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Making a Battery Operated EF95/6AK5 Hybrid Tube Amplifier

Experimental tube amplfier project The completed amplifier I decided to make this as I could not find any EF95/6AK5 battery operated tube amplifiers. Also I was bored and fancied a challenge, by the end of this project I had learnt a lot of things, I will now be working on new projects. It seems I can't stay idle for too long.
Recent posts

Designing and building a DC to DC high voltage booster for tubes

Alternative to high output voltage transformers The completed module I spent quite a bit of time searching for a high voltage booster schematics, I found some discrete examples and a few based on the UC3843 chip popped up. In the end I decided to settle with the UC3843, as I've seen these chips get used in other tube amplifiers.

Designing and Making a 4S Battery Protection Board

Dodgy over discharge voltages The auto activation version I needed a battery protection board for my battery powered tube amplifier, I decided to buy several battery protection boards from Ebay, the reviews looked good and most of the boards seemed very popular. Once I received and tested the boards I noticed a few problems: All of them were using the ABLIC S-8254A IC, but the product code did not match the manufactureres datasheet, this led me to believe these ICs were fakes.

Designing and making a 18650 lithium battery charger with the TP4056

Charging lithium batteries safely Testing the module, 3 18650s charged to 4.18v I needed a PCB module to charge four 18650 lithium batteries for my (battery powered) tube amplifier. I ended up making two different versions of the module, the first design was too compact and got a bit toasty. The second version has more heatsinks and is wider but still reaches 70°C, I could reduce the charge current but decided that if I reduce the supply voltage from 5v to 4.55v, this reduces the max power dissipation by about 0.25W.

Designing and building a speaker start delay circuit

Gold plated rear input and output banana sockets. Did I need to make this? Earlier this year I purchased a hybrid EF95/6AK5 hybrid tube amp from Amazon. The make and model was Fosi Audio T20. The amp cost about £70 and is a great little amp for driving loudspeakers or listening via headphones, the input is fed through the tubes and then amplified using a TI solid state amp. So obviously it's not a 100% tube amp but a hybrid one. One thing I noticed is that there is a large amount of DC when turning on the amp, this is not good for the speakers. This can be avoided by flipping the toggle to the off position, however this keeps power to the amp on and it gets slightly warm. Now this being something that is cheap and coming from China, I didn't trust it enough to leave it on like this all the time. So this is when I decided to make a circuit using relays to delay the speaker connection and to add in inline power switch, this meant the power is fed to my circuit as well as the ampl