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I've been meaning to get a test records. How do you actually use them? Testing by ear?

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Overhang, offset angle, vertical tracking angle, tonearm effective moving mass, vertical tracking force and lateral anti-skating force ALL affect how a cartridge sounds. Making judgements about how different cartridges sound when auditioned without knowing all of the parameters is fraught.

 

What!!...No SRA or Azimuth mentioned.... :P  :P

 

Tase.

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I've been meaning to get a test records. How do you actually use them? Testing by ear?

 

Which ever test record you buy, read the instructions on how to use it. Most test records are designed to allow evaluation 'by ear' however a lot of knowledge is required before you can 'know' what to listen for. Be warned that errors in cartridge alignment can be interactive; it is easy to draw incorrect conclusions. 

 

I use test records in conjunction with more than forty years of experience, a dual channel CRO, a frequency meter, an accurate level meter, a wow and flutter meter, electronic and mechanical stethoscopes, and a specially designed channel nulling transformer, amongst other tools. I use a personally hot-rodded battery operated preamplifier, headphone amplifier and high end Audio Technica in-ear buds so I can exclude ambient noise and focus on the noise floor of the system under test and can precisely hear phasing errors between the channels. And because no test record is perfect, or has every diagnostic tool required, I have several. For example, both the "Hi-Fi News Analogue Test LP" and "Professional Test Record" do not have a 3150 Hz track for testing speed and wow and flutter, the "Ultimate Analogue Test LP" does, but it has its own built in wow and flutter(!) so for that that test I use the 3150 Hz track on the "Clearaudio Trackability Test Record" which is better but still not perfect.

 

The last test I perform is to listen to a well known and revealing recording. I often do this while I am doing something else, like writing the service report for the turntable. I find that when relaxed and not concentrating on listening for faults, I get a more accurate subjective impression of how good the turntable is performing. I also use this technique for evaluating loudspeakers sometimes. The final test is feedback from the owner of the turntable a few weeks down the track, often measured in bottles of vintage wine  :hiccup

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 Testing by ear?

 

.....Is the most sensitive instrument there is IMO 

 

Training once self to evaluate good sound can take an age though, however as John says above being in a relaxed state is a must not concentrating and letting it all flow in is the best method I have found....

If I have a had a bad day for example I would not contemplate evaluation........in any case I find its best to listen early in the morning at a moderate level.

 

Cheers Tase.

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For me the thought of putting the tip of that miniscule diamond right in "the sweet spot" with all the variations that are available must be something that has to learned and earned through practice, trial and error.

Like your first par, birdie and then eagle. I've had many of the aforementioned but never a hole in one!

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@@Newman, @@Owen Y, I put this post this here rather than the Nasotec forum it was previously being discussed in as it was off topic there however it i relevant to this thread. My own experiments have shown that belts make a huge difference to turntable performance with the potential to improve speed stability, reduce wow and flutter, and reduce noise from both the motor and environment. The following is from an engineering paper from Basis Audio, a manufacturer of very high end turntables, and confirms the assertions I made previously:

 

 

Belt driven turntables’ chief advantage over direct drive, idler wheel drive, and other drive systems is isolation from motor noise. The belt can be modelled as a classic mass-spring-damper system. Extensible, highly damped materials offer the greatest isolation from motor cogging and noise as these materials bring spring and damping properties to the drive system.

 

Careful analysis of flexible drive belts will show that the effective radius of a pulley is the measurement from the center of the pulley to the neutral axis of the flexible belt (plane in the belt where stress is zero as it is curved around the pulley), which is near, but not exactly at, the center of the belt. Simply stated, the thickness of the belt factors into the calculation of the drive ratio of the pulley and platter. The ramifications of this are numerous:

 

  1. Different thickness belts will cause the driven pulley (platter) to run at different speeds.
  2. Changes in thickness along the length of a belt will modulate the speed of the platter.
  3. Round cross-section belts will attempt to roll in order to achieve the lowest potential energy state, in addition to their scuffing action and increased propensity to hunt.
  4. Any splice in a belt changes the effective radius as well as stiffness, causing spikes in the critical measured parameters of wow, flutter, and drift.

 

The ultimate speed stability cannot be achieved without near perfection in the uniformity of thickness along the length of a drive belt. Limitations in casting techniques of rubber belts places a severe compromise in the speed stability in turntables using belts in the as-cast condition. To achieve more critical tolerances and greater precision a grinding process must be employed.

 

Edit: I found a working link for the paper: http://www.basisaudio.com/docs/acs_sbt_specs.pdf

Edited by johnmath

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going back to discussion of using a low MC cart what kind of performance does MC Pre Preamp gives compared to a step up transformer. At the moment I'm considering to make a boozehound labs phono pre pre http://boozhoundlabs.com/products/bhl-audio-jfet-moving-coil-pre-preamp-phono-kit-2sk170 which is known to be a great MC Pre Preamp

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going back to discussion of using a low MC cart what kind of performance does MC Pre Preamp gives compared to a step up transformer. At the moment I'm considering to make a boozehound labs phono pre pre http://boozhoundlabs.com/products/bhl-audio-jfet-moving-coil-pre-preamp-phono-kit-2sk170 which is known to be a great MC Pre Preamp

 

A SUT offers potentially "noiseless" gain, but may introduce noise and distortion characteristic of transformers. On the other hand, an MC preamp potentially offers more signal linearity, but may add more thermal noise (transistor noise). A good SUT will be better than a poor MC preamp, and a good MC preamp will be better than a poor SUT.

 

It may be that one approach suits your particular setup better than the other. The best option is SIAS (suck it and see). Expect to spend similar amounts of money either way.

Edited by johnmath

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going back to discussion of using a low MC cart what kind of performance does MC Pre Preamp gives compared to a step up transformer.

 

John has provided a good summary.  :thumb:

 

At the moment I'm considering to make a boozehound labs phono pre pre http://boozhoundlabs.com/products/bhl-audio-jfet-moving-coil-pre-preamp-phono-kit-2sk170 which is known to be a great MC Pre Preamp

 

I prefer using a 'head amp' (MC pre pre) to using a SUT and the BHL one looks like it should do the trick - though I would recommend powering it with a 12v SLA, not alkaline batteries, for best sound.  But then of course, you have to rig up a charging mechanism.

 

Just one thing to be aware of is that cart loading will now take place on the input of the head amp - not your phono stage.  According to the manual, this is R2 - and they supply 100ohm resistors for this.  This may or may not be optimum for your DL110 - and whatever LOMC you might buy in the future - so what I suggest a better idea is to (for each channel):

  • leave out R2 from the PCB, and
  • instead have a 2nd input RCA in parallel with the main one (which the phono cable is plugged into) so you can insert a "load plug" - ie. an RCA plug with a resistor soldered across it.  That way, you can make up a variety of pairs of load plugs and experiment with which loading optimises the sound of the DL110.

 

Regards,

 

Andy

 

PS:  I would recommend Hugh Dean's "Paris" head amp but I think he no longer offers it?

Edited by andyr

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Given that that thread agrees with me, you should have written that comment to me. ;)  Then I would have responded dismissively with something like, "yeah, you and me both (smirk)". Actually, I wouldn't do that.

 

 

@@Newman, @@Owen Y, I put this post this here rather than the Nasotec forum it was previously being discussed in as it was off topic there however it i relevant to this thread. My own experiments have shown that belts make a huge difference to turntable performance with the potential to improve speed stability, reduce wow and flutter, and reduce noise from both the motor and environment. The following is from an engineering paper from Basis Audio, a manufacturer of very high end turntables, and confirms the assertions I made previously:

 

 

Belt driven turntables’ chief advantage over direct drive, idler wheel drive, and other drive systems is isolation from motor noise. The belt can be modelled as a classic mass-spring-damper system. Extensible, highly damped materials offer the greatest isolation from motor cogging and noise as these materials bring spring and damping properties to the drive system.

 

Careful analysis of flexible drive belts will show that the effective radius of a pulley is the measurement from the center of the pulley to the neutral axis of the flexible belt (plane in the belt where stress is zero as it is curved around the pulley), which is near, but not exactly at, the center of the belt. Simply stated, the thickness of the belt factors into the calculation of the drive ratio of the pulley and platter. The ramifications of this are numerous:

 

  1. Different thickness belts will cause the driven pulley (platter) to run at different speeds.
  2. Changes in thickness along the length of a belt will modulate the speed of the platter.
  3. Round cross-section belts will attempt to roll in order to achieve the lowest potential energy state, in addition to their scuffing action and increased propensity to hunt.
  4. Any splice in a belt changes the effective radius as well as stiffness, causing spikes in the critical measured parameters of wow, flutter, and drift.

 

The ultimate speed stability cannot be achieved without near perfection in the uniformity of thickness along the length of a drive belt. Limitations in casting techniques of rubber belts places a severe compromise in the speed stability in turntables using belts in the as-cast condition. To achieve more critical tolerances and greater precision a grinding process must be employed.

 

Edit: I found a working link for the paper: http://www.basisaudio.com/docs/acs_sbt_specs.pdf

 

@@johnmath, I don't know what your generic thoughts are about white papers, but I don't put a lot of store in them if they don't conform with engineering texts. So, I'll trump your very-high-end turntable manufacturer white paper reference with a genuine engineering reference, Theory of Machines and Mechanisms - II by Phakatkar, which agrees generically with the above but adds an additional factor by stating, "Owing to the slippage and extensibility, belt drives have a variable velocity ratio." What the bit in italics means is that for a completely inextensible (unstretchable) belt the effective radius is different than for an easy-to-stretch belt. For an inextensible belt (of uniform material property throughout its cross section) the effective radius equals the pulley radius plus half the belt thickness. But as the material increases in extensibility, the effective radius moves steadily inwards until with a completely floppy/stretchy belt it is the same as the pulley radius.

 

Flat turntable belts are completely floppy belts.

 

By way of illustration, consider a belt made of very stretchy rubber but coated on one side with a layer of thin steel, which bends effortlessly but will not stretch. To use the terminology of the basisaudio writer, the "neutral axis of the flexible belt (plane in the belt where stress is zero as it is curved around the pulley)" varies dramatically depending on whether you mount the belt with steel on the outside or on the inside. With steel on the outside, the effective radius equals pulley radius plus the full belt thickness. With steel on the inside, the effective radius equals pulley radius. 

 

When a flat turntable soft rubber belt wraps around a pulley or sub/platter, it effectively assumes the pulley as that bonded steel layer in the above illustration. It doesn't slip, it just stretches (and stresses) as required, and the pulley surface is the neutral axis.

 

Hope this helps (a lot more than, say, a smarmy put-down).

 

[edit: @@Owen Y in case you are still interested]

Edited by Newman

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Flat turntable belts are completely floppy belts.

 

On the contrary flat and round turntable belts are not 'floppy' belts. both types of belt barely change their thickness or diameter or thickness as they go around the pulley, and the neutral layer remains almost exactly at the middle of the belt.

 

The trouble with mechanical engineering texts that focus on the design of power transmission by pulleys is that don't consider the special case of a turntable, which has two fundamental differences. Firstly in a normal mechanical situation where 'straight' belts are used, there relationship between input and output is non-critical. Where the gear ratio is critical, toothed belts are used. For a non-critical application, the approximation of the ration calculated by pulley diameters and assuming an infinitely thin belt is more than accurate enough, but for a turntable it is not.

 

Secondly, turntable belts are not tensioned for maximum power delivery, which means they are typically not stretched any more than is needed to provide enough friction to transmit the meagre amount of power required to rotation a low friction platter. The more a belt is stretched, the closer the neutral layer will move to the pulley surface. In a turntable, the neutral layer stay very close to the centreline of the belt, and that is why the effective pulley diameter is the pulley diameter plus the belt diameter or belt thickness for o-ring and flat belts respectively. In high power transmission systems (such as a fan belt) the neutral layer is defined by a non-elastic layer of fibres embedded in the belt and the effective pulley diameter is the diameter at contact plus twice the height of the constraining layer above the pulley surface.

 

Hope this helps (a lot more than, say, a smarmy put-down).

 

As much as might like to think otherwise, the smiley on my post was not directed at you; it was addressing a different post. Why so sensitive?

 

 

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Maybe a 'white paper' isn't a definitive text, but I think a 'white paper' based on years of research that focusses on a specific topic may add some insight on that specific topic, information that might be missing in a generalised text that deals with different circumstances.

 

But what do engineering texts have to say on the topic of belt drive ratios? From "Elements of Mechanism", written by Peter Schamb, Professor of Machine Design (Retired), Massachusetts Institute of Technology, Allyne E. Merrill, Professor of Mechanism, Massachusetts Institute of Technology, and Walter H James, Associate Professor in the Department of Mechanical Engineering, Massachusetts Institute of Technology, and printed in 1905:

 

There is a section between inner and outer which is neither stretched nor compressed and the name neutral section may be given to this part of the belt. In the case of a flat belt the neutral section may be assumed to be half way between the outer and inner surfaces. An imaginary cylindrical surface around the pulley, to which the neutral section of the belt is tangent, is the pitch surface of the pulley, the radius of this being the effective radius of the pulley. A line in the neutral section of the belt at the center of its width is the line of connection between two pulleys and is tangent to the pitch surfaces, and coincides with a line in each pitch surface known as the pitch line. 

 
The text then gives an example of the gear ratio with the belt thickness in the equation.
 
Jumping forward to 1944, the International Textbook Company published a textbook on belt drives titled "Pulleys and Belting" with the following text:
 
The formulas in Art. 4 are based on the assumption that the thickness of the belt is so small in comparison with the pulley diameter that it can be negleced. Actually, only the centre line of the belt has a constant speed, v; hence, if t denotes the thickness of belt, the effective radii are Ra+½t and Rb+½t, and the effective diameters are Da+t and Db+t, respectively.
 
Jump forward to 2003 and Dr James B. Calvert, Associate Professor of Engineering, University of Denver, has this in his course materials:
 
The effective diameter of a pulley in a band drive is the actual diameter plus the thickness of the band. The correction in adding the thickness of the band is usually negligible, however. 
 
The even more contemporary "Theory of Mechanisms and Machines" by C.S Sharma and Kamlesh Purohit, was published in 2006 and includes this passage:
 
When an unstretched* belt is wrapped around the two pulleys located at a certain distance apart, the outer and inner faces of the belt are subjected to tension and compression stresses respectively. In between these two faces, there is a neutral section which remains neutral and is free from either type of stress. While analysing a belt drive the effective radius of pulley is taken at this neutral section which is the sum of the radius of the pulley and half of the belt thickness.    (*The effect of stretching the belt is to move the neutral layer closer to the pulley surface by a small factor.)
 
Then follows an illustration showing the effective radius of a pulley halfway through its associated belt.
 
So nothing has changed in 100 years of engineering texts that show there is a relationship between belt thickness and gear ratio in belt drives, confirming the turntable 'white paper' and my empirical tests.
 
I sincerely hope that this post puts to death once and for all the idea that the speed of belt drive turntables is not affected by drive belt thickness!
Edited by johnmath

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On the contrary flat and round turntable belts are not 'floppy' belts. both types of belt barely change their thickness or diameter or thickness as they go around the pulley, and the neutral layer remains almost exactly at the middle of the belt.

 

I explained why the axis moves, and where to.

 

The trouble with mechanical engineering texts that focus on the design of power transmission by pulleys is that don't consider the special case of a turntable, which has two fundamental differences.

 

Correct. So I ignored those sections and found the relevant point. Saved you some time.

 

Secondly, turntable belts are not tensioned for maximum power delivery, which means they are typically not stretched any more than is needed to provide enough friction to transmit the meagre amount of power required to rotation a low friction platter.

 

I never said they were. My explanation does not rely on the belt's tension to be relevant.

 

The more a belt is stretched, the closer the neutral layer will move to the pulley surface. In a turntable, the neutral layer stay very close to the centreline of the belt,

 

No it doesn't, as I explained, and as Mr Anon Basisaudio explained, the neutral axis has no 'stress' (I would have preferred that he said strain). Which point on the cross-section of a TT belt has no stress/strain? I have answered this.

 

 

 

Maybe a 'white paper' isn't a definitive text, but I think a 'white paper' based on years of research that focusses on a specific topic may add some insight on that specific topic, information that might be missing in a generalised text that deals with different circumstances.

 

It certainly might, but not in this case. That's the trouble with white papers: wheat and chaff.

 

But what do engineering texts have to say on the topic of belt drive ratios? From "Elements of Mechanism", written by Peter Schamb, Professor of Machine Design (Retired), Massachusetts Institute of Technology, Allyne E. Merrill, Professor of Mechanism, Massachusetts Institute of Technology, and Walter H James, Associate Professor in the Department of Mechanical Engineering, Massachusetts Institute of Technology, and printed in 1905:

 

There is a section between inner and outer which is neither stretched nor compressed and the name neutral section may be given to this part of the belt. In the case of a flat belt the neutral section may be assumed to be half way between the outer and inner surfaces. An imaginary cylindrical surface around the pulley, to which the neutral section of the belt is tangent, is the pitch surface of the pulley, the radius of this being the effective radius of the pulley. A line in the neutral section of the belt at the center of its width is the line of connection between two pulleys and is tangent to the pitch surfaces, and coincides with a line in each pitch surface known as the pitch line. 

 
The text then gives an example of the gear ratio with the belt thickness in the equation.

 

Mate, I have studied this stuff professionally and I know all the above by heart. As I explained to you yesterday, the bit in bold is the bit that we need to consider very carefully for our TT belt of high elasticity and low stiffness. Same for the other texts you quoted.

 
So nothing has changed in 100 years of engineering texts that show there is a relationship between belt thickness and gear ratio in belt drives, confirming the turntable 'white paper' and my empirical tests.

 

 

And I have been explaining how that relationship applies to this case from the start. All the texts, even the white paper, are consistent with my statements when you correctly apply the position of the neutral axis, based on a proper understanding or structural analysis of a typical TT belt being wrapped around a pulley. The bit in contact with the pulley doesn't shorten, and therefore it is the neutral axis by definition. The rest of the belt does stretch, and therefore none of it is the neutral axis by definition. If you want to argue that the middle of the belt doesn't stretch, in the case of a highly-extensible piece of rubber being wrapped around a pulley, then I would like you to explain the mechanism by which it resists such stretching. There isn't one. For a flat power transmission belt (rarity though it be without vee or teeth) there is such a mechanism: the belt reinforcement.

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And I have been explaining how that relationship applies to this case from the start. All the texts, even the white paper, are consistent with my statements when you correctly apply the position of the neutral axis, based on a proper understanding or structural analysis of a typical TT belt being wrapped around a pulley. The bit in contact with the pulley doesn't shorten, and therefore it is the neutral axis by definition. The rest of the belt does stretch, and therefore none of it is the neutral axis by definition. If you want to argue that the middle of the belt doesn't stretch, in the case of a highly-extensible piece of rubber being wrapped around a pulley, then I would like you to explain the mechanism by which it resists such stretching. There isn't one. For a flat power transmission belt (rarity though it be without vee or teeth) there is such a mechanism: the belt reinforcement.

 

Then can you pease explain why a Rega turntable that has a 250 rpm synchronous motor, a drive pulley contact diameter of 12.50mm and a sub-platter diameter of 101.25mm runs at 33â…“ rpm and not 30.86 rpm?

 

And then explain why a Systemdek IIX that has a 250 rpm synchronous motor, with a drive pulley diameter of 20.10mm and a sub-platter diameter of 155.50mm runs at 33â…“ rpm and not 32.32 rpm?

 

In fact, if you calculate the size the drive pulley needs to be to achieve 33â…“ rpm in each example, the difference between 'your' pulley size and the actually pulley size it the height of the neutral layer x 2, or another words almost exactly the thickness of the belt. You should be able to work out the belt thicknesses if you know your stuff.

Edited by johnmath

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Then can you pease explain why a Rega turntable that has a 250 rpm synchronous motor, a drive pulley contact diameter of 12.50mm and a sub-platter diameter of 101.25mm runs at 33â…“ rpm and not 30.86 rpm?

 

But AIUI, Rega TTs are deliberately engineered to make the platter spin very slightly fast - like 33.5rpm instead of 33.333333. :confused:

 

This was a Roy Gandy 'trick' to make Rega TTs sound more pleasing. ;)

 

 

Andy

Edited by andyr

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But AIUI, Rega TTs are deliberately engineered to make the platter spin very slightly fast - like 33.5rpm instead of 33.333333. :confused:

 

Maybe, I don't know. My own Rega with the TT-PSU and an Edwards Audio 'Little Belter' drive belt runs at 33.38 rpm or 0.1% fast. Most of the Regas I have serviced this year have run pretty spot on, with maybe one in ten running a bit fast. In an attempt to find the ultimate belt over the past few months, I purchased about 20 'standard' and 'upgrade' belts from all the normal outlets. No two belts run the turntable at the same speed with some running at nearly 34 rpm. One white silicone upgrade belt from 'you know who' had a thick half and a thin half, which meant that for ½ revolution the platter runs fast and then for the other ½ revolution runs slow. (Note these are half revolutions of the belt, not the platter!) On a strobe disk this effect is seen as the dots 'hunting' forward and backwards at a slightly longer period than a single revolution.

 

Any turntable that has an induction or synchronous motor will be affected by the frequency of the mains, and of course the mains frequency varies cyclically at least twice per day. In the morning as power consumption peaks (people wake up and industry starts up) the mains frequency slows down as the generators struggle to keep up with demand. Later around mid morning when the load has stabilised, the utility generators speed up the mains frequency to make up the lost Hz, basically so that clocks with synchronous motors keep proper time. This whole process is repeated after the late afternoon peak as people get home from work and turn on their air conditioners or heaters. By around mid-evening everything is back to 'normal'.

 

The Australian Standard requires electricity generators to keep the mains frequency normally within 49.9 to 50.1 Hz. For load changes the limits are 49.5 to 50.5 Hz. This equates to a range of speeds from 33.00 to 33.67 rpm. Better turntables have their own crystal locked, temperature compensated frequency generator to drive the synchronous motor. My own Rega TT-PSU tests as stable to better than 5 significant figures, namely 50.0000 +/- 0.00007 Hz.

 

Frequency variation of the mains is one problem, but there is another, possibly worse, one. The mains frequency 'warbles' and this cyclic variation adds to the wow & flutter (speed instability) of turntables that are locked to the mains frequency. Of course, if you have a Pro-Ject Speedbox, Rega TT-PSU, or other frequency reconstructive speed control this 'warble' effect is eliminated.

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Maybe, I don't know. My own Rega with the TT-PSU and an Edwards Audio 'Little Belter' drive belt runs at 33.38 rpm or 0.1% fast. Most of the Regas I have serviced this year have run pretty spot on, with maybe one in ten running a bit fast. In an attempt to find the ultimate belt over the past few months, I purchased about 20 'standard' and 'upgrade' belts from all the normal outlets. No two belts run the turntable at the same speed with some running at nearly 34 rpm. One white silicone upgrade belt from 'you know who' had a thick half and a thin half, which meant that for ½ revolution the platter runs fast and then for the other ½ revolution runs slow. (Note these are half revolutions of the belt, not the platter!) On a strobe disk this effect is seen as the dots 'hunting' forward and backwards at a slightly longer period than a single revolution.

 

Any turntable that has an induction or synchronous motor will be affected by the frequency of the mains, and of course the mains frequency varies cyclically at least twice per day. In the morning as power consumption peaks (people wake up and industry starts up) the mains frequency slows down as the generators struggle to keep up with demand. Later around mid morning when the load has stabilised, the utility generators speed up the mains frequency to make up the lost Hz, basically so that clocks with synchronous motors keep proper time. This whole process is repeated after the late afternoon peak as people get home from work and turn on their air conditioners or heaters. By around mid-evening everything is back to 'normal'.

 

The Australian Standard requires electricity generators to keep the mains frequency normally within 49.9 to 50.1 Hz. For load changes the limits are 49.5 to 50.5 Hz. This equates to a range of speeds from 33.00 to 33.67 rpm. Better turntables have their own crystal locked, temperature compensated frequency generator to drive the synchronous motor. My own Rega TT-PSU tests as stable to better than 5 significant figures, namely 50.0000 +/- 0.00007 Hz.

 

Frequency variation of the mains is one problem, but there is another, possibly worse, one. The mains frequency 'warbles' and this cyclic variation adds to the wow & flutter (speed instability) of turntables that are locked to the mains frequency. Of course, if you have a Pro-Ject Speedbox, Rega TT-PSU, or other frequency reconstructive speed control this 'warble' effect is eliminated.

 

Yes, for the last 12 months I have been using a prototype of Steve Tuckett's about-to-be-commercially-released "Number9" AC motor speed controller - which generates its own frequency for the motors (it supports 2), which you can adjust to 3dp, to get the speed exactly to spec (at 33 and 45) ... or even a little faster, to compensate for stylus drag.  :thumb:

 

A very interesting - and IMO highly desirable - feature is the the ability to increase the voltage fed to the motor.  I am currently running my 24v (Rega) Premotecs at 32v - this voltage increase delivers a major benefit in terms of SQ.  However, you can't take advantage of this until you have minimised motor vibration by optimising the phase angle between the 2 pairs of motor wires (it's not the 90 deg delivered by the 'phasing cap'!) - so adjustment of phase angle to minimise motor vibration is the 3rd advantage of the 'Number9' speed controller.

 

Of course, in Regas - where I am told the motor is enclosed in a small space - you may not be able to take the voltage up to 32v (as this makes the motor get hot) but in my situation, the motors are off-board, in clear air, so they remain cool.  And in LP12s, the motor just sits under the top-plate, in an open plinth - so I expect this would be fine, too.

 

 

Andy

Edited by andyr

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@@Newman, @@Owen Y, I put this post this here rather than the Nasotec forum it was previously being discussed in as it was off topic there however it i relevant to this thread. My own experiments have shown that belts make a huge difference to turntable performance with the potential to improve speed stability, reduce wow and flutter, and reduce noise from both the motor and environment. The following is from an engineering paper from Basis Audio, a manufacturer of very high end turntables, and confirms the assertions I made previously:

 

Hi John - I've spent maybe 30+yrs messing seriously with belt drive TTs & had a lot of enjoyment, but these days I get more kicks out of rim drive.

I ended up using mylar tape drive on my last BD TT.

 

Nothing is perfect (despite designer's/manufacturers' assertions).

I listen to live music a lot & the things that rim drive does well, does it better for me.

Just my current personal preference.

 

Cheers, Owen

Dark Lantern blog - http://darklanternforowen.wordpress.com/

Edited by Owen Y

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Of course, in Regas - where I am told the motor is enclosed in a small space - you may not be able to take the voltage up to 32v (as this makes the motor get hot) but in my situation, the motors are off-board, in clear air, so they remain cool.  And in LP12s, the motor just sits under the top-plate, in an open plinth - so I expect this would be fine, too.

 

Hi Andy - what gets hot on Regas is the big R that drops mains 230-240vac down to 90-100vac for the Premotec mtr.

The mtr windings are seldom or never perfectly balanced, resulting in varying degrees of vibration.

 

Just from my experience w Regas.

Cheers, Owen

Dark Lantern blog - http://darklanternforowen.wordpress.com/

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I know there is alot of tweaks can be done to rega turntable. But one tweak that I can't get my head around is upgrading the counterweight. Can anyone explain how would changing counterweight can make any sonic difference? I mean weight is weight no moving parts or anything that may effect vibration

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I know there is alot of tweaks can be done to rega turntable. But one tweak that I can't get my head around is upgrading the counterweight. Can anyone explain how would changing counterweight can make any sonic difference? I mean weight is weight no moving parts or anything that may effect vibration

 

The counterweight has an effect on the inertia of the headshell at the other end of the arm.  This is called the "effective mass" of the arm.  If you can remember your high school physics, the same 'weight' (on the arm's pivot point) can be had by:

  • a smaller weight further away from the arm pivot point, or
  • a heavier weight nearer the arm pivot point.

The latter is better for an arm.

 

Also, an 'under-slung' counterweight (which has its c.o.g.below the arm pivot) is better than a cylindrical counterweight which has the same mass around the arm stub.  (Duc - 'lovetube' - sells these.)

 

 

Andy

Edited by andyr

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There's at least three issues with counterweights that affect the tonearm performance. The specific weight or density of the counterweight affects how far behind the pivot point the weight needs to be to balance the cartridge. A tungsten counterweight is 2½ time heavier than a steel one of the same size, so can be closer to the pivot point. This has the effect of reducing the rotational inertia of the tonearm. When the stylus is pushed by an off centre record or a bump, it has to move the whole tonearm, so if the tonearm has a lower inertia, it is easier to move. This has the effect of raising the cartridge/tonearm resonance as well. Another cheap trick to reduce a Rega tonearm effective mass with is to apply the tracking weight by moving the weight forward, rather than by dialling it in with the adjuster. Of course you need accurate scales to do this, but it can be worthwhile if the cartridge / tonearm combination has too low a resonance, and can help tracking stability enough to make a difference.

 

The second difference in counterweights is how rigidly attached they are to the tonearm stub. The conventional wisdom is to break the tonearm into two, three or even more seperate masses joined with compliant couplings. This has the effect of lowering the severity of the tonearm resonance, generally considered to be a good thing. However some people make counterweights that do away with Rega's o-ring coupling and rigidly attach the counterweight to the stub. Of course this will have some impact on sound but it is hard to see how that impact would be beneficial unless something isn't right somewhere else.

 

The third difference with counterweights is the 'underslung' counterweight which moves the centre of gravity of the counterweight to below the axis of the tonearm. This has the effect of making the tracking weight dependent of the tonearm angle. If all your records are perfectly flat and the same thickness this doesn't matter, but on a record that has surface bumps the tracking weight at the top of the bump will be less than at the bottom, and the stylus will track with less weight on thick 'audiophile' records than thin standard records. I don't know if this is a good thing or a bad thing but I can't see how it would be particularly helpful, especially as the anti-skating force will also only be correct at the on the thickness of record that was assumed for the setup.

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Thanks for the detailed explanation guys. Totally made sense now

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