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Kenwood KA 9100 Upgraded and Singing!

  • Thread starter Thread starter 2x6spds
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2x6spds

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Well, I finally got my KA 9100 back from superradiogeek, a great guy and an incredible tech. One of the amp's circuit boards had a problem, he resoldered every connection, well over a hundred of them. He fabricated a plastic plate for brass speaker terminals instead of the horrible little "cages" Kenwood used. Beautiful workmanship! He also swapped out the junky little OEM power cord with a great big honking Bob Crump design power cord. It will never starve for power.

This Kenwood is a wonderful amplifier.

It's now driving a pair of Mission 77ds bipole surround speakers for channels 6+7. I'm happy. System sounds great. Kenwood looks incredibly good.

Will post some pictures soon!
 
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Yes, it is a nice amp indeed. The main amp board uses a couple of TO-92L devices to drive the output hybrid module, and they aren't really up to the job and lead to dry solder joints after pushing the amp for a while. I routinely replace them with heatsinked TO-126 devices to ensure it doesn't happen again.

The 9100 is a sonofabitch to work on...the phono amp and preamp sections are buried well, and the troublesome output relay circuitry require the power supply filter caps to be unsoldered :eek: But once working, it has one of the best phono stages I have ever heard, and a very neutral sound overall. I plan on keeping mine for a very very long time.
 
9100 mods

Echo, do you think that there any mods that would be considered the biggest return for the least work on a ka-9100? Are there some mods that are not too hard to do but make a large difference in sound?

I'd like to so some mods to mine if they wont take forever or require special equipment other than a soldering iron and a dmm.

Any suggestions?

David
 
Change out the cheap DC offset pot with a good Bourns trimpot, and replace the TO-92L pre-drivers with 2SD669 (need 2) and a 2SB649 (need 4). Neither will change sound quality, but are more for reliability.

The output relays on these old amps sometimes are pretty worn, and the contacts beat-up. Doesn't hurt to put a new one in.
 
Here is a picture of the upgraded speaker binding posts and honking power cord.

i.pl
 
The speaker posts look nice, but in actuality the stock ones are much better than average (at least they aren't the spring loaded ones). As far as the power cable, the 9100 is pretty efficient even for a Class AB amp, and at full-bore probably does not pull much more than 4 amps or so from the line (if that much). The new one looks nice, but technically doesn't do much for you (except, as I said, look good).

Nice work though.
 
That's exactly what superradiogeek told me. But the cord sure looks good, doesn't it?
 
What color are the lamps for the meters on your 9100?
Mine are yellowish.
Being that I bought mine used, I'm wondering if this is the original color of the lamps.
 
If they are yellowish, then someone replaced the original lamps (8V 150mA) with a higher voltage model. The higher voltage model will show up yellow, as there is not enough voltage present for them at shine as bright as they should.

The original lamps are not very bright, but they are nevertheless not yellow. All Electronics sells a nice replacement here. These are leaded, and some splicing to the original wires (or wirenuts) to connect will be necessary. FWI, the lamps are serised, and if one goes out....
 
Hi joZmo
My meters light up a "cool" subdued white. Not very bright. Not yellow.
 
Don't know if JoZmo has lost interest ot not, but here is how the lamps are configured in the 9100. Because of the limiting resistors, you are not free to substitute any-old 8V lamp in place of the 150mA ones. It is concievable that you could swap out the resistors and use a brighter lamp, but the board that the resistors are mounted to is the right-channel diode board, and to get to the resistors means unsoldering the 12,000µf power supply capacitors :eek: . I have had to do it on several 9100 to repair the protection relay circuit, but it is a serious PITA. Easiest to just put in the proper lamp and be done with it, and live with the 'not-so-bright' 150mA lamps.
 
OK. I looked closer and I guess the meter lights are more white than yellow, but subdued like you said 2x, so that's why I thought they might not be the originals.

Also, I thought that the originals might be green or blue, but I guess not.

Thanks for the info anway Echo, if I ever need to replace the lamps now I know what I need.
:thmbsp:
 
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