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TAFELRUNDE TIPS The speed regulation is meant to be a very fine tuning of the speed. With a base frequency 50 Hz: - the regulation at 50 mHz gives 0.1% change for every turn (50mHz / 50Hz = 50 mHz / 50,000mHz = 0.001 = 0.1%) - the regulation at 5 mHz gives 0.01% change for every turn (5mHz / 50Hz = 5 mHz / 50,000mHz = 0.0001 = 0.01%) We are sorry for the inconvenience of 45 RPM not working. This is caused by a malfunctionment of the external power supply. This constitutes of: 1 power supply board, 1 control board; 1 amplifier board. Basically it transform 220 VAC into DC, then it splits into two oscillating stages (one for 33 RPM and one for 45 RPM), then back again into one single amplifier driving the turntable at 115 VAC. The cause of the problem can be: bad connection of the flat cables inside; broken oscillator; broken quartz; broken PIC. Headshell offset was not factory set. In the instruction manuals there are instructions to carry out this adjustment: 1) Position the shell straight in relation to the arm tube (tighten the shell screw very slightly). The correct setting is the point on the template nearest the centre of the record (use the included template), obtained by sliding the base of the arm among the bars that enter in the rectangular plate. 2) Move the needle to the second point on the template (the point furthest from the centre of the record). At this point, the setting is not correct. To fix it, turn the shell until you have the correct setting at this point (tighten the shell screw again very slightly) 3) Move the needle to the first point, nearest the centre. At this point, the setting is not now correct. Then move the base of the arm along the bars which joins it with the pin again until you have the correct setting. 4) If you move the head to the point on the template furthest from the pin again, the situation in point 2 above returns. Turn the shell as described in point 2 above. Obviously, when we verify if the setting is correct, moving from the furthest point to the nearest one, and conversely, we must slightly move the template making the turntable rotating. Continue to repeat these two operations, moving from the point furthest from the point to nearest to the record, always moving the arm base when you check the head on the template at the point nearest to the centre of the record and modifying the angle between arm tube and shell when you check the head on the template furthest from the centre of the record. Repeat this operation 4/5 times. The setting is perfect at the two points of the template where no move is required (neither the distance between the record player pin and arm nor shell angle moving required). You now have the right setting for the angle of the shell and the correct distance between arm pin and record player pin. The head is now set. Boffins at Klimo in Germany. The following reply came from Luca in Italy, in direct response to your query. We were aware of this but perhaps should have explained it. The headphones chosen varied in price from £160 to £1,000. How is this a fair comparison given that cheaper headphones may have to make some compromises in comparison to a £1,000 pair of headphones (where it looks as though the compromises were made on its build/looks) Choices of music seemed a little strange - a mono recording from 1958, a Beatles recording and an 80’s recording. I have the same set up as the one the reviewer was using and switch between many headphones via an Earmax, X-Can V8 and V2 (Modded) both also with beefier power supplies and one of my Headphones, the K701 took a long time to settle. What the reviewer seems to be describing is how they sound out of the box. Did he also miss the ‘airiness’ that the 701’s produce. Had he worn in any of the headphones before launching into this article? I used to think that your magazine was more serious about hi fi than this. No measurements taken, just a reviewer and his rhetoric. Could the magazine please take headphones a little more seriously and ask someone with proper experience of them to do some fair reviews of like with like, the effects of output impedances on them, the impression of ‘space’ in the sound presentation, how each headphone has been designed to be used and make sure that they are fully ‘loosened’ by playing them for some time before reviewing?
A low impedance source does not interact with varying load impedance, which is why headphone amps have low output impedance, and why we used two headphone amps with low output impedance. Headphones have either a very high non-flat impedance, like the Sennheiser HD650s, which vary from 50 Ohms to 500 Ohms, or a lower but flat impedance of around 40 Ohms (all the others in the group) which does not react significantly with a low output impedance source. We measured impedance and frequency response but impedance is of little consequence for the reasons stated and frequency response strictly non-flat unless a dummy head is used, which we do not have.
Sennheiser HD650 frequency response. Bass rolls off because they are not on-head (i.e. measured in open conditions). Sennheiser HD650 impedance, not flat but very high at 500 Ohms maximum, and 50 Ohms minimum. The review was a broad look across the price spectrum, an approach that is useful for spotting bargains. Finally, with transducers such as loudspeakers and headphones, there are so many variables that it is impossible to make any judgement of them except subjectively. We use the widest range of the most sophisticated measurements with loudspeakers, including swept distortion spectrums, decay spectrums and much more, measurements beyond the capabilities of many manufacturers, yet still we describe them in subjective terms. The same applies to headphones. So at the end of the day it is one person’s judgement. In this case that person was musically experienced, uses headphones, and used low output impedance sources to avoid interaction. The headphones had been measured too, to ensure they worked normally. NK The reason we routinely run a ‘spread’ of prices in group tests is to give a sense of perspective onto the subject. Obviously, we are not expecting the £160 phones to be better than the £1,000 ones, but an interesting question is ‘how much better is the most expensive than the cheapest?’ I think a ‘we tell you the best £1,000 headphone’-type group test is too narrow in its remit, whereas our approach throws open the possibility of a surprise or an upset; sometimes the cheapest isn’t the worst. Again, different types were used, to give a sense of what is possible with different engineering philosophies. Paul very accurately conveyed the difference between the Stax electrostatics and the other dynamic headphones, I thought. When auditioning, the music wasn’t limited to just that stated in the test; Paul chose to single out the tracks he did for the purposes of brevity in the write-up because again they epitomised key differences between the ‘phones. Paul had the headphones for over six weeks before he filed his report, so yes, he did have plenty of time to bed them all in, and - importantly - time to experiment to see which ones suited the valve buffered Musical Fidelity phono stage and which suited the ANT Audio Amber 3T solid-state stage. |