A minty KA-880D

mprince

Super Member
I haven't been able to find much information on this amp, I purchased it new in July 1988 for $267 (I think MSRP was something like $430). It got used until about 1997 at which point it was stored. I took it out last week and hooked it up, still sounds great.

I had a few scratchy controls so I opened it up today for a cleaning and DeOxit treatment. Sounds even better now. To my untrained eye all of the internals looked to be in good shape, no bulging or leaking caps.

I think it's a Class A amp (that's what the board said), 100 watts/ch of clean power.

Anyway on to a few pictures:

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Thanks for posting. I had one of these a few years back. This was before I became interested in the inner workings of amplifiers.

Interesting that the main PS cap markings say "For Audio Elna". Are these the original caps?

I enjoyed my KA-880D. It was not in as good a shape as yours. I got mine well used and it continued along that path after I got it.

Mine had a problem: the mounting screws holding the output (and other?) transistors to the heatsink would come loose. I remember tightening them up several times. At the time I was not aware of the importance of this issue. I did not then, and still do not, understand why the screws would repeatedly work themselves loose. Eventually the amp blew and I gave to a friend who was a repair tech. Wish now that I had kept it. You might want to check those mounting screws on your amp.

I do not believe that this is a Class A amp, could be wrong. Where is it marked "Class A", on one of the PCB's?
 
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Thanks Roger. The amp is completely original, today was the first time the cover had ever been removed.

Are you talking about the bolts on the back of the heatsink (shown in the 4th photo)? They were all tight on mine. I did check all of the screws in the amp and all were snug.

I'm not sure what class the amp is, there is very little info out there on this amp (at least through Google searches). I have the owner's manual and other than the basic amp specs and what each knob is for there's not much there. The board was marked "Class A" between the faceplate and the heatsink.

I was surprised how much better it sounded after I DeOxit'ed/Gold the RCA's on this and the tuner/CDP. Really a night and day difference to me.

I don't ever see myself getting rid of this, it has sentimental value as my first "real" component (and it has plenty of power). So somewhere down the road I will likely learn how to replace the caps.
 
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Had it open again today, checked and the main PCB is marked "A Class", not "Class A". So it isn't a Class A amp.
 
I am not an expert.

Class A is a pretty big deal. For marketing purposes, I would think that a manufacturer would make that fact known by markings on the amp, in the manual, etc. Class A amps also put out a lot of heat which requires large heatsinks to dissipate.

I don't think this amp is Class A, but I can not rule out that possibility. Maybe someone who has more knowledge will pop in here to verify. The majority of home-audio amplifiers are Class AB.


If those transistor mounting screws are tight I would not worry about them. Like I said, my KA-880D was well worn when I got it. I am thinking it may have been worked on.

If or when you decide to venture into recapping, Audio Karma is the best place to seek knowledge in that area. There are tons of existing threads that you can search. And of course you can start your own new thread specific to that project. It is mostly about soldering skills and knowing what caps to use as replacements. Typically only the electrolytics and tantalums (your amp may not even have these) need replacement. Two popular suppliers are mouser.com and digi-key.com. You would need to get a Service Manual.
 
That's identical to the minty one I resurrected to perfection with a simple Deoxit night before last. I'd bought it many years ago at a thrift hoping to use it with the bedroom TV, but it had horrible scratchy control issues (and I do mean horrible). Sat in a box in my garage for about 10 years. Got inspired after deoxing my neighbor's Kenwood to haul the 880 out. Cleaned all switches and pots. Working like a champ. No place to put it really, so it's living on the top tier of the garage set, with an EICO set below that, and a Fisher set on the bottom, attached to some Kenwood speakers, to boot. I think I paid $5.00 for it. Added a couple of bucks of Deox. I'm thinking I already got $7.00 worth of joy out of it as I sat listening to it in the garage till dawn, so it's all gravy from here on out. It was truly fun to get from almost no sound to great sound so simply.
 
Nice pics; each channel has its own power supply rectyfiers and buffer capacitors (15.000uF per channel), that's not the average design. The black flatpack blocks are which STK model? Voltage amplifiers? Are those white cemented resistors 2-in-1 output package? Never seen that; could you perhaps a picture showing their printed side?
 
More Pics

View from Front
KA-880D-0925-8.jpg


View from rear
KA-880D-0925-9.jpg


Moving across heatsink from left rear to right rear
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KA-880D-0925-7.jpg


Black flatpacks
KA-880D-0925-1.jpg


Cemented resistors (I think this is what you were asking for)
KA-880D-0925-4.jpg


Miscellaneous stuff
KA-880D-0925-2.jpg


KA-880D-0925-3.jpg


Mine had some scratchiness in the controls too - I DeOx'ed it Saturday and and that helped a lot but to get it completely sorted I removed the face PCB yesterday and got all the pots really good (and cleaned out a piece of wet dust from the volume pot that caused some uncontrollable volume). Running like a champ now.

My next step is to get some better speakers hooked up to this. I think I am going to order Paul Carmody's Overnight Sensations MTM kit soon and build a set. They are 4 ohm but this amp is rated to handle it.
 
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I own a Kenwood KA-9x and that amp was fine, bass heaven. Too bad I blew it at a house party and turned it to a MOSfet Frankenstein to make it operational again. Im liking your KA-880D, sweet in black.

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Thanks for the spec sheet. When I paid a few bucks for mine, knowing nothing about it, I had no idea the numbers might be that respectable, but it earned my respect listening to it after the thorough deoxing.
 
Btw I just bout these yesterday $100 for the KA-880D and GE-1100. Testing them now.
 

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Why does Kenwoods from this era have 1000 Damping factor?

This amp, like the M2, M2A, KA-1100D, and more were Class G amps (also frequently referred to as commutating rail amplifiers), many of which sported these stratospheric damping factors, and some included what Kenwood branded the Sigma Drive, which added an extra set of connections to pull the electromechanical speaker feedback into the electrical equation.

Fun times.

Class G (and Class H) fell out of favor due to complexity, fears of distortion at the transistor switchover point among purists (which were largely nonexistent in well-engineered examples), and broader market forces ("Big Iron" Class A amps on the high end, cheaper rack systems and receivers on the lower end). Kenwood ditched the Sigma Drive before this because few understood the "Why?" and wiring up the Sigma connectors improperly leads to amplifier destruction - which people did, frequently.

Also, bringing this thread back because I just picked up a KA-880D and will be refurbing it. :cool:
 
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