DIY tube amplifiers
Lately I have been reading up on understanding how the headphone amplifiers I built work and trying to understand how tubes work too. I am quite surprised that the designs are really quite simple and quite similar.
I also noticed that with the tube amplifiers that I have, they seems to be very noisy, even with my linear power supply that I built.
However, when I tried powering it from a SLA lead acid battery, then it played without any noise at all and the music that was masked with the noise actually sounded very good.
I went to a local headphone shop that opened recently and tried out a portatube headphone amplifier that is worth $700AU. Then I compared it to my amp and was surprised to find that my DIY tube amplifier sounded just as good as this portatube.
I then found my really early DIY tube amp which also was quite noisy and tried it with the battery. It too was very noisy on a power supply, but on battery it was silent and I could really enjoy the music. I didn’t like the sound signature of the opamp inside the amp, so I swapped it out with some of the other chips I had. I took out the JRC4556 opamp and replaced it with a LM1458. I was looking for a LME49720 I thought I had, but couldn’t find it. The LM1458 sounded closer to my taste and matched well with my Shure 535 IEM earphones. Also I swapped the old tube in it with a Baldwin piano/organ maker tube and that also improved the clarity of the music.
I’ve been now just looking at different tube amp designs and looking into making a speaker amp. I’m still unsure if I should make a hybrid or full tube amplifier. Making a full tube amplifier means that you need some non-standard transformers which could be difficult to obtain. A hybrid however would mean that I could use a normal solid state power supply and transformers and use a tube for the amplification part. Although tube amps don’t produce as much amplification as solid state ones, so I need to find/make a design that will be powerful enough to drive the speakers I want to listen with.
I’ll take a look around in Japan when I go next week, but the power is 110v there instead of 240v, so I may consider a kit off eBay china instead as China shares the same 240v voltage.