DIY Vacuum Tube (Valve) Amplifier Projects
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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! A couple of the tube projects are low voltage and if you are new to tubes and high voltage safety you should start with these. For those comfortable with high voltage, the S-5 Electronics tube amplifier kits make good inexpensive first tube amplifier project. If you have a DIY tube project that you would like to share with others through this website, please contact us.
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Follow DIY Audio Projects
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DIY KT88 Push-Pull Monoblock Tube Amp Kit - 30 November 2009  NEW!
A build and review of the Odd Block KT88 Series 1 Tube Amp Kits. The monoblobk 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 plath. The result is a very nice sounding tube amplifier kit that performs well. |
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DIY 5751 SRPP / EL84 (6BQ5) Push-Pull Tube Amp - 19 October 2009 
Bruce has constructed another one of his great sounding OddWatt tube amplifier designs. 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 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. |
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DIY 6418 Tube Preamplifier / Headphone Amplifier Kit - 24 August 2009  Low Voltage
Mark discovered this low cost and low voltage tube amplifier kit that preforms well. The small tube kit can be powered from a single 9V battery and this makes the kit ideal for those new to electronics and high voltage. Mark reports good sonic performance from the little kit which can be used as a preamplifier or a headphone amp. The kit is $27AU (less than $25US August 2009) but you will have to add your own enclosure and hardware. |
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DIY 12AU7 Tube Preamplifier Project - 24 November 2008
This is Alan's very simple tube preamplifier using common 12AU7 vacuum tubes. The preamp is built around parts that Alan had on hand. To keep costs down, the preamp can be built using 12V transformers put back to back in order to get the required high voltage. Total costs for this project were about $30, most of which went towards the enclosures and RCA jacks. |
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6T9 Push-Pull Tube Amplifier Project - 8 November 2008
Inspired by the Spare Time Gizmo 6T9 Tube Amp, Steve has put together a push-pull amplifier using 6T9 compactron vacuum tubes. Circuit ideas for the push-pull output stage came from an EICO HF-81 and a RCA Receiving Tube Manual and a 12AX7A tube is used in the preamp stage. The enclosure is made from a sheet of brass and the wood is Poplar that has been stained with Minwax Red Mahogany stain and finished with an Amber Shellac. |
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DIY 6T9 Single-Ended Ultra-Linear Tube Amplifier (external link) - 4 September 2008
Mark's second single-ended (SE) 6T9 Compactron tube amplifier built using the printed circuit boards from Spare Time Gizmos. The tube amp is built into a steel chassis. Audio output transformers from Edcor were used. Mark completed a number of small upgrades to the basic circuit and has wired the output stage to operate in ultra-linear mode. |
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KT88 Push-Pull Mono Block Tube Amplifier Project - 29 October 2008
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. |
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12AU7 (ECC82) Tube / IRF612 MOSFET Headphone Amplifier - 5 August 2008 Low Voltage
A compact and simple hybrid (Vacuum Tube / Solid State) headphone amplifier. This head amp uses a single 12AU7/ECC82 tube for the voltage gain and a FET follower stage to supply high current. The 12AU7 tube operates at low voltage (12-13V) so there is no high voltage shock hazard. Total costs for this project are about $40 and Rogers is very pleased with the results. |
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DIY 6T9 Tube Amplifier Project - 28 July 2008
A small single-ended tube (valve) amplifier project based around the 6T9 compactron vacuum tube. This tube amplifier project has been built using a purchased PCB and for the enclosure Mark used an inexpensive baking pan. The small amplifier only has a few Watts of output, but Mark reports very good results with high efficiency speakers. |
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KT77 Push Pull Tube Amplifier Project - 19 May 2008
Bruce has followed up his "OddWatt" project (EL84/6BQ5 Push-Pull) with the Oddwatt 225. The Oddwatt 225 is a scalable tube amplifier which will work with a number of octal tubes. In this build the driver stage is an SRPP with 6SL7 tubes and the output stage is a Class A UL SIPP with KT77 tubes. LM317 Regulators are used for the cathode CCS. |
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EL84 Push Pull Tube Amplifier Project - 22 October 2007 
Bruce latest project, the "OddWatt" is a EL84/6BQ5 Push-Pull Tube Amplifier. The driver stage is an SRPP with ECC802S tubes, while ultra linear operation is used for the output stage with Sovtek EL84 tubes. LM317 Regulators are used for constant current sources (CCS) of the output stages. 12VDC is used for the tube heaters. |
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K-502 Valve (Vacuum Tube) Amplifier Kit - 9 July 2007 
Given the low cost and great sound of these tube amp kits, it is no surprise they are popping up everywhere. This is Scott's build of the inexpensive K-502 tube amp kit. It features a fantastic looking enclosure and uses a stepped attenuator for volume control. |
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KT88 Single Ended (SE) Tube Amp - 11 June 2007 
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. |
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The "Beauty" - 12AX7 Tube Preamp - 1 May 2007
Bruce has put together a 12AX7 Tube Preamplifier to accompany his LM3875 Chip Amp. He has named the tube preamp "Beauty" as it sweetened the sound of his LM3875 Chip Amplifier. For the enclosure, Bruce used a readily available plastic and aluminum project box from Radio Shack. Similar to what Mark discovered with this economical tube preamplifier kit is that you get a very quiet preamp that can compete with ones that cost much more. |
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K-502 Tube Amplifier Kit and The DelSol Speaker - 5 April 2007
This is Barry's build of a K-502 Tube Amplifier Kit and The DelSol Speaker which uses the Aura NS3-194-8E fullrange driver. The enclosure for the K-502 Tube Amp Kit is wood and plexiglass. Together these two projects make a great looking hi-fi unit. Nice work Barry! |
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5687 LED Biased Tube Preamplifier - 1 March 2007 
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. |
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12AX7 Tube Preamplifier Kit - 12 February 2007
This is Mark's build of a simple and inexpensive tube preamplifier kit. The preamp kit is based around a common 12AX7 dual triode. What makes this kit inexpensive is that power comes from a switch mode power supply, fed from a 17 volt DC wall wart! Mark's modifications to the kit include snubbers and upgraded capacitors. The end result is a simple DIY tube preamplifier that sounds great and will keep some money in your pocket for the next project. |
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More Modifications for the K-12M Tube Amp Kit - 25 January 2007
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. |
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A Case for the K-12M Tube Amplifier Kit - 9 November 2006
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. |
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DIY Single-Ended (SE) 50EH5 Tube Amplifier - 14 May 2005
Having completed my first tube amplifier project, I decided to go back to the basics for my next project and construct a very simple Single Ended (SE) amplifier. This SE amplifier is based around the 50EH5 power pentode. The component count in this amplifier is very low and the result is a small (1.4W) neutral amplifier that sounds very good. The total costs for this project were less than $15US! |
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K-12M Tube Amplifier Kit - 2 January 2005
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. |