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Thread: Radford STA15 with Big Tannoys

  1. #1
    Join Date: Mar 2016

    Location: New Forest

    Posts: 100
    I'm Clive.

    Default Radford STA15 with Big Tannoys

    I thought I would share my experience in finding the ideal amp to drive my Tannoys.
    I have been trying for a couple of years to find the perfect amp for Tannoy 15” Monitor Reds. I used to own AN/Es paired with my Shindo D’yquems and the sound lived up to both the reputation of Shindo and the liquid musicality you would expect from a 300B SET design.
    I then came across a pair of original condition Tannoy GRF Corner Horns. They were fitted with 15” MGs and whist they sounded ok with the D’yquems something was missing in terms of dynamics and speed. I had the drivers re-coned and then external cross-overs built by Paul Coupe at RFC which improved the sound a lot but still something was missing, so I bit the bullet and bought a pair of Monitor Reds, which being 15 ohm would be an easier load for the amps. Again, even with new external cross-overs from RFC the sound was not quite there, so reluctantly I decided that no matter how much I loved the Shindos, I had to find a replacement better suited to the big Tannoys.
    I have tried more powerful SE designs with KT88s and the PP EAR861 but still felt I was not getting the combination of musicality and dynamics that I was looking for.
    Paul at RFC, who probably knows more about Tannoys than anybody recommended I try a Radford amp. I also followed Tom (Montesquieu)’s posts on here about his use of Radford with his Tannoys.
    So when an unmolested STA15 in good condition became available I took the plunge. I had never heard a Radford before and had my doubts about 15w being adequate.
    It was obvious as soon as it was turned on that I was on to something. There was a clarity and foot tapping pace to the music that had been missing, together with a musical mid range, sweet highs and plenty of controlled bass. There were some obvious issues due to the amp being in original condition but already new rectifier and input valves have resolved most of them. A quad of NOS Mullard EL34 resolved the rest and sound-wise there is nothing else required.
    I know it will need to go off for a full service and probable replacement of some internal components but I have heard enough to know that the STA15 is a great match for the Monitor Reds and has more than enough power for the job. That such a small amplifier can sound so good after over 50 years is a testament to the design and manufacturing skills of its maker.

  2. #2
    Join Date: Aug 2009

    Location: Staffordshire, England

    Posts: 37,779
    I'm Martin.

    Default

    I remember hearing a Radford STA15 after a long day of many good amplifiers. And it was just right - to the point where I realised all the others, good as they were, were slightly wrong.


    Exceptional bit of kit, congratulations.
    Current Lash Up:

    TEAC VRDS 701T > Sony TAE1000ESD > Krell KSA50S > JM Labs Focal Electra 926.

  3. #3
    montesquieu Guest

    Default

    No surprise that even an expensive 300b amp was unable to control the big cones - all these big Tannoys (Golds, Reds, HPDs) need a decent damping factor, something you will never get from a 300b SET.

    I settled on Radford after experimenting with more than 40 amps across 12in and 15in Golds and HPDs. The Reds won't need many watts but they do need the control the Radford provides. Surprised you didn't like the EAR 861 but perhaps with Reds it was simply overkill!

    There is something magical about the Radford amps with Tannoys, it's just a super combination. As you have discovered

    Nice one!

    (BTW the STA15 still gives out about 28 watts per channel, the STA25 with the solid state rectifer about 36 watts ... people sometimes get confused by the name and compact size but it's not a weedy thing at all!).

  4. #4
    Join Date: Nov 2011

    Location: wirral

    Posts: 245
    I'm frank.

    Default

    A few days ago I had Marchbanks from PFM over to mine to audition some 15" HPD Amesburys that I'd just finished fully restoring.
    He brought along his STA15. The combo produced pure magic, more than enough power and the Amesburys sang a sweet musical song with great articulate bass, liquid mids, astonishing ambience and sweet sweet top. A match made in heaven.
    Frank

  5. #5
    Join Date: Mar 2016

    Location: New Forest

    Posts: 100
    I'm Clive.

    Default

    The 861 is a lovely amp and with the Tannoys, is better than the Shindos in terms of control, but not musicality. The STA15 has even better control than the 861 and is to my ears more musical. Its something to do with timing and clarity, you want to tap your feet more with the Radford.

  6. #6
    Join Date: Mar 2017

    Location: West Sūþsēaxe

    Posts: 2,015
    I'm Edward.

    Default

    I came to this perfect match the other way around. I had Radford STA25s for years driving a variety of speakers (Harbeth, Radford, PMCS etc) and was always delighted. Then experienced Adam's Tannoys and was floored. More so when I took the Radford over to drive his Tannoys.

    So when some Eatons came up with Tom I was round there pdq and grabbed them. Not one once of regret.

    Now still mulling over getting bigger Tannoys for all the good reasons.

    Mind you I'm currently using a Sugden Masterclass amp driving the Eatons, that works very well also.

    E

    Via Tapatalk
    Current: [P20] Roon/Tidal > Custom PC> Chevron Paradox NDF16 > Phast Pre > Neuro. 686 > Tannoy Berkley (RFC tweaks)


  7. #7
    Join Date: Mar 2016

    Location: New Forest

    Posts: 100
    I'm Clive.

    Default

    I suppose its not surprising they match so well, since these amps were produced in the mid sixties and were expensive for the time, so were mainly used by professionals or serious audiophiles, with whom 15" Monitor Reds were very popular.
    But what I find amazing is how the STA15 has more than enough power for these speakers, even taking into account Tom's point above about the real power output of these amps. I am having to use -20dB attenuators on the amp's inputs to get the pre-amp volume control to work over a sensible range.

  8. #8
    montesquieu Guest

    Default

    Quote Originally Posted by CliveG View Post
    I suppose its not surprising they match so well, since these amps were produced in the mid sixties and were expensive for the time, so were mainly used by professionals or serious audiophiles, with whom 15" Monitor Reds were very popular.
    But what I find amazing is how the STA15 has more than enough power for these speakers, even taking into account Tom's point above about the real power output of these amps. I am having to use -20dB attenuators on the amp's inputs to get the pre-amp volume control to work over a sensible range.
    That's not a power question that's input sensitivity .. Will built some attenuation into the inputs of mine so that it could be used with a normal high-gain preamp. Doesn't affect the power rating ... you don't lose any power by running attenuators, you just have more control over the input signal and the resulting output volume. A higher gain input signal just means you reach maximum output (and distortion) faster.

  9. #9
    Join Date: Mar 2016

    Location: New Forest

    Posts: 100
    I'm Clive.

    Default

    Quote Originally Posted by montesquieu View Post
    That's not a power question that's input sensitivity .
    Point taken Tom. In my view its a pity more amps do not have variable input attenuators to solve this problem, like the EAR 861 and Shindos. Makes life a lot easier.

  10. #10
    Join Date: Oct 2016

    Location: London

    Posts: 313
    I'm David.

    Default

    A Radford STA25 I've just serviced and upgraded sounds great with my Tannoys as does a Radford TT100 I've more or less completely restored so there's two that work well! I more or less wrote off the Radford STA 25 as a combination with my Tannoys before its service and upgrades but now it's really sounding great, so just shows what a difference running correctly and sympathetic upgrades can make!

    The Radford TT100 of course has a lot of extra power but as Clive says about the 15, the smaller Radfords can certainly pull weight and on my 96db sensitive Canterburys certainly go loud enough for decent volume levels
    David

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