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Production version with acrylic transformer cover.
Elekit TU-8340 Prototype
Semi Automatic fixed bias adjustment system
Stock Tube Set EL34 X 4 + 12AT X 4
Options : 6L6GC, KT88, Kt90, KT120, KT150
Max output EL 34 (UL) 41W X 2
( Triode) 21W X 2
KT150 (UL) 50W X 2
(Triode) 28W X 2
Available in November 2016
The TU-8340 in either version is available from the late October 2016. We are accepting orders in advance with a 5% discount prior to launch.
TU-8430 without tube set $1,250.00
ADD EL34 X 4 + 12AT7 X 4 -------> 155.00
ADD KT120 X 4 + 12AT7 X 4 ------> 260.00
ADD KT150 X 4 + 12AT7 X 4 ------> 450.00
The following upgrade options will be available for TU-8340
- Takman 1/2W TEX 2% Audio Grade carbon Film resistor
- AMTRANS 2W AMRG 1% Audio Grade carbon resistor
- Mundorf 0.47 EVO Supreme Silver Gold or Supreme coupling caps
- Lundalh LL 1623 custom made for TU-8340
more to come..
Push-Pull (Class -AB) Stereo Power Amplifier will be available soon
You can view this wonderful design by MR Y Fujita in The SHOW 2016
ELEKIT SEMI-AUTOMATIC BIAS ADJUSTMENT SYSTEM
This model of ELEKIT amplifier includes an Innovative "Semi-automatic" bias adjustment system for the tube output stage.
- Commonly, there are two methods of biasing a vacuum tube amp. "Self-bias" (automatic) and "Fixed bias". For a Push-Pull amplifier- the "Fixed bias method" is more effective and advantageous since each power tube can be adjusted for bias. The drawback with the "Fixed bias" method is each tube needs to be checked and adjusted for bias manually one by one.
-The ELEKIT "Semi-automatic" bias adjustment system incorporates "Fixed bias method"- but with no manual steps other than a simple push of the "Auto Adjust" button. The tube bias settings are managed by a microcontroller that adjusts the tube bias in less than a minute- a very unique and innovative system that EK JAPAN is introducing into the tube audio market.
Using the "Auto Adjust" Semi-Automatic Bias Feature
When the "Auto Adjust" button is pressed, the microcontroller executes the following steps automatically.
NOTE: Please make sure before using the Auto Adjust bias feature that the power tubes are fully warmed up (at least 2-3 minutes of being powered on) and the volume on the amplifier is set to the lowest level. Incorrect bias settings and/or an error condition will occur if tubes are not warmed up and if the volume is not set to the lowest level. During the tube biasing process the LED near the output tubes (orange LED in the prototype) will flash rapidly while the bias is being set.
1. In the first step the microcontroller drops bias voltage to a very low level called the "safety zone" to reduce the output tube current. This takes place slowly as to not induce pops or noises to the output to speakers. If the bias current is already detected to be in the "safety zone" it will immediately shift to the next step.
2. The bias voltage is then slowly and automatically adjusted so the cathode current of each output tube is set. NOTE: At this step if "Not Adjustable" is detected (no output tube installed, bad tube, etc.) the microcontroller automatically will return to the "safety zone" and will display an error (flashing LED).
3. When the bias adjustment is finished and stable- the bias value is stored into the flash memory in the microprocessor. If there is an error state- the bias value detected during the "safety zone" (and the error data) will be stored.
4. The amplifier "reads" the stored bias data (and error data if applicable) and outputs it as a fixed bias. Adjustments are finished.
5. If the Auto Adjust biasing finishes successfully- the LEDs will turn OFF. If there is an error- the LED closest to the problematic output tube will flash every 2 seconds. If the output tube does not reach the rated value- the LED flashes once. If the value is more than the rated value (even if in the safety zone) the LED will flash twice. (For safety- it is recommended to turn OFF the power to the amp if the LED is flashing twice). The LED will flash next to the problematic output tube to indicate it is in the safety zone.
You can always have the bias in the safety zone by pressing the "SAFETY RESET" button while the power is ON- even when the output tubes are not warmed up or while the music is being played. When you exchange output tubes, it is safe to press this RESET button and have the bias in the safety zone before turning off the power (or right after turning on the power after tube exchange). When the bias enters the safety zone, the LED stays ON. (It flashes when there is an error.)
We confirmed that our prototype model can automatically adjust the bias of EL34, 6L6GC, KT88, and KT150 tubes.
(Prototype- specifications are subject to change)
EL34/KT120/KT150 Push-Pull (Class -AB) Stereo Power Amplifier
Price :TBA Made in Japan
Designer : Mr. Y. Fujita
VACUUM TUBE Stock tube set: 4 X EL34(6Ca7), 4 X 5965A (or 12AT7)
You can also use :6L6GC,KT88, KT120 or KT150
Edits: 05/26/16 05/26/16 05/30/16 08/17/16 08/17/16 08/20/16 08/20/16 08/24/16 09/26/16 09/26/16 09/26/16 10/30/16Follow Ups:
Very exciting. I don't see a headphone or source switch. Any guess as to the wattage? Do you know when they plan to release more info and ship dates.
I'm enjoying the TU-8200 daily.
It is a power amp. With KT150, it will give 47.50W under UL mode.
This amp has a micro processor to control the bias. Will be available in the coming few months..
Is there much soldering here, or is it mostly 'assembly' work?
"To Learn Who Rules Over You, Simply Find Out Who You Are Not Allowed to Criticize."
not much... it is fun to build
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