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Thread: Radford STA15

  1. #1
    Join Date: Nov 2017

    Location: Midlands, UK

    Posts: 174
    I'm Kim.

    Default Radford STA15

    I think this counts as Past Masters if itís older than me...



    Anyway, I picked up this lovely sounding STA15 the other week. Itís been to David Coe/AD Audio within the last couple of years for new caps, speaker binding posts and valve runners and sockets. The transformer cage is showing itís age, but a new one should be on its way from Will at Radford Revival. The main casework is a little beat up, but thatís a much bigger job!

    Sounds great already. I was worried my speakers wouldnít be sensitive enough, but no issues there in my small room.

    I wanted to ask about othersí valve choices with these?

    This is currently fitted with the following:
    Mullard/Zaerix GZ34
    2 x Telefunken ECF82
    2 x Telefunken EF86
    4 x Svetlana EL34s

    Which valves (output/signal/splitter/rectifier) tends to have the greatest impact on SQ?

    Iíve been looking around at EL34s and may get a set of the Winged ĎCí valves as I think it currently has the reissues fitted. These seem to be a good balance between cost and reputation.

    What about KT77s? Iíve seen someone singing the praises of 6CA7 Shuguang Treasures which I think may also work?

    Grateful for anyoneís advice. Iím in no rush as it already sounds good to my ears, just interested in having a play.


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    Time flies like and arrow.
    Fruit flies like a banana.

  2. #2
    Join Date: Jan 2009

    Location: Essex

    Posts: 22,257
    I'm openingabottleofwine.

    Default

    My STA15 Mk.III uses Mullard (Blackburn Road) EL34s, a Mullard GZ34, with Telefunken and Siemens & Halske small signal valves.

    The amp is a 'spare' and is not often used, so I haven't done much in the way of tube rolling. I'm of the general opinion that the designer of a particular valve design usually manufactures the best samples - hence Mullard/Philips EL34.

    Nice example of the Radford you have there Kim, it's in better cosmetic condition than mine.
    Barry

  3. #3
    Join Date: Nov 2017

    Location: Midlands, UK

    Posts: 174
    I'm Kim.

    Default

    Taken from a flattering angle Barry, I assure you!

    I have looked for Philips EL34s, but they seem rare and very expensive!


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    Time flies like and arrow.
    Fruit flies like a banana.

  4. #4
    Join Date: Apr 2019

    Location: Bristol UK

    Posts: 10
    I'm Roger.

    Default

    Mike Davis (ex - Radford/Woodside) fitted JJ EL34s IIRC to my STA25 when he restored it - sounds good to me.

  5. #5
    Join Date: Jan 2020

    Location: South Yorkshire

    Posts: 2,467
    I'm Andre.

    Default

    You never see stuff like the old Pye 'PF-91' , 'HF-25' Which were well sexky..

  6. #6
    Join Date: Jan 2009

    Location: Essex

    Posts: 22,257
    I'm openingabottleofwine.

    Default

    Quote Originally Posted by Made in 1968 View Post
    You never see stuff like the old Pye 'PF-91' , 'HF-25' Which were well sexky..
    There is a member here who uses a pair of Pye valve amps. Forget his name, but I did post a circuit diagram for him.
    Barry

  7. #7
    Join Date: Jan 2020

    Location: South Yorkshire

    Posts: 2,467
    I'm Andre.

    Default

    You never see the Audiomaster 'IIA' They would be cool with Marco's Tannoyz

  8. #8
    Join Date: Nov 2017

    Location: Midlands, UK

    Posts: 174
    I'm Kim.

    Default

    I've had a weekend of tube rolling and so felt I should add my thoughts.

    For the signal valves, I've tried new Svetlana, GE and a nice pair of Dario Philips cryo EF86 tubes from Watford Valves, but still tend to prefer the Telefunkens that came with the amp. Though differences here are not as great as with the output valves to my ears.

    For output valves, I've now heard JJ EL34s, new Svetlana EL34s, new Genalex Gold Lion KT77s and Amperex NOS xf4 EL34s. I've been really impressed with the KT77s and would happily live with them, but (as per Barry's comment above), the xf4 valves work best for me - perhaps not quite as revealing as the KT77s, but emphasise the midrange a little more and sound lovely.

    So, in summary, I seem to like the sound of the really expensive valves more than cheaper ones!!! I think there's probably some bias going on here


    I like the amp a lot though. So much so that I bought an STA25 that was for sale on here recently as I thought a little more power might suit my speakers better (it does). I'm about to send it to David at AD Audio for a little cosmetic work and a service and will do a side-by-side comparison when it comes back.
    Time flies like and arrow.
    Fruit flies like a banana.

  9. #9
    Join Date: Mar 2008

    Location: Galashiels

    Posts: 13,058
    I'm inthescottishmafia.

    Default

    NOS RFT are well thought of. Not sure what the prices are like these days though. Probably not as good as Mullards, but a lot cheaper!
    ďMusic has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radioĒ

    Hunter S Thompson

  10. #10
    Join Date: Nov 2017

    Location: Midlands, UK

    Posts: 174
    I'm Kim.

    Default

    Thanks for the tip - not tried RFT valves before, but will give some a try in the future.


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    Time flies like and arrow.
    Fruit flies like a banana.

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