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Rebuild of classic Krell KSA50 fan heater

Over the past few days I’ve been running my Krell with an active pre, and yes, Tony and Jez were right. It is better.

If anyone wants to sell me an excellent but cheap passive volume controller with around 10K impedance - I only have a single source, then please let me know.
 
So here are my impressions of various preamp trials with the Krell.

My system goes Logitech Media Server - Museatex DAC - Crossover and then branching to a pair of passive subs and ESL 63s (with the Krell.) The crossover has a volume control for the subs, but not the main speakers. When I use a preamp, I put it between the DAC and the crossover. Sorry if it’s too much information, but I’m not sure how much of it matters.

1. I cannot hear any significant difference between a direct connection of DAC to the crossover, and a 10k pot passive pre between them.

2. I can hear a significant difference when I use the pre-out of my Electrocompaniet, both to the timbre and the image.
 
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No. Probably "DC on mains". There's threads about it in "Audio". Krell was silent most of the time here but a small amount of buzz from transformers just now and then. The cooling fan in my PC was louder and I wouldn't have done anything about it personally....

That you couldn't hear any difference from putting the 10K passive between DAC and amp shows just how transparent it is!
 
Do you think that DC blocker would be a good first project for someone like me, who’s never soldered anything before? Or too dangerous?
 
mandryka said:
Do you think that DC blocker would be a good first project for someone like me, who’s never soldered anything before? Or too dangerous?
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Good question really... it doesn't get much simpler electrically but it's 240V AC and high power involved... probably best to stick to something that can't electrocute you or burn your house down as a first project;)
 
mandryka said:
Over the past few days I’ve been running my Krell with an active pre, and yes, Tony and Jez were right. It is better.

If anyone wants to sell me an excellent but cheap passive volume controller with around 10K impedance - I only have a single source, then please let me know.
Click to expand...

Just noticed this.. I don't think I was saying it's better with an active pre... I was saying it sounds great with a low ish value passive like 10K. If it sounds "better" with an active pre... well with a specific one, that's just the colourations of that pre being "nice". The DAC when used as a vol control has exactly the same low output impedance etc as a pre would and you said putting the new 10K passive after the DAC made no difference (transparent).
 
mandryka said:
Do you think that DC blocker would be a good first project for someone like me, who’s never soldered anything before? Or too dangerous?
Click to expand...
Would be a lot less stressful if you make a dim bulb tester (cheap and easy). In fact, you can probably make sure there are no shorts with a dim bulb tester, then test the DC blocker output by plugging a lamp or radio or something into the output.
 
Arkless Electronics said:
Just noticed this.. I don't think I was saying it's better with an active pre... I was saying it sounds great with a low ish value passive like 10K. If it sounds "better" with an active pre... well with a specific one, that's just the colourations of that pre being "nice". The DAC when used as a vol control has exactly the same low output impedance etc as a pre would and you said putting the new 10K passive after the DAC made no difference (transparent).
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In my post today I carefully avoided saying that one was better than the other. It isn't and I was wrong to say that last Sunday.

That being said, the active pre is different and I've left in in place just to get more familiar with what it's doing.

There's a couple of other things I want to mention. With the active pre I have more volume, and maybe more dynamic range -- I don't know. I think going into the ESL 63s it's a good thing to have that extra volume.

And second, the difference with the active pre isn't just colour, I think it's also to do with depth of image and texture of sounds --the materiality of the sound of bow on violin string is different.

But I've not got the ability to judge these things quickly, I need to live with it for a couple of weeks to get clearer about what's going on.
 
booja30 said:
Would be a lot less stressful if you make a dim bulb tester (cheap and easy). In fact, you can probably make sure there are no shorts with a dim bulb tester, then test the DC blocker output by plugging a lamp or radio or something into the output.
Click to expand...


I'm just not going to do it, I'm a coward! The transformer hum isn't a big deal, if it comes, it goes pretty quickly.
 
Interesting the comments about the Krell with a Passive Pre . I would agree that it sounds very good indeed but when I used one with a 10 K Stepped Attenuator I found that the passive did not have enough drive and you could very quickly get to the end of the volume ladder without the sound being loud enough on some low level recordings (Ry Cooder Bop Till You Drop being a good example) . For this reason I switched to an active pre (Concordant Exhilarant Valve Line Level Pre) and this gave the Krell the drive it needed . This was only using Digital sources which were all at the 2v level so should in theory have been enough to drive the Krell but just did not .
 
With 26db of gain in the ksa amps there's something wrong there, 2v should drive it to deafening levels with any high 80s db speakers.
 
I wonder if in my case the crossover is the culprit. I just don’t feel like moving amps and untangling cable any more, but next time I’m in the mood I’ll take the crossover out. It’s made by a Swedish company called MT, no longer in existence.
 
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