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 NEW    Bruce Heran outlines the details and construction of his simple DIY 6DJ8 (ECC88) Tube Hi-Fi Headphone Amplifier Project.

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Jan6814HPAmpIISmall.jpgJAN6418 portable Triode Headphone Amp MkII2257 viewsThis is a straight build of the oatley electronics sub-mini headphone driver and preamp. In other builds where the basic cct. brd. is used as a preamp the passive components are upgraded and the PT2308, headphone driver chip, though very good, has been upgraded. Not here. This build uses the stock components that came with the kit. See the JAN6418 Valve (Tube) Preamplifier / Headphone Amp Kit project page for more information and other build variations..
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6T9-Tube-Amp-Front.jpg6T9 Hi-Fi Tube Amplifier Project2309 viewsDIY build of a single-ended 6T9 Tube Amplifier using the PCBs from Spare Time Gizmo. The power and audio output transformers are from Edcor. Mark's 6T9 ultra-liner tube amp modifications were used.
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6T9-Tube-Amp-Rear.jpg6T9 Hi-Fi Vacuum Tube Amplifier2113 viewsRear view of the DIY 6T9 Tube Amplifier. The amplifier uses circuit boards purchased from Spare Time Gizmo. The power / filament transformer and audio output transformers are from Edcor. Mark's 6T9 ultra-liner tube amp modifications were also used.
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TeaBoxRearSmall.jpgTwinings Tea Box 12AX7 Tube Preamp with Remote PS2487 viewsIn this image you can see the RCA connections and power connections for the remote PS. An XLR plug and socket provide a solid connection for the power cord. Two sets of switchable inputs allows two devices to be selected. A three wire power cord provides 250VDC HT, 6VDC and common earth to the preamp.
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TeaBoxPreampSmall~0.jpgTwinings Tea Box 12AX7 Tube Preamp with Remote 5Y3 PS2326 viewsThis is my second build of the Twinings Tea Box 12AX7 tube preamps with separate 5Y3 valve rectification. Others I have built used an internal or remote SMPS. This build used the massive and expensive Jensen copper, paper and oil caps. Silver wire, WBT silver solder, Solen Teflon caps (feedback) component-2-component wiring make this an exceptional build. There is no cct. brd. A remote PS with valve rec. (Ozzie 5Y3) and Hammond power transformer and 12H choke provide very clean robust power to the preamp Tea Box.

The sound is very 3D with sound stage deep and wide. The full passion of the music comes through with staggering detail making most instruments (acoustic anyway) sound very different. This build has been commissioned by a very astute audiophile in Denver, Colorado. I know he will be pleased. It goes with well used AWA (Amalgamated Wireless Australasia) 12AX7 valves, rare but sweet sounding.
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TeaBoxInsideSmall.jpgTwinings Tea Box 12AX7 Tube Preamp with External 5Y3 Power Supply2394 viewsIn this build I used the Jensen copper, paper and oil caps for the input, output and inter-stage coupling and Solen Teflon for the feedback capacitor. The preamp is a two stage triode (12AX7s AWA-Australian) with global feedback and is the original Silicon Chip design with some modifications. They are bigger caps all round and no printed cct. brd. Construction of brds. was component-2-component wiring which means there is NO additional wire used on the brd. construction. At the brd. level this is better than point-2-point wiring. This cuts down on soldered connections/junctions and cct. length. All 99.999% pure silver wire with heat shrink insulation is used in the signal path to connect brds. to RCAs and Alps blue velvet pot etc. Medium gauge OFC hook-up wire brings power to the brds. Heavy bituminised Al foil lines the light timber case to provide a ground plain and RFI/EMI shielding. The remote PS employs a 5Y3 rec. tube (Australian made in this case) Hammond 370X power tranni 193B 12H choke.
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JJ-Tesla-Blue-Glass-KT88-Vacuum-Tubes.jpgJJ / Tesla Blue Glass KT88 Tubes2439 viewsA set of Blue glass envelope JJ / Tesla KT88 vacuum tubes used in the Odd Blocks - KT88 Push-Pull Class A DIY Tube Amplifier
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KT88-Push-Pull-Vacuum-Tube-Hi-Fi-Amp.jpgKT88 Push-Pull Tube Amplifier with 12SL7 Driver2377 viewsKT88 Push-Pull Tube Amplifier with a 12SL7 Driver stage and a 6NO30 thermal delay relay tube. The amplifier is build following Bruce's 12SL7 SRPP / KT88 Push-Pull DIY Tube Amp build. The power tubes are new production KT88 Gold Lions made by Genalex.
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Genalex-Gold-Lion-KT88-Vacuum-Tubes.jpgGenalex Gold Lion KT88 Vacuum Tubes2434 viewsClose up view of the Genalex Gold Lion KT88 Vacuum Tubes. The amplifier topology is Push-Pull and built following Bruce's KT88 Push-Pull Class A DIY Tube Amp with 12SL7 Driver build. The extra tube is a 6NO30 which delays the B+ so the tubes have time to warm up.
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Jan6418JewelBox.jpgRaytheon JAN6418 sub-mini valve preamp in a Jewelery box2316 viewsNot much to see here except to note this is an extremely "pretty" jewelery box of the timber variety. The box was reduced from $60 to $30 and this purchase prompted me to build the preamp. I like my pretty and cute enclosures. See other images for more detail. The preamp modules are part of a kit from Oatley Electronics Australia but many parts have been upgraded. The back holds a brushed Aluminum bar with the input/output RCAs and power switch. Should battery voltage fall below 6.8V (two lithium 9V batteries power the unit) a led on the cct. brd. will light. Lifting the gold catch and taking a look will disclose this.

The box is heavy and the wood thick and the Makassar timber pattern on the lid makes this a stunning enclosure, especially if you are bored with putting your creations into plain tin boxes. The preamp plays well but the tubes take a few hours to burn in so be warned.

Full details and variations to this tube preamp kit are available on the JAN6418 Valve (Tube) Preamplifier Kit page.
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Jan6418JewelBoxInside.jpgInside the sub-mini Jewelery box preamp2738 viewsI have a weakness for "cute" enclosures, particularly timber ones. The mirror is just a bonus. The circuit board is part of a kit from Oatley Electronics Australia. I have replaced the carbon resistors in the kit with metal film, the 0.1uF MKT caps with 0.47uF polypropylene types, the 220uF electrolytic caps (output) with 470uF low ESR types. Also the PT2308 headphone driver chip was replaced with a Burr-Brown OPA2134 OP amp chip. 2 X 9V lithium batteries provide 9V to a L4949 regulator which controls filament current to the Raytheon JAN6418 sub-mini valves. Attenuation is trim set and volume controlled by external devices.

Three grommets are used as valve dampeners. These tiny valves can be extremely microphonic. Three grommets stops the microphonic problems dead! The amp is extremely quiet. See the JAN6418 Valve (Tube) Preamplifier Kit page for full details.
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Jan6418JewelBoxRear.jpgJAN6418 Sub-mini preamp in a plush Jewelery box2137 viewsThe rear of the Jewelery box has a brushed Aluminum plate to hold the input / output RCA connections and on off switch. The wood was too thick to mount the RCAs directly. See other photos of this build for more info about the JAN6418 Sub-mini preamp.

Complete details about this low cost and low voltage tube amp kit are available on the 6418 Tube Preamplifier Kit page.
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12AX7-Tube-Preamp-Kti-Enclosure.jpg12AX7 Tube Preamplifier Kit2545 viewsA finished photos of the 12AX7 Tube Preamplifier Kit. The volume control is an Alps pot salvaged from an old Sony amp. I added a second input and switch to allow multiple inputs. There is also a second out for a subwoofer.

The preamp is dead quiet and the sound is far more than I had hoped for. My spouse was skeptical, shall we say. But when she heard familiar music she was hearing things never heard before and the bass was thicker and richer. I heard a much bigger sound stage, sparkling highs. Very impressive. Thanks to Bruce Heran for all his help with this project.
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12AX7-Tube-Preamp-Kti-Bottom.jpg12AX7 Tube Preamplifier Kit - Bottom2666 viewsAn underside view of the 12AX7 Tube Preamplifier Kit . The chassis was made from scrap cherry wood finished with stain and varnish. The top plate is 2mm thick aluminum, from a metal fab shop.
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JAN6418HPD_GalleryII.jpgRaytheon JAN6418 sub-mini valve headphone amp 2501 viewsThis shot shows the Oatley Electronics Kit in a small case to be constructed as a headphone amp/driver. The small cct. brd. is double sided, plated through, solder masked and screen printed. Construction is simple and this $AU27 kit makes an excellent first valve kit of any DIYer. See the other image for the completed headphone amp. The L4949 5V reg. chip lights the led for the first second it is on then only re-lights when the battery voltage falls below 6.8V. Nice touch. The reg chip supplies 5V to the filaments which are in series with a 270omh resister. The amp only draws 12mA. Two 9V lithium batteries power the unit. In the preamp version the PT2308 headphone driver chip was replaced with a Burr-Brown OPA2134. Excellent sound stage and rich bass. And it is a portable headphone amp!

There is more information available on the JAN6418 Valve (Tube) Headphone Amplifier Kit page.
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JAN6418HPD_Gallery.jpgRaytheon JAN6418 sub-mini valve portable headphone amp2466 viewsJust when you thought you had seen it all something "different"comes along. This 9V valve front-end headphone amp/driver is based on a Oatley Electronics (Australian) kit. I built the kit stock standard and loved the sound. Then upgraded most parts to make a "Signature" strength preamp version. A L4949 5V regulator chip and PT2308 headphone driver come with the kit which also has two Raytheon JAN6418 sub-mini valves. As a preamp (replace the PT2308 with an OPA2134) or headphone amp the kit is excellent. I run both on two 9V lithium batteries in parallel.The amp only draws 12mA! Soundstage is excellent and bass rich and extended. The bandwidth is <10hz to 50Khz (-3db points).

See the JAN6418 Valve (Tube) Preamplifier / Headphone Amp Kit project page for full details.
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furniture_014_YMax_red.jpgSET Tube Amo with 6BX7 twin triode3102 views6BX7 Single Ended Triode tube amplifier, 3 watts per channel, Transcendar audio Output Transformers, a 12 LED Watt Level "Meter", built with Poplar and Brass
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DIY-6s45p-300B-GU-48-Tube-Amplifier.jpgDIY 6s45p / 300B / GU-48 Tube Amplifier - 125 Watts4091 viewsMy 125W tube amplifier. The input tube is 6s45p which drives a 300B and is followed by a GU-48 (replacement for the 833 tube). The 6s45p input tube is DC coupled to a 300B. There are no resistors or capacitors in the signal path. The 300B is coupled to a GU-48 tube through a step-down interstage transformer. Driver and output tubes are fixed biased for more natural and dynamic result. Output tube is working at 1000V-250mA. Amplifier gives me 125W single ended sound in class A2 mode. It has very powerful deep bass, mids are very loud and lovely. Highs are very clear. I am feeling like in concert hall. The case is made from 20mm thick African Wenge wood. Chassis is 2 mm thick electrostatic painted steel. The total weight is 50 kg.
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6s45p-300B-GU-48-Tube-Amplifier.jpg6s45p / 300B / GU-48 Tube Amplifier - 125 Watts3736 viewsA 125W DIY tube amplifier. Tube compliment is a 6s45p input tube that drives a 300B tube and followed by a GU-48 tube. See the other DIY 6s45p / 300B / GU-48 Tube Amplifier photo for a full description on the tube amp.
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DIY-6V6-Push-Pull-Tube-Amp.jpgDIY 6V6 Push-Pull Tube Amplifier2750 viewsA photo of a 10W 6V6 Push-Pull Tube Amplifier put together by Michael S. Holden. Michael has put together a detailed set of instructions for this tube amplifier project:

10W 6V6 Push-Pull Vacuum Tube Amplifier (Class-AB) - Michael S. Holden - (PDF 3.4MB)
234 files on 12 page(s) 7


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