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November 2010 issue - Page 4

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November 2010 issue
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CASSETTE COLLECTOR

I have just finished putting my old cassettes into genre and alphabetical order. I then played some live broadcasts of choral work taken from Radio 3 using my Nytech receiver. I was absolutely blown away with the naturalness and delicacy of the recordings. Then I noticed that the cassette player had a headphone socket. That’s my late night listening sorted for a while. Well, until I can afford decent headphones and ‘amp.

Ray Spink

 

Rock on, Ray! DP

 

SEE THE LIGHT

What a wonderful discovery this magazine has been. After years of reading What Hi-Fi (great though it is) I’m not sure it really caters for the real hi-fi lover, and certainly not for classic hi-fi lovers. After reading the July issue feature on Pioneer’s magnificent SA9500 amplifier it brought back not only the first memories of my father’s brand new Technics system of the early eighties with more lights, switches and knobs than a Concorde cockpit, but of the many classic hi-fi components I have owned since (the SA9500 being one of them).


Now don’t get me wrong, my current Audiolab 8000 preamp., 8000 CD and 8000 monoblocs running into Monitor Audio’s RS1 and my beloved Technics SL-1200Mk11 and Arcam T32 tuner make a wonderful sound, but where are my fluorescent peak meters, my backlit tuning dial and weighted tuning knob, not to mention my backlit VU meters? Now, I’m not saying that this classic equipment is better sounding than modern hi-fi, only a direct comparison would decide that (maybe that’s an interesting feature for Hi-Fi World to consider) but owning such kit that was also a joy to look at, the fantastic build and the features were all part of it. At the time of writing this I noticed a Pioneer A80 150W monster of an amp for a mere £175 on eBay. Now where could you buy an amp of that build and power output for that money? I guess what I’m trying to say is, we all listen to classic rock, classic soul or rock-n-roll, people buy classic cars, so why shouldn’t we still enjoy classic hi-fi?

Jason Hall

 

Indeed, and why not? DP

 

BAD VOLUME

I have the original PS1 version of the Icon Audio PS1.2 Signature which won your phono stage group test. Tony Bolton preferred the Icon when connected directly into his power amplifiers, making use of its onboard volume control. I too initially used the PS1 to drive my Leak Stereo 20 and found that I rarely needed to use the volume control beyond the 10 o’clock position to achieve good sound levels.


I then tried the PS1 connected to my preamp which is a passive design by Classique Sounds, built into the casework of an original Leak Point One Stereo. Tony Bolton reviewed it favourably back in 2007 and I ended up buying the review sample. With this combination the Icon can be run at full volume and I have found this gives superior sound quality, with a more extended top end and improved depth of image, providing a more involving listening experience. I was prepared for a change in sound quality but did not expect to hear an improvement.


As good as the passive preamp is - and it is very good - I have always suspected that it was the Icon running flat out which caused this improvement. In the Measured Performance section of the PS1.2 Signature review, Noel mentions that a volume control impedance matching problem in earlier models has been cured, so now frequency response changes little with level. Could he elaborate on this point? I would be interested to know how much the frequency response of earlier models differed with changes in volume as this might explain my subjective findings.


The Mono switch is only mentioned in passing during the review but it’s worth pointing out that besides giving better focus when playing mono records it also eliminates unwanted groove noise, particularly noticeable on 45s from the 1950s and 1960s.

John Pickford

 

pioneer-sa-9500

 

Pioneer's SA9500 amplifier, a beauty from the 1970s.

Hi John. How a volume control degrades frequency response at half volume is a trifle technical, if simple in terms of circuit design. It is a ‘hidden’ phenomenon many designers overlook however, so is not an uncommon problem.


A circuit analysis using LTSpice is shown here, together with the resultant frequency response. The designer simply has to ensure the volume control slider does not see a capacitive load, to avoid the problem.


I recall frequency response was around -2dB down at 20kHz, easily enough to be audible. I also suspect the volume control was not a super high quality audio type, like an Alps Blue, so when at half volume it had most sonic impact and produced general degradation. It almost certainly explains what you heard.

Thanks for the Mono switch observation. Tony Bolton makes this point as well: a Mono switch usefully cancels groove noise. NK

 

volume-circuit1

graph3

 

A 10k volume control set half way offers maximum source impedance. Capacitance seen by the output slider will roll down treble. Diagram and analysis by LTSpice.

 

LOWTHER LABOURS

I hope you could advise me. I have a pair of Lowther Acousta 115 folded horn speakers with DX3 drivers. One of the drive units was damaged so bad it was replaced. Simple enough. When I replaced the driver, I noticed that the internal cable looked like the original; some fifty year old bell wire!!! So this is my question/ dilemma to which an answer would most appreciated:


Is it worth replacing the internal cable for a modern oxygen free one and replacing the binding posts for gold plated ones?

 

My dilemma - after speaking to Lowther they advised me to replace the cable by attaching the new cable to the old one and pulling it through; this represents some issues for me. Firstly and most importantly, if it undoes while threading it through the two 180 degree corners of the horn, well, that’s the end of my speaker - cable lost forever!!!!

 

Secondly, for some reason, Lowther can’t tell me if the cable was nailed in throughout the wood work or not. I understand that the craftsman that made the speaker are probably dead but that’s not the point, they still have the plans to which they would have followed. If the internal cable is dangling loose then it should be a straight forward job but surely a manufacture of this calibre would have nailed it in place, due to bass frequencies vibrating the cable. Surely, you would hear that? I put this to Lowther and the response was - if it nailed in just drill a hole through the cabinet! Now, wouldn’t that ruin the acoustics????

After going through all that, will I actually hear the difference? Please help me as I do not want to tackle this without some professional advice due to the fact there is nothing actually wrong with them, in fact they sound excellent but can I better them?

Jonathan Highman

 

We do not know about the construction of your Lowthers and can only offer general advice.


If you are able to remove the drivers to access their terminals then can you try running them with a temporary substitute cable jury rigged from the front, to see whether any improvement is going to be worthwhile? It seems likely it will to us, but Lowthers don’t draw much current and gains might be less than expected. It’s difficult to say.

Just pulling on the cable would tell if it is free, or attached, would it not?  You may like to consider poking a stiff springy wire through the loudspeaker, perhaps piano wire, to see if it follows the same path as the bell wire.


Rather than pulling heavy weight new cable through, dragged by old bell wire, I suggest you pull through strong, flexible nylon cord first. DIY shops have this sort of thing. Then use the cord to drag through the new wire. Good luck! NK



 

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