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Hi all,

Any advice out there?

I have an incredible pair of 4 way transmission line Radford Studio Monitors. I had daydreamed of a Radford STA-25 and Radford SC 22P to power them. The opportunity to buy an STA-15 and Radford SC 22P came up and I have demoed these with the Radford speakers and it seems I was trying to push the STA-15s too much with them. I am considering whether to build a setup around the STA15/SC22P (or STA 25) or whether to get a more powerful valve amp able to drive the Radford Studio Monitors, which I LOVE. There is the possibility to acquire a lovely STA-25 too, but the question is whether this too may be borderline for power as I don't want to push it too much and muddy it's characteristics.  There are also a pair of Radford/Woodside MA50s available so I'm also playing with that option. The other option is to give up the dream of full Radford set up and simply get something else that would pair well with the Radford speakers.

I love 60's (Beatles, Beach Boys, Janis Joplin, Small Faces, 70's (Deep Purple, Humble Pie, Sabbath, Zep, Linda Ronstadt), 80's (Iron Maiden, Dire Straits, Suzanne Vega, Midnight Oil), 90's (Sinead O'Connor, Live, RHCP, and 2000's (the Libertines...), blues (early John Lee Hooker to John Mayall). 

So: Questions-feel free to respond to any or all:

  • Is this music too much for tubes to start with?
  • What would be a great pre-amp to pair with STA15 or 25?
  • What would be a great pre-amp to pair with MA50
  • What would be great (and accessible) speakers to pair with STA15 or 25?
  • If none of these amps, and rather, build the amp around my current speakers, what would be a terrific valve amp (stereo, mono blocks, preamps or integrated pre/power) to pair with my Radford Studio Monitors? I have never heard a pair of IMF TLS 80's, but they have very similar enclosures and some of the same drivers-B139,  Goodmans Mids, HF1300, HF2000, so I assume some similar amps to those that would suit these or similar 4 way 60s-70's transmission line speakers.
  • Thanks for considering people. I feel like my Radford speakers are 'forever' speakers and I'm after a 'forever' amp

All the best,

Rockrolley

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Hi there, Thanks for your recent input. I'll add more detail soon. For the meantime, here are some pics of the actual unit as taken by the seller. I'll take some more close up pics in the next da

Hi all, For your interest, here are the docs that I received with the MA50s. FYI, they came in the original boxes from Woodside too, which are very complex and useful for keeping them safe in tra

Agree with Graywulf, keep the STA15. I always want one because it's got valve rectifier compared to STA25 and to me valve rectifier helps massively in tuning the sound. I listened the STA15 with Tanno

Can you describe a setup that’s worked well with the Radford speakers so far? I had the impression that the IMFs you mention as comparable to your Radfords love a powerful amp, so I’d expect your speakers to be similar. Obviously the room and volume levels you prefer are big factors as well. Also condition of valves and other components in 50+ year old gear.

 

No question tube amps can sound amazing with the music you mention. But I think in general much more powerful tube amps or solid state is what you’ll need for those speakers, with their low sensitivity (and maybe low impedance?)

 

Don’t give up hope anyway 🙂 Only a demo will really determine what works best. 

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21 minutes ago, RCAJack said:

 

No question tube amps can sound amazing with the music you mention. But I think in general much more powerful tube amps or solid state is what you’ll need for those speakers, with their low sensitivity (and maybe low impedance?)

 

 

As RCAJack said, @RockRolley, I suggest you need a very powerful amp - preferably solid state - to make your Radfords sing.

 

My suggestions are:

  • Magtech (very happy with a 2 ohm load).
  • March Audio P451
  • Ncore 400.

In tubes, say, a 250w VTL or an AR 250 would drive them well, too.

 

Andy

 

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Posted (edited)

Hi RockRolley,

  firstly congratulations, and secondly, don't you DARE get rid of the STA-15. (Unless it's for the Woodside/Radford MA-50's).

   Firstly as an ex Radford owner (STA-100) I can assure you it is the biggest regret of my HiFi  Journey.

Possibly the MA-50, or an STA-60 may well power your Radford Transmission line speakers. I have a pair of KEF Concerto's of that era, and the Radford design crossover is a well known upgrade for these speakers. I can certainly tell you the STA-100 would. I also had the SC22P with the amp.

 The STA-15 is probably THE 'sweetspot' amplifier in the STA range. I  have heard one in a direct back to back (all fully restored by the same tech) on the Quad radiator's (ESL's). I can assure you the Radford showed up just how budget and overrated the Quad2's are. possibly biting the bullet and going for high efficiency (period?) speakers to match the '15 is  a definite way forward. But even my Concerto's would not run well on the 15 watts. Maybe Wharfedale RRSD-10 based speakers, or Goodman's?  Obviously there are plenty of modern high efficiency speakers to suit. The MA-50's? Would certainly power many classic speakers of the era, including the Concerto's. There were several 'boutique' UK manufacturers using the classic KEF line up Like Nightingale, Tangent etc.

 The SC22P, is 'OK' as a pre-amp, but to be honest, I ended up using an ASL (Antique Soundlabs) SQ2001 pre, which was far better, but no phono stage on it.

  I listen to similar music to you, so have a pretty good idea of how your system could sound set up with the right gear to compliment the STA-15. Or, and I would certainly look at the MA-50's.  

As you probably already know, Woodside was owned by John Widgery, Radford's right hand man, so any of their equipment is generally considered 'as good'.

 

Edited by Graywulf
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22 hours ago, RCAJack said:

Can you describe a setup that’s worked well with the Radford speakers so far? I had the impression that the IMFs you mention as comparable to your Radfords love a powerful amp, so I’d expect your speakers to be similar. Obviously the room and volume levels you prefer are big factors as well. Also condition of valves and other components in 50+ year old gear.

 

No question tube amps can sound amazing with the music you mention. But I think in general much more powerful tube amps or solid state is what you’ll need for those speakers, with their low sensitivity (and maybe low impedance?)

 

Don’t give up hope anyway 🙂 Only a demo will really determine what works best. 

Thanks very much for your input. I don't own any IMFs but I've been very interested in TLS 80-to the point where I have managed to source all drivers and crossovers and am preparing to have enclosures built to spec for them as they rarely come up for sale in Australia. All the reading I've done says that they aren't very efficient and love some power. I'm hoping to track down some more technical info on the Radford Studio Monitor specs, but don't have details at the moment. I have powered them fine with Pioneer A400 and also Pioneer A300r Precisions 40 and 30 wpc respectively, and they power them fine, so I don't think they are that thirsty. When I trialed the STA15, I had to push it pretty hard and it seemed to be asking a bit too much of the STA15. I managed to liten to a demo of the MA50 monoblocks last night, albeit through smaller Harbeth speakers, but the MA50 seemed to have plenty of power and I feel pretty confident that they could power the Radford Studio Monitors well. I'm glad to hear that tubes would work well with my musical tastes, thanks for that feedback. The owner of the STA15 has had his tech go over it and says it looks A-OK and I certainly take him at his word, so, it seems maybe just a mismatch... p.s. I have just landed a lovely looking set of B&W DM3 speakers that look like they'd pair great with the STA15... so now I'm daydreaming of both the STA15 AND the MA50 hahaha

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22 hours ago, andyr said:

 

As RCAJack said, @RockRolley, I suggest you need a very powerful amp - preferably solid state - to make your Radfords sing.

 

My suggestions are:

  • Magtech (very happy with a 2 ohm load).
  • March Audio P451
  • Ncore 400.

In tubes, say, a 250w VTL or an AR 250 would drive them well, too.

 

Andy

 

Thanks Andy,

I'll definately check out your recommendations. As mentioned they didn't seem to like the STA 15. I have, however driven them well with 30 and 40 watt solid state amps as well as 100 wpc. I also recently got a Radford solid state ZD100 that drives them well. I trialed the Radford MA50s last night, not on my system, but they seemed to have a very good amount of power so I'm thinking that may be a good match. That potentially leaves the question of a well-paired preamp for the MA50s. Any ideas there? Thanks,

Simon

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"Driving them well", @RockRolley is not quite the same as "driving them so they give their best".

 

Andy

 

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I'd be inclined to follow Graywolf here, Radford is better know for their amps, It's their amps that have the almost cult following.

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On 12/05/2021 at 12:06 AM, Graywulf said:

Hi RockRolley,

  firstly congratulations, and secondly, don't you DARE get rid of the STA-15. (Unless it's for the Woodside/Radford MA-50's).

   Firstly as an ex Radford owner (STA-100) I can assure you it is the biggest regret of my HiFi  Journey.

Possibly the MA-50, or an STA-60 may well power your Radford Transmission line speakers. I have a pair of KEF Concerto's of that era, and the Radford design crossover is a well known upgrade for these speakers. I can certainly tell you the STA-100 would. I also had the SC22P with the amp.

 The STA-15 is probably THE 'sweetspot' amplifier in the STA range. I  have heard one in a direct back to back (all fully restored by the same tech) on the Quad radiator's (ESL's). I can assure you the Radford showed up just how budget and overrated the Quad2's are. possibly biting the bullet and going for high efficiency (period?) speakers to match the '15 is  a definite way forward. But even my Concerto's would not run well on the 15 watts. Maybe Wharfedale RRSD-10 based speakers, or Goodman's?  Obviously there are plenty of modern high efficiency speakers to suit. The MA-50's? Would certainly power many classic speakers of the era, including the Concerto's. There were several 'boutique' UK manufacturers using the classic KEF line up Like Nightingale, Tangent etc.

 The SC22P, is 'OK' as a pre-amp, but to be honest, I ended up using an ASL (Antique Soundlabs) SQ2001 pre, which was far better, but no phono stage on it.

  I listen to similar music to you, so have a pretty good idea of how your system could sound set up with the right gear to compliment the STA-15. Or, and I would certainly look at the MA-50's.  

As you probably already know, Woodside was owned by John Widgery, Radford's right hand man, so any of their equipment is generally considered 'as good'.

 

Thanks, Graywulf,

There seems to be problems, at least in my system, with the STA15 and SC22P. I'd love it to be as incredible as I've heard they are. Perhaps it needs new valves or a re-cap, I'm in new territory and I'm not sure what it would take to get that legendary experience from it, so I'm a bit intimidated... still, I'm ultra curious and still tempted to go with it. The demo of the MA50 blocks was fantastic, it seemed to pack a good amount of power and did everything great, just at the right time. The STA 25 seemed tight and liquid all at the same time-it was gorgeous. Tough choices-I'd love'em all. As far as my current system goes, the mono blocks seem the best fit. I'm not ashamed to admit that I'm into aesthetic qualities, and the mono blocks just look stunning too. Re the 15, based on your 'back to back' demo experience, maybe it's just a matter of getting a tech used to this type of gear to bring the 15 up to original form. Re: High efficiency speakers, I'll check out your recommendations. I have some concertos too, but as you said even these may not be a right fit. Just got some B&W DM3 speakers-haven't picked them up yet, maybe a good match for the STA15?

Was the STA100 from Radford or Widgery era? I'd love to hear more about the sonic charecteristics of these?

Thanks again

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Agree with Graywulf, keep the STA15. I always want one because it's got valve rectifier compared to STA25 and to me valve rectifier helps massively in tuning the sound. I listened the STA15 with Tannoy Gold 15, it sounded great. I also listened to STA25 with ESL57, what a great combo. I just wish I'd get a chance to listen to the STA15 with ESL57 someday. Cheers.

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@Graywulf @Jehuty @muon* @andyr @RCAJack

Hi guys,

Thanks for all of your feedback. I couldn't help myself. I got the MA50s and also got the STA15 and SC22P. The MA50s are powering my large radford speakers nicely. For the MA50s I have the preamp on 1 where my Pioneer A-300r Precision used to be on nearly half volume to get the same level, so the speakers seem to like it power wise. Soundstage is incredible as is detail. It's a little brighter than expected. I'm currently using a solid state Radford ZD22. I'm going to look out for the matching woodford tube pre which may warm it up a bit. Also, the MA50s don't have the recommended brand of tubes, does anyone know if tube brand can influence brightness/warmth? Certainly open to other tube and preamp recommendations for warming it up.

I haven't got the STA15 and SC22P home at this stage, and I will take my time to match these with appropriate speakers. I've blown my budget getting all these units so I need to raise some funds before getting more gear. Still open to ideas for ideal speakers for the STA15. That said, I'm not likely to spend over a couple of K. 

Thanks again guys. I'll post some pics soon too.

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Posted (edited)

Kirk  @xlr8or may be able to help with tube recommendations to add warmth and combat brightness in the MA50.

 

Would be helpful to know what tubes are in it now?

 

MA50.jpg.cb0e0971c4b25f7ceab555f6feb54093.jpg

Edited by muon*
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Congrats on these acquisitions!

 

You could tube roll the ECC81 and ECF82 fairly economically to tune the sound somewhat. Switching power valves will be a bigger investment! What about auditioning the SC22P (when it turns up) with the monoblocks to see how that affects the sound you’re getting? Could be a useful data point. 

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Posted (edited)
2 minutes ago, RCAJack said:

Congrats on these acquisitions!

 

You could tube roll the ECC81 and ECF82 fairly economically to tune the sound somewhat. Switching power valves will be a bigger investment! What about auditioning the SC22P (when it turns up) with the monoblocks to see how that affects the sound you’re getting? Could be a useful data point. 

Would these be the MA50 Renaissance?

 

Was there an original Radford MA50 non Renaissance?

 

Edit: as far as I can work out off the net the Radford MA50 is from 1989, I'm not sure if the Renaissance one is the same, just wondering if there are any differences including pre amp tubes used. (given the schematic I posted above is the Renaissance)

Edited by muon*
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@muon i thought the Radford/Woodside MA50 was the Renaissance circuit as it’s not a 60s era product?

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1 hour ago, RCAJack said:

@muon i thought the Radford/Woodside MA50 was the Renaissance circuit as it’s not a 60s era product?

Probably correct, I didn't know so had to ask :)

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Posted (edited)
25 minutes ago, muon* said:

Probably correct, I didn't know so had to ask :)

 
Well I’m more confused now! 😅

 

The Stereophile review of the Woodside MA50 Renaissance describes a different valve lineup, along with a presumed typo re the ‘ECC811’ (sic)? But it’s pretty different otherwise...

 

Quote

The MA50's front end is said to be stable. It uses an ECC811 direct-coupled input stage with an active-load twin-triode 12AX7, followed by a second tube, a 12AU7, used as a cathode follower to avoid Miller effect

 

ETA a link to an eBay listing of “Legendary Woodside / RADFORD MA50 Renaissance Series Valve Power Amplifiers” showing the valve lineup in the circuit diagram above. 

https://www.ebay.ie/itm/112075098502 

 

Edited by RCAJack
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Posted (edited)

If @RockRolley can share a few close up photos of his amps in particular the 9-pin minis in use we can help recommend vintage types to 'soften' up the sound. I suspect the most influential tube to roll would be the first ECC81/12AT7, which would be V1 in the input stage.

Edited by xlr8or
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Hi there,

Thanks for your recent input. I'll add more detail soon. For the meantime, here are some pics of the actual unit as taken by the seller. I'll take some more close up pics in the next day or so. I love the look of them...

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MA50 Renaissance

 

Nice looking amps.

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19 minutes ago, muon* said:

MA50 Renaissance

 

Nice looking amps.

 

Fully agree. 😍

 

It needs a Mullard makeover with vintage types from the Blackburn and Mitcham factories. Fire up your spare cash @RockRolley you're going to need it. 😁

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40 minutes ago, xlr8or said:

 

Fully agree. 😍

 

It needs a Mullard makeover with vintage types from the Blackburn and Mitcham factories. Fire up your spare cash @RockRolley you're going to need it. 😁

Thanks for your comment. This is my first valve amp so I’m unsure of what to expect to pay for replacement quality valves. Can you advise a ballpark figure? 

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Posted (edited)

About $1.5-2K if all 8 EL34's are rolled as well.

 

Edit: I recommend focusing on applying incremental changes along the way and have a good listen at first to determine if any further change is required. I suggest rolling the ECC81/12AT7 at first and evaluating its influence on the tonal characteristics of your system.

Edited by xlr8or
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To offer a less heart stopping perspective than that of my learned colleague, an octet of new production EL34s costs around A$300. At the moment, the amps appear to have Groove Tube branded EL34s which could be sourced from a bunch of places (Groove Tube are a reseller) and I'll guess these are from JJ originally. The amps probably shipped with something similar.

 

In the front end, the ECC81 is sought after so NOS examples aren't super cheap but US$100 will get you a pair of British Mullards (maybe not the most desirable ones but I'd expect very good!)

 

NOS ECF82 and equivalent 6U8 are readily available (and not in current production AFAIAA). Triode Electronics have NOS versions for US$14 each and Watford Valves in the UK were quoting £30 for Telefunken examples. From appearances, I think the amps have old stock valves in the preamp and driver positions right now.

 

All up that's around A$500... not that you need to spend it necessarily! Have you considered getting the amps bench tested? Depending on age, the amps might even need a service to test electrolytic caps etc. and it'd be an opportunity to see how the current valve line-up checks out.

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Posted (edited)

The ultimate would be NOS Mullards all round including XF2 EL34's, and I think what Kirk is suggesting....would be no worries about being bright there.

 

For a little less expense I'd go for NOS Svetlana EL34 Winged C's with NOS Mullards up front. The NOS Winged C's would be a be better than any of the new productions IMO, but the ultimate would include the NOS XFx Mullard EL34's.

 

Pretty much all the new production EL34's apart from the Chinese ones are out of either one of two factories in Russia and owned by New Sensor. It surprises me how similar a lot of the new production EL34's are to each other in construction, some are virtually identical to one another but different brand names.

Edited by muon*
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I think these amps came with Tesla EL34's as original, I'd need to go back and read all those reviews ect' again to be sure.

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I've messaged the OP with my recommendation/s. Just confirming for others following this thread the use of Mullard vintage Xf2's will transform the Radford EL34 amps significantly. I believe their conceptual design was based on the sound characteristics of this specific tube. They cost a lot to source but well worth it in the end.

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59 minutes ago, xlr8or said:

I've messaged the OP with my recommendation/s. Just confirming for others following this thread the use of Mullard vintage Xf2's will transform the Radford EL34 amps significantly. I believe their conceptual design was based on the sound characteristics of this specific tube. They cost a lot to source but well worth it in the end.

 

I'm sure they do, x.  But they're still:

  • tube amps, and
  • low powered!

So - as far as the OP's spkrs are concerned - I suggest a high current ss amp (like a Magtech) will make the OP's Radford spkrs sound much better (as I betcha they drop to a low impedance).  Radford might well've recommended their amps to drive their spkrs - but back in the day, no-one was producing amps with the current delivery capacity of something like today's Magtech.

 

Andy

 

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Posted (edited)

Just adding to my previous post, I've rolled Radford EL34 amps before for other owners and most refuse to use any other EL34 tube except for the Mullard Xf2 made in the 1960's in the Blackburn plant UK. The OP's challenge is finding an octet set of these wonderful sounding tubes. The MA50's are an impressive set of monos to look at especially when naked. Those iron OPTs would weigh quite a bit I bet. I would recommend acquiring Xf2 singles at a reasonable price over time until an octet set has been collated. 👍

Edited by xlr8or
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Posted (edited)
On 17/05/2021 at 2:51 PM, RockRolley said:

@Graywulf @Jehuty @muon* @andyr @RCAJack

Hi guys,

Thanks for all of your feedback. I couldn't help myself. I got the MA50s and also got the STA15 and SC22P. The MA50s are powering my large radford speakers nicely. For the MA50s I have the preamp on 1 where my Pioneer A-300r Precision used to be on nearly half volume to get the same level, so the speakers seem to like it power wise. Soundstage is incredible as is detail. It's a little brighter than expected. I'm currently using a solid state Radford ZD22. I'm going to look out for the matching woodford tube pre which may warm it up a bit. Also, the MA50s don't have the recommended brand of tubes, does anyone know if tube brand can influence brightness/warmth? Certainly open to other tube and preamp recommendations for warming it up.

I haven't got the STA15 and SC22P home at this stage, and I will take my time to match these with appropriate speakers. I've blown my budget getting all these units so I need to raise some funds before getting more gear. Still open to ideas for ideal speakers for the STA15. That said, I'm not likely to spend over a couple of K. 

Thanks again guys. I'll post some pics soon too.

 

16 hours ago, andyr said:

 

I'm sure they do, x.  But they're still:

  • tube amps, and
  • low powered!

So - as far as the OP's spkrs are concerned - I suggest a high current ss amp (like a Magtech) will make the OP's Radford spkrs sound much better (as I betcha they drop to a low impedance).  Radford might well've recommended their amps to drive their spkrs - but back in the day, no-one was producing amps with the current delivery capacity of something like today's Magtech.

 

Andy

 

Sounds like the MA50's are doing a good job powering those Radfords, and from RR's post they are sounding very good with them and just need some extra warmth.

Edited by muon*
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2 hours ago, muon* said:

 

Sounds like the MA50's are doing a good job powering those Radfords, and from RR's post they are sounding very good with them and just need some extra warmth.

 

 

I agree with you, Ian - the 50w tube Radford amps seem to be doing a good job - and the OP is happy with the resulting sound.

 

However, my point is ... that there's a world of difference between "making the spkrs sound good" and "allowing the spkrs to deliver their best"! :)

 

Andy

 

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11 minutes ago, andyr said:

 

I agree with you, Ian - the 50w tube Radford amps seem to be doing a good job - and the OP is happy with the resulting sound.

 

However, my point is ... that there's a world of difference between "making the spkrs sound good" and "allowing the spkrs to deliver their best"! :)

 

Andy

 

But, Andy, better drive is not a guarantee of better subjective performance, will for an example a Class D amp provide the beautiful liquid midrange or the encompassing soundstage that is likely the result of the Radford amp?

 

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The same could and is said about driving my ML-1's, but for myself it would be one step forward and two steps back, and why I'm driving them with a 20w-25w PP EL34 amp :)

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1 hour ago, muon* said:

 

But, Andy, better drive is not a guarantee of better subjective performance, will for an example a Class D amp provide the beautiful liquid midrange or the encompassing soundstage that is likely the result of the Radford amp?

 

 

Absolutely it (a Class D) won't, Ian - compared to a great tube amp.

 

But tube amps are not generally good with low impedance spkrs; it's an assumption - as I can't find any specs - but I suspect the OP's spkrs drop to a low level of impedance.  Back when they - and the amps - were designed noone was making high-current ss amps that actually sounded good ... today, there are such beasts.

 

So whilst I'm sure a high-powered tube amp such as the AR 250SE or a VTL 250w amp would make the Radford spkrs sound much better than the MA50s (with all that "beautiful liquid midrange or the encompassing soundstage") - these are seriously expensive amps, compared to, say an ME850 or a Magtech.

 

Andy

 

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On 17/05/2021 at 11:41 PM, RCAJack said:

Congrats on these acquisitions!

 

You could tube roll the ECC81 and ECF82 fairly economically to tune the sound somewhat. Switching power valves will be a bigger investment! What about auditioning the SC22P (when it turns up) with the monoblocks to see how that affects the sound you’re getting? Could be a useful data point. 

Thanks @RCAJackill definitely test the SC22P when it arrives. 

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Posted (edited)

Lovely looking photos. You've already got a Mullard Mitcham CV4024 in there. 👍

 

Can you also share some photos of your speakers to help identify the model you own?

Edited by xlr8or
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18 minutes ago, xlr8or said:

Lovely looking photos. You've already got a Mullard Mitcham CV4024 in there. 👍

 

Can you also share some photos of your speakers to help identify the model you own?

These are my actual speakers but as photographed by the previous owner. I believe Kef B139, goodmans mid, Celestion hf1300 tweeter and hf2000 super tweeter. I think called Radford Studio Monitors. Thanks for your input 

2D6915F8-C9EB-41EC-992B-E978077C5155.jpeg

336ACB61-2872-45A0-9DE2-6D71F15389C5.jpeg

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It appears you have the same speakers as the ones shown below. If that's the case then they are 8-16 ohm nominal load speakers. The speaker below is circa 1967. I suspect your ones may be the same vintage imported from the UK by one of the previous owners.

 

Can you confirm if there are any similar labels or markings on the rear?

 

Edit: Yep, confirmed. You have these speakers, which are in fact 16 ohm nominal load speakers:

 

https://www.radiomuseum.org/r/radford_studio.html

 

What taps are available on the back of the MA50's? 4-8 ohm only?

 

Second Edit: I think you need the STA25 (even an STA15 will work) with 16 ohm taps to drive your 4-way studio speakers from the 1960's into the 1960's era of fabulous music. If you do this I'm coming over to your place regularly to listen. 😁

 

The MA50's are probably better suited to drive an 8 ohm nominal load speaker of the modern era that is designed for use with tube amps.

 

images.jpeg-34.jpg

 

images.jpeg-35.jpg

Edited by xlr8or
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11 hours ago, xlr8or said:

It appears you have the same speakers as the ones shown below. If that's the case then they are 8-16 ohm nominal load speakers. The speaker below is circa 1967. I suspect your ones may be the same vintage imported from the UK by one of the previous owners.

 

Can you confirm if there are any similar labels or markings on the rear?

 

Edit: Yep, confirmed. You have these speakers, which are in fact 16 ohm nominal load speakers:

 

https://www.radiomuseum.org/r/radford_studio.html

 

What taps are available on the back of the MA50's? 4-8 ohm only?

 

Second Edit: I think you need the STA25 (even an STA15 will work) with 16 ohm taps to drive your 4-way studio speakers from the 1960's into the 1960's era of fabulous music. If you do this I'm coming over to your place regularly to listen. 😁

 

The MA50's are probably better suited to drive an 8 ohm nominal load speaker of the modern era that is designed for use with tube amps.

 

images.jpeg-34.jpg

 

images.jpeg-35.jpg

3F53BFA0-B6CD-4ECD-9CCA-231FE1C05261.thumb.jpeg.cda34f9126ce391919fa5710175d8edb.jpegYes, same diagram, that is fantastic thanks. I had the STA 15 set to 8ohms, I’ll try it on 16 when I get it back. I’ve collected all parts to build a set of IMF TLS80, do you think the mono blocks could drive those nicely? Thanks again 

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