to their own headamp. The headphone amplifier is similar to the previous version in that a single 12AU7 (ECC82) vacuum tube is used for voltage gain and an IRF510 MOSFET follower stage is used to provide current to drive demanding headphones. The hybrid tube and MOSFET amplifier operates off a 12V SLA battery so there are no high voltage concerns. The main difference from the original version is that a LM317 regulator is used as a CCS to bias the MOSFET into class-A operation instead of a load resistor. The project includes PCB image files and can also be built on a protoboard. This simple headphone amp can be built for about $40-50.

DIY 6L6 / 5881 Single-Ended (SE) Tube Amplifier DIY 6L6 / 5881 Single-Ended (SE) Tube Amplifier - 9 February 2010  Thai Flag

This fantastic looking tube amplifier was put together by Mr. Chey in Thailand. The DIY enclosure is constructed from aluminum sections and the audio output transformer covers are built using copper clad board. The circuit is very simple, a single-ended output stage using 6L6 or 5881 tubes, driven by 6SJ7 or 6SD7 cutoff pentodes. Mr. Chey is very pleased with the results and has replaced his solid state amp with this beauty. Nice work!

DIY KT88 Push-Pull Monoblock Tube Amp Kit DIY KT88 Push-Pull Monoblock Tube Amp Kit - 30 November 2009  Canadian Flag    KIT 

A build and review of the Odd Block KT88 Series 1 Tube Amp Kits. The monoblock tube amp kit uses an SRPP input stage with 5751 driver tubes and a push-pull output stage with KT88 power tubes. A constant current source (LM317HVT voltage regulator) is used to force the output stage into class-A operation. A solid state power supply is used. The tube amp kit comes with a nice steel enclosure and the power output is about 25 watts. The amplifier circuit is very simple with minimal parts in the signal path. The result is a very nice sounding tube amplifier kit that performs well.

5751 SRPP / EL84 (6BQ5) Push-Pull Tube Amp 5751 SRPP / EL84 (6BQ5) Push-Pull Tube Amp - 19 Oct 2009  USA Flag   UPDATED  (8 Oct 2012)
Bruce has constructed another one of his great sounding OddWatt tube amplifier designs, the PoddWatt. This one is very similar to the first Push-Pull EL84 (6BQ5) Oddwatt project from nearly two years ago. The tube amp uses EL84 / 6BQ5 valves in a self-inverting push-pull (SIPP) topology with a 5751 SRPP driver stage. The amplifier measures well and Bruce has reported that the sound is very good with clean detailed mids and highs and a great sound stage.


DIY KT88 Push-Pull Tube Mono Block Amplifiers KT88 Push-Pull Mono Block Tube Amplifier Project - 29 October 2008  USA Flag   UPDATED  (9 Oct 2012)
Bruce's second follow up to his original "OddWatt" project are the "Odd Blocks", a pair of KT88 Push-Pull Mono Block Tube Amplifiers. Like the Oddwatt 225, the mono block tube amplifiers will work with a number of octal tubes (KT77, 6CA7, EL34, 6L6GC, KT88, 6550, KT90). Like the previous projects the driver stage is an SRPP but this time with the 12SL7 tube and the output stage is a Class A UL SIPP with KT88 tubes. LM317HV Regulators are used for the cathode CCS.

KT88 Single Ended (SE) Tube Amp KT88 Single Ended (SE) Tube Amp - 11 June 2007  Philippines Flag

Alex has pulled together a single ended tube amp based around the popular KT88 valve. EL34 tubes can be used in place of the KT88 tubes. The preamplifier tube is a inexpensive 6N1P, but the 6DJ8 / ECC88 / E88CC family of tubes can also be used. The power supply uses a 5U4 dual rectifier.

5687 Tube Preamplifier 5687 LED Biased Tube Preamplifier - 1 March 2007  Singapore Flag

Vincent has pulled together a fine looking preamplifier that is based around the 5687 twin triode. Each channel uses both sections of a 5687 vacuum tube with LED biasing used on each section. To keep potential hum at a minimum, the heater filaments are supplies with DC. To further minimize the potential for unwanted noise, the power supply is external to the preamp section and consists of a RCA-83 mercury rectifier and two 50H chokes. Very nice work Vincent.

S-5 Electronics Tube Amplifier Kit More Modifications for the K-12M Tube Amp Kit - 25 January 2007  USA Flag    KIT 

Another S-5 Electronics K-12M Tube Amplifier Kit! This is Bruce's build of the popular and inexpensive Tube Amplifier Kit. Bruce has completed several modifications which include many of VoltSecond's mods, new input and coupling caps, a beefed up power supply and upgraded output transformers wired in Ultra Linear (UL) Mode.

S-5 Electronics Tube Amplifier A Case for the K-12M Tube Amplifier Kit - 9 November 2006  Australian Flag    KIT 

This is Mark's build of the S-5 Electronics K-12M Tube Amplifier Kit. In fact, Mark has built three of these fantastic kits! His modifications include snubbers, a beefed up power supply and upgraded power and output transformers.

K-12M Integrated Tube Amplifier K-12M Tube Amplifier Kit - 2 January 2005  Canadian Flag    KIT 
This inexpensive Tube Amplifier kit has been available for a number of years now and makes for a nice little tube amp. Don't let the inexpensive price tag fool you, as this tube amp can go head to head with amps that cost $800. With its very modest price tag, this kit is an affordable step into the wonderful world of vacuum tube audio. I have provided information about my experiences with the K-12M kit as well as several modifications and upgrades that I have tried out.

Discontinued Tube Amplifier Kits and Superseded Tube Projects

The following projects pages are of diy vacuum tube amplifier kits that are now discontinued or tube projects that have been superseded by a more up to date project.