• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Odd Watt Audio Alpha Build and initial review

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I have a desire to challenge myself and keep my mind active as I grow older. One of the things I knew would be a challenge was to learn a bit about electronics and to build a tube amp. I work for a large international Christian broadcast organization with highly trained engineers who have specialized in high power shortwave and medium wave transmitters. So I have several mentors to help without belittling me...too much. :) The kit I decided offered the best chance for success is the Odd Watt Audio Alpha. I ordered it and it arrived very well packed and nothing damaged.The kit comes with everything you need to build a complete amplifier. The instructions are comprehensive and very understandable. Bruce and Rodney at Odd Watt have been responsive and terrific to work with and very helpful. I took my time and put it together in about 8-10 hours 1-2 hours at a time. I encountered no real issues during the build even as a noob. Again thanks to advice from my friends and Bruce and Rodney. I went through the checklist for first power up and flipped the switch on. The little green indicator light came on, the tubes glowed and there was a very low hum from the transformers. Okay, not sure if thats normal or not. So go ahead and hook up the speakers and crank up the volume. The very low level hum is still there but it does not increase in volume. Hmm, so turn it back off, hook up the CD player and crank the volume again. Same thing, very low level hum from the speakers. Okay pop in a music CD and crank it up. Wow! I suddenly forget about the very low level hum as the music comes out of the Klipsch KG3.5 speakers. I know it's only one watt but this little amp sounds really darned good. With the help of my friends we'll check out the hum which is at most -50 dB and is not noticeable even during quiet piano passages during a piece like Debussy's Arabesque. I listened for about two hours and threw Linda Ronstadt, Carly Simon, The Beatles, The Philadelphia Orchestra and Artur Rubinstein performing Rachmaninoff's Piano Concerto #2, Spyrogyra, Chicago and more at this little amp. All sounded just excellent. The Alpha uses 2 Russian 6F5P NOS tubes which is the Russian equivalent of the American 6GV8/ECL85. You might wonder how loud one watt really is. The KG3.5's sensitivity is 94DB spl, so fairly efficient. While the volume won't make your ears bleed, I found myself turning the volume down on some songs like "Roundabout" by Yes on my turntable. My friends concurred with Bruce at Odd Watt that a very low hum is not unusual with an amplifier of this type. And as I said once the music starts the hum disappears behind even very low passages of music. And we will chase it down, but I am not going to let it affect my enjoyment right now. I highly recommend this little kit for someone not familiar with electronics or tube audio but wanting an inexpensive introduction to both. But find someone who can mentor you and especially teach you how to solder and what all those resistors, capacitors and diodes are all about. Fun times.
 

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low watt tube amp is good experience.but why you use pcb ?it is simple fix 2 ... 9 pins socket on metal panel .this is point by point .
tubes likes this way .you can use correct ground .
with this item your speaker is quite.
yes filter chock helps to reject hum but small amps can reject hum with lpf resistor and cap in power supply. we have good western made tube like ecl86..ecl82. they are magic for music lovers .
when we need to tubes in music and sound ...quality is first point .
Russian tubes and pcb:confused::confused:
so i think best way is no easy way .before my country was friend to usa and now we have many of good usa made hifi tubes. here we dont use Russian tubes
most of our people believe us and us technology but i believe Japanese skills in hifi circuit design.:rolleyes:
 
If hmm is constant, not deppending of volume potentiometer, this is hmm from tube constant inner current, that goes from filter of PS. Try to improve filtering with chock. /try to decrease tube currents and hmm will go down.....hmm is riples in filter, decreased current multiplied to inner resistance of PS, will give you decreased riples..Ohm law...right way is adding chock/
 
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Nearly three years have gone by since I built this little kit Designed by Bruce Heran of Oddwatt Audio. Recently I had some issue with the right channel being intermittent. Then the amp went dead. I discovered I had not properly soldered a wire. Resoldered that, found another loose wire, resoldered that. Put another tube in and it sings quite nicely. All to say that if a person wants to have a good experience putting together an amplifier with great support, this is a good first experience. It also sounds quite nice as well. Only 1 watt but pair it with efficient speakers and it does the job.
 
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