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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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6N7-Tube-Preamp-Heavy-Metal.jpg
6N7-Tube-Preamp-Heavy-Metal.jpg6N7 tube preamp (Heavy Metal)3250 viewsConstruction is in a timber box. There are three switchable RCA inputs and power is supplied by an external 18V 2.2A AC power pack. Internally 255V is developed with a linear PS and regulated 12VDC for the heaters which are wired in series.

An Alps blue velvet potentiometer is fitted at the output for attenuation control with a fine solid brass knob to compliment the gold right-angle RCA jacks, name plate and ventilation holes. Wire wrap wire is used in the signal path. The power supply and amplifier are on separate circuit boards. Bitumanised heavy aluminum foil is used to line sections of the timber box for resonance control.

For more info, see the 6N7 metal tube preamp thread on the discussion forum.

Mark Houston – retro-thermionic
ONKYO-DX-C380-CDP-Modifications.jpg
ONKYO-DX-C380-CDP-Modifications.jpgONKYO DX-C380 CDP Modifications3243 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
Rear.JPG
Rear.JPGOPA2134 Opamp Preamp - Bees Wax Paper Capacitor3231 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.
Sony-CDP-315-Modifications-and-Upgrades.jpg
Sony-CDP-315-Modifications-and-Upgrades.jpgSony CDP-315 Modifications and Upgrades3230 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
OatleyPhonoPreInsideS.jpg
OatleyPhonoPreInsideS.jpgMongrel Dog Audio JAN6 418 valve phono preamp3223 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
DIY-50EH5-25EH5-Tube-Amp.jpg
DIY-50EH5-25EH5-Tube-Amp.jpgDIY 50EH5 / 25EH5 Tube Amplifier3216 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).
MongrelChamp.jpg
MongrelChamp.jpgFender Champ 5F1 valve guitar amp.3216 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.
S-5-Electronics-K-16LS-kit-enclosure.jpg
S-5-Electronics-K-16LS-kit-enclosure.jpg3214 viewsI'm running this stock apart from the Alps Blue volume pot which I upgraded after the original sprang a leak. I'm using quite a few components bought from: http://www.mafaudio.com/pro/propage.aspx.

There are seven LED's that light up the feet and fronts of the brushed aluminum transformer cases. The LED's are powered from a 12v mains transformer bought from Maplin in the UK. The VU meters also run from the extra transformer. The chassis is made from wood bought from the local yard. To cut the VU meter holes I used a 32mm Spade bit then used a file to open the hole up to just under 34mm. The main volume control area was drilled using a 50mm Forstner bit and the tone controls a 30mm Forstner bit. It's coated in about 5-6 coats of clear varnish and involved an awful amount of sanding.

There are more photos available in my photo library.

Luke Collings,
Wiltshire, UK
4SUTea_I_retro.jpg
4SUTea_I_retro.jpg4SUTea - Super Simple Single Stage (4S) Tube preamp3182 views4SUTea is another Super Simple Single Stage (4S) Tube preamp that I have built. This one features single board construction with PS and amplifier together and no PCB. All housed in a Twinings timber Tea Box: Bitumanised aluminum foil controls enclosure resonance and Russian paper in oil caps link the modulated HT to the real world. Silver solder is used throughout. Heavy duty high grade gold plated RCAs grace the back and all is powered by a 24V 1A plug pack. There are two switchable inputs, Alps blue velvet pot and black chromed solid brass knob.

See the project page 4S Universal Preamp for 12A?7 Valves.

Mark Houston (Australia)
retro-thermionic
mwhouston: retro-thermionic
KT88-Push-Pull-Tube-Amplifier.jpg
KT88-Push-Pull-Tube-Amplifier.jpgMonoblock KT88 Push-Pull Tube Amplifier3181 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.
4-channel-400W-amplifier.jpg
4-channel-400W-amplifier.jpg 4 channel, 400 W amplifier3171 viewsThis 4-channel 400 W amplifier uses Hypex UcD400HG modules together with the corresponding power supply.
The whole is mounted inside a Galaxy 330 x 230 x 80 case.
For building instructions, have a look at this project's wiki.
Two such amplifiers has been working for over 2 years in my lounge, driving Linn Komponent 110 loudspeakers which each have 4 speaker inputs.

Francois Corthay - Switzerland

Project Page: 4 channel 400 W amplifier using Hypex UcD400HG modules
C3m-Tube-Preamp-Menatzchim.jpg
C3m-Tube-Preamp-Menatzchim.jpg"Menatzchim" - C3m Tube Preamplifier3170 viewsThis C3m tube preamplifier uses the same power supply I have used in my last dozen preamp builds. An external 24VAC 1A wall wart is stepped up to 250VAC by using a step down transformer backwards. Double filtration and a DC filament supply ensure a dead quiet preamp. Wire wrap wire is used for signal hookup wire and heavy duty gold plated RCAs are employed. No shielded wire or PCB is used. An Alps blue velvet pot is on the output for attenuation. Jensen Copper, paper and oil caps with silver leads are used on the output. Three sets of input RCAs are selected by two small power switches.

The sound stage is extremely deep and voice and instruments have a uncanny natural sound and feel about them. With symphonic pieces you get the unnerving feeling you are in row twelve and right in the center. I would highly recommend the construction of this preamp.

For more info, see the C3m preamp thread on the discussion forum.

Mark Houston – retro-thermionic
DSCN0061_M1~2.jpg
DSCN0061_M1~2.jpgMy Black Velvet OTL headphones amplifier 3169 views6AS7G RCA & Rare RV200/600 Tungsram-Germany & PCC88 Siemens /golden pins/
OTL for headphones 200 and more ohms. Loftin-white, only 1 cap ELNA between output stage and headphones.
12AX7-Tube-Preamp-5AR4-Power-Supply.jpg
12AX7-Tube-Preamp-5AR4-Power-Supply.jpg12AX7 Tube Preamp with 5AR4 Tube Power Supply3153 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.
OPA2134-opamp-Headphone-Amplifier.jpg
OPA2134-opamp-Headphone-Amplifier.jpgOPA2134 CMoy Style Portable Headphone Amplifier3148 viewsThis simple headphone amplifier is based on the high performance OPA2134 opamp chip. This headphone amp\driver is good sounding and portable. The schematic is based on the very popular CMoy headphone amp design with some changes in passive parts values. For the power supply I elected to power the amp from two 9V batteries (18V) which provides longer playback time and greater dynamics.

There is only 100 mm of hookup wire in the signal path and all connections are component-2-component on the protoboard. Low ESR 200uF caps and a resistive network provide the differential voltages required to operate the chip without an output capacitor. The brd. is silver soldered with Mil. spec machined chip socket and Russian PIO caps on the input. Power only comes on when both phone jacks have plugs in them and the power switch (at the back) is on. The enclosure is impact resistant and lined with heavy aluminum foil for shielding and enclosure resonance control. The sound is clean and bright with good volume and dynamics. The amp is dead quiet with no signal.
VTR-ST60-Tube-Amplifier.JPG
VTR-ST60-Tube-Amplifier.JPG VTR ST60 Tube Amplifier3124 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).
KT88-Monoblock-Tube-Amplifiers.jpg
KT88-Monoblock-Tube-Amplifiers.jpgDIY Monoblock KT88 Push-Pull Tube Amplifier Kits3124 viewsShown in the photograph are a pair of DIY Monoblock KT88 Push-Pull Tube Amplifier Kits. See the review for additional details of this great sounding tube amp kit. Also shown in the photo is a NAD C521i CDP used a transport and a Behringer SRC2496 which is being used as an up-converting DAC. The little black box is a DIY Lightspeed (optocoupler) Attenuator.
KitAmpUnderSmall.jpg
KitAmpUnderSmall.jpgKT88 SE UL tube power amp - underside3122 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.
Blue_Velvet_Pre_Night_shot.jpg
Blue_Velvet_Pre_Night_shot.jpgBlue Velvet Tube Preamp - Night Shot3114 viewsThis is my second audio DIY project. A Blue Velvet Preamplifier. Picture taken in the dark.
a1little1.jpg
a1little1.jpg6V6 12AX7 Stereo Amp3114 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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