Kenwood L-05M Vintage Amplifier Review

[AdamG]

At what level are these issues?

Let’s take this off topic conversation to a separate thread. This is an official review thread.

Thank you for your understanding and support.

 

[ObjectiveSubjectivist]

Yes but based on measurements of dozens of similarly designed amplifiers and on circuit analysis the guess is quite qualified. Much more than a mere debate or a forum reading arguments. Of course not 100%, but that’s not needed.

Probably you are right. Still curiosity is just too high

 

[DanielT]

Vintage amp test. Superb Amir.

Anyone thinking about old vintage amplifiers, my advice: Research, find out how much hum comes from the transformer. Not sound out via loudspeaker, but from the transformer itself. Some may find this really annoying. It's the same sound level on this hum so it's not audible when the volume is turned up BUT it CAN be heard if the amp is on and no music is playing (depends, among other things, on how far away from the amplifier you are) .Of course, this does not apply to all vintage amplifiers, all models. It probably depends on many different factors if this is the case.

Edit:
In Sweden, the electricity grid changed from 220 to 230 VAC a few decades ago. If that could be the reason? Or do transformers just dry out, when they have reached their lifespan and this is the result?

 

[dtaylo1066]

A well designed product, regardless of its place in the modern era timeline, can endure.

 

[phoenixdogfan]

Holds up pretty well, doesn't it? I almost bought a pair of these back in the day. Today, I think, an Aiyima A07 with an upgraded power supply will match or exceed its performance for around $150. Still, if you want a piece of audio history, not a bad way to go.

 

[levimax]

Vintage amp test. Superb Amir.

Anyone thinking about old vintage amplifiers, my advice: Research, find out how much hum comes from the transformer. Not sound out via loudspeaker, but from the transformer itself. Some may find this really annoying. It's the same sound level on this hum so it's not audible when the volume is turned up BUT it CAN be heard if the amp is on and no music is playing (depends, among other things, on how far away from the amplifier you are) .Of course, this does not apply to all vintage amplifiers, all models. It probably depends on many different factors if this is the case.

Edit:
In Sweden, the electricity grid changed from 220 to 230 VAC a few decades ago. If that could be the reason? Or do transformers just dry out, when they have reached their lifespan and this is the result?

IE transformers tend to physically vibrate so often make a little mechanical noise. There is nothing to dry out. The advantage of IE is no "soft start" circuitry is required.

 

[DanielT]

IE transformers tend to physically vibrate so often make a little mechanical noise. There is nothing to dry out. The advantage of IE is no "soft start" circuitry is required.

Well, it's something, depends on something and I don't know what it depends on. It's pretty annoying anyway. With some vintage amp's I've had anyway.
Imagine a large transformer station. That kind of hum, albeit on a smaller scale, I've experienced many times with vintage amps.

...little mechanical noise... you probably have to accept that, in that case.

 

[gvl]

So, this machine is from the early 80s of the last century (no later than 1981).
There are 42 years old capacitors inside and so on.
And after 42 years, the amplifier shows the parameters declared by the manufacturer.
This is what we are losing in the flood of cheap Chinese nonsense.

This amp was overhauled with all caps replaced, but this probably didn’t change much.

 

[beefkabob]

I am impressed by this old gear.

 

[oldsysop]

Amid all the class D crap, it's nice to see the review of a real amp.
Thanks Amir!

 

[MerlinGS]

Found this link: https://hifi-wiki.com/index.php/Kenwood_L-05_M

“Original price approx.: 60'000 Yen (Japan, 1979), corresponds to about 1'198 DM”

60K Yen = $452 USD in 1979

Using this site to calculate the cost in todays (2022) money value: https://www.aier.org/cost-of-living-calculator/

Result is this unit costing almost $3000 USD. ($2956.06 to be precise). So for a pair you’re talking $6 grand.

Yes, but in those days, $900 USD for a pair of monoblocks would have been considered fairly cheap. Most 100 watt rated amps from the USA, Canada, UK, NZ, Germany and France would have cost substantially more ($2k-$5K). Even the Hitachi HMA 8500 stereo amp was likely a little more expensive than the Kenwoods. I paid $1.3K USD (I think MSRP was $1.5), for a brand long defunct (Acoustic Electronics, Model Air 2.2.). It was a low feedback design (if memory serves it operated with internal voltages around 300v, despite being SS). It killed transistors for a living. An APT Holman would have cost around $500, be far more reliable and more accurate, and be worth something today...but then again, Absolute Sound didn't give it a rave review Live and learn.

Apparently the last time the Air 2.2 was repaired by the manufacturer, it was modified and was stable down to 1 Ohm (the Scintillas were the thing then), but it still destroyed transistors for a living.

 

[beefkabob]

Amid all the class D crap, it's nice to see the review of a real amp.
Thanks Amir!

Boo! Class D is awesome.

 

[Timcognito]

Love this Thank You @amirm. Hey restorers, an innocent question from an ME; could those all new components inside have improved its performance over original? Would a well kept original test and sound as good?

 

[DonH56]

I loved these old Kenwood monoblocks. Did not own a pair but had them for a while and heard others. Note the "remote" input is not a 12 V trigger circuit; this was long before that became common, but was a nice if not necessary feature since they elected to put the power switch on the back (blah).

Surprised the restore replaced all but the large filter caps, since those are the ones I would expect to have degraded the most, though small coupling caps could also cause issues. I think the main reason I remember this, and an integrated Denon amp, are because some coupling caps got leaky and were a bear to find. As I've stated before, it is not the blown amps that are hard to fix, it is the one that measures 0.01% THD instead of 0.001%...

 

[Labjr]

I like reviews of 70's-80's hifi. BTW, how is the channel balance? Separation?

 

[anchan]

@amirm how is that you are showing SNR at 5W at 96dB but the FFT also at 5W showing a lot of spikes higher than 90dB. 120Hz is peaking around 86dB for example. Perhaps in misinterpreting

 

[GWolfman]

Cool surprise from the past!

 

[levimax]

Really nice measurement results. If one owns this amp, there is no real reason to upgrade, if not more power is required. Surely, there has been same progress in amp technology, THX, Class D etc, but nothing will be audibly better.

I own some vintage Quad amps, 306 and 606 for being specific. I would really like them seen measured here as well.

Send them in and @amirm will test them

 

[Doodski]

Send them in and @amirm will test them

I imagine there are tens of thousands of peeps or more that would be interested in the test results of vintage Quad amps. Very interesting gear with a history.

 

[Rottmannash]

It looks like my old college roommate's Carver Cube amp.