Join me as we examine the gorgeous Kenwood KA-4002A integrated amplifier, part of my new ‘baby amplifiers’ series.

Many people like small amplifiers—let’s call them baby amplifiers—for various reasons. In this series, we will examine a few of my favourite baby amplifiers in the hope of enlightening and maybe even inspiring a few people to purchase one. I hope you enjoy!

Baby Amplifiers

There is something particularly endearing about modest pieces that don’t cost the earth and punch above their weight. Who doesn’t love simple, reliable, well-made things?! Baby amplifiers are small, simple and affordable models, offering a bit less of everything, in exchange for less money, performance and improved reliability vs larger, more complex designs.

Whilst I love crazy high-end hifi gear and some might say I’m obsessed with it (!), what I love most is good, well-engineered hi-fi gear, regardless of cost. Baby amplifiers are the most affordable discrete hifi stereo amplifiers available, but that doesn’t mean they are poorly engineerered.

They typically lack the overall fidelity of more powerful designs and lack adequate dynamic capabilities in all but a handful of edge use cases. That said, many of the classic baby amplifiers were just as beautifully made as their more expensive counterparts, minus the fancy circuitry. In small and less ambitious systems, baby amplifiers can work surprisingly well.

With this in mind, and given that I work on a lot of these affordable pieces for people who genuinely enjoy them, I’ve decided to write articles about some of my favourite baby amplifiers, starting with the venerable Kenwood KA-4002A. I’ve written about others, like the gorgeous Naim Nait 15-Watt gem, previously. There will be more in this series over the next couple of months.

Baby Amplifier Use-Cases

Before everybody goes nuts and buys a baby amplifier, it’s important to understand their limitations. These amplifiers cannot play loudly or with realistic dynamics and bass in scenarios involving ‘normal’ rooms and loudspeakers of 87 – 91dB/Watt sensitivity. They also feature pared-back circuitry and low quiescent current designs to save costs, so don’t expect to find the world’s best phono preamplifier inside one of these, or massive heatsinks.

Their low power output limits their usefulness and dynamic capabilities and therefore requires the use of sensitive speakers, small rooms, lower listening levels and realistic expectations. This concept of dynamic capability is a foundation of high-fidelity music reproduction and is important to understand. I’ve written more about it in this FAQ.

In the right use case, though, and with sensible expectations, baby amplifiers can be the perfect solution. Here are some use cases for which baby amplifiers are well-suited:

• First and children’s systems
• Office and small room systems
• Non-critical listening scenarios
• Sensitive speakers, 96dB/Watt and over

Kenwood KA-4002A Features

Even though the Kenwood KA-4002A was an affordable model, it is a proper integrated amplifier from the early ’70s. That means that it is well-made, full-featured and includes a decent phono preamp with two phono inputs, tone controls, low and high cut filters, a headphone socket and tape monitor.

Like others from the time, no matter how lacking in power, it also features two sets of speaker terminals and can run both pairs of speakers at the same time. This is a bad idea with a baby amplifier. One pair at a time, only please!

In terms of build, almost everything is made of metal and wood. The knobs have metal shells, the pushbuttons are metal, the switches and pots are all proper old-school ALPS metal types. This little nugget 18-Watt per channel amplifier, is more robustly constructed, more serviceable and nicer to use than any new $1000 amplifier.

It probably sounds better, too, or at least as good. That’s the kicker. For me, a Kenwood KA-4002A is far more interesting and desirable than cheap new offerings. We’re still talking about and using this baby 50 years later. This will not be the case with the Cambridge Audio AXA25.

Specifications

Courtesy of our friends @ HiFi Engine

Power output: 18 watts per channel into 8Ω (stereo)

Frequency response: 20Hz to 40kHz

Total harmonic distortion: 0.5%

Damping factor: 50

Input sensitivity: 2.5mV (MM), 150mV (line)

Signal to noise ratio: 60dB (MM), 70dB (line)

Output: 150mV (line), 30mV (DIN)

Load impedance: 4Ω to 16Ω

Dimensions: 352 x 118 x 240mm

Weight: 5.7kg

Year: 1970 – 1973

Service

The owner of this baby brought her to me because he just acquired her and knows that she’s likely never been serviced and desperately needed it. Equipment needs periodic maintenance. Without it, things seize up, get dirty, noisy, etc.

The controls in this KA-4002A were stiff and notchy, some were loose, and the amplifier was filthy, to be expected after likely being loved for 50 years. This baby certainly needed a little TLC. Oh. And it was dirty…

Results

With this lovely vintage Kenwood KA-4002A integrated amplifier cleaned and serviced, she now runs like a champion and sounds glorious, especially when one considers her low price of zero dollars in this case, and the low cost of an hour’s service. That’s what you call value, and budget-conscious hifi-ing!

I dare say that, even completely original as she is, she will still give years more enjoyment to her new owner. Thankfully, none of the recappers got to her first, so she is unharmed and unpopulated with HungLong, Swellong and Suntan capacitors.

A full overhaul is a sensible idea if keeping a beauty like this KA-4002A, and happy to invest a little more into her. For now though, she runs perfectly and sounds great. I would take this over a new entry-level amplifier any day.

Should You Buy?

If you need a low-cost, low-power hifi stereo amplifier with a phono preamp and the ability to swing with smaller systems, then yes, I can unhesitatingly recommend the Kenwood KA-4002A, or its predecessor, the KA-4002.

There are many other good options from this era, too, and we will examine more of them in coming articles, but the KA-4002A flies under the radar and is more affordable because of it. Let’s hope it stays that way.

That said, if you own power-hungry monitors or larger floorstanders and enjoy electronic music, rock, or metal, then baby amplifiers are not the right choice and will deliver underwhelming results. In those cases, keep adding to the piggy bank until something more substantial can be afforded.

Thank You!

As always, thanks for visiting, and I hope you find articles like this useful. If you’d like me to service or repair your lovely old Kenwood KA-4002A or any other vintage Kenwood or decent vintage hifi amplifier, get in touch via our contact page.

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