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Radford STA25 Mk III -- a lot of questions.

mandryka said:
But modern fans are very quiet, my Krell has a modern fan.

I wonder about the mains in my house. There's a slight hum from the Radford. When it was given its recent MOT and Service it was in deepest Surrey (Henry "Toprepairman") I asked him if it hummed for him and he said no. It hums for me.

That makes me think of the Plastique Bertrand song, Ca plane pour moi!
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They do hum a bit mechanically but should be silent through the speakers. There is a factory modification sheet that addresses the issue but nearly all of them have had the extra resistor fitted... it helps but doesn't eliminate it entirely.
 
Arkless Electronics said:
KSA50 fan is virtually silent. It's a sleeve bearing fan of low air flow rate and the lowest noise spec type available.
You have to have your lug 'ole within about a 3-4 inches of the fan blades to hear it at all and then you would need to be in a very quiet room!
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IIRC the KSA 100 is pretty much two KSA 50s in one box, so twice the fans and everything else (including electric meter spinning ability). The 100 Mk II I knew well was certainly much noisier than I’d want myself. As an example I’m currently listening to my Leak/149 near-field system playing a very sparse and spacious Jakob Bro CD (ECM), which sounds wonderful, and no way would you miss the Krell’s fans in this context. Same goes for string quartets, solo piano etc.

Obviously that KSA 100 may have had noisy fans, I have but a sample of one to go on, but at that point (late-90s) it wasn’t that old. It actually kind of put me off trying to hunt down a KSA 50 as I do listen to a lot of quiet music quite quietly. What I really want is a KSA 25, but they never made one!
 
Tony L said:
IIRC the KSA 100 is pretty much two KSA 50s in one box, so twice the fans and everything else (including electric meter spinning ability). The 100 Mk II I knew well was certainly much noisier than I’d want myself. As an example I’m currently listening to my Leak/149 near-field system playing a very sparse and spacious Jakob Bro CD (ECM), which sounds wonderful, and no way would you miss the Krell’s fans in this context. Same goes for string quartets, solo piano etc.

Obviously that KSA 100 may have had noisy fans, I have but a sample of one to go on, but at that point (late-90s) it wasn’t that old. It actually kind of put me off trying to hunt down a KSA 50 as I do listen to a lot of quiet music quite quietly. What I really want is a KSA 25, but they never made one!
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It would dissipate a lot more heat than a 50 and apart from having two fans would quite likely use ones that shift more air and hence make more noise. It could be the ones you heard were on their way out of course....

A KSA50 with good fan is for all intents and purposes totally silent. As I said you literally have to have your ear within a couple of inches of the actual fan blades to hear anything at all!
 
Arkless Electronics said:
They do hum a bit mechanically but should be silent through the speakers. There is a factory modification sheet that addresses the issue but nearly all of them have had the extra resistor fitted... it helps but doesn't eliminate it entirely.
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The hum is just not an issue, at least in its current position.

I’ve been listening to it a lot recently, and in truth the more I listen to it the more I think it makes a realistic sound come out of the sp1s, which is exactly what I have been looking for for the past 30 years.
 
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mandryka said:
There's one for sale now on Art of Sound. I have a good mind to buy it, bring it to your house, tie you to a chair and make you listen to the sound until y



The hum is just not an issue, at least in its current position.

I’ve been listening to it a lot recently, and in truth the more I listen to it the more I think it makes a realistic sound come out of the sp1s, which is exactly what I have been looking for for the past 30 years.
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Ah we're at crossed purposes I think! I was referring to the hum from the Radford! "They all do that mate":)

If there is any DC on your mains the Krell's toroidal transformers will be much more affected that the conventional transformer on the Radford... but as I say the Radford will hum...

DC on mains often varies a lot with time of day and what other people/industry has switched on at the time... I heard some mechanical hum now and again from the Krell but not at all often.. probably a couple of 1/2 hour episodes during the week or so I had it switched on. Most of the time it was just completely silent.... other than the feint whirr of my electricity meter:rolleyes:
 
Marchbanks said:
I’m glad you are another switch-at-the-back man. I know several people who have Radfords the other way round because, well, what’s the point of having knobs and sockets and switches and not showing them off?

Of course if you bought an SC22 that would switch the STA25 too. Not that I am trying to influence you in any way!
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This is like the Big Endians and the Little Endians in Gulliver’s Travels.

I would like to hear a SC22, but I’m not sure I want to hear one enough to commit to buying before trying,
 
I've just bought my STA25 a big brother. A TT100. Pick up Sunday if all goes to plan.

Part of the reason for getting it is that someone restored one and wrote about it on Art of Sound -- here

https://theartofsound.net/forum/showthread.php?58283-Radford-TT100-the-saga-begins

And it turns out that his company, AD Audio, is based about 10 minutes away from where I live in Wimbledon!

He's agreed to have a look at it for me, see if there's anything to worry about, and advise me about any work which may benefit it.

Apparently it was serviced last year by Sound Systems Technology in Middlesex, I'm not sure what they actually did, though I do know that it wasn't recapped.

http://sstonline.co.uk/
 
Ah the hybrid Radford.... and the world of KT88's...
Opposite of most hybrids in that the output stage is valve and the rest solid state!
 
mandryka said:
I've just bought my STA25 a big brother. A TT100. Pick up Sunday if all goes to plan.

Part of the reason for getting it is that someone restored one and wrote about it on Art of Sound -- here

https://theartofsound.net/forum/showthread.php?58283-Radford-TT100-the-saga-begins

And it turns out that his company, AD Audio, is based about 10 minutes away from where I live in Wimbledon!

He's agreed to have a look at it for me, see if there's anything to worry about, and advise me about any work which may benefit it.

Apparently it was serviced last year by Sound Systems Technology in Middlesex, I'm not sure what they actually did, though I do know that it wasn't recapped.

http://sstonline.co.uk/
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Mandryka

Ask the Techie how much to convert or modify the TT100 to use the alternative O/P Valve to be changeable with the cheaper but better O/P Valve, GEC TT21. :D

https://tubedatabase.co/tubes/gec-tt21

gec-tt21-01.jpg
 
/\ Certainly doable as TT21 basically a KT88 with top cap anode for use in transmitters. I doubt they're particularly cheap though... even if probably a lot cheaper than genuine GEC KT88's.
 
In his note to me he said that he thought that " It would thrive eg with some better regulators in the preamp power supply! " But I don't want to get too ahead of myself. I've got to pick it up, check it over, like it . . . .
 
That’s a good question and the same thing occurred to me when I got the message. We shall see what he meant last week!
 
mandryka said:
That’s a good question and the same thing occurred to me when I got the message. We shall see what he meant last week!
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I had a look at TT100 and I reckon he means for the solid state part of the amp. I would replace the op amps before the regulators personally...
 
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