Building My DIY Stereo Integrated Amplifier: A Step-by-Step Journey.
Ever felt the urge to create something with your own hands, especially something you use daily? That was the motivation behind this project. The personal satisfaction of building something with own hands, understanding its all intricacies, and then enjoying music through it can be deeply satisfying.
In this post, I’ll walk you through the entire process, from inception to the final tune.
Key features and main units of the amplifier:
- Power amplifier based on STK4231
- Tone controller unit based on LM1036
- Spectrum analyzer based on LM324 driver ICs and KA2284 level indicators
- Turn on/off thump protector unit for speakers
- FM/Bluetooth/USB kit
- Transformer
- Power supply unit
- Enclosure
The Building Process: The journey began with purchasing the amplifier enclosure that I wanted. If I didn’t get what I had in my mind, I wouldn’t start this project. :) Luckily, I was able to find one from a local shop a bit far away from Colombon (you see it in the first picture). Then I purchased the rest of the components and got to work.
At the initial shopping attempt, I was not able to find everything required. So the picture above doesn’t contain the full list of components. I had to visit about a dozen shops at different times in First Cross Street Pettah and shops around Colombo to get the list completed.
Step 1: I started off work with the power supply unit. So I could easily test the rest of the units with the aid of it. I’ve got a transformer with output voltages 36–0–36v and 12–0–12v 5A for this. 36v dual supply is for the power amplifier. The other one is for providing power for other units. I equipped a basic power supply PCB available in the market and did some hacks and cracks there to fix the voltage regulators.
The power supply unit inputs a 12VAC dual supply and outputs:
- Regulated 9V (to power the tone controller and FM/Bluetooth/USB unit.)
- Regulated -5V-0–5V (to power spectrum analyzer)
- half rectified and slightly smoothed 12v (to power the speaker protection unit)
Step 2: Then I created the power amplifier. I decided to use STK4231-based amplifier because it's compact enough (personally I didn’t like the hassle with a large transistor amplifier) and absolutely powerful enough for the speakers I’ve got (Sony VX5 speakers). I tailored my solution for indoor house/room usage with shelf-size speakers. A 100W + 100W output power is good enough for that.
Powering up the amplifier for the first time was nerve-wracking! Fortunately, everything worked. I connected the amplifier to speakers and played various music genres to test its capabilities.
Step 3: I created the tone controller based on LM1036, one of the best DIY tone controller kits I’ve ever experienced so far. The boosting and controlling capability is phenomenal and provides crystal clear highs and a beautiful gain in the low range. By referring to the datasheet, the controlling ranges can be easily customized to make the solution match your music-listening taste or speakers. The contribution of tone control makes a significant impact on the listening experience. Thus I had to do some customizations to the control ranges of the circuit to get the best results for the speakers I intended to use (in my case I used Sony VX5 speakers).
Step 4: After testing the amplifier with the tone controller unit I realized a really bad shock comes to the speakers when power turning on and off. This usually occurs when capacitors of the system discharge at different times in the event of power on or off. It is much worse when the power amplifier is connected to the LM1036 tone controller. So I created the following relay switch unit which turns on with a delay set by a basic transistor timer. Speakers are connected through this relay unit. It has to be switched off immediately at the point of power off. To address that, I’ve modified the power supply to get a half-rectified DC 12 voltage which is slightly smoothed enough to function the circuit.
Step 5: Spectrum analyzer display was something I am really obsessed with. It has 2 parts a driver unit and a display unit. Driver unit is driver by LM324 op amp which separates the frequencies into 7 bands. The display unit consists of 7-level indicators driven by KA2284.
The default circuit of this spectrum analyzer has an inherent problem with low response to high frequencies delivered by most devices. I fixed it by modifying it with a high-pass filter and adjusting the input resistance to match my FM/Bluetooth/USB kit.
Step 6: Integration: all units mentioned so far are integrated. The FM/Bluetooth/USB kit and other external inputs are connected to the tone controller through a band selector switch. The output from the band selector directly goes to the tone controller and spectrum analyzer. I was very careful about making all cables that carry signals shielded and avoiding ground loops and implementing proper grounding mechanisms to prevent any hum or hiss noises.
Step 7: Finally, a lot of wiring work and fitting circuits in the enclosure. Drills, bolts, and spacers helped with that. I got support from a lathe workshop to get the power amplifier heatsink drilled. The rest of the work was managed by myself with a manual drill. The enclosure I purchased was tailored for my solution. It's a straightforward task to fix potentiometers and switches. However, fitting things correctly and making things neat and steady took some effort.
I have added a high-level architecture of the components to this post later, as requested by some for better understanding.
Final Results: The finished amplifier is not just functional but also a testament to hands-on creation. The sound quality is crisp, with deep bass and clear mids and highs.
Don’t forget to visit some video clips I’ve recorded throughout this process: :)
The build process of the DIY stereo integrated amplifier using STK4231 and LM1036 https://www.youtube.com/watch?v=I45-fSAdTtk
I connected my own made amplifier to this Sony VX5 speakers. The result was phenomenal! https://www.youtube.com/watch?v=Cx3EwPUKW00
