Great video The volume control gets stuck on mine when I turn it on. I think it is a Great amp but I Wonder what they were thinking when they decided that the only way to shut it off is to pull out the cord
Good video. I've also worked on alot of older Krell. They had alot of bad sprague caps even though they did have good factory specs. Krell went with nichicon for most of newer stuff which is more reliable-not counting the surface mount stuff which is not so reliable. Connectors are a problem I've run ito also for older Krell
The layout of that main board reminds me of the build standard used in aerospace modules, everything laid in same orientation with the component bodies placed over an invar heat ladder/thermal plane which was in good contact with the case. What surprises me is that Krell designed a preamp circuit that generates so much heat, preamps generally don't run hot but there's a huge number of transistors in there so I guess that's where the heat is generated. Looking at the layout I noticed four long rows of transistors at the connector end in the middle o the board. Do you know what that section of the circuit does? Initially I thought it's many transistors wired in pardallel for a low noise MC front end but you mentioned the phono board is separate. Thanks for the video, it's good to see inside quality gear.
Thanks for commenting and I agree, I own a lot of high end test and measurement gear and the layout in some of those pieces is similar. I'd need to refer back to the schem, but Krell (and others) were known for using multiple paralleled TO-92 devices for example in phono stages to reduce noise and we certainly also see that here. Just a lovely piece of gear!
Very interesting review of this piece of gear. Krell is very highly regarded but I have always felt that the insides of the unit look more sexy than the outside!! ; )
Nice vid and sets me up for recapping my KRC-2. I changed my encoder about 5 years ago as it gave up. Lucky I have the remote so still had use and like you had to strip the unit just to replace that, so the caps will be fun I'm sure....
If I sent my receiver to you dunno which I'd enjoy more, the sound quality or the video feature. But you don't feature every piece of gear that comes through I assume.
Hi Toby, thank you and yes good point, hopefully both would be worthwhile! You are correct though, I don't make videos about most pieces actually. For every video, there's 5 or 10 repairs, services and pieces that don't have a video made about them.
On a KRC-HR how do I remove the anodized aluminum volume knob that is connected to the optical encoder. I removed the Allen screw but I am having a hard time pulling it. I am hesitant to force it. I just need to solder the red and black wires that provides power to the volume knob's LED. Everything is working except the volume's LED will not light as adjust the volume via remote control.
I'm kind of new to your channel and have really been enjoying your videos. One thing I've noticed that is distinctive about your videos is that the systems you work on are gorgeous. The circuit boards are like works of art. Is that an Australian thing or do you just only work on gear with cleanly laid out circuitry. /s 😉✌ (just kidding...sort of...) Q1: I hear you say the phrase "...down on C..." a couple of times when referring to capacitors. Does that just mean that the capacitors capability to hold a charge is reduced? I'm kind of guessing that's what you mean, but thought I'd ask. Q2: Regarding capacitors, do they effect to tonal qualities of a piece of gear or do you judge a "quality cap" by it's ability to hold the labeled amount of charge and their longevity? Cheers! (I promise to not add more to this comment. 🙄✌ )
Hi Frank, glad you are enjoying the channel, despite the very low-key production values of the video side of things! Great questions - 'down on C' is me describing low capacitance with respect to the value the part is specified at. For example, if a 100uF capacitor, when tested, has a capacitance of 64uF, and probably high ESR, it's down on C. Regarding capacitor quality, this is potentially a long conversation! Capacitors most definitely affect the sound quality of gear and all good designers understand this. In some cases capacitor choice is critical and only certain types can be used in a certain circuit location. That's one aspect of quality, another is build quality and specification. Some cheap caps will leak after 1000 hours or less, others are specified with lives of 20,000+ hrs and are fit for use in satellites. There are a bunch of other construction and electrical aspects that factor into a capacitor's quality, something one becomes familiar with, over time and with experience.
@@LiquidAudio So capacitors can effect the quality and character of gear? Holy crap, I honestly wasn't expecting that answer. So do companies provide "preferred" brands of replacement electronics to maintain the integrity of their products? Or as long as you use "quality" parts you won't deviate too far from the original tonal quality of the device?
Hi Frank, this is is a potentially long conversation and not one we have space for here unfortunately. It's not as much down to brands, more the types of capacitors and their specifications. There are premium audio grades of capacitors for example and these are offered by several major manufacturers. There are low ESR caps, low leakage caps, high temperature caps, and so on. Experience and understanding the design and circuit allow selection of the correct parts in a particular use case. I'm different from most repairers in that I use parts that are better, often far better than original, wherever possible, customer budget dependant of course!
Hi Michael, agreed and yet sadly I see this quite often. To be honest, and at the risk of sounding glib, many technicians shouldn't go anywhere near this stuff, maybe not even anywhere near electronics! If you want to see a really bad Krell hack, visit my hall of shame - liquidaudio.com.au/hi-fi-repair-hall-of-shame/ - and look for the Krell KRC-HR there. It is truly the worst 'repair' I've ever seen and was not salvageable.
Thanks for your nice video, i have my eye on a krc 3 preamp, the problem is there a lack of volume even when turned way up, also it is 115 volts but am living in the UK, do you know if it could be converted to 230 vols, thanks in advance.
Hi Anthony, sounds like you might need access to a really good technician if you purchased this one. Multi-voltage capability depends on the model and I cannot recall whether the KRC-3 has this or not. Consider checking with Krell. If not, you could simply use a quality step-down transformer. The other problem sounds more serious. Note that some of the Krell amplifiers detect both line voltage and frequency, so they really started to make it tricky to move equipment across territories.
How come you don't use in the audio path paper in oil and mundorf silver oil gold caps, aren't they the best? What about using Scotty diodes in the power supply are they wise to use for less noise, what about full bridge rectifiers who do you recommend is the best to use in pairs replacing a single Cheers. You could use copper tape for missing pads get a leather punch and cut them out to the size you want, I'm not sure about what glue would be good for heat resistance usually the sticky back is good for joining broken traces anyway. Is there such a thing as a silver dip to coat the pins in pure silver? It would be better to put nylon washers than cutting the pins! on both sides if it doesn't need to be earthed! to give it some isolation maybe it did have it originally and was forgotten to be put in. How do you see the hall of fame?
Hi John, lots of technical discussion points here that we don't really have the scope to properly discuss here unfortunately. I do use PIO where the situation dictates, but sometimes the negative effects of large caps with flying leads outweigh the benefits. I also try to honour the original design intent in most cases, whilst also improving it. Don't need the copper tape for missing pads in this case and most cases in fact. Schottky diodes can be good, but there are many ways to improve power supplies. Snubbering is especially important and there is a school of thought supported by the great Nelson Pass for example that favours standard low speed diodes, with effective use of premium snubbers and bypass caps where appropriate. I am more aligned with this approach these days.
Thank you and yes I agree. These actually are repair videos in most cases, but at this stage the intricate details go into my website articles at liquidaudio.com.au. I try not to spend too much time on the video side of things but this will evolve over time!
Yes these are crazy overbuilt, all Krell from this era is. Lots of paralleled devices means there is a need for lots and lots of resistors. Everything has to be fed precise voltages and current, that's just one reason there are so many.
@@LiquidAudio Reminds me of a talk I had with an HP engineer, who mentioned how this board would occasionally malfunction, so they just added more caps to stabilize the power. But I thought such problems were more in the domain of digital circuits. I wonder in the modern era, with accurate circuit simulations, if they could have simplified it a bit. But making low noise amplifiers seems a black art, in some ways.
Hi Michael, no doubt the design could be simplified, but not because of any new design tools or understanding. There is nothing new that would improve the design of low speed analog circuits like this. They deliberately chose this complex design for sonic reasons, mostly around lowering impedance and noise. Simplification saves money of course and that's why you don't see many designs like this now and it's a real shame, but designing a product like this takes a really talented team and costs a small fortune.
A lot of those resistors are the volume control, the volume encoder switches in/out the discreet resistors according to a Krell designed profile so, there is no conventional 'pot' only a single or possibly a combination of high quality resistor(s) in the signal path at any one time. It means there is no or very little volume/channel imbalance especially at low level as you get with almost all pot based volumes controls I've ever used. It's not just a pot-in-a-box for loads-a-money.
great video , BUT you move your camera too much , I get headache and dizzy after a while , try to move as little as much m make how to find fault , it is most interesting part, but the way you move the camera I get tired
Because it's a complex circuit, it uses many paralleled transistors to reduce noise and lower impedance at each stage. Each device needs a precise bias point and current stabilisation and resistors do this, amongst other things.
There's a lot there... however it's not necessarily overly complex. Part count is high due to usage of discrete components as opposed to integrated circuits etc.
