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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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furniture_014_YMax_red.jpgSET Tube Amo with 6BX7 twin triode3030 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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Simple-SE-6L6GC-Tube-Amplifier-Kit.jpgSimple SE 6L6GC Tube Amplifier Kit3023 viewsTop view of the Simple SE Tube Amplifier using a PCB from tubelab.com. 6L6GC tubes and Edcor output transformers.
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IMG_1479.JPGChassis and plastic3021 viewsBending the plastic was a pain, i did it with a hair dryer and a LOT of patience... i don't recommend you to try to do it, it takes a lot of effort and time.
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IMG_2675.JPG50EH5 / 25EH5 Tube Amplifier Internals3021 viewsFinally, the internals of the 50EH5 tube amp. I think I went a bit extreme on the fancy parts as I used 100uF Black Gate's and 62 ohm Riken's on the cathode bias of the tubes. As for the preamp I used more Riken's and a couple of 0.1 Mundorf plate caps. I also used a 12AT7 rather than the 12AX7, although they are interchangeable to what ever you decide. I then re-used a 500K pot as the volume control instead of the 100K (because that is what I had) and added a switch between preamp and line in.
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6P15-Tube-Amp.jpg6P15 Tube Amplifier (also EL84 or SV83)3021 viewsThe tubes I'm using are a 5Y3 rectifier, Soviet military 6P15 output tubes (similar to the EL84 or SV83 either will work) and a 5963 signal tube The output transformers are inside the chassis and are vintage ones salvaged from a 1960's console amp. The power transformer and power supply choke are also salvaged.

The two volume controls are the 100K Single Series Single Shunt Stepped Attenuator (S5 Attenuator). They are the -20 to -50 dB versions which is fine with my Loth-X speakers but would be too restrictive with less efficient speakers.
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Finished.JPG"not another chip amp" - Enclosure3003 viewsThis is where most new amps end up for a few weeks burn in, sitting atop the NAD C542. This is my latest chip amp which I promised I would never build. I started and completed the amp in one day. The amp modules had been built a some time before so most of the hard work was marking and drilling then assembly. On start-up it had a bad hum which I have managed to reduce to a low level. See the other image ("not another chip amp") for the inside shot. This amp feels like it has the power to deliver big time and it certainly sounds nice enough. Will I make another chip amp? Stay tuned.
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IMG_1480.JPGMaking the chassis, bottom view3001 viewsHere are the two pieces that make the chassis put together. Bottom view.
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50year-old-tube-amp.jpg50 year old triode tubes single ended 3.5 WPC3000 viewsThis amp uses all triode tubes in single ended configuration and thus the circuit as short and sweet as possible. The result was 3.5 watts per channel, with 0.07% distortion at 1kHz, 1 watt and not much worse at the extremes. We also did not have the deep pockets to try the more exotic transformers and coupling capacitors available. I'd like to, though, and set up my A/B switch box to see if I could discern any difference. The A/B test with myself and others paired with a high end solid state amp with 0.007% distortion, or ten times less did not reveal any discernible difference. I have a notion that some high end speakers might make the biggest difference of all. The row of LED's are a clever circuit we designed which indicate 3 decibel increments of sound pressure level (SPL). Each 3 decibel increase in loudness requires a doubling of wattage, as many of you know. These light up in sequence , e.g. 0.04 watts, 0.08, 0.16, 0.30, 0.7, and so on to 8 watts total.
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Rear.JPGOPA2134 Opamp Preamp - Bees Wax Paper Capacitor2966 viewsThis is the third of these diy opamp preamplifiers I have made using the Burr-Brown OPA2134 chip. In this build as with my last (which was sold to an audio buff in Denver) I included two switchable inputs. I used 1uF Bees Wax and Paper Jupiter caps (see other photos) which have increased the bass depth a lot. A lot of resonance dampening has been employed. This is a smart looking and very smart sounding preamp. The stereo focus has increased dramatically.
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ONKYO-DX-C380-CDP-Modifications.jpgONKYO DX-C380 CDP Modifications2943 viewsOk, so I got this Onkyo CD Player and noticed that it was really worth modding.
Its a 6 CD player and its well constructed. It also uses the very common Sony KSS-213 pickup (the same one the Marantz 5001 and 5003 uses).
Since I had just got some Elna Cerafine caps, I decided to try them in. Here's what I did:

1- Replaced all coupling caps with 100uF/50V Elna Cerafines
2- Replaced all PS and decoupling caps with Ultra-Low ESR Rubycon ZLs.
3- Added a line supply Cap (1uF X2 Rated)
4- Added a power input choke.
5- Bypassed supply caps with smaller (1/10th capacitance) caps
6- Replaced JRC2968 OPAMP with Burr-Brown OPA2134

The end result was amazing. This is now a truly Hi-End player. It just amazing how good those Elna Cerafines sound int this kind of application. I was willing to try some Black Gates in place, but these Cerafines sound so good in there that I just gave up.

Bernardo
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LePacific-MC-PrePre.jpgLe Pacific MC pre preamp2943 viewsHere is one of three Le Pacific MC pre preamp builds. All the construction is on veroboard (strip board). These builds have been tested with a two different cartridges with an output of 0.35mV and all work extremely well. The J-FETs are 2SK170 BL which are matched. The output capacitors are Russian mililtary PIO. The case colour is Sungold the same used on Paris. All phono preamp builds are battery powered.

Mark - retro-thermionic
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Sony-CDP-315-Modifications-and-Upgrades.jpgSony CDP-315 Modifications and Upgrades2939 viewsOK, so I also got a Sony CDP-315 single disc player and decided to try modding it. This one was much harder as It had a pair of SMD opamps and replacing them with a pair of 8 pin DIP sockets wasn't easy, but I managed to do it just fine.

So, here are the mods:

1. Installed 0.15uF X2 power filter cap
2. Intsalled a pair of ferrite chokes (on on power cord and another on the line out flat cable)
3. Replaced original opamps with NE5532 and later with Burr-Brown OPA2134 (2134s do sound better).
4. Replaced electrolytic coupling caps with a pair of Jantzens 4.7uF/630V.
5. Replaced RCAs connectors with gold plated ones.

The increase in performance was great too, but nos as good as my ONKYO DX-C380 CDP. I plan on replacing all supply and decoupling caps with Rubycon ZLs to improve it further.

Bernardo
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parallel-push-pull-300B-tube-monoblock-amplifier.jpgParallel push-pull 300B tube monoblock amplifiers2926 viewsParallel push-pull 300B vacuum tube monoblock amplifiers build by Rudolf Moers.

More information including schematics for this amplifier build are available here: Parallel push-pull 300B tube monoblock amplifiers.
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Nelson-Pass-B1-Buffer-Preamp.jpg2921 viewsThe Pass B1 Buffer Preamp complete in Hammond Aluminum case. The B1 is a very transparent and PS tolerant preamp/ driver. Because it is a source follower some signal is lost (about 15%). But it is an excellent attenuator and offers a high impedance input and low output and is dead quiet. This build shares the same components as the DIY JFET BoZ preamp but sounds quite different.

For more information about this build see the Russian Pass B1 FET Preamp/Buffer thread on the forum.

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OatleyPhonoPreInsideS.jpgMongrel Dog Audio JAN6 418 valve phono preamp2918 viewsThis is the new tube phono preamp kit for MM cartridges from Oatley Electronics. The small tube preamp kit comes with all components required, including NOS JAN 6418 sub-miniature tubes and a wall wart for the switch mode power supply. The wall wart PS has multi-outlet adapters to fit most mains power outlets worldwide. The PS auto-switches to the correct mains voltage to provide 5V DC to the kit. There are two tube stages with each stage supporting a FET buffer to the next. The PCB is plated through and screen printed.

See the 6418 Tube RIAA Stereo Phono Preamplifier Kit project page for more details and a review of this kit.

Mark Houston
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MongrelChamp.jpgFender Champ 5F1 valve guitar amp.2908 viewsMy build of the Fender Champ 5F1. It is a SE three stage tube amp based on the 6V6 power valve and 12AX7 triode. The amps were first made in the late 40's up to early 80's. And re-issued in 2006. The original schematic had valve rectification. I added a 10H open choke. There are only two inter-stage caps and one by-pass cap on the 6V6 cathode resistor (not counting PS caps). I went for a Classic Champ sound by using cotton covered, single core, tinned copper wire as the hook-up wire, bees wax (Jupiter originals) inter-stage caps, an original Ozzie made 12AX7, Ozzie 5Y3 and 6V6 Black Glass (original). PS caps were increased from 8uf to 47uf and an effects loop added (between stage one and stage two). I didn't install the NFB loop from the OPT secondary to stage two. Instead I made the output stage UL (Edcor tranny). The amp is stable even when over-driven heavily. When hooked-up to a Pioneer PA 12" driver (4" Al/vented dust cover) it sounds excellent. Very clean highs and gutsy lows.
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DIY-50EH5-25EH5-Tube-Amp.jpgDIY 50EH5 / 25EH5 Tube Amplifier2901 viewsThis tube amplifier project uses the parts from a junked Fleetwood console stereo. It uses a 6AX4 full wave bridge rectifier two 5A 400V fast recovery diodes. The preamp tube is a 12AX7 and the power tubes are 50EH5. I followed the basic ideas from Gio's DIY 50EH5 Tube Amplifier Project. This is my super sized version of the amp with all DC regulated filament supplies and even does a lower frequency response than usual because of larger output transformers (underneath the chassis).
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KT88-Push-Pull-Tube-Amplifier.jpgMonoblock KT88 Push-Pull Tube Amplifier2900 viewsPhoto of a KT88 Odd Block without the protective cage. This tube amp design will work with a number of octal tubes (KT77, 6CA7, EL34, 6L6GC, KT88, KT90 and 6550). SRPP driver stage using a 12SL7 tube. Output stage is a Class A Ultra-Linear SIPP with 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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VTR-ST60-Tube-Amplifier.JPG VTR ST60 Tube Amplifier2897 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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12AX7-Tube-Preamp-5AR4-Power-Supply.jpg12AX7 Tube Preamp with 5AR4 Tube Power Supply2882 viewsTwinings Tea Box preamp with external valve rec. PS

Another Tea Box valve preamp but this time with a valve rec. remote PS. The rectifier valve is a 5AR4. The iron consists of a Hammond power transformer and 10H choke. Golden Dragon tubes are used in the 12AX7 Tube Preamp . The preamp uses silver hook-up wire, Alps Blue Velvet attenuator, brass cones and 4oz brass knob. Jupiter hand made beeswax caps are used in the amp modules and silver solder throughout. The sound stage has gained greater dimension and detail has improved over my SS preamp.
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