A 1971 Op-Amp Embarrassed Every Premium Chip in a Blind Phono Stage Shootout

The winning chip’s best trait is something most spec sheets would call a defect.

In March 2024, someone on the DIYAudio forum sanded the part numbers off seven op-amps, painted them different colors, and mailed them to a four-person listening panel. The panel scored all nine chips through a Pearl 3 phonostage.

Their top pick, at 8.2 out of 10, turned out to be the MC1458. It’s a dual uA741 from 1971. It costs $0.57 at DigiKey. The $49 Muses02 it outscored costs roughly 86 times more.

“No data sheet parameter predicts this ranking,” wrote mworthin.

How the Test Worked

Op-amp debates on audio forums usually run on brand loyalty and confirmation bias. This one ran on anonymized serial codes. So, DIYAudio member Mark Johnson proposed a blind evaluation through the Pearl 3 phonostage, a Wayne Colburn / Pass Labs design built for component swapping.

Johnson assigned each chip a random serial code, locked the identity table behind encryption, and withheld the decryption key until every listener had posted scores. Seven anonymized chips plus two sighted references, the JRC kit standard and the Muses02, made the full roster. No one could change their mind after the fact.

Member Lvandoorn ran the listening panel. He recruited his spouse, an audiophile friend, and a semi-professional musician. They evaluated each chip through a Lenco L75 turntable, Ortofon MC30 cartridge, and custom horn speakers with JBL drivers, scoring bass clarity, midrange character, treble, speed, and “life feel” on a 1-to-10 scale.

Then they posted their scores. And Mark released the decryption key.

A539 Had a Secret

The scores landed in a tight band. Nine op-amps fell between 7.0 and 8.2 out of 10, a spread of just 1.2 points. All sounded capable through the Pearl 3. The differences were in character and what the panel called “life feel,” and the four listeners agreed almost unanimously on which chip had the most of it.

A539 sat at the top.

Three days later, Johnson released the decryption password and photo attachments, each image showing a chip with its serial code and true identity exposed.

A539 was the MC1458, with a datasheet dated February 1971.

The original uA741 came out of Fairchild Semiconductor in 1968. Motorola later dual-packaged it as the MC1458, two identical circuits in one chip.

With 1 MHz of unity-gain bandwidth and no external components required for stability, it became the most basic op-amp topology the industry still manufactures. Engineers call it a “jelly bean” part.

Boydk called it “a revelation” that the oldest and slowest chip had taken the top spot. 6L6 was less charitable. Maybe the objectively poorest-performing chip was simply making the biggest subjective difference, he suggested, and the panel had mistaken “lots of difference” for “good.”

Lvandoorn didn’t flinch.

“I can state objectively that we stand by our subjectivety!” he replied.

Then Wayne Colburn, who co-designed the Pearl 3, weighed in with measurement data. The question became not what won, but why.

Why the Worst Specs Won

Colburn had already noticed something about his own design. Every op-amp he tested in the Pearl 3 measured well on standard benchmarks, yet the harmonic structure shifted from chip to chip.

Slew rate, bandwidth, and noise floor all looked fine. The differences lived in how each chip colored the signal through the Pearl 3’s RIAA equalization network. When the blind test winner was announced, he went back to his data.

He was working from memory alone, not a published measurement report. No THD figures or spectrum plots appeared in the thread. But the direction was clear enough. The one chip that sounded best to four listeners was also the only one producing elevated second-harmonic distortion.

Distortion as a feature

The second harmonic sits one octave above the fundamental frequency. Play a 440 Hz A note, and the second harmonic is 880 Hz, the A one octave higher. It’s a consonant interval that reinforces the original pitch rather than clashing with it.

That consonance is why even-order harmonics register as warmth and fullness, while odd-order harmonics come across as grit. Tube amplifiers lean heavily on even-order distortion, which is also why they maintain devoted followings despite THD numbers that look terrible by modern standards.

The MC1458, it seemed, was doing something similar. Rick Miller made the connection explicit, comparing the result to Single Ended Triode amps that “measure poorly, but some people love the sound of them.”

Lvandoorn took the argument further. Some amplifier designers deliberately introduce second harmonics for this exact coloration. He invoked a Pass Labs community aphorism.

“It is entertainment not dialysis,” he wrote.

But framing distortion as a feature only works if you accept that a phonostage’s job is to flatter the listener, not faithfully reproduce the signal. Not everyone in the thread accepted that premise.

Four Listeners, One Session, Zero Consensus

The test had real limitations, and the forum wasn’t shy about naming them. Lvandoorn was the first to admit it.

Others pressed harder. Invaderzim argued that short-term listening sessions reward novelty over accuracy.

If the MC1458’s elevated second harmonic made it sound noticeably different, a quick A/B test would reward that difference regardless of whether it held up over weeks of listening.

But even if long-term listening confirmed the preference, a deeper structural problem remained.

Op-amps swapped into circuits designed for different components introduce variables the designer never intended, a point Jitter pressed in the thread.

The Pearl 3’s RIAA network was voiced around a specific chip. Drop in a 1971 dual-741 and the circuit itself behaves differently. The MC1458’s top score might say more about the Pearl 3 than about the MC1458.

Even that objection, though, assumed the test had enough data to interpret. It didn’t. Mark Johnson had hand-assembled fourteen SOIC-to-DIP adapters for the original test and ran out of patience at seven unique pairs.

No other testers ever completed their own blind evaluations. So, the entire result rested on four listeners, one system, and one session.

Twelve months of quiet defection

The thread went dark for twelve months. Then, it came back to life in April 2025 with builders posting their own experiences.

This time, the premium chips weren’t winning converts.

Builder after builder landed on budget options instead. Whether the blind test planted the idea or they reached the same conclusion independently, the direction was the same. The community had quietly moved away from premium op-amps.

One blind test with four listeners didn’t settle the op-amp debate. But it did expose the uncomfortable gap between what audiophiles measure, what they hear, and what they’re willing to pay for the difference.