Kenwood KA 9100 Part 5 of 5 - It was worth repairing!

[@HazeAnderson]

I have garnered some experience with "rattle can" painting on metal surfaces. I start by cleaning the surface thoroughly ... in the case of fresh aluminum enclosures I sand them down first and wipe them clean with naphtha. I then apply 3 coats of primer, waiting 10 minutes between each spraying. After a few days, I lightly sand back the primer, gently wipe with a small amount of naphtha, and then start applying the base coat: 3 coats of the base color, waiting 10 minutes between each spraying. Wait a few days. I repeat this TWO more times until I have a total of 3 coats of primer and 9 coats of base. Finally, I lightly sand back, gently wipe with a small amount of naphtha and either apply the final clear matte or paint labels and art, and then apply the final clear matte. This works amazing for the guitar pedals I build. Cheers!

[@AudiophileTommy]

Your videos are such a joy to watch ❤❤❤❤

[@thomaskendall452]

Thank you, Tony, for breathing new life into this vintage classic! The pre-AccuPhase Kenwoods, as this KA-9100 most likely is, are glorious pieces of gear. Now, this one can be enjoyed for decades, rather than being condemned to the parts bin. Congratulations!

[@EdwardLehman]

With vinyl making a comeback, having a nice vintage piece of equipment goes along so well and plays very well!

[@IAWAF]

Beautiful job Tony. You are really a craftsman working on these vintage pieces. Satisfying to watch you work. 👏👌

[@charlesjefferis8812]

outstanding job, Tony. FWIW, I’m a fan of the early vintage Kenwood amps. . . I bought a Kenwood KA-6000 amp in the late ‘60s . . . built so solid… wish I had kept it.

[@davidwolverton4858]

Great job Tony!

[@KillerKlipsch]

Loved watching this journey from start to finish, so glad you chose to fix it, well done sir.

[@garygranato9164]

considering how many issues it had it turned out really well

[@DanielMelendrezPhD]

Fantastic repair series. The only problem I have from watching your videos is that I feel strongly compelled to browse eBay and search for similar broken amps and repair them myself (I do that as a hobby too and I still have 4 amps ready and waiting to be sold). Cheers, Tony

[@AudiophileTommy]

There is a ton on there for sure !

[@Efston]

Great job! I have this exact amp but it won’t power up. Why couldn’t you repair the back lights for the vu meters?

[@jaybats7865]

What a phenomenal transformation. Great series! From parts amp to show stopper….nice job Tony. Enjoyed it very much, thanks for the fun 🤩

[@davids4610]

Tony, you're amazing!

[@petertimp5416]

Nice…thanks again.

[@braddokken9191]

Great series Tony! So happy you decided to complete this build. I know it was a toss up at one point but you ended up with a receiver that's better than the day it was built.

[@chrislewis1149]

Very well done, you didn't skip or miss anything and it shows in the results. Good thing you didn't give up on the transformer.

[@zambrano966]

Excelente Tony, si vale, si valió la pena restaurar este amplificador, lo dejaste para que funcione otros 30 añas mas .

[@jdmccorful]

That's the best answer. "You can hear it and you can tell". Enjoyed the series! Thanks!!!

[@craigm.9070]

Excellent results on this project; sound and performance is amazing! Thanks for your time Tony.

[@Dutch-linux]

I knew it was worth it to repair.... glad you have repaired it thanx Tony

[@TriAmpMyFi]

Sweet vintage work-horse ready for duty. Very nice. 🔈🔉🔊

[@PracticallyFixed]

You read my mind in real time! I just thinking "I need to ask Tony about his mic!" And then you immediately talked about it. Thanks so much, ordered. Wonderful job Tony. To think, the fellow who said, "psst, there is a thermal fuse inside the transformer..." made the right comment at the right time; so thanks to him too! Thanks again for a terrific series.

[@stevefoster2700]

Tony, you are a gem for the amount of work you put into this! I learn so much from you and have added my Patreon support. Your videos are engaging to watch straight through and I thank you for not having ads pop up in the body of them. I recently added a Kenwood KA-701 to my collection of projects and believe this brand is underrated. Thanks again.

[@gearheadted9210]

the electron sheepherder strikes yet again,great video and amp,thanks from an old retired auto mechanic drifting on the fringes of electronic competency now must go gather some shrubbery..:)

[@haqitman]

You've built a fighter jet out of a Cessna. Awesome Tony. Really amazing!

[@R.AudioElectronics]

Great video! Turned out great. Not only performs well but it is looking great. Good touch on the color. Of course as far as the sound goes it’s limited with your expensive microphone. I have restored my KA 9100 with original output modules and it sounds great. Like you said very clean and nice dynamic sound. I might have to pick up some of those aftermarket modules just in case. Thanks Tony very enjoyable!

[@jimomertz]

To get rid of the glare on the oscope, just go buy a matte screen protector for an iPad, and cut it to size. I did this on my oscope and it works perfectly. It makes cleaning the screen easier too because it is touch screen.

[@xraytonyb]

Great idea!

[@pybelleau]

Another great videos series. We will stick around for sure.

[@morrisonAV]

Great work on this video, Tony. I passed on a Sony receiver due to it having those Darlington modules but it looks like there is now an alternative. Also, I would definitely increase the brightness of those VU LED meters.....too faint in a lit room.

[@davidocampoi9602]

Great job Tony, we learn a lot from you. Greetings from Colombia.

[@brianwood5220]

What a wonderful job, Tony. Those figures are excellent. You should be so proud of your work. Thanks for sharing.

[@alejandroclerico8529]

Great job, i started follow your channel. Greetings from Argentina. You have a lovely lab.

[@nickpopa7260]

Congratulations! The device looks better than when it was new. It sure works better than the original.

[@brotherbrian5625]

This was excellent Thankyou for sharing

[@jmcbeady8210]

Excellent work 👏.

[@mcgjohn22]

Really nice work Tony, and a lot of work on top of it. If memory serves correctly, I believe the KA-8100 was very similar (true dual mono) but had a few less watts per channel and used all discrete components in the output stage. This era of Kenwoods always had a very nice appearance to boot.

[@davorst699]

Nice to hear you had good experience with spray paint in cans. Here in Croatia i tried couple of brands and results we're really different,but most of that cheap spray paint i used took a lot of time to get completely dry. If you go do paint shop and they mix you some custom color and fill a can in front of you, those are pretty good and can be completely dry fast but that costs quite a bit more then spray pain from shelf. But what i have found is that powder coating is great. Maybe a bit more expensive then custom filled spray can,a lot cheaper then professional lacquer(like car ones),but a lot more resistant then pain and price is really acceptable. I would say i would pay maybe 20-30$ for top and bottom cover. Lucky me i got company that does powder coating maybe 50km from place i live so i always go to them when i need to pain some chassis,covers and that stuff.

[@matthewfrazee3352]

I bought this amp and a pair of Yamaha ns 1000ms from a naval officer when I was in college in the early 90s. Both stayed as my main system until 4 years ago when I sold both speaker and amp for multiple times what I paid for them after nearly 30 years.

[@Nixima81]

Grate job, looking and sounding good. For the record the mic you shown for 8$ it's a steal i might have to order one just to have.

[@andymouse]

Awesome ! 0.009 @100W I think thats a record for me as a viewer....cheers.

[@FJL4215]

Beautiful!

[@JamesE707]

Awesome distortion figures.

[@equam55]

Hi Tony, If you would like to take on a project. I have a KA8004 amplifier & KA8005 tuner. I enjoyed watching your work on these vintage electronics.

[@jutukka]

Nice job! 👍 But now you can just for fun change those transformers to toroidal ones and test if it sounds better! 😜

[@TriAmpMyFi]

Very Interesting......................

[@itsonlyme9938]

$8 for the mic sounds great. It would be interesting to do a frequency sweep and look at the response.

[@63MGB1]

I believe you tested the amps power at 8 ohms. It would be interesting to see the output at 4 ohms. I have a KA 9100 that I use to power a pair of Maggie's that are nominal 5 ohms, and it performs great. Bought the amp new in 1978.

[@esci8978]

Great Series Tony… Impressive test results….! What are your thoughts on component “burn in” with respect to test results and sound quality..? In other words do you believe that test results and/or sound quality “can/will/may” improve after “X” amount of hours..?

[@xraytonyb]

Vacuum tubes will change somewhat after an initial burn in period, when they are new. As for solid state gear, I have not personally seen a situation where the amp changes after an initial operating period. I know that there are some comments out there about it, but I have not noticed it myself. Thanks for the question!

[@esci8978]

@@xraytonyb Thank you for your reply.. :)

[@charlessmyth]

[14:35] That's a better slew rate than most high-end, audio op-amps :-) As for the cost of the output stage -- that looks like it could do with a second pair of output transistors, and heftier pin-outs and traces -- it could have been a lot harder on the pocket: It could have been a Marantz 2500 you were repairing :-)

[@TheJimmydan67]

thats one heck of a mic for 8 dollars...very good sound quality....im sure you could do a frequency sweep and find it's range

[@davidgriffin79]

0:59 Could you show us the the paint you used. I have a similar dilemma with an Arcam Alpha 7 amp I recently repaired, the paint on the casing is scratched up and I've been looking for something that would be acceptable to paint it with; this spray looks just the ticket.

[@xraytonyb]

I first used a can of Rust-oleum bonding primer followed up with Rust-Oleum Advanced all in one spray paint. All purchased from Lowes.

[@victormihai3929]

@@xraytonyb Looks great. Rustoleum makes a 'textured' paint that leaves a nice close to original finish.

[@EnochLight]

Beautiful restoration! But you said the (wattage) meters are working perfectly, yet - they don’t light up. 😢 ** EDIT - ok, I see at the end that they’re very faintly lighting up. My bad! Those would look sweet with some brighter LED’s inside.

[@Parkhill57]

Probably just the white balance on the camera. Too bright can be obnoxious when your snuggling with the cat in a dimmed room listening to the Moody Blues...

[@EnochLight]

Not judging! #cats_rule

[@jackgabbert3233]

Hi Tony, Looks like I'm the 1st to comment. Love all your videos.

[@mitkothemacedonian]

Testing for thd at 1kHz is too easy on the amplifiers. Testing it at 20kHz will reveal if the slew rate is right, or if any oscillation occurs, or if it rolls off the highs lower than the hearing range. If it tests at the same amplitude and thd at 40hZ and 20kHz, that's a real piece of engineering.

[@xraytonyb]

I did. I showed it in the video. THD held steady at 20, 1k and 20kHz. I also did slew rate test.

[@adalbertus777]

Does anyone know what was the mode reverse switch designed for? I know how it works. What puzzles me is what are the benefits of swapping the channels when listening to music.

[@xraytonyb]

It swaps the right and left channels. Right channel comes out of left speaker, left channel comes out of right speaker when reverse is selected.

[@adalbertus777]

@@xraytonyb Thanks Tony, although I knew that already and you also mentioned this on the video ;). I was curious why anyone would like to swap channels when listening to music. Would it sound better that way? I would assume music producers know what they're doing while working on a final mix so if, let's say, guitar is on left it should go on left.

[@hoobsgroove]

What is fantastic about low THD?? that doesn't make an amplifier good, and really you want to know what the individual harmonic distortion is more important, and can be high in certain aspects like second harmonics eight harmonics etc to three or four percent. I bet that amplifier sounds sterile

[@HazeAnderson]

"I bet that amplifier sounds sterile" so now you can fine tune it with your multi-band EQ.

[@paulb4661]

Hi-Fi or high FIDELITY, the clue is in the name. Voices and instruments are devoid of harmonic overtones, the aim of the designer is to ensure the gear distorts the signal so that these are added in prescribed ratio, or the voices and instruments carry harmonic overtones and the aim of the designer is to ensure the gear preserves this structure intact.

[@hoobsgroove]

@@paulb4661 no I disagree with that in a professional application yes not for home listening, and you are destroying the overtones even if there's no distortion in the amp. By your thinking there should be only one amplifier and having an amplifier that gives you great dynamics great sound stage good separation of instruments is wrong. No Hi-Fi system represents an instrument correctly anyway, and by having distortions makes it more realistic like tube gear. Who really wants to listen to a sterile type of sound it's uninteresting uninspiring not very engaging and not very realistic but everybody to their own if that's what you like, majority of audiophile don't want that. You should try and listen to some good quality tube gear and then make the decision.

[@paulb4661]

@@hoobsgroove First sentence makes no sense, so I''ll skip that."You are destroying the overtones even if there's no distortion in the amp" is the most absurd assertion you make, explain why that is the case- there's no distortion free amplifier in existence, so how come you establish that? By my thinking, the aim is to reproduce the recorded signal, not tinker with it. I agree no system can transport you to the venue- that's why I go to concerts, but the better ones can offer a pretty convincing illusion. No, tube gear is not more realistic and painting all tube gear with the same brush, regardless of circuit arrangement is just simplistic, or plainly speaking - ignorant. You should try to get serious about learning the inner workings of amplifiers and then make an informed decision. Finally, there's about 4, or 5 opinions in a room containing 2, or 3 audiophiles, I'm surprised you know what they want, since usually, they don't know themselves.

[@andymouse]

@@paulb4661 Bravo Sir ! and yes, the first statement is odd but to be honest Audiophiles are like wine connoisseurs full of....................wine.