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KitAmpUnderSmall.jpgKT88 SE UL tube power amp - underside3521 viewsThe underside of a KT88 SE UL power amp consists of, Edcor XSE series OPT, Hammond 10H choke, rectifier unit with SF diodes and 200uF of filtering. Turret boards were used for the KT88 sockets (ceramic), cathode resistors and bypass caps. All other components are wired, point-to-point, on a smaller circuit board X2 caps are used for the coupling caps. All component are inexpensive and readily available. The amp suffered from hum until the filter caps were increased. 100uF before and after the choke are required. The PS delivers a very quiet 410V. 30V is dropped across the cathode resistors which provide the biasing to the power tubes. At idle 63mA is drawn per tube. The sound is extended and detailed with a 6W delivery. Excellent sound stage depth. Frequency range is from 35Hz to 46kHz (-3dB points).
The amplifier follows the Single-Ended (SE) KT88 Tube Amplifier Schematic by Mikael Abdellah.
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SE-EL34-Signature.jpgEL34 Signature - SE - Mark3520 viewsThis amp is my new EL34 the "retro-34UL", Signature EL34 amp. Valve compliment is NOS Svetlana EL34 and Svetlana 6N1P. Edcor GXSE 6 ohm ultra-linear audio output transformers, the 10H choke and power transformer are Hammond. Inter-stage capacitors are Jensen copper, paper and oil with pure silver leads. Biploar capacitors are used as bypass caps on the EL34 with ceramic sockets to hold the audio tubes. The rectifier valve is a Golden Dragon 5U4. The audio output transformers are rubber mounted. The top plate of the amplifier chassis is ABS plastic and base is Australian Spotted Gum (oiled). Feet are filled with lead sinkers and rubber glue, silver solder and silver plated wire used throughout the build. The circuit topology is Single-Ended with Ultra-Linear operation.
Mark Houston – retro-thermionic
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Blue_Velvet_Pre_Night_shot.jpgBlue Velvet Tube Preamp - Night Shot3517 viewsThis is my second audio DIY project. A Blue Velvet Preamplifier. Picture taken in the dark.
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a1little1.jpg6V6 12AX7 Stereo Amp3487 viewsLittle stereo vacuum tube amplifier built for a friend who wanted a tube stereo at minimal cost. It used mainly parts on hand, including a vintage radio power transformer, vintage tube sockets, and NOS 5 watt Zenith audio output transformers made for 6V6 single-ended output stages. The driver tube is 12AX7 and the tube rectifier is 5Y3G. Output tubes are old Zenith 6V6G tubes, the tall ones that look prettier than the GT style. The tube amp delivers great sound with an MP3 player as the audio source.
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TDA7294-chipamp-6N3-tube-input.jpgTDA7294 Chip Amplifer with 6N3 Tube input3487 viewsFrom a $48 printed circuit board and a bag of parts (eBay) I fashioned this very functional looking 80W amplifier. The parts include a 6N3 valve (preamp stage), two TDA7294 high performance power chips and all the parts required to populate the circuit board. You have to source the chassis, heatsinks and connectors yourself and that's where the expense starts.
The amplifier has been constructed in attractive charcoal black 2U 19" rack enclosure. Three sets of switchable RCAs on the back and 4 oz volume knob and Alps pot to control loudness. Speaker protection is included on the PCB and there is a delay (anti-thump) complete with flashing LED before the amp is ready for use. Very clean sound, holographic presentation.
For more details and impressions see the Chips and Tube - 6N3 and TDA7294 integrated amp thread.
Mark Houston – retro-thermionic
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VTR-ST60-Tube-Amplifier.JPG VTR ST60 Tube Amplifier3450 viewsVTR ST60 tube amp. Just bought this one. Sounds great and has a very good bottom end, unlike the others. Uses SED 6550 (I’ll be replacing them with gold lions KT88 soon).
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12AU7-IRF630-LM317-headphone-amplifier.JPG12Au7 / irf510 Headphone Amp3441 viewsThis is the final amplifier. Takman metal film resistors everywhere except for the pink ones (cathode resistors) which are carbon film. Elna Silmic II Electrolitic capacitors and Solen film capacitors. The sound is great!
Project Link - DIY 12AU7 (ECC82) / IRF510 Headphone Amplifier
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KT88-OddWatt-and-ForeWatt-Preamp.jpgKT88 OddWatt Tube Amp and 5751 ForeWatt Tube Preamp3440 viewsWooden enclosures for a pair of Bruce's KT88 OddWatt Tube MonoBloc Amplifiers. Between the two mono amps is a new project - a 5751 (SRPP) ForeWatt tube preamplifier. The KT88 tubes are JJ / Tesla KT88 Blue Glass.
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KT77-CCS-Push-Pull-Tube-Amp.jpg6SL7 / KT77 Push Pull (PP) Tube Amplifier3421 viewsFront view with cage of the Oddwatt 225, a 6SL7 SRPP / KT77 SIPP (Push-Pull) DIY Tube Amplifier. 6SL7 SRPP driver stage with KT77 PP output stage. Cathode constant current sources are made using LM317 Regulators.
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12AX7-ECC83-Tube-Preamp.jpg12AX7 / ECC83 Tube Preamp3418 viewsHi, I have built preamp with double triode 12AX7 from your web site.
The sound of this preamp is very very nice, detailed and realistic.
Pipa (from Czech Republic )
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PDC400s.JPG$50 Teac PDC400, as good as a $700 NAD C5423406 viewsOf course in its day this five CD player with four times oversampling and dual DACs would have cost a lot more than $50. But from a secondhand store, in a sleepy fishing village in southern Australia, this was a real steal! It has removable cover and hinges. No remote. And it works 100% flawlessly and is in excellent condition. Seen here with my headphone driver and ATH-AD700 headphones. I obtained two identical CDs and identical cables and put both the NAD and Teac through an A/B switch.Queued both CDs perfectly and switched from NAD to Teac repeatedly to try to resolve which played better. There was absolutely nothing between the two. The Teac performed as well as the NAD in every area. I have been told that if Teac went to the trouble of installing dual DACs it would definitely be a good player. I have about thirty hours of play on it in a very short time and it delivers clear and detailed music and works very well with my 2N3055 based headphone driver. Yes, a real steal!
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BillsAmps.JPGBills Cymer valve monoblocks3401 viewsThese valve monoblocks deliver as well as they look. The sound from the complete system was natural and authoritative. Expensive but nice.....
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IMG_1960.JPGMini 12AU7 Tube Preamp3400 viewsAnother picture of the 12AU7 tube preamp close up showing the input/output plugs on the side. The preamp got its name from being nearly impossible to wire the internal parts because of the small case.
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5751-SRPP-EL84-6BQ5-Push-Pull-Tube-Amp.jpg5751 SRPP / EL84 (6BQ5) Push-Pull Tube Amp (PoddWatt)3399 viewsAnother OddWatt tube amplifier. This one uses EL84 / 6BQ5 tubes in a self-inverting push-pull topology for the output stage driven by a 5751 SRPP. The gain is sufficient to allow direct connection to a portable mp3 player. As will all the OddWatt amplifiers, it measures very well and Bruce reports that it sounds very good. See the 5751 SRPP / EL84 (6BQ5) Push-Pull DIY Tube Amplifier project page for full details.
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Jan6418JewelBoxInside.jpgInside the sub-mini Jewelery box preamp3380 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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Nagra-300i-300B-Integrated-Amplifier.jpgNagra 300i Integrated Tube Amplifier (300B)3372 viewsThe new Nagra 300i Integrated 300B Tube Amplifier on display at the 2011 Salon Son & Image show.
The integrated amplifier uses four JJ 300B directly heated triodes in a push-pull configuration in class-A operation. Output power is 20Wpc.
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KT88-Push-Pull-Tube-Amplifier-Cover.jpgKT88 Push-Pull Tube Amplifier (monoblock)3369 viewsThe third of the "OddWatt" tube amp projects. This one is the Odd Blocks which will work with a number of octal tubes (KT77, 6CA7, EL34, 6L6GC, KT88, KT90, 6550). The driver stage is an SRPP using a 12SL7 tube. For the amp shown above, the output stage is a Class A UL SIPP using Gold Lion KT88 vacuum tubes. LM317 Regulators are used to provide the cathode CCS.
For more information, see the 12SL7 SRPP / KT88 Push-Pull DIY Tube Amp project page.
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OddWatt-KT88-Push-Pull-Tube-Amp-Kit.jpgOddWatt / OddBlock KT88 Push-Pull Tube Amp Kit3363 viewsA finished OddWatt / OddBlock KT88 Push-Pull Tube Amp Kit. This KT88 tube amplifier kit can be purchased from OddWattAudio.com. The tube amp kit comes with a NOS JAN Philips Branded 5751 (US made) preamp tube. The output tubes are and new production Genalex Gold Lion branded KT88 tubes (Russian made). As you can see, the power and audio output transformers are from Edcor.
Complete DIY instructions to build the similar OddBlocks 12SL7 SRPP / KT88 SIPP (Push-Pull) Tube Amplifier are also available.
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SE-807-Tube-Amp.jpgSingle-Ended (SE) 807 Tube Amplifier3363 viewsAfter picking up a couple of cheap ($7) ATS25/807 tubes a volunteer from the forum, Matt, designed me an amp to go with them. This project stagnated for over a year and a half and now is finally finished. The colours are strong between the Edcor 25W OPTs and power tranni and the “Red Delicious†top plates. The bases are Australian Spotted Gum. Remote PS carries a 5H 300mA Hammond choke and 5Y3 power tube (upgraded to Golden Dragon 5U4). The amp section has all ceramic sockets and plate cap, the driver tube a Sovtek 6SN7 (has been upgraded to Shuguang 50 Year Treasure). Bipolar bypass caps are used on the 6SN7 and low ESR caps on the 807s. The amp looks smart and sounds excellent. It plays loud for its 2.7 measured Watts and has huge dynamic head room.
Mark - retro-thermionic
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PreProduction-Odd-Block-Tube-Amps.jpgOddWatt / OddBlock KT88 Push-Pull Tube Amp Kit3350 viewsThis is a pre-production photo of the OddWatt / OddBlock KT88 Push-Pull Tube Amplifier kits that are available from OddWattAudio.com.
Full details of the tube amplifier topology along with complete DIY instructions are available on the 12SL7 SRPP / KT88 SIPP (Push-Pull) DIY Tube Amplifier project page.
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