Hot on the heels of the original review of the Radford Revival STA15 I had the chance of a direct comparison with the original recently.  I won’t say “with the real McCoy” as the Revival unit is just as “real” in terms of circuit topology and design.  There were a few critics doing the rounds voicing opinions that older valves in unrestored versions were bound to sound softer, so setting the newer version in a glowing light, but if you read on, you’ll see that they completely missed the point.

During a brief recess in the downpour, which had been of biblical

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proportions of late, a knock came at the door last Friday and I found William Moores from Radford Revival was at the door accompanied by a large box containing an original STA15.  The revival unit was still with me following the last review and so we settled down to an uninterrupted afternoon of music and amplifiers.  They way it was going to go was to first listen to the system playing the recordings used for the previous review (all on LP) so that Will could get a feel for the system and each of the recordings before switching from my own amp to the Revival unit, then immediately to the original STA15.  An important (as far as I was concerned) part of the review was to compare not just the sonic merits of each ‘amp, but also the physical characteristics, looking at internal build quality, exterior appearance and discussing measurements for both amps.

What’s immediately apparent is just how similar both units are – you have to look really hard to spot which is the Revival unit.  A brief glance shows both to be identical, and only on second inspection do the slight changes become apparent.  The biggest giveaway is the Revival unit is newer looking and everything is a little shinier, but look closer and you’ll see almost identical but better quality switches around back (taps for the transformer) on the new model, and notably that the casework lacks the crude folds of the original and is smoother and better finished on the newer model.  Transformer casings are almost identical and there’s a story behind that too.

Old and New Transformers

The man behind the original transformer casings does in fact still make them (in a Bristol workshop) for the new amplifier, so there’s some of the original DNA from the same pair of craftsman’s hands involved in the new amp.  It’s great that Will and Steve have managed to keep some of the links with the original amp manufacture.  Their attention to detail and passion for these amplifiers is what makes them what they are, true but improved copies of the original.

For those who haven’t yet read the earlier review on the new unit, without replicating too much, it’s important to note one main thing.  The new STA15 is not a new version of the original, it is the original, down to every line on the circuit design blueprints.

Old and New PCBs

There are some improvements such as the better quality of newer components and transformer insulation (and the way the wire connections are soldered to the new transformers), but for all intents and purposes, the amplifiers are identical in design… so were they identical in sound?

Before I come onto sound quality, the myth surrounding the comparison seems to be that the older amp would have worn out valves so would somehow be softer with more rolled off treble.

Old and New Innards

Well, happily I can report that the unrestored original was measured and the output showed no roll off within the HF audible range, in fact, it measured pretty much identical to the new unit, so we can put to bed that argument.  The valves whilst obviously used and with some hours on them (some of the lettering was wearing away) were even the same JJ E34L output valves, but still with plenty of life in them.

 

Sound Quality
The same recordings used for the first review were spun up gain.  Firstly with the new unit, then for the older amp.  No surprises to say that my initial conclusions for the new amp still stand and looking through my notes for each piece, I stand by the initial review.  No big surprises there.  A brief recap was that I found this quite a gutsy amp with a surprisingly neutral presentation, although I felt that the bass was slightly curtailed and that with some pieces, I found a slight forwardness in the treble.  Overall though it was a fine performer and carefully partnered, could do most music genres justice, allowing the listener to concentrate on the music.  The qualification was that rock fans might want to look elsewhere.

Onto the original STA15.  Having seen some of the dents in the internal capacitors, and the cobwebs present, along with the corrosion on the RCA sockets, there was a moment just before I flicked the power switch where I wondered whether rubber gloves,  wellington boots and some Kevlar body armour might be a wise precaution, but I flicked the switch anyway.  What was a surprise was that for such an obviously old unit was how quiet the transformer was.  No audible buzzing until it got well and truly warm, and even then, that was inaudible to my ears from beyond a metre.  Like the newer unit, once warmed up, I turned the volume to maximum (no source connected) to get a feel for circuit noise.  It was as commendably silent as the new version.  So far, so good and both amps were level pegging.
First up was Radiohead’s Karma Police on a 1997 Parlophone pressing.  The introduction had immediate impact, with good treble detail and channel separation.  The vocals were well presented too, and if anything a little softer than the new unit, but it was a very close call indeed.  I’d say that the new unit was a tad more detailed but that’s where the differences ended. Once a bit of bass kicked in, the main difference (on this track) became apparent.  The original had a little more wallop and apparent extension, albeit at the cost of some control.  We were listening with both amps switched for the 8 Ohm output settings, and perhaps a switch to the 4 Ohm setting may have benefitted the older amp, but as this was an equal comparison, we left well alone.

A switch of recordings to the opening section from Richard Strauss’ Also Sprach Zarathustra revealed a well controlled organ note underpinning the opening, very clean brass (something I was particularly impressed with on the newer amp) and wonderfully fruity timpani with almost pin-point imaging.  The timpani also exhibited good decay and impact.  If anything, I would say that the newer unit had the edge on the cleanliness and natural presentation of the woodwind, particularly the brass which exhibited some great rasp without becoming harsh or muddied.  In keeping with the first album reviewed, the bass had some additional punch and extension on the older unit, but perhaps at some loss of control over the newer amplifier.

This theme was exhibited with all other recordings and the only one where I really preferred the older amplifier’s bass was on John Lee Hooker’s “That’s Alright” from the Healer album. The presentation just seemed to benefit from that extra twang at the lower end with the bass note lingering for a short while.

Will and I discussed the differences, and in fairness, had the newer amplifier been configured identically to the older one, I have no doubt that the differences would have paled to nothing, zero, nihilum. The reason, it transpired as to why the bass presentation was a little different was simple.  Will has configured the new amp with a different resistor in the bias circuit to make the E34L output valves run a little less stressed.  This together with a slight difference in one of the output capacitors could explain the difference (slight difference) in presentation.  For those wanting identical performance, that is very easy…when ordering the new amp, just ask for the bias to be set the same as the old amp.  I can’t really see the point in doing so myself because there does come a little loss of bass control with the valves running a little hotter and these changes taking effect.

The fact that both amps sounded so similar is testament to two things:
1.The expertness with which William has assembled the new amplifier in terms of attention to detail and
2.The effects of negative feedback used in the (original;) design ensuring that even an old well used and abused sample still won’t “soften” up too much in the sound stakes as it seems to retain the low distortion frequency response of the new unit.

Ok, so this brings me to the crunch.  Given the choice of an original unit or one of the newer units, which way should people go?  The answer I guess depends on your outlook and reasoning.  If you’re not interested in long term reliability and just have to have and original for the historical context of the thing, then that’s the way you’ll no doubt go irrespective of rationalised reasonable argument.  What is the argument for the new amp?  Well, the answer is in three main parts. Firstly, whilst remaining true to the design of the original down to every nut and bolt, the advent of better quality components, especially the transformer and caps, means that the circuit should be more reliable and better quality. The casings will also be better quality and better finished- the second reason for buying the newer version.  The main reason in my mind though focuses on the PCB boards of both amps.  The older amp uses (by modern standards) a pretty poor quality PCB that will not take well to servicing and swapping out of components.  In most cases, I suspect that come major service time what would actually happen would be that the original PCB would be better removed and discarded in favour of the newer and far superior quality fibreglass PCB.

Conclusion

So there you have it. Want an STA15 or even an STA25 but can’t decide on which?  One look at the innards of the older units should be answer enough for you; it was for me.  I remain convinced that the new unit is faithful in every respect, and think that the market is still wide open for it, particularly the Far East which has a record for snapping up quality British hifi.  Buy an old unit and it’ll work well for while, maybe even for quite some years to come.  Just don’t fool yourself into thinking you have something that sounds unique or is somehow superior to the new version, as the opposite is so obviously true.  One thing is almost certain though…at some point, a well used original, to remain safe will need work doing to it.

Old v New? New would seem to be the obvious choice!

At this point, as few if any original transformers are available, let alone PCB’s, you’ll probably end up having the innards of the new unit installed in terms of physical characteristics of the newer version but in a casing of poorer quality.  It’s at that point that you’ll probably kick yourself for not buying the Radford Revival unit in the first place.  Its that simple.  The new unit also comes fully guaranteed which is more than you can say for buying used.  However, the original will still hold that historical value for some.  Both sound almost identical, so you pays your money and makes your choice, although a good used example is becoming very hard to find these days and prices are rising to beyond what they are really worth in hifi terms.  The same cannot be said of the Revival unit.

Author – Paul

Hifi Pig would like to thank Steve and Will at Radford Revival for making this comparison possible.

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1 Comment

  1. Good afternoon.

    I am very happy to learn this wonderful reissue amplifier STA 15 and what may be the reissue of STA 25 (KT 88) with the inlet valve 86 with an EF phase inverter with Schmitt ECF 82 and not on the STA 25 “Renaissance” which had as one inlet valve ECC88 circuit and especially against simplify feedback.

    Pierre.

    Ps: excuse my English, I’m French.

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