Thanks Gordon!

Thanks Toby!

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.

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!

Great question and I don't know, perhaps someone else might be able to shed some light on that.

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.

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.

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 Nathan, no this is a different unit, thankfully 'Frampton' wasn't allowed anywhere near this one!

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.

Hi Matt, yes you can reach us via our website contact page, details in the video description. We are fully booked at present but get in touch.

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.

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!

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.