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BoydSmall.jpgJAN6418 sub-mini valve preamp kit MKII3351 viewsYet another build of the Oatley JAN6418 valve preamplifier / headphone amplifier kit. This one was built to order. An Alps blue velvet pot and 4oz brass knob and pure silver hook-up wire add to the build quality.
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00005.jpg25EH5 / 50EH5 Tube Amplifier3342 viewsAnother view of the amplifier from the top. As you can see, I was using headphones as I took the effort of adding a jack with impedance matching resistors so I could listen to my music in peace. The funny thing is that I can apply just about any load to the amplifier without any audible change other than volume.
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TeaBoxII.JPGTea Box 12AX7 Valve Preamp II3341 viewsSee the previous photo for more detail. In this image you can see the solid brass cones, 4oz brass knob and another view of the preamp. The SMPS is contained inside making one very neat and attractive looking valve preamp. Golden Dragons replace standard 12AX7 valves.
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000pbs6w.jpg25L6G Tube Stereo Amplifier3340 views25L6G Tube Stereo Amplifier
A work in progress. This is only an assemblage of parts so far with nothing bolted together, but it gives sort of a preview of the finished project. The chassis will be painted black wrinkle much like the transformer covers in the back. The driver tubes are 12SN7s and 6SL7s
-Steve (zstrat)
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DIY-6V6-Push-Pull-Tube-Amp.jpgDIY 6V6 Push-Pull Tube Amplifier3338 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)
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rectifier_tube_150_amp_6_phase.jpgMassive Rectifier Vacuum Tube (Valve)3329 viewsWhat a tube! This is a vacuum tube rectifier. 150 Amps with 6 channels.
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EL84-Push-Pull-Tube-Amplifier-OddWatt.jpgEL84 Push-Pull Tube Amp after OddWatt3318 viewsEL84 Push-Pull Tube Amplifier built following the concepts of the OddWatt EL84 Push Pull Tube Amplifier Project.
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SynergyII-Cu-LM3875-Gainclone.jpgSynergyII\Cu - LM3875 Gainclone3314 viewsSynergyII\Cu started with 3.6kg of 100% very thick copper plate. The enclosure was selected, a 1U, 19" rack mount. The challenge was to build a pure Gainclone with its three resistors and simple 1500uF storage capacitors in a compact 1U enclosure. Everything had to fit in this tiny space including two 48VAC toroidal transformers for the dual mono supply, The LM3875 amplifier weighs 9.6 kg. The sound is clear, clean and solid with bass extended and very controlled.
See the original Synergy LM3875 Gainclone Amplifier (Chip Amp) project page.
Mark Houston – retro-thermionic
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Oatley-Electronics-K295-Tube-Buffer-Kit.jpgOatley Electronics K295 Tube Buffer Kit3296 viewsThe production version of the K295 has been cased in a bitumanised Al lined plastic plastic case. Guitar jack input and outputs are on the rear and large numbered knobs on the front. The blue led indicates "0" position of the attenuators. The preamp can be plugged directly into the mains. Good sounding and simple to build.
There is more information in the K295 stereo JAN6418 tube buffer / preamp kit thread.
Mark Houston (Australia) - Mongrel Dog Audio
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71-A-Tube-Amplifier-SE.jpgUX-171A Tube Amplifier3283 viewsThis amplifier uses the UX-171-A tube (matched pairs) which are rare and produce only 1/2 W of output power. There are no resistors or capacitors in the audio circuit. A Hammond 124B nickel core inter-stage transformer couples to the power tube. Edcor 10W OPTs in the metal case. Bias is provided by 3 x 9V batteries and 230V by two step-down transformers wired in reverse. The rectifier tube is a very old "80". Power supply filtering is under the top plate (ply timber). The base houses the power transformers and is a 1940s wooden pot stand. The tube amplifier sounds excellent.
For more info, see the 171-A single-ended amplifier thread in the forum.
Mark Houston – retro-thermionic
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RH84_-_SE_EL84_Tube_Amp.jpgRH84 - SE EL84 Tube Amplifier3277 viewsThe first tube amp I built and I love the sound... pentode power with triode sound! The amplifier topology is the RH84 from designer Alex Kitic. I am using JJ EL84 and Sylvania 12AT7 tubes. The most important aspect of this ingenious design is the plate to plate partial feedback without global feedback, 2nd harmonic distortion is slightly increased giving the impression of listening to a SET amp. Damping factor and bandwidth are also improved. The OPT are from a salvaged an RCA console - a gift from Dave of Planet10 (thanks).
What a great amp !
Isophon, Canada
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KitAmpTopSmall.jpgKT88 SE UL Tube Power Amplifier3267 viewsI had put the partially finished amp in the gallery some weeks back. Now finished not a lot of difference on the outside except for the many silver colored screws on the top plate and some feet. See the other image for the underside shot. After a number of hours of careful listening and listening to it though others CD players, pre-amps and speakers I can say that most liked the sound. SE tube amps produce absolute and exquisite mid-range and silky highs and deep sound stage but this amp has a slightly narrow sound stage presentation. Bass improved and hum vanished with additional PS filter caps. With a brushed Al top plate and Mirabue timber thick timber base, Edcor XSE OPTs and component-2-component wiring on all circuit boards (including rectifier broard) this amp represents a clean and easy build with in-expensive parts. Though low powered (6W+) for a few hundred dollars you can experience the benefits of a tube SE UL design. So easy, so nice!
Here is a link to the KT88 Single-Ended (SE) Schematic I followed.
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Tube-Amp.jpgSV811-10 single-ended tube amp.3267 viewsRussian Svetlana SV811-10 Single Ended Monoblock tube amp.
Circuit by Eric Barbour.
See it on YouTube. @closin99
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photo-4.jpgBob's Dynaco ST-35 with VU Meter3263 viewsTube amp using Dynaco ST-35, Edcor iron and a plasma VU meter using IN-13 nixie tubes.
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Single-Ended-300B-Tube-Amp-MockupIIs.jpgSingle-Ended 300B Tube Amplifier - Mockup IIs3253 viewsThis is my first 300B tube amplifier. The power supply will be separate from the amp. The tubes are $1200 rrp TJ Full Music 300B/SE carbon plates. The 6SN7 is a 50 year Treasure. The audio output transformers are 30W Hammonds. The base is Mirbeau and the top and bottom plates are 2mm thick aluminum. Signal wiring is 0.7mm pure silver wire and super heavy gold plated speaker binding posts.
For the design information see the 300B SET Design Project thread on the forum.
Mark Houston (Australia) - retro-thermionic
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12AX7-Tube-Preamp-Kti-Bottom.jpg12AX7 Tube Preamplifier Kit - Bottom3249 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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SE-6AS5-Pentode-Amp_.jpg6AS5 Micro-Power 1W/channel UL Amp3244 viewsA nice class-A stereo amp based on the 6AS5 pentode. The amp uses a 6CG7 driver tube to drive the output stages in UL mode. The chassis is black walnut with a strip of lacewood inlay for contrast. Power level is only 1 watt per channel calling for high sensitivity loudspeakers. The input sensitivity for full output is a little over 1v peak so this amp can be driven by just about any MP3 or CD player or even a simple line level input.
Matt Renaud
Pacific Northwest, USA
Project Thread: Micro-power UL - The Amp that Never Ends
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PhonoFront.JPGPhono Preamp Kit with RIAA Equalization3239 viewsAfter resurrecting the Rega TT and RB300 tone arm with a Grado Sonata wood body cartridge I went on the hunt for a phono preamp. The Pro-Ject PhonoBox SE preamp was a value for money purchase, a neat and good sounding unit. This phono premp kit cost under $AU100 to build (including AC adapter) and challenges the Pro-Ject on a the sonic level. I can find no fault musically with the kit which has no hiss or hum and a natural sound quality. It is available from Jaycar Australia. Better than the Pro-Ject by provide the facility to have three different selectable compensations including RIAA and early DECCA (ffrr) and a host of others to select from. And to go one step better again there is a gain control to balance between CD and phono input levels. The case is ABS plastic and tar and foil lined. Gold RCAs used (see other photos). A +/- 12V regulated PS is include on the one peace cct. brd. The PS is shielded. Distortion is rated at .014% and RIAA accuracy is better than 1db. Signal to noise is -84dB.
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Oatley-Electronics-K272B-prototype.jpgOatley Electronics K272B prototype3235 viewsSoon to be released Oatley Electronics K272B prototype. I recently made two CMoy style, OPA2134 based, HP amps but now prefer the better sounding, harmonically rich, K272B build. Two 9V batteries are used in parallel to prolong battery life and switching phone jacks, power switch and “on†LED ensures it is difficult to accidentally leave the amp on. The enclosure is impact resistant ABS which is heavy Al foil lined. Volume control is via your player and the “6418-B†will drive low impedance phones. Where the CMoy style, chip based, HP amps are clean, clear, bright and clinical, the “6418-B†has a much richer, more harmonically complex sound and a smoother all over delivery. Really it all gets down to taste. I would recommend building the K272B when released around early February 2013. I suggest you upgrade the Oatley passive parts and chip socket to better quality parts.
For more info, see the
Oatley K272B JAN6418 headphone amp and preamp thread in the forum.
Mark Houston – retro-thermionic
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parallel-6C33C-tube-power-amplifier.jpgDon's parallel 6C33C tube power amplifier3232 viewsDon the amp builder (who’s 300B amp is posted in the gallery) has put together this parallel 6C33C power amp. Though not complete it’s not hard to see this is going to be a great looking amp. With the twin power tubes the primary impedance of the OPTs can be lowered to produce greater output power. The toroidal transformer is for the heaters which draw a huge amount of current. The top plate is ABS and Don made the base and is now making bases for me. All other trannies are Dyne who a local winders (Victoria Australia). Can’t wait to hear this one. Don also has a 2A3 almost finished.
Mark Houston
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