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April 2012 Issue - page 3

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April 2012 Issue
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IMPURITY

I have over the years been an avid reader of Hi-Fi World, primarily because of the balanced and informative reviews over a wide range of equipment prices. Those reviews plus my own listening have resulted in the following system, which until about one month ago was entirely vinyl based. Having started on the hi-fi trail some 20 odd years ago as an impoverished student I have worked my way from an STD 305M, Pink Triangle PT Too, Michell Orbe onto one of Rafael Todes castaways – an Acoustic Signature Challenger. Please let him know it’s continuing to provide excellent service!

Arms (Rega, SME, Origin Live) have come and gone over the years, but a Jeff Spall Audiomods arm with VTA adjuster currently resides on the turntable – which I happen to think is both excellent value for money, but also a great listen. My cartridge is a lowly, but fun Dynavector 10X5. At some point in the future it will be replaced by a Moving Coil – probably the Clearaudio Concept MC you reviewed favourably.


Phono stage is the Clearaudio Balance + with Accuvue battery supply, which I think is excellent. Incredibly quiet and with full balanced ins and outs – though that’s another upgrade path altogether!


Loudspeakers are Martin Logan Purity, which work surprisingly well in my smallish 5m x 4m front room. I took a bit of a gamble on these as I realise they ideally need a larger room to breathe properly, but placed 3 feet from the front wall they work very well. Even my wife likes them and noticed the improvement!


Now for the subject of my query. I originally drove the Purities via a pair of Trichord Alecto mono-block amps via long speaker cable (QED XT Anniversary bi-wire), but having sold the Alectos, and with the intention of going down a purer route i.e. phono stage driving the Purities directly via long (8m) interconnects (Wireworld Solstice) I find the sound to be veiled and duller in comparison, which is not to my preference. I like a transparent, balanced, open sound with imaging which can exploit the Purities capabilities.


Now I realise the Wireworld interconnect is a relatively cheap cable and I could look to replace it with perhaps the DNM solid core, but my question is slightly more fundamental. Are the Purities better driven via a long interconnect or via long speaker cable – my ears tell me the latter, but I appreciate I am not comparing apples with apples.


Just to compound matters further, I finally relented and purchased my first CD player – a Shanling MC 30 – for occasional CD, Tuner, and Hard Disk (IPod or similar) based music. I have to say it is a fantastic bit of kit for the money and sounds perfectly acceptable (though not as realistic or satisfying as the turntable) through the Purities via the QED speaker cable. Veiled and duller via the Wireworld interconnect.


So, in my ideal minimalist world I would like to wire my turntable through the Shanling’s auxiliary input and then connect the Shanling to the Purities via long interconnect or speaker cable – depending on your advice. Given that this is likely to cost close to a £1000 for some 10m of cabling your advice would be greatly appreciated! I am of course assuming here that the Shanling’s single ended amp is good enough to do justice to my phono-stage?


An alternative strategy would be to connect the phono-stage directly to the Purities via a long interconnect and the Shanling to the Purities via long speaker cable, as the Purities can accommodate both sets of cables simultaneously. Martin Logan warn against using both sets of connectors, however whilst both sets of cabling would be engaged I would be listening to the Shanling or the Turntable, but never both at the same time!!

I hope the above makes some sense to you and that you are able to shed some light on the problem.


One final question. Would you kindly recommend an indoor FM aerial for the Shanling. I live in Southgate and get pretty good reception via Ally Pally.

Many thanks for your advice, and keep up the good work with the magazine.

Regards,

Scobie Alvis

 

 

martin-logan-purity

Martin Logan Purity loudspeakers have two inputs, Line and Loudspeaker. Both feed an internal amplifier that drives the woofer and the electrostatic panel. Long cables to the Line input raise matching issues.

 

It sounds very much as if the long 8 metre run from preamp to each loudspeaker offers too great a capacitive load for the output impedance of the preamp. This is rolling off high frequencies, producing dull treble. It is why the Alectos, with their very low output impedance, did not sound dull.

You could check this by making up or buying some short interconnects of 1-2m and connecting them to the loudspeakers to see if the balance returns to normal. Because 1nF, a typical capacitance figure for 8m of cable,  exhibits 8k Ohm reactance at 20kHz either the cable is very capacitive or the output impedance unduly high, suggesting a different preamp, or cable, or both, would not suffer such dulness. This suggests you should listen to alternatives if possible. You seem to have an unfortunate set of conditions there.


In our review of the Purity in the September 2008 issue we do note that the internal amplifier drives both subwoofer and electrostatic panel and that the loudspeaker input is simply attenuated down before going through the internal amp, so you are right that the line input is best used, as we note in the review. This being the case you are probably best off not using the Shanling power amp if you can avoid it.


Ally Pally doesn’t transmit VHF/FM as far as I am aware; the BBC’s list of English Radio transmitters (http://www.bbc.co.uk/reception/transmitters/radio/england_fm.shtml#Wrotham) does not list it. It transmits TV and DAB only I believe. This is not good news for you because it means you have a nearby transmitter, one mile due South of you, that you need to reject, not accept. But you have to point the aerial South to get commercial VHF/FM stations from Crystal Palace, and South East for BBC national stations from the Wrotham transmitter, Kent – see our map.


You should ideally use a highly tuned VHF/FM aerial able to attenuate out-of-band TV and DAB signals in this role, meaning a large multi-element array. Getting decent VHF/FM in Southgate doesn’t look easy to me, from inspecting maps and looking at BBC transmitter lists. I live in North London too and have a massive array on my roof to get a decent signal from Wrotham, but luckily Ally Pally isn’t near enough to be a nuisance. Finding a knowledgeable and experienced local aerial fitter would be a help.


It may just be you will get best results by swinging the aerial to point away from Ally Pally in the hope of picking up a distant VHF/FM repeat transmitter. Search the BBC’s on line transmitter lists and maps to find one! NK

 

 

 

london-map

 

Here's your geographical problem: Alexandra Palace transmitter comes between you and the transmitters you really, really want – Crystal Palace (or Croydon) and distant Wrotham, all of which serve London. Our map is to scale.


FOGGY SOUND

As your publication has been most helpful in the past regarding my numerous queries and letters, I thought I would ask your advice once more. My system is now pretty much in place. it is a Townshend Rock Reference turntable SME V arm, Transfiguration AF-1 cartridge (looks OK at 60 x MAG on Stylus Tip), I also have a substitute Ortofon MC-2000, so I can check my fault with this perhaps.


Quicksilver Full Function preamplifier, Quicksilver V4 Monoblocks, Celestion A3 speakers. I use an ALLNIC Phono (new) Stage H1200 Phono Stage into a Line Input of the preamp. I had a step up MC transformer but it suffered from hum, so I went for this alternative.

This system seems to have lost its high frequency response and when listened to it sounds like there is a layer of fog in front the detail, to use a cliche; it is like listening through a veil. Bass response is very good, mid is good also.


I wondered about valve change outs on the old preamp as I have many spares, but also wondered about the main capacitor change outs, as these will be of a certain vintage. Its one of these. Main CAPS also shown. However, I am not really sure if this solves the problem as I am not sure exactly what the CAPS do in terms of the extremes of frequency response.


I do have a considerable amount of all round engineering knowledge and I am dashed handy with a soldering iron if need be.

Your advice would be greatly appreciated.

Scott Ewan (WGPSN)

 

 

 

quicksilver-amp

 

Internal view of Scott Ewan's Quicksilver amplifier.


 

I am a bit confused about your system here Ewan, and exactly what capacitors you wish to change, in what preamp. Surely you need to do a little detective work first, do you not?


I am very suspicious about your new Allnic phono preamp. You do not say if all was apparently correct before, if you could tell when suffering hum that is. I suspect there may be a matching problem between here and preamp, or it does not suit the Transfiguration cartridge, although MC cartridges have such low output impedance (a few ohms DCR) that they will feed just about anything. The only thing some will not feed is a step up transformer with a very high step up ratio, meaning an ultra low input impedance (the Allnic may have a step up transformer inside).


If the cartridge has developed a problem, or is a poor match, then swapping to your Ortofon MC-2000 would show this up. Did you buy the Allnic from a dealer who could lend you an alternative? You really do need to isolate the culprit in your system and I am sorry to say I cannot be certain what it is at a distance. NK



 

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