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.

Parasound HCA-1206 Amplifier: Recap & High-bias Setup

I bought this amplifier by the end of last year and I can say this Parasound HCA-1206 is the best sounding solid-state amplifier I've ever heard.

Previously, I've owned and heard many amplifiers in my own audio system. Not on others system to be clear. So, I know the difference in the sound quality. This amplifier is a keep. Although it is very heavy, about 40 kilos, but the weight is equal with its built-quality. The designer of this amplifier is one of the most famous amplifier designs: John Curl. Probably you may know that this guy also designs the amplifier for Mark Levinson.

In this post, I will do some improvement with this amplifier. Let's check it out.

Parasound HCA-1206 Multi Channel Amplifier, Optimized For Stereo Only

This Parasound HCA-1206 is a multi-channel amplifier that intended for home theater audio setup.

No wonder this amplifier has 6-channel identical amplifier in one chassis, together with the THX certified label, it delivers 120-watt power per channel.

This amplifier is my fresh catch not long time ago after I got the Parasound DAC-1000 before. The condition is like new and I was thinking that this amplifier would be a match pair with my DAC since they are built at the same year.

And I was right! This amplifier is sound wonderful. It really matching with the DAC in term of the style and sound.

That is why, in this post, I will make this multi-channel amplifier optimized for use in the stereo system only.

300B Amplifier Hum Problem Solved

My previous post about the 300B tube amplifier build was a breakthrough. At least for myself. That was my first 300B amplifier build which if I remember, a decade ago, it will never across my mind to build such this expensive amplifier.

I learn a lot from that build and the 300B tube by its nature is direct-heated triode which I read everywhere saying that DHT will always have small hum present at the output, especially when pairing with the speaker sensitivity above 90 db.

My 300B amplifier built intended to drive a headphone. It is also can act as pre-amplifier. Small hum might be a problem for the listening enjoyment. Probably I should accept it.

But when the amplifier is done, the hum is worse than my expectation. It is loud and not at the acceptable level at all. The hum always presents at all time, even with the volume control fully closed.

I think more than a month and I tried to figure it out how to solve this issue. With the help of my friends, now this 300B amplifier is completely free of hum.

Yes, you are read it correctly. No hum at all, it is dead silent.

Only great music.

300B Tube Amplifier Build

The 300B tube can be the holy grail of every tube amplifier. Everyone praises for its sweet sound. Personally, I never compare directly between one amplifier to another amplifier using 300B tube, but I still believe the reputation of this 300B is not a false statement.

More specific, the single ended 300B design are well known for the best sounding amplifier compare with the push-pull. Single ended is also more economical approach since we only need a pair of 300B tubes. But it has the drawback, it is the low power output. It is about 6 watt per channel.

That is why in this 300B tube amplifier build, I will make this amplifier in single ended design with 6SN7 driver and 5AR4 rectifier to drive a headphone.

For headphone? Pretty disappointed?

I guess not. I hope the sweet sound of 300B can be heard more closely to my ears.

OPA1622 Vs. OPA627 High Performance Op-amps Comparison

This op-amps comparison topic is actually boring, but at the same time, many of us still curious about what others think about it. The reason is simply because of the op-amps variation are hundreds and they are depends by the implementation.

The op-amps are considerably cheap and an interchangeable electronic components but they are not built for the same function. So in this discussion, I will focus on the modern Vs. vintage high performance op-amps in the simple non-inverting pre-amplifier gain stage.

Mauro Penasa My Ref LM3886 Amplifier Build

This Mauro Penasa LM3886 amplifier is not typical Gainclone amplifier because it is not what it is.

This amplifier is published over 10 years ago and the designer name is Mauro Penasa. He was mimicking and redesigning this amplifier from his nostalgic good sounding vintage amplifier, the Musical Fidelity A370 amplifier.

If you read his design notes, he was really like the A370 amplifier so much and he think that today amplifier is not as good as it. The sound of A370 can only be compete with most linear class A amplifier that inefficient, hot, and heavy. That is why he redesign the A370 but using LM3886 IC for more economical approach. This LM3886 act as current pump and the op-amp is LM318 act as voltage gain.

Yes, it is using op-amp, same like the original design as well. The goal for this amplifier is like having a good class A sounding amplifier with the efficiency of class AB just like the A370 original design.

This amplifier is quite famous in DIY audio for years and I will try to build it now.

Troubleshoot STAX SRM1 MK2 Professional & Lambda Headphone Driver Unit

When you hear the name STAX headphone amplifier, first things comes in mind is the electrostatic headphone which is made in Japan and expensive.

It is all make sense since STAX never selling their unit cheap, same with many of the Japanese product as well.

Speaking for the STAX headphone amplifier, I have one long time ago here, but the entry level STAX headphone amplifier and I can say it sound really good. The sound is so much open, larger soundstage, so much detail and very natural music presentation. I may called it the STAX sound signature.

But if I get a cheap old STAX headphone amplifier that intended use for the professional, will it sound better then what I have before?

Before jump to that conclusion, lets see the unit that I just got here first.

The ACA - Amp Camp Amplifier Built

The ACA amplifier was initially designed for beginner in DIY audio so they can start to build a discrete class A amplifier. And because of this reason, so the components and the design should be as simple as possible. This simple approach always shared the same philosophy as the designer itself, the Nelson Pass who own the Pass Labs and the First Watt.

The ACA amplifier is using only 2 transistor in the signal path. The JFET for voltage amplifier and MOSFET for current amplifier. Interestingly this amplifier can be powered with a pair of SMPS laptop power supply.

I heard from others that have tested it, this amplifier sound great.

So, since I already have the ACA PCB on hands, why don't I start building this amplifier?

I am also a beginner:)

A Simple DIY Amplifier Project For Cheap

The story of this amplifier built is came 2 month ago when my friend asked me if I could build small amplifier that sound good enough to drive his 2 way bookshelf speakers.

He just moved to the new house and the living room design is now more minimalist. Previously those bookshelf speakers are connected to the home audio receiver, so he can watching TV, playing games, and listen to the music with the same setups.

In the new house, that home receiver cannot fit to the new cabinet. He replaced it with only using a Yamaha sound bar. It is sound good for movies and playing games, but not for music. That is why, he contacting me to build a small affordable good sounding amplifier that can fit inside his new cabinet so He can still using the bookshelf speaker just to listen to the music only.

Since this build is simple, I think this is a good share for everyone who want to build an amplifier.

Reisong A10 Single Ended Tube Vacuum Amplifier (Part 3) High Bias 6L6

In this part 3 of the Reisong A10 single ended vacuum tube amplifier, I will share the upgrade progress to make this amplifier sound better by replace all the vacuum tubes and increase the bias on them.

On the previous upgrade, I have changed this amplifier configuration from ultra-linear to triode. The triode is well known for better sound but has lower power output compare to the ultra-linear. This lower power output will become an issue if the speakers connected to this amplifier is having low sensitivity. But because this amplifier is intended to use for balanced headphone amplifier only, so the power output is not become my concern.

This amplifier is having so much potential, so keep reading for this final progress of this amplifier upgrade.

Reisong A10 Single Ended Vacuum Tube Amplifier (Part 2) Balanced Headphone Out Modification

Continue from the previous post about the introduction of this great affordable vacuum tube amplifier, so in this post, I will share my first modification to the layout of this amplifier.

This layout modification is quite radical, because I will put balanced headphone out via 4 pin XLR in this amplifier and defeat the speakers out. The reason for this is this amplifier dimension is small enough for the headphone amplifier compare if I am using the KT88 amplifier here.

We never see Reisong build amplifier for headphones, so I should make one with this unit.

Keep reading.

Reisong A10 Single Ended Vacuum Tube Amplifier (Part 1) Introduction

This Reisong A10 is a very popular vacuum tube amplifier. This is because the price is very cheap consider to it's high built quality.

I got one in this second hand condition for about US$250. The amplifier condition is like new.

In my opinion, it is a great small amplifier. It weight about 7 kilos and the casing is all stainless steel, beautifully mirror finished, and well arranged components inside out.

In this post, I will make a review about what this amplifier gives for the price.

I think, this could be the entry point for anyone who want to explore the excitement of do it yourself audio, especially for vacuum tube amplifier. So let's begin.

DIY Speaker To Headphone Amplifier Converter

For the desktop headphone amplifier, it doesn't need a dedicated one if you already have a home speaker amplifier. Especially if the home amplifier is great sounding and you like the sound from it, then connect it to your precious headphone can be done by following this project.

But they cannot connect directly from the speaker terminal to the headphone jack. The first reason is the current from the home amplifier is too large that may damaging the headphone connected. The second reason is sometimes the DC offset from home amplifier are too large for the headphone could handle. And the third reason is the unmatched impedance between speaker and the headphone. This third reason is more technical to discuss but this is what we will do with this DIY speaker to headphone amplifier converter.