Category: Life

After Modifying My Stam Audio SA-2A

Hello! I’m Jooyoung Kim, mixing engineer & music producer.

Today, I’ll talk about what I did after the article, Record Before Modifying the Stam Audio SA-2A, and how sound changed.

First, let’s review the problems I encountered.

  1. Output gain is similar to input gain, when the GAIN knob is too low.
  2. Compression is started when PEAK REDUCTION knob is too high.
  3. It sounds so dull, like high frequency response is cut off

Otherwise, The Compress and Limit switch was positioned incorrectly. It was simply solved by wrench.

1) Potentiometer Changed..1

If you take off the cover of SA-2A’s knob, you could see a100k potentiometer at each parts. So, I thought that if I change a100k to a50k for gain knob, amount of change is more lower. Also, change a100k to a250k for peak reduction knob, compression would be change more earlier.

So I changed them first.

The green line is SA-2A hardware, the pink line is Waves’ CLA-2A.

It doesn’t seem bad at all! Otherwise, output gain is similar to input gain, when the GAIN knob is too low yet, I ordered A25K and A10K potentiometer too.

2) Vacuum Tubes Changed

I changed my 12AX7 tubes from jj electronics to mullard.

Frequency response and compression curve was not that different compared to jj electronics’. But it sounds much better than before. Harmonic distortion seems to have changed many aspects of the sound.

3) Changed Potentiometer Once Again..2

Upper image is a25k, The lower image shows the a10k potentiometer. You could see frequency response improved when the lower value of potentiometer is used! The problem isn’t solved but it sounds really good.

Red curve is UAD LA-2A Silver face, pink curve is WAVES CLA-2A, green curve is SA-2A.

Compared to UAD, it’s nice that it doesn’t add such an overwhelming saturation. And compared to Waves, I like that it doesn’t have that overly compressed feel.

I think it’s worth trying out more simple tools like this in the future. Next time, maybe an EQ or a Comp DIY kit…!

See you in next post! 🙂

I Released a New Song After a Long Time… The Tremor

Hello! I’m Jooyoung Kim, a mixing engineer and music producer.

I always introduce myself as a singer-songwriter, but honestly, I’ve been working as an engineer so much that I sometimes question whether calling myself a singer-songwriter is still accurate. 😅

That said, I finally released a new song after what feels like forever!

It took way longer than expected… haha. Doesn’t my outfit look a bit chilly? This was filmed in mid-October, and it was still slightly warm back then. But I got so busy in the meantime that everything kept getting delayed until it was freezing winter.

The song itself was actually written late last year. Yes… this too got pushed back, as you might have guessed.

I remember coming up with the idea after I left my job at Forest Record. I was feeling a bit deflated, like a balloon losing its air. Around that time, I applied to graduate school at Sangmyung University.

I spent an entire day playing a simple guitar chord progression and thought to myself, “Right, this is the sound that made me fall in love with music in the first place. Let’s cheer up and get back to it.” And that’s how this song was born.

Thankfully, my song was featured on the front page of the Latest Music section on Korea’s streaming platform, Bugs.

It was also showcased by 821 Sound, where I had it mastered.

I’ve always been a fan of Director Namwoo Kwon’s mastering work—it suits my taste perfectly every time.

These days, I sometimes feel like releasing my own music is just a form of self-satisfaction. Of course, it’s exactly this kind of satisfaction that motivates me to keep making songs.

As time goes on, I find myself letting go of my ego little by little and viewing things from a broader perspective.

This winter, I’m planning to write another book, wrap up my overseas research papers, and submit them for publication.

Let’s keep striving forward!

See you in the next post. 😊

Record Before Modifying the Stam Audio SA-2A

Hello, this is Jooyoung Kim, mixing engineer and music producer.
Until a few days ago, I was planning to sell my Stam Audio SA-2A second-hand and purchase a product from a Japanese brand.

However, it didn’t sell easily, and with the sudden rise in the Japanese yen… So, I decided to modify the unit myself instead of selling it.

Identifying the Problems

Here are the issues I identified with the SA-2A:

  1. Dissatisfying Sound
    • Excessive saturation and dull highs give the audio a muffled feel.
  2. Gain Parameter Adjustment
    • The output volume only matches the original level when the Gain knob is significantly reduced.
  3. Peak Reduction Sensitivity
    • Compression only activates when the Peak Reduction is turned up considerably.
  4. Limit and Compress Switch
    • The switch works in reverse.

Initial Steps in Modification

Addressing Problems #2 and #3

  • Inside the unit, I found a variable resistor labeled A100K.
    • This logarithmic resistor seemed unresponsive at lower ranges.
    • However, since we perceive audio in dB, it made sense to use a logarithmic curve for the Gain control.
  • I decided to replace:
    • Peak Reduction with a B100K (linear) resistor (ideally A200K, but it was unavailable).
    • Gain with a lower resistance A50K resistor.

I placed the order for these parts and will replace them soon.

Fixing Problem #4

  • The Limit/Compress switch was simple to resolve—just unscrewed it and rotated it half a turn.

Investigating Sound Quality Issues

The core problem remained the sound quality. After extensive research:

  • I contacted Stam Audio for the circuit diagrams.
  • I emailed Cinemag, the transformer manufacturer, to get specifications for the input/output transformers:
    • Input: Cinemag CM-5722, winding ratio 1:5.
    • Output: Cinemag CM-2570, winding ratio (18:2):1 = 9:1.

While considering transformer replacements (e.g., Sowter), I found several insights:

  1. Cinemag’s CM-5722 input transformer is already highly rated and doesn’t need replacement.
  2. Discussions on Gear Space suggested that tubes or the T4 cell impact the sound more than transformers.
  3. A post from 2016 or 2017 on Gear Space mentioned that replacing a single input tube can significantly improve sound.
  4. A YouTube video comparing various 12AX7 tubes on a Marshall amp highlighted sound differences between tube brands.

From this, I concluded that the JJ Electronics 12AX7 (ECC83) used in the V1 position is likely the main culprit behind the sound I dislike.

Based on the video, the JJ Electronics tube produced a tone that immediately felt off to me.

Planned Tube Replacements

I decided to replace:

  • V1 Tube: JJ Electronics ECC83 with Mullard 12AX7, a sound I much prefer.
  • V4 Tube: JJ Electronics ECC83 with another Mullard 12AX7 for consistency.

However, due to unexpected expenses this month (e.g., AES membership fees, domestic conference fees, paper review fees, and repairs for another compressor), I’ll postpone the tube replacement until next month.

Side Discovery: DIY Compressors

While researching, I stumbled across a site selling DIY cases and PCBs.

https://collectivecases.com/

While there are plenty of LA-2A clones on the market, the PYE compressor clone caught my eye.

  • PWM-based compressors are rare, and even the clones are scarce.
  • The original units are prohibitively expensive.

Although the schematics look complex and sourcing components would require significant time and money, I feel deeply drawn to this project. Maybe someday, with enough budget, I’ll take it on.

For now, this concludes my record of the SA-2A before modification. Once I replace the tubes and complete further changes, I’ll share my experiences and the sound improvements in a follow-up post.

See you in the next update! 😊

Audio Expo Seoul 2024 (AES 2024) Recap

Hello, this is Jooyoung Kim, a mixing engineer and music producer!

I always tell my fellow music creators never to overlook hi-fi products.

The term “hi-fi” itself is short for “high fidelity,” meaning playback that is as true to the original sound as possible, without distortion.

Among hi-fi manufacturers, there are many companies with advanced technology that deliver excellent measurements. Working with such devices can be highly beneficial.

All passive speakers, rarely seen in professional audio environments!

I also work in this kind of environment.

However, since anechoic chamber measurements provided by companies don’t tell the whole story, it’s crucial to assess how the devices sound in real working environments and how the sound changes depending on the listener’s position.

With that preamble, let’s dive into my experience at the Audio Expo Seoul, which runs from yesterday through tomorrow. Here’s my review after my visit.

Venue

The event took place on the 30th to 32nd floors of Novotel Ambassador Yongsan and the 2nd floor of Yongsan Electronics Market.

Attendees could check in and receive wristbands at the 1st-floor lobby of Novotel Ambassador.

I explored the exhibits in the recommended order: 32nd floor → 31st floor → 30th floor → Yongsan Electronics Market 2nd floor.

Dynaudio Contour Legacy

First up was Dynaudio’s Contour Legacy, a well-known name even in the pro-audio industry.

It was impressive. I’d love to test it in a more controlled listening environment.

Avantgarde Colibri C2

This was one I’d been eager to hear. However, in the hotel room setup, midrange resonances were quite noticeable.

I switched positions to see if it was a placement issue, but my impression remained the same.

ub+ dB1

At first glance, I thought it was a new release from Devialet, but it turned out to be another brand.

Its sound was decent for the price, and the design was intriguing enough to spark some buying interest. If I recall correctly, the pair was around ₩900,000.

Harbeth Super HL5 plus XD

I finally got to experience Harbeth. It reminded me a bit of ATC in terms of sound character.

Monitor Audio Gold 100 6G

Monitor Audio is known for producing excellent measurements. This model felt somewhat restrained, which might make it suitable for certain types of studio work.

Focal Diva Utopia

Focal is another brand known for its professional audio monitors. While solid, it wasn’t to my taste this time.

Piega COAX 811

Piega’s coaxial ribbon design intrigued me, but the midrange resonance was noticeable—perhaps due to the room acoustics.

Tannoy Kensington GR, Classic Gold

Classic Tannoy sound—impressive as always. It made me consider its potential for studio use.

Wharfedale

Great value for money. While not mind-blowing, the quality was solid for the price point.

Marten Mingus Septet

Visually stunning, though the listening experience didn’t fully convince me.

Audio Physic

Although I don’t recall which model I listened to, it left a positive impression.

Genelec

Genelec, a staple for many engineers, had a setup with coaxial speakers and subwoofers. Unfortunately, the playback was marred by distortion, likely from the LP source.

JBL L100 Classic mk2

Solid, dependable sound, living up to expectations.

Revival Audio Sprint

A standout for me. I could see myself using it in a studio setting. The price was also quite reasonable.

YG Acoustics Hailey

A solid performer with tight, well-defined low frequencies.

Avalon PM 3.2

The most impressive speaker I heard at the expo. Its tight bass and wide frequency range were perfect for modern music production.

B&W 801D4

Sadly, the LP setup held back this speaker’s potential. I’d love to hear it in a better environment.

Overall Highlights

My top picks from the expo:

  1. Dynaudio
  2. Tannoy
  3. Audio Physic
  4. Revival Audio
  5. Avalon

The Revival Audio models particularly stood out for their affordability and performance.

Attending events like this is refreshing for both the mind and soul. That’s all for now—see you in the next post!