I have KAV300i and intend to upgrade all the caps after looking at your excellent video. I understand you have used high grade capacitors from different brands. Kindly advise me which brands are the best for upgrade to improve sonic quality equal or better. Also I noticed operation amp IC including couple of Zena diodes were replaced. Kindly just advise me from where you normally source these parts either in Australia or outside Australia. Thanks once again on your superb restoration projects.
Apologies, thought you'd commented in relation to another video. These main filters were starting to go and my customer wanted a restoration, as per the one I completed on his KAV-300i. They aren't large caps physically, so they suffer more from the effects of heat cycling and smaller thermal mass than physically larger capacitors. I agree though that often times larger main filters can be left as is.
The case is too simply small for all that power and with not enough vents in the lid and no obvious vents in the base to aid convection, not helping longevity.
Hi Mark and thanks for the comment. At this stage, I shoot everything hand-held, with one camera. This creates the obvious dilemma of not being able to have separate angles, edits etc. There are also some content/direction choices I've made around this and, due to being super-busy running liquidaudio.com.au, the videos tend to come down the list of priorities. I'm working on it!
Late here, but what was the age of this unit? Im looking at used Krell amps, but dont want to replace so many components. I have a Carver amp & pre amp from 1980. Just had them recapped 2 years ago. Im guessing this Krell wasnt near that old.
Correct, these are from the late '90s. Like all Krell gear, they run warm and this kills caps. I have quite a few Krell articles over on my website, this might help: liquidaudio.com.au/?s=krell
@@LiquidAudio Thanks, Ill check them out. Thats fair, any unit 20 -25 yrs old is due to be recapped. Id probably be safe with an amp no more than 10 yrs old.
Good question Boris, with one main answer - heat. Small electrolytic capacitors are most susceptible and sure enough, these were the leaky ones. Even the best small electrolytic caps have service lives in the low thousands of hours and these have long since been exceeded in this design from the mid-'90s. Add in the relatively low thermal inertia of small parts and lots of cycle times and its a recipe for failure. Krell could have used higher grade parts too, that would definitely have helped things last better, but this was not their premium line, so parts were scaled back accordingly.
Hi and thanks for your feedback. Costs vary according to the condition of the unit, faults, budget etc, so its best to contact me offline via my website - liquidaudio.com.au - to continue that discussion. Having said that, restoration like you see here is a small fraction of the cost of a new unit, so very worthwhile. Thanks for your interest and don't hesitate to get in touch if you are thinking of having your unit restored.
It looks like those two electrolytics that leaked are too close to the TO-220 power devices and consequently run much hotter than they should. I suspect all the other electrolytics you replaced didn't need to go.
Prices vary quite a bit depending on symptoms (if any), what you'd like done and so on. Happy to discuss price privately if you'd like to email me regarding your unit. Keep in mind this was a restoration though, much more involved than a service.
Hi BR, costs depend on the condition of your unit, any faults it has, your budget and how much you'd like me to do. Best to start with an inspection, the form on my Contact page allows you to submit all your details. liquidaudio.com.au/contact/
How can Krell use such poor quality components, given the price of the units? There's no reason for modern electrolytics to have such short lives if they are properly rated. I doubt the film caps are a problem. Wow, that bodging on the board is awful! Krell really are on the slide.
Hi, thanks for commenting, but let me clarify a couple of things. Krell hasn't used poor quality components, they used good parts which simply far exceeded their service life (by thousands of hours!) in this unit. This isn't the fault of Krell or the caps, the unit needed maintenance and didn't receive it until it failed, sadly a common occurrence. Small electrolytic caps like these will always fail in heated environments and owners need to recognise the need for periodic maintenance. The bodging really is bad, but we couldn't establish when or how it happened. If it was a factory job, it's awful, but we can't be sure about that. I'd say it happened in the field.
@@LiquidAudio I don't expect to have to recap my expensive amp every 10 years or so. Especially as the pcb is at serious risk in such circumstances. But I guess Australia is a hot place so aging will be faster. The board word is obviously a correction of a design fault, whether carried out in the field or not. Thanks for the sharing your work.
@@mfr58 No problem, much more detail can be found on my website - liquidaudio.com.au. Leaking caps are always a disappointment and may be due to other design considerations or oversights, like excess ripple current for example. Sadly, they are a common occurrence, even in the most expensive gear. Part of what I set out to do years ago with my website was to educate people about the need for maintenance with electronic equipment so that we hopefully see fewer cases like this one. The board might have been modded for a number of different reasons. It could be for performance improvement purposes or it might be someone's attempt to modify the amplifier, completely unrelated to a design fault, or to Krell. I had a long conversation with my contact @ Krell about this, as these kludges don't appear in all units, Krell has no official record of such board changes, so for me, the jury is out on exactly why they were present in this unit.
@@LiquidAudio Hi, I have a suggestion. When replacing caps and/or other components with higher quality vs standard quality why not show us some more concrete testing? Show me on the screen using scopes/analyzers/meters etc. before and after showing how this performance is improved. I do the same type of restorations here for myself not business, but I find Audiophile types HATE when you bring up hard proof of tests that show something is there or isn't there that they think they hear. Might help convince someone to spend the extra money where needed/recommended. For instance, when I hear some guys tell me the power cord makes an amp sound better they know not what they speak of. Thanks
@@smarafino10 Great suggestions and I agree on all points. The issue for me is time, energy and resources, more of which go into doing the work than making the videos. But I'm working on it and really appreciate the suggestions!
Awsome skills!! Wish you were in the uk, my PAM 5 is starting to give me some problems after almost 30 years
Jamicon capacitor, I see that capacitor brand on the 20 US$ cheapo mini amplifier. Surprising that high end amplifier used the same capacitor brand.
I have KAV300i and intend to upgrade all the caps after looking at your excellent video. I understand you have used high grade capacitors from different brands. Kindly advise me which brands are the best for upgrade to improve sonic quality equal or better. Also I noticed operation amp IC including couple of Zena diodes were replaced. Kindly just advise me from where you normally source these parts either in Australia or outside Australia. Thanks once again on your superb restoration projects.
Fabulous restoration 👍
The large filter caps may be just fine. They rarely fail.
Apologies, thought you'd commented in relation to another video. These main filters were starting to go and my customer wanted a restoration, as per the one I completed on his KAV-300i. They aren't large caps physically, so they suffer more from the effects of heat cycling and smaller thermal mass than physically larger capacitors. I agree though that often times larger main filters can be left as is.
Great work and a credit to you, nice power amplifier by the way.
You sir, are a Magician!! lol Thanks for the content
My pleasure!!
The case is too simply small for all that power and with not enough vents in the lid and no obvious vents in the base to aid convection, not helping longevity.
Weird at its age so much has been replaced.
Do you ever post videos of you doing the work (removing parts, installing parts, washing the board, etcetera).
Thanks for the video!! 👍🏼
Hi Mark and thanks for the comment. At this stage, I shoot everything hand-held, with one camera. This creates the obvious dilemma of not being able to have separate angles, edits etc. There are also some content/direction choices I've made around this and, due to being super-busy running liquidaudio.com.au, the videos tend to come down the list of priorities. I'm working on it!
Late here, but what was the age of this unit? Im looking at used Krell amps, but dont want to replace so many components. I have a Carver amp & pre amp from 1980. Just had them recapped 2 years ago. Im guessing this Krell wasnt near that old.
Correct, these are from the late '90s. Like all Krell gear, they run warm and this kills caps. I have quite a few Krell articles over on my website, this might help: liquidaudio.com.au/?s=krell
@@LiquidAudio Thanks, Ill check them out. Thats fair, any unit 20 -25 yrs old is due to be recapped. Id probably be safe with an amp no more than 10 yrs old.
This is a relatively young piece of equipment. How can it have such leaky caps? Bad supply back in the day? Or a bad circuit design?
Good question Boris, with one main answer - heat. Small electrolytic capacitors are most susceptible and sure enough, these were the leaky ones. Even the best small electrolytic caps have service lives in the low thousands of hours and these have long since been exceeded in this design from the mid-'90s. Add in the relatively low thermal inertia of small parts and lots of cycle times and its a recipe for failure. Krell could have used higher grade parts too, that would definitely have helped things last better, but this was not their premium line, so parts were scaled back accordingly.
did you know bias current for krell kav 2250 ??
krell help me fix my amp they are awesome !
Thanks Kim and I agree, on a professional level I always find Krell extremely helpful and great to deal with.
Hi there : ) thanks for the great video , how much is it for a restoration like this? thanking you.
Hi and thanks for your feedback. Costs vary according to the condition of the unit, faults, budget etc, so its best to contact me offline via my website - liquidaudio.com.au - to continue that discussion. Having said that, restoration like you see here is a small fraction of the cost of a new unit, so very worthwhile. Thanks for your interest and don't hesitate to get in touch if you are thinking of having your unit restored.
It looks like those two electrolytics that leaked are too close to the TO-220 power devices and consequently run much hotter than they should. I suspect all the other electrolytics you replaced didn't need to go.
What kind of cost should someone expect to pay for a service like this?
Prices vary quite a bit depending on symptoms (if any), what you'd like done and so on. Happy to discuss price privately if you'd like to email me regarding your unit. Keep in mind this was a restoration though, much more involved than a service.
Krell got left behind a long time ago with the likes of Moon and Boulder.
Yep, sadly modern Krell is completely different from the lovely older stuff I work on.
some other people just to want to fix in an easy way. they dont care the beauty of the circuit.
Absolutely correct, it's great to know my viewers understand this difference. For me, it's only worth doing something like this properly.
@@LiquidAudio we're doing the same! Your good!
How much to do this restoration on mine
Hi BR, costs depend on the condition of your unit, any faults it has, your budget and how much you'd like me to do. Best to start with an inspection, the form on my Contact page allows you to submit all your details. liquidaudio.com.au/contact/
How can Krell use such poor quality components, given the price of the units? There's no reason for modern electrolytics to have such short lives if they are properly rated. I doubt the film caps are a problem. Wow, that bodging on the board is awful! Krell really are on the slide.
Hi, thanks for commenting, but let me clarify a couple of things. Krell hasn't used poor quality components, they used good parts which simply far exceeded their service life (by thousands of hours!) in this unit. This isn't the fault of Krell or the caps, the unit needed maintenance and didn't receive it until it failed, sadly a common occurrence. Small electrolytic caps like these will always fail in heated environments and owners need to recognise the need for periodic maintenance. The bodging really is bad, but we couldn't establish when or how it happened. If it was a factory job, it's awful, but we can't be sure about that. I'd say it happened in the field.
@@LiquidAudio I don't expect to have to recap my expensive amp every 10 years or so. Especially as the pcb is at serious risk in such circumstances. But I guess Australia is a hot place so aging will be faster. The board word is obviously a correction of a design fault, whether carried out in the field or not. Thanks for the sharing your work.
@@mfr58 No problem, much more detail can be found on my website - liquidaudio.com.au. Leaking caps are always a disappointment and may be due to other design considerations or oversights, like excess ripple current for example. Sadly, they are a common occurrence, even in the most expensive gear. Part of what I set out to do years ago with my website was to educate people about the need for maintenance with electronic equipment so that we hopefully see fewer cases like this one. The board might have been modded for a number of different reasons. It could be for performance improvement purposes or it might be someone's attempt to modify the amplifier, completely unrelated to a design fault, or to Krell. I had a long conversation with my contact @ Krell about this, as these kludges don't appear in all units, Krell has no official record of such board changes, so for me, the jury is out on exactly why they were present in this unit.
@@LiquidAudio Hi, I have a suggestion. When replacing caps and/or other components with higher quality vs standard quality why not show us some more concrete testing? Show me on the screen using scopes/analyzers/meters etc. before and after showing how this performance is improved. I do the same type of restorations here for myself not business, but I find Audiophile types HATE when you bring up hard proof of tests that show something is there or isn't there that they think they hear. Might help convince someone to spend the extra money where needed/recommended. For instance, when I hear some guys tell me the power cord makes an amp sound better they know not what they speak of. Thanks
@@smarafino10 Great suggestions and I agree on all points. The issue for me is time, energy and resources, more of which go into doing the work than making the videos. But I'm working on it and really appreciate the suggestions!