Krell Duo 300 Stereo Amplifier Repair

Insufficient pressure between output transistors and heatsink prevented proper heat transfer. Output transistors overheated and and shorted. The thermal pads melted and stuck to the transistors and heatsink. The left channel shorted transistors and drivers where replaced, each and every semiconductor was checked and all output transistors were re-seated with thermal grease including the ones on the working channel to prevent them from failing just like the left channel did.

[@lawchoongseng789]

I love your thoroughness in the repair. Attending to the working channel earns my deepest respect. Subscribed. 👍👍👍👍👍

[@Tinybench]

Thank you, thank you, thank you so much! You made my day! 🙂🙏

[@frankfirst6863]

Krell is but a fraction now of it's past quality and engineering. So sad to see and hear this😢

[@andycrane]

Joche, you are the best! Krell wanted a fortune to fix the amp. You came through and made it better than original! Mad respect. But you forget to mention that you talked me into buying those Cornwalls on OfferUp for nothing and you fixed the mid voice coil and recapped the the crossovers. Oh and you make a mad Cuban coffee!

[@Tinybench]

Thank you Andy! Thank you so much!!!!

[@sonusancti]

That will definitely sound better with upgraded filter caps. Great job.

[@Tinybench]

Hello teammate! thank you very much for watching my video and commenting. It’s a shame that some manufacturer decideto save a few dollars by compromising the reliability of a very expensive, unit with inferior parts.

[@sonusancti]

@@Tinybench Yeah, pity the newbies. But for us DIYers, its always fun to make improvements ourselves haha. Still have a box full of Supertech caps.

[@Tinybench]

@@sonusancti Thank you very much Bobby! I like your picture! Super cool! I would be terrified to jump over rocks like that !!! 👏👏👏🙂👍💥💥💥

[@sonusancti]

@@Tinybench We are always in transition from one place to another. Jobs, relationships, materialism to spirituality, earth to our eternal home with our Lord and all men of goodwill.

[@Tinybench]

@@sonusancti Very wise words teammate! 🙂🙏

[@etiennedelange6428]

Your skill is amazing

[@Tinybench]

Hello teammate! I consider myself a beginner and an apprentice who learns something every day, but I do have a driving passion and I really enjoy the process! Thank you thank you thank you so much you made my day. Also, thank you very much for watching the video liking and commenting and if you haven’t subscribe, please do so because it would really help my channel grow!

[@samuelcain5426]

The Krell gear of the 90's were built to a much higher standard damn shame what happen to Krell

[@Tinybench]

Hello, and thank you so much for watching my video. When I made this video, it was not my intention to make Krell look bad or expose them. The amp did sound amazing. There are a couple of things that, as an engineer, I would’ve done differently, such as the brand of caps, and thermal management options but other than that it seems like a very good quality product. In engineering, there is always a budget, and decisions have to be made. Engineering is also a process of iterations, and I believe that at least the thermal management has been taken care of by using different hardware. Once again, thank you very much. I want to wish you well being, peace of mind, and happiness. I also wish Krell the best as a company as well as for their employees. 🙂🙏

[@robertwear1675]

Great job! I had one of these. Now I have the 175XD.

[@Tinybench]

Hello teammate! Do you think there was any difference in the sound?

[@robertwear1675]

I can't really hear a difference. Maybe because my speakers are pretty sensitive. The 175 runs cool and the fans are silent though. I've owned many Krell amps and still have a KSA 250S.

[@Tinybench]

@@robertwear1675 What speakers are you using teammate ?

[@robertwear1675]

JBL 4343s. But I also have a few more. I used to be a dealer and had many given to me.

[@Tinybench]

@@robertwear1675 Wow!!!!! Sweeeeeeeeet!!!!! I have never seen them in person. I bet they sounding incredible. Great speakers for tube amplifiers. They look stunning too with the blue front baffle! I hope you enjoy them very much teammate!

[@jameswarren1831]

I think Dan was pushed out of Krell and that's when the cheaper parts were used?

[@Tinybench]

Hello teammate! I am not familiar with them! It was shocking for me to find those capacitors in such a high-end unit.

[@johntrott9513]

Well done on the repair. I really enjoy watching your videos.

[@Tinybench]

Thank you, thank you thank you so much!!! 🙂🙏💥💥💥

[@_Scintill8tor]

Nice work! It also shows me to never ever buy a Krell unit.

[@Tinybench]

Hello! thank you so much for watching my video! I really appreciate it! 🙂🙏

[@Jonas_Aa]

Nice video, great work! Some hifi guy will tell you that it wont sound right due to having solder tin that was not sent for electron alignment first.

[@Tinybench]

Hello and thank you very much for watching my video! You are 100% correct! LOL!!!! 👏👏👏😂👍

[@walterkeller4568]

You are great, cracy, but genieus. Great work !!! Greetings from switzland, Krell Fan

[@Tinybench]

Hello teammate! Thank you very much! 🙂🙏

[@aransmitch]

Did you grade the transistor before replacing it? I mean the beta measurement.

[@Tinybench]

Hello and thank you very much for watching my video. I used matched transistors from the same batch. 🙂🙏

[@corradoo.646]

Very good job 👏👏👏👏

[@Tinybench]

Thank you very much teammate! I appreciate it!🙂🙏

[@jeffrauso4957]

This is the result of Dan D'Agostino departure from Krell. He never liked class D technology. The reviews on 10 Audio speak in volumes and Pass Labs are the new reference in amplification at this juncture! When a leader is gone, their slogan becomes a memory.

[@Tinybench]

Thank you very much! 🙂🙏

[@martinvegas1327]

It's class A B not D!

[@leemartin2978]

Great work ethic

[@Tinybench]

thank you very much teammate! 🙂👍

[@adaboy4z]

$13k and cheap caps... If I pay that much it should last 40 years like my Yamaha B2 no repairs.

[@Tinybench]

Thank you very much for watching my video! You’re 100% right! Saving a few dollars by using cheap caps on such an expensive unit is a disgrace!

[@Jonas_Aa]

The melting of thermal pads could be that is a type of thermal pad that is built up of a foil and then has some kind of wax on both sides like the Bergquist Hi flow 625. And the wax will melt some when it gets warm to get better contact. I guess then it also gets a fraction thinner which does not work so well with screws, at least without spring washers.

[@Tinybench]

Hello and thank you so much for watching my video. These are a very commonly used silicone thermal pad. No foil or wax. They didn’t really melt, but overheated to the point loosing its integrity. 🙂👍

[@drdyna]

Wow, these are not made nearly as well as they used to be. Nice repair, but man, as a guy that had Krell gear drawn on his bedroom walls as a kid, these amps make me sad a little.

[@Tinybench]

Hello teammate! I am not familiar with the previous Krell products. I will be on the lookout to get my hands on vintage Krell amps. I thought this unit was very nice and sounded beautiful. Is there any vintage Krell amplifiers in particular that you would recommend looking for? Thank you very much once again, teammate!🙂🙏

[@drdyna]

I have a KSL preamp from back in the day that I need to work on, but I can't find a service manual and it's got about 10 trimpots on the board that have all been messed with, so I've been putting it off because I know it's gonna be trouble getting it all back how it's supposed to be without the manual, so it's been sitting until a rainy day sometime. But yeah, the build quality is incredible, for example the power supply board is connected to the main board not with a wiring harness and connector, but with bolts that go through the traces on one board into the other lol@@Tinybench

[@Tinybench]

@@drdyna Have you tried calling Krell to ask if they have the service manual? They were nice enough to help me with the service manual.

[@drdyna]

Way back in 2021 when I first got it, I e-mailed them to ask if they had the service manual, the reply I got back (direct quote from Timothy Rogers at Krell "unfortunately we do not have any information regarding this unit."

[@gtxguy]

Very Nice Work!

[@Tinybench]

Thank you very much! 🙂🙏

[@samuelcain5426]

Excellent work on your repair, but Krell build quality left when Dan Agostino was forced out it looks cheaply made to 90's Krell...smh.

[@54Forrester]

I am a budget-conscious audio enthusiast and own a Krell Duo 175 that I bought used on ebay. I watched your fine video with great interest. I'm wondering how much it would cost for upgrade of the thermopads and, while you are at it the capacitors? The thermopads would be my priority.

[@Tinybench]

Hello Teammate, and thank you very much for watching! You might be OK. It’s a different model so let’s not assume that you have the same issue. do you have a technician nearby that can remove the cover and inspect it?

[@gilbertwashburn7095]

Thanks for the video now it's fixed properly what were they thinking at the factory have a great day

[@Tinybench]

Hello teammate! Thank you very much for watching liking and commenting. If you haven’t please subscribe because it helps the channel immensely. Once again, thank you thank you thank you very much! 🙂🙏

[@markwroblewski6500]

Nice tutorial.What is the brand of the desoldering iron you used?

[@Tinybench]

@@markwroblewski6500 Hello teammate! Thank you, thank you very much! I really appreciate it. Don’t hesitate to reach out if I can help. It’s a Hakko. I love it! I guarantee you that this soldering stations are worth every penny. You will never be able to go back to that spring loaded soccer once you get used to these vacuum pumps! Hey, if you haven’t subscribed yet, I would really appreciate it if you did so because it really helps my channel grow. Be well happy and healthy ! 🙂🙏

[@etiennedelange6428]

Have you ever worked on the krell 250 a before.??

[@Tinybench]

Hello teammate! I have not! That was my first Krell. 🙂🙏

[@rjprivate]

Subscribed 👍

[@Tinybench]

Thank you Thank you Thank you very much !!!! 😄🙏

[@etiennedelange6428]

This amp from Mr D agastinos time

[@Tinybench]

Hello teammate! I didn’t know that. Thank you for letting me know and thank you very much for watching liking and commenting. I really appreciate it and if you haven’t please subscribe it would really help the channel. thank you thank you thank you so much.

[@williamwong5627]

The cost of output transistors would bankrupt you.

[@Tinybench]

Hello teammate! Thank you very much for watching liking and commenting. If you haven’t, please subscribe. It would help immensely. You better remember correctly the Alans sisters were about $10 each. The good thing is that with the thermal paste and the tighten hardware they last forever! Thank you very much once again! 🙂🙏

[@frankgeeraerts6243]

Very detailed ......but NOT bright ! ..........right as should be .........;lacking in quite a lot of amplifiers or rolled off to hide the problems...... Have a nice day. ( was quite a job ! )

[@Tinybench]

Hello teammate! Once again, thank you thank you thank you so much for watching liking and commenting. I really appreciate it and if you haven’t, please subscribe. Thank you very much once again!

[@frankgeeraerts6243]

@@Tinybench Always a pleasure !

[@factotumindustries]

You pulled out the module then showed 130v stored in the caps? Don't "keep your fingers to yourselves" - discharge the damn caps! Why leave the chance of an accident?

[@Tinybench]

OMG !!!😂😂🤣 You had me laughing hysterically! I discharged the capacitors immediately after showing the voltage in the video to show people how dangerous it is. So keep your fingers to yourself teammate!!!!!😂🤣😂🤣 Thank you thank you thank you so much for watching my video and commenting. I really appreciate it.

[@jimmcclung9067]

So… Why didn’t you just replace those crappy caps while you were at it? They will be the next thing to fail…

[@Tinybench]

Hello! Thank you very much for watching liking commenting and subscribing. Please let me know which crappy cups you are referring to . I quite frankly don’t remember. It’s a relatively new unit. Literally brand new in the box.

[@JKUadventures]

Did you get it at a discount because it was broken?

[@Tinybench]

I fixed it for a friend! Thank you very much for watching! 🙂👍

[@tyronenelson9124]

That amp is not worth all that much in the UK. It has no protection on the outputs and high end audio equipment normally has torroid transformers.

[@Tinybench]

Hello teammate and thank you thank you thank you so much for watching my video! 😄🤚

[@seanlynch1841]

Sir could I pay you to repair my vintage Harman Kardon 930 receiver?

[@Tinybench]

Hello Teammate! How are you doing? Are you in Miami? What’s wrong with it?

[@Tinybench]

I would love to fix it for you! 🙂🤚

[@seanlynch1841]

@@Tinybench great! What is the best way to contact you directly? Thanks🙏

[@Tinybench]

hello Shawn! I tried to message you directly on your channel, but the about section is empty and there is no contact information . I tried to find you on FB, and was unable to. I have to get back to work now, but I will try again later.

[@Tinybench]

Are you in Miami?

[@cv507]

täk för repairing this pretentiöv$ pökk?? anyway checkout the burm€€$tärß theyre pöllärt´$ xD

[@Tinybench]

Thank you very much!🙂🙏

[@jebrehbaker8613]

Looks like a cheap computer case

[@Tinybench]

Hello teammate! Thank you very much for watching liking commenting. I really appreciate it. If you haven’t please subscribe it would really help me. When it comes to Engineering, sometimes this things happen. To credit the Amplifier did sound beautiful and with the thermal paste, it should last a long time because the transistors will be able to dissipate heat properly. Teammate once again, thank you very much. I really appreciate it. 🙂🙏

[@tommyma6562]

Jamico is not a brand for quality components. Especially the price they charge for the unit

[@Tinybench]

Thank you very much for watching my video and commenting. I appreciate it! They save a couple of dollar by using Jamaicon capacitors.😂

[@edwingallagher2095]

🙌 Promo sm