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A DIY Radford STA25 restoration

Mike P said:
I'm not going to get drawn into an in-depth comparison yet but I can already say that it's going to be a close call between my Leak ST20 and my Radford STA25. Based on my initial impressions they're fairly evenly matched overall.

We're talking about 40-60 year old amps here and condition is everything. All it would take is a knackered valve, a dried out cap or an out of spec resistor to easily swing the result one way or another.

Both of mine are fully rebuilt so it's a reasonably fair contest but if anything the Leak has a slight advantage because it is running a selection of the crème de la crème of NOS valves.

Both are lovely, which is all that really matters to me.
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Nice rebuild there MIke:)

My own comparisons between the two were that the Radford comfortably beats the Leak really.... the only area where the Leak wins is in it having zero mechanical hum from the mains transformer! My much modded St20 would I think give the Radford a good run for its money though.
 
Arkless Electronics said:
Nice rebuild there MIke:)

My own comparisons between the two were that the Radford comfortably beats the Leak really.... the only area where the Leak wins is in it having zero mechanical hum from the mains transformer! My much modded St20 would I think give the Radford a good run for its money though.
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Thanks Jez, and nice to have you back BTW.
 
I read this thread - like daily updates from a soap opera, but one of genuine quality.

What Jez says above about Leak having silent mains transformers is interesting and for me a game changer in choosing between Leak and Radford. I hated the infamous Naim transformer buzz, and that was my main criticism of the more powerful Naim pieces. The Nait 5i was very much better with transformer noise compared to say a Supercap or XPS power supply ...

I do find that the ears soon just to the characteristics of any given replay, so that if it is reasonable quality one does not become annoyed by its weaknesses over time, but transformer noise can become increasingly irksome over time - even when the sonic from the speaker is very fine.

My Troughline has zero transformer noise, but my Quad II Forty has its moments! Most annoying on very quiet music where the hum can produce a pedal note that is harmonically un-related to the music that is being played. Putting the II Forty on a wooden lower shelf of an Ercol table has reduced the buzz at the listening position, but it remains an occasional annoyance. If the Leak's mains transformers really are near silent, that would be decisive in my chosen way forward, even if the Radford amps may actually be finer, according to taste.

Best wishes from George
 
I can only speak for my STA-25 and it has a slight noise but it's inaudible from more than a couple of feet away.
 
George J said:
What Jez says above about Leak having silent mains transformers is interesting and for me a game changer in choosing between Leak and Radford.
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Hello George. Radfords do buzz - at least the five or six I have encountered all did - but mine doesn’t annoy me in the slightest. Certainly it isn’t as loud as my HiCap could be when it chose, and from more than around 1m away I can’t hear it. But I admit my ears are in decline, so you might find it intolerable. I know some do.
 
I've always found it most odd that so many people find a slight mechanical buzz from transformers, inaudible from more than a few feet away, such an issue! I'm no "headbanger" but even so I would never play my hi fi so quiet that such a buzz was at all audible above the music. other than those very very few times I've known a transformer to buzz so loud its clearly audible from across a room it's something I just couldn't care less about.... Obvs YMMV!
 
My Leaks Stereo 20's have no discernible transformer noise. The Radford does buzz a little but certainly not enough to annoy me or be audible above even very quiet music.
 
That's the factory mod I referred to up thread. I can't recall seeing one without at least the resistor added and I guess many/most will be late enough to have the full mods described. They still buzz. Will at RR will know more about it I'm sure. You wouldn't even hear it over the vinyl roar of the lead in groove of an LP never mind when the music starts. It's really not a problem. With the STA25 on the floor about 5' away from me I wasn't aware of it at all. You hear it when right up close adjusting the bias but that's about it.
 
Arkless Electronics said:
That's the factory mod I referred to up thread. I can't recall seeing one without at least the resistor added and I guess many/most will be late enough to have the full mods described. They still buzz. Will at RR will know more about it I'm sure. You wouldn't even hear it over the vinyl roar of the lead in groove of an LP never mind when the music starts. It's really not a problem. With the STA25 on the floor about 5' away from me I wasn't aware of it at all. You hear it when right up close adjusting the bias but that's about it.
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My STA25 III was built with the resistor etc. already in, and is virtually silent, however, my friends STA20 (very rare) was terrible when he bought it, the resistor mod made it acceptable.
 
I have a STA 25 series 5 bought from Will about 12 months ago,if you put your ear up
to it you can hear a slight hum.
You cant hear it when even stood next to it
Clive Smith
 
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JTC said:
What's the current wait like on the RR STAs? (I'm in the queue btw, just curious whether I need to start digging the pennies out the back of the sofa etc.)??
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Will get back to you on that shortly after looking at my list :)

Radfordman said:
I presume that Will builds in the mod described in the Radford Information Sheet.
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Indeed. I use an HT resistor (in the 25s), the mains transformers are vacuum impregnated and the transformers are mounted on rubber. They still do it a bit :D
 
I know this is OT but I made the unnerving discovery today that certain mail providers are silently junking my email replies despite our mail servers and domain being on absolutely zero blacklists. Fantastic :confused:
 
JTC said:
What's the current wait like on the RR STAs? (I'm in the queue btw, just curious whether I need to start digging the pennies out the back of the sofa etc.)??
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Sorry for the delay - have been dealing with Computer Trauma!

Yours (making a fairly easy guess as to which person on the list you are ;)) should be ready by around late autumn / early winter
 
Radford Revival said:
Sorry for the delay - have been dealing with Computer Trauma!

Yours (making a fairly easy guess as to which person on the list you are ;)) should be ready by around late autumn / early winter
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Send you a PM just in case. That gives me a better idea of when to list my current amp and sort out the pennies for the new one :)
 
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