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A DIY Radford STA25 restoration

All done :)

The used pre-set potentiometers I bought from ebay arrived today. They came as a lot of three with 1x 2M and 2x 25K. The first 25K I tried gave unreliable readings but fortunately the second was fine.

Here's a final pic of the finished underside. Nothing much different to earlier pics other than the rectifier diodes are now in the correct orientation.

P1110681 by Michael Pickwell, on Flickr

With the replacement trimmer fitted all four EL34's biased up nicely.

Choices choices....

P1110683 by Michael Pickwell, on Flickr

P1110686 by Michael Pickwell, on Flickr

At the moment the four small valves are still the ones that the amp came with, however I've already bought these:

P1110682 by Michael Pickwell, on Flickr

And also a single NOS Mullard ECF82. If anyone has another NOS Mullard ECF82 (or a pair of something nice) sitting idle in a drawer please drop me a P.M.

Finally, a big thank you to everyone that helped, especially Alan, Will and Jez.
 
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Really pleased you have it all together. So should you be!
Look out for Sylvania 6U8 tubes (valves) for the ECF82 locations... Then see if you can find some original Svetlana winged 'C' EL34s (Not the current Svetlana production).
Enjoy, Alan
 
Mike, I’d be inclined to give it more headroom than that. My 15 gets pretty hot, certainly after a few hours continuous use. I did ask Will about this - I don’t want to misquote him because I don’t remember his exact answer, but I think he suggested three or four inches above the top of the case.
 
The angle of that photo makes it look like there's much less space than there actually is but yes I agree it'll need more room. I just shoved it in there for the photo.

It does throw out far more heat than the Leak.

Don't worry I'll be taking the bottom CD player and shelf out before running it for any length of time.

It might be some time until I've managed to do enough listening to make any meaningful comparisons with the Stereo 20. Toddlers and valve amps don't mix well.
 
But.... go on.... first impressions of the sound? Also, any transformer noise/buzzes/etc.? (A personal fixation of mine)
 
I’m likely wrong on this, but in my experience frame transformers are very quiet, the ones that buzz acoustically seem to be the big toroidal ones (Naim, Densen etc). Nothing audible from my Leak, pair of Quad 303s, ‘70s Sony integrated, valve guitar amp etc with their old-school frame types. May even be how they are bolted to the case, the frame ones usually have four bolts rather than one through the centre.
 
Tony L said:
I’m likely wrong on this, but in my experience frame transformers are very quiet, the ones that buzz acoustically seem to be the big toroidal ones (Naim, Densen etc). Nothing audible from my Leak, pair of Quad 303s, ‘70s Sony integrated, valve guitar amp etc with their old-school frame types. May even be how they are bolted to the case, the frame ones usually have four bolts rather than one through the centre.
Click to expand...

That's been largely my experience too. Toroidal transformers seem to be much more prone to buzzing when there's DC on the mains. I have had a very noisy non-toroidal transformer in an Arcam Alpha 5 CDP but that's a known issue with that particular player/transformer. Arcam's 'fix' was to wrap a zip-tie around it and sometimes the buzz can be reduced by simply retightening the zip-tie.
 
My wife has taken my daughter out for a walk so I've finally manged to have a proper listen to the Radford (only for 45 mins though).

I'm sorry to have kept you all waiting so long but it really is impossible to safely use the Radford with a toddler roaming around the house!

Anyway, it's clearly firing on all cylinders now and sounds absolutely superb. It is a very refined and neutral sounding amp with great imaging/stereo separation and bags of detail which allows you to hear 'deep into the mix' as they say.

Hum from the amp itself is very minimal. I would be straining to hear from more than 1 or 2 meters away and it certainly won't bother me. Hum through the speakers is again minimal. This is a very quiet amp.

I'll attempt to make comparisons with the Leak Stereo 20 after living with it for a while and swapping them over a few times.
 
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I would love to hear it. If only to (a) appreciate your sterling restoration efforts and (b) to get the chance to listen to one ahead of buying my own (which, as you will no doubt be aware, I am a bit nervous about as I've never spent that much money on a totally unheard bit of equipment before). But very glad it's sounding great. I'm also interested in a comparison against things I have heard, just for context. But that's difficult; the Venn diagram of 'amps I have heard/owned' and 'amps others have compared against a Radford' being very small, and subjective too..... anyway, I sort of wish I just had to pay my money for mine now to get it 'committed' and be done with it :)
 
JTC said:
But.... go on.... first impressions of the sound? Also, any transformer noise/buzzes/etc.? (A personal fixation of mine)
Click to expand...
Similar amount of buzz on my 15 to that described by Mike. It’s silent through the speakers, although I did have a tiny bit of hiss and hum until recently. This disappeared after a re-racking and cable re-jigging. I can’t really explain how that removes hiss, unless my tinnitus got slightly worse at exactly the same time and now swamps it.

If you want to hear it (not a 25, I know) you are welcome to visit Marchbanks Towers. If you are where I think you are it is a lengthy day trip by rail, but doable. I did it myself in the reverse direction back in the '80s so I could see a play at the Citizens' Theatre.
 
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