300B Amplifier Driver Stage Redesign

Looking to this 300B amplifier built, it was designed with similar philosophy of Luxman MQ-300. The driver stage is 6SN7 tubes configured in parallel for higher current output, lower impedance and distortion. Instead the original Luxman MQ-300 using total 2-stages amplification in the driver stages, I only use a single stages. The reason for this is because the limitation in the chassis spaces.

The sound quality for this 300B amplifier using a single stages 6SN7 in parallel is actually meet my expectation, but the gain is quite low. My listening loudness is around 55 to 70 dB maximum, not too loud, and the volume level position around 12 to 3 o'clock for 3-volt output from the source. This might be an issue for someone who looking for the gain, but for me this is still acceptable.

The main issue for this amplifier is actually with the sound quality depend with the source level output. I am using my own built DAC or few commercially available source and not all of them can produce 3-volt output. Normally around 2 volt or less. This is become an issue for low gain amplifier like this because low voltage input shrinks the sound-stage and limiting the dynamic. So, my choice for using different kind of source become very limited. On the others words, this amplifier is picky to the source level input.

In this post, I redesign the driver stage and also few clean up the cables inside this amplifier.

The 300B Amplifier Updates

Welcoming this year, I always hope that this 2026 will be blessed with joy and happiness, with all things we are doing, we doing with fun and excitement.

For the past week, I actually got flu and not really into this hobby for quite long time. But I was concerning to revisiting this newly built amplifier again. Is not 100% complete, few things need to change and add to suit my sound preference.

So, here it is. The new updates for this 300B amplifier.

300B Amplifier Build Based On Luxman MQ-300

This 300B amplifier build is coming far earlier than expected.

This amplifier build was initiated around 6 months ago. Then it starting from sourcing the major components such as the amplifier case, tube sockets, resistors, capacitors and the tubes itself. All of them are mostly imported and with a long waited, they've just arrived two weeks ago. The other key components such as output transformer, power transformer and choke required a week to custom made based on this 300B amplifier schematic and idea.

It is very common when building an amplifier from a scratch like this, there is an issue appears after it complete. Most common issue is the hum. This annoying hum can ruin my time to troubleshoot it. Especially when building 300B amplifier, hum is mostly present at the speaker output. But this project is different. This 300B amplifier is finished without the annoying hum issue. This amplifier working like a charm since the first time it powering ON.

And the sound is really good.

The Finishing Touch For My Luxman LXV-OT7 Clone

I am visiting this Luxman LXV-OT7 clone for the finishing touch.

From the time this amplifier project finished, some of the parts are using what I have left in my bin. This amplifier is working fine but just not perfect. So, after my imported components came last week, I start to open this amplifier again. Those components that need to replace are RCA female plugs and potentiometer.

Elekit TU-8900 Components Upgrade & The Reason I Sold it

Here we go for tube amplifier again!

I have this Elekit TU-8900 amplifier for a short time before I sold it. I was enjoying the music with this amplifier for quite a while, and I can say this amplifier is powerful enough to drive my 86 dB sensitivity speakers with lots of dynamic and bass slam.

This Elekit TU-8900 is popular because it is the cheapest 300B or 2A3 amplifier that still made in Japan. This amplifier was coming as a kit, meaning you should install it by your own with the included manual and all parts scattered. Since I bought it second hand, it is assembled from the previous owner already.

In this post, I don't think I would add the same review again because you can find many good reviews about this amplifier everywhere. What I will share to you is actually there are few components that can be easily upgrade for the better sound.

Let's check it out.

Luxman LXV-OT7 Clone Build

This new amplifier build is a clone from the original Luxman amplifier kit that was sold in Japan. This kit was came as bundled with the magazine, it is the Luxman LXV-OT7, a hybrid amplifier using tube as an audio buffer and a stereo IC amplifier.

The power output from this amplifier is small, just 3 watt per channel at 8-ohm, but good enough to drive my 88 dB sensitivity speaker. The tube is use for audio buffer before the amplifier and this what makes this amplifier looking good and sound special.

I make this clone with all components packed in a small amplifier case. Of course, with the improvement on the power supply section that has direct effect to the sound improvement.

Let's check the build.

The Introduction For Luxman LXV-OT7 Clone

For more than two months, I never listen the music on my system anymore. This simply because all of my amplifier was sold. They had moved to their new house, of course with the new satisfy owners. One-by-one are gone until I realized, I've sold all my amplifier.

If I count, it is all gone started from my simple LM3875 gainclone amplifier, Mauro Penasa design LM3886 amplifier, Elekit TU-8900 amplifier, and Parasound HCA-1206.

So, I don't have anything to powering up my speakers right now.

Of course, I always have a plan, but sometimes the plan is not run as expected. My new amplifier project is delayed due to the imported parts is not delivered yet. I still have to wait a month for the parts to come, not to count the making process for the new amplifier project yet. So, maybe I should be waiting for the next 3 month until the new amplifier project finished. And right now, no amplifier = no music.

I only browsing from the internet, reading some reviews and looking to beautiful audio photos. Until one day, I saw the Luxman kit that sold many years ago in Japan, I got my interest on it.

Detail PCB Way Built Quality For PCM58 DAC

This post is a series from my the previous post about my PCB order at pcbway.com. Please check the details on their websites PCBway

The PCB that I ordered from PCB Way is actually consisting of main board for PCM58 DAC with an op-amp output per channel for IV conversion and low-pass filter. This DAC is in non-oversampling and using shift-register for I2s input. The I2s input is chosen because it is more flexible for me to put the digital input module, either USB or SPDIF input, as long as the output from receiver module is I2s.

The other PCB is for the power supply board. This power supply is consist of rectifier and capacitors, then goes to DC regulator using 2 pair of LM317 and LM337.

Now let's see how good is the PCB quality ordered from PCB Way and how easy to soldering the pads with the components installed on it.