22 April 2014

Elekit TU-8200 Tube Amplifier Kit (SE 6L6)

Over the past several years I have been enjoying an Elekit TU-879S Stereo Tube Amplifier Kit paired up along side of Fostex FE206E high sensitivity speaker drivers in Dallas rear-loaded horn enclosures.  I put a number of hours on the TU-879S, enough to fully consume the stock EH 6L6 tubes and to cycle through a number of power tube sets before deciding on JJ EL34 blue glass tubes.  Throughout this time the Elekit TU-879S has been reliable and a good performer sonically so it was disappointing to hear that the popular TU-879S tube amp kit was discontinued in late 2013. 

Elekit TU-879S with Fostex FE206E Rear-Loaded Horn Speakers
Elekit TU-879S with Fostex FE206E Rear-Loaded Horn Speakers

However, there is good news - the descendant to to the wildly acclaimed TU-879S, the Elekit TU-8200 is available from TubeDepot (USA). The renowned Elekit designer, Mr. Fujita, has gone back to the drawing board to design a superior tube amplifier kit. The TU-8200 has many enhancements that will allow the builder to enjoy exquisite tube audio in just a few nights.

Elekit TU-8200 - 6L6 Tube Amplifier Kit - Parts
Parts - Elekit TU-8200 Tube Amp Kit

Some of the improvements over the TU-879S include:
  • Selectable output modes - Ultra-linear, Triode, or Pentode by changing a jumper on PCB.
  • TU-8200 kit ships with a R-core power transformer that supports 4 different voltage environments 100V, 115V, 200V, and 230V. 
  • Improvements to the audio and power supply circuitry.
  • Headphone output.
  • Optional Elekit PS-3249 DAC to decode audio directly from computer USB source.

The TU-8200 ships with Electro Harmonix 6L6GC power tubes, but also supports a wide range of other power tubes such as 6CA7, EL34, KT66, KT77, KT88, 6550 (and others) with no modifications and no need to re-bias.

Elekit TU-8200 - 6L6 Tube Amplifier Kit - Rear
Elekit TU-8200 - 6L6 Tube Amplifier Kit - Rear

Elekit TU-8200 Main Specifications
  • 2 X 6L6GC, 2 X 12AU7 (can also use KT88, 6550C or EL34)
  • Output: Ultra-linear, Pentode or Triode mode (8 ohm loaded):
  • 6L6GC (Ultra Linear) 8W + 8W
  • 6L6GC (Pentode) 8.2W + 8.2W
  • 6L6GC (Triode) 4W + 4W
  • Speaker Impedance: 4-6.3 ohm and 8-16 ohm
  • Headphone: Standard jack (6.4mm DIA)
  • Power Consumption: 60W (with 6L6GC)
  • Weight: 14.55lbs (6.6 kg)
  • Dimensions: Width 9.92" (252mm) x Height 6.22" (158mm) x Depth 11.22" (285mm)
At $699US the new TU-8200 kit looks quite tempting.  What I like most about the TU-879S was the seemingly endless tube combinations that were possible.  Now with the ability to select between Ultra-linear, Pentode or Triode output modes, the number of possible tube combinations are endless.  Additional details of the kit and the building instructions are available on the Elekit TU-8200 page at TubeDepot.  We are planning to take a closer look at one of the TU-8200 tube amp kits soon so please stay tuned for more updates.

Elekit TU-8200 - 6L6 Tube Amplifier Kit
Elekit TU-8200 - 6L6 Tube Amplifier Kit

28 March 2014

300B Single-Ended-Triode Amplifier

300B Single-Ended-Triode (SET) Amplifier Project

The DIY 300B triode amplifier shown below was completed by Stamou Tasos (Greece).  The 300B triode amplifier was built following the 300B single-ended (SE) tube amplifier schematic by J.C. Morrison.

DIY 300B Single-Ended-Triode Hi-Fi Amplifier

DIY 300B Single-Ended-Triode Hi-Fi Amplifier

For this single-ended (SE) 300B triode amplifier build Stamou has used premium parts, Lundahl audio output transformers and a DIY chassis. The 300B Single-Ended-Triode (SET) amplifier circuit uses a direct coupled 6SN7 driver stage. The output stage is a SE 300B triode and the maximum power output is about 8 Watts per channel. A pair of reasonably sensitive (~91 dB+) loudspeakers will be required with this 300B SET amplifier. 

300B Single-Ended-Triode Amplifier - Point-to-Point Construction

300B Single-Ended-Triode Amplifier - Point-to-Point Construction

The 300B SET amplifier was built using point-to-point construction.  The chassis for the 300B triode amplifier was also built by Stamou.  The frame is made from 20 mm thick MDF wood which was finished with spray primer and paint. The top plate is made from a 4 mm thick aluminum plate and the bottom plate from a 2 mm thick aluminum plate.   Your enclosure will require good ventilation.  "This is a great sounding 300B triode amplifier that I am sure DIYers will find to be very rewarding."  For the full 300B SET amplifier project details see the DIY 300B Single-Ended-Triode (SET) Hi-Fi Amplifier project page.

More 300B Triode Amplifiers

15 December 2013

4S Universal Preamplifier for 12A_7 Tubes

The 4S Universal preamp is a Super Simple Single Stage (4S) line stage preamp that works well with the entire range of 12A_7 tubes - 12AU7, 12AV7, 12AY7, 12AT7, 12AZ7, and 12AX7. You can change the tube type to vary the gain of the preamplifier by quite a large margin. 

4S Universal Preamp for 12A_7 Tubes
4S Universal Preamp for 12A_7 Tubes
The preamp uses a 6CA4 tube rectified power supply which is very quiet. The preamplifier is built using point-to-point construction techniques and into a die cast aluminum enclosure from Pomona.  The attenuation control is on the output of the preamp.

4S Universal Preamp with 6V6 Lacewood Amp
4S Universal Preamp with 6V6 Lacewood Amp
The 4S Universal is a preamp that can be adapted to the task at hand simply by swapping tubes. It also allows some tube rolling to compare various tubes in your stash. The 4S Universal preamp is a great little unit to really bring out the most in your power amps.  For full details see the 4S Universal Preamplifier Project pageComments and questions about this project are welcome in the 4S Universal Tube Preamp Project (12A*7) thread.

Super Simple Single Stage (4S) preamp with Genalex Gold Lion 12AU7
Super Simple Single Stage (4S) preamp with Genalex Gold Lion 12AU7
The photo above is one of Mark's Super Simple Single Stage (4S) preamplifier builds.  For more information see Mark's 4S Universal Preamplifier for 12A?7 Valves.

14 July 2013

Cheap Open Baffle Speakers (COBIES)

Bruce has put together a pair of Cheap Open Baffle Speakers - the COBIES.  Relative to most DIY speakers this open baffle project will be quite easy to build.  One of the main design goals for Bruce was to keep the total parts cost under $150US.  The open baffle speaker project was inspired by the "Big Air" open baffle system by Jim Strasser.  

Cheap Open Baffle Speakers
COBIES - Cheap Open Baffle Speakers
Each open baffle uses a GRS 12PF-8 woofer and two Goldwood GT-25 paper cone tweeters.  One tweeter is mounted on the rear of the baffle pointed upwards about 45 degrees.

Rear Mounted Goldwood GT-25 Tweeter
Rear Mounted Goldwood GT-25 Tweeter
Bruce experimented with various crossover points settling on 3.6 kHz finding that lower crossover points put too much of a demand on the GT-25 tweeters.  Using a calibrated microphone and RTA the in-room response from 100 Hz to 10 kHz was quite smooth and free of any large irregularities. Response below 100 Hz was affected by room nodes but quite good down to 40 Hz.  Above 10 kHz was certainly excellent (up to about 18 kHz).  The overall speaker system sensitivity is estimated at 93 dB / 1 watt at one meter. Bruce uses a pair of 5 watt (each) tube mono block amplifiers (EL84 PP) with the open baffle speakers. 

"The sound is something you will either love or hate. As I said earlier open baffle speaker systems are bi-polar. I really like it, some individuals will not. The speakers have an excellent overall sound. They have a lot of ambiance and provide a good listening experience. Bass is quite clean and robust ..."

Full details are available on the  COBIES (Cheap Open Baffle Speakers) project page.  Comments and questions about this project are welcome in the Open Baffle Speaker Project thread.