Krell, KSP 7b, single ended, class A, dual mono pre-amp.

[bogle111]

Too bad it's not a perspex lid, seems a shame to cover up such mastery.

Regards
Pete

[sq225917]

I couldn't really give it a decent listen last night, but this morning it is sounding lovely. Solid and detailed in the bass, with greta stereo specificity and quite startling resolution. I might get round to plugging in the phonostage in a bit.

I've never heard Fess sound so good.

[nat8808]

Out of interest, what did you replace the ROE caps with and did you choose value based on the stated value?

I always think it's a leap of faith to assume the stated cap value on the can is the intended value as some manufacturers measure values from bulk purchases and then store according to more accurate measured values within their range so they can be matched. Might not apply to the lower end Krell though. Did it improve things?

Err what did you do with the removed caps? Might be handy for replacing definate failures within vintage gear as you know what it can be like sometimes re-selling gear that has non original parts, replaced by the owners.. even though it's probably fine, people don't always trust it. Certainly they are the same caps as in my 90's LFD phono stage.

[sq225917]

Yes I always assume manufacturers buy capacitors in values other than those required so that they can store them and use ones that have gone off- rather than simply buying the caps in the values that they actually require. Obviously the most sensible way to purchase parts for any manufacturer is to buy ones that they do not want and hope that some shelf magic makes them into the right parts.

To be honest I'm surprised that they even bother purchasing any specific parts at all. They could just throw any old shite in the box and hope that quantum physics makes it work for them.

Curiously my own experience with selling gear that I've serviced or modified doesn't seem to mirror your own, if anything i find that gear I've modded tends to carry a premium over unserviced examples of the same gear because of the reputation I have for lavishing the utmost care and attention on the gear that I own and only ever replacing like for like or with better specced parts where older alternatives are no longer available.

[sq225917]

Right then this one comes back to life.

As the phonostage was off in one channel and the transistors were utter unobtanium I had shelved the final steps of the restoration of this, not enough time and certainly not the inclination to hunt down remaindered transistors from the web, and match a suitable quantity. Time to farm the job out...

So I dropped it off with Jez@Arkless, the guy who designed some of the Alchemist amps. A week later and £135 lighter he's managed to source the transistors that i couldn't even find on the web they were so old and for the others (j74) he has stock of the part that Toshiba replaced them with- bonus.

So it's up and running again, completely re-capped in the PSU and the main pre-amp and the front end of the phonostage has all new transistors in it and it's all biased up to the correct spec and should be better than ever.

I'll pick it up some time this week and see how it sounds.

[YNWaN]

Cool, glad to hear that it's working again .

I'm not really sure what Nat is on about regarding capacitors. Some manufacturers may match capacitors so that they are within tighter tolerance than the manufacturers spec, but the basic value is always the same.

[DSJR]

Those old Roe caps may have looked to be good what the Krell was first made, but they do seem to be intolerant of being run hard. Simon, am I right in saying that many of these were bulging on top? The Roe's in my 1980 vintage Quad 33 were fine, but I've seen similar in old B&O gear where they'd all but exploded with thermal? stress.

[sq225917]

Dave, You'd struggle to make the ROE's bulge, they are capped in phenolic, they just pop.

[Reid Malenfant]

Well done getting it sorted Simon

The chap I mentioned that had the KRC-HR apparently took a look in the PSU & decided he'd better get something done about it before it expired From the description he gave me I thought it had actually packed up, but no, even though he said it looked like some kind of forest fire had visited it was still working

He sent it away to a place that'll remain nameless (though is very well known) & still hadn't got it back the last time I happened to be over his way, I hope he's actually got the thing back now as I'm off over with a friend some time this coming weekend.

If only he'd have mentioned it I'd have offered to do the re-cap myself...



I hope yours gives years of trouble free service now it's all good again

[nat8808]

Cool, glad to hear that it's working again .

I'm not really sure what Nat is on about regarding capacitors. Some manufacturers may match capacitors so that they are within tighter tolerance than the manufacturers spec, but the basic value is always the same.

I just meant that in order to get tight tolerance components, some manufacturers have been known to buy looser torerance components (say 5%) and measure each individual component value so they can then sort them into 1% catagories. Saves buying the more expensively manufactured components whilst still providing close tollerance.

Certainly Kef used to do this for crossovers in their reference series and Stan Curtis used to do this so that their standard TDA1541s were effectively closer to 'spec' than the official (expensive) S1 and S2 close tolerances. For example anyway.

So the values stated on the components could perhaps be 10% from their measured and deliberately used values.

I guess it would be a bit anal to take that into account though if the bits really do need changing.. and they might drift out over time too.