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April 2012 Issue - page 4

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April 2012 Issue
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AUDIO RECORDING

Some years ago when the C60 type cassette was considered an acceptable recording/replay medium I owned a small (150mm x100mm x 50mm!) portable recorder, which I think was manufactured by Sanyo. The plus point was that an external microphone could be used for enhanced quality and the benefits were evident when played back through the hi-fi system.


The mini cassette is still widely used for dictation today, but there are digital equivalents available. My question is whether the latter, when used with an external microphone, can produce the same or enhanced quality relative to my original C60 cassette machine of yesteryear, or is there a better way forward?


As a foot note, a colleague used to take a small recorder such as mine on his travels feeling that sounds and voices were more evocative than pictures. Modern digital cameras now try to capitalise on this thinking with “video clips” but the sound in hi-fi terms is relatively basic.

I would appreciate your comments and suggestions.

With thanks.

Glyn Wreakes

 

 

korg-mr2

The Korg MR-2 will record super high resolution audio in PCM (24/192) or DSD (1-bit). A great unit if you want good quality live sound.

 


The market is more diverse today and perhaps a little bit more confusing and impenetrable as a result. There’s no end of dictation machines but they are not all so easy to use. The art of recording seems to have vanished from hi-fidelity, heavens knows why. The pro market offers an interesting range of products, including hand held audio recorders of quality that typically start at £100 and run up to £500 or so. I suggest you go to www.studiospares.com and take a look at portable recorders. Most have on-board microphones to record speech, vocals or instruments live, recording to USB or SD card at up to 24/192 resolution. Very interesting is the Korg MR-2 that records in PCM at up to 24/192 and it can record in 1-bit DSD code as used on SACD. Price is £560.


An important feature on digital recorders is the peak limiter or compressor. Where old analogue recorders overloaded gently, digital recorders do not – and they must be kept out of overload to avoid severe distortion. Even with 144dB of dynamic range available from 24bit resolution it is still difficult. Note also that many of these recorders record to SD card, but few hi-fi media players will play back from SD card; most work with USB memory sticks. There’s something of a gap here.


Modern video cameras prioritise video, not audio, and 16bit at 48kHz sample rate, stereo, or Dolby surround sound is about as good as it gets. The on-board mics are not so clever either, until you reach semi pro models with external mics sitting on top and these are too bulky and expensive for audio recording alone. Compare the Canon HF G10 with its semi-pro version the XA10 to see what I mean. NK


IMPEDANCE PROBLEM

My question concerns valve amplifiers and their ability to work well with relatively low impedance speakers, since I’ve been told that this can be a problem. My speakers are Elac FS-207a with an impedance curve which drops to 3.4 Ohm at 220 Hz. Would it be problematic in any way – or not desirable – to use for instance, an Icon Audio Stereo 40 III to drive these speakers?

Thank you in advance,

Kind regards,

Nils Olsen,

Copenhagen

 

 

 

icon-audio-stereo40mk3

The 4 Ohm output of a valve amplifier will easily drive 3 Ohm loudspeakers.


 

Hi Nils. Valve amplifiers handle low loads with ease, providing they have  4 Ohm output terminals. As Icon Audio note with the Stereo 40 it works down to 3 Ohms without difficulty. Where transistors will break down quickly, like a fuse, if too much current is drawn through them, valves will not. They just get a little hotter and distortion rises. Valves are very robust in this sense and will endure the output terminals being shorted for many seconds. A 4 Ohm tap valve amp will match and drive a low impedance loudspeaker better than a transistor amp in truth. With the latter distortion rises into a low load as current draw goes up and, ultimately, the output transistors will fail or – most likely these days – output current limiting protection circuits will act. These may “chatter” or just turn the amp off in disgust! NK


IDLE PRAISE

I have finally finished my Commonwealth Electronics Turntable. I would not have even started the project if Hi-Fi World had not highlighted how good idlers can be properly plinthed (my plinth is 32kgs). At first switch on after all the work I was more than a bit nervous it might sound a bit naff, but I need not have worried as right from the off not properly set up it sounded amazing with no rumble at all and amazing timing and the bass is just amazing!! Anyway thanks for the guidance.


I recently bought a DNM series 2a preamp from a friend, it was made in 1984 I think, and apart a smoking cap at first switch on (since replaced them all) it sounds really nice, which was a surprise for such an old preamp. I have had a Google for info on it and found very, very little indeed, not even that many seem to go for sale. Just a thought, but IMO it would make a good old World article any chance? I would lend you mine, but being here in Aus it is a bit far away.

Regards,

Chris Allman

Queensland, Australia


 

 

aus-turntable

 

Chris Allman's massive Commonwealth Electronics turntable, so heavy it prevents Australia floating away!




 

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