Hi Roger,
yes, there are some disturbances on long wave (Langwelle) radio (noticed with my Telefunken Concerto 2500 tube receiver). It might disturb other equipment as well. I do not have the equipment to run EMC testing, but I guess it would fail to be certified. This is another reason, which makes it extremely difficult to sell assembled units.
Also, as noted in the "disclaimer" of the manual, the 31 kHz switching frequency might be present in the audio signal (at a VERY low level). It is very unlikely, but may damage speakers if amplified to a high volume.
These are just observations and they should have no impact on the operation of the unit.
Hi Patrick,
the MagicQuartz (and I guess the Phoenix as well) was designed to deal with rather slow speed drifts. These happen mainly due to: (1) decreasing friction when the pickup moves to the center of the record, (2) warming-up of the turntable's mechanics/bearings and (3) dust collecting at the needle (
), which also reduces the speed. These effects can be quite significant. Yes, it is highly debatable if these can even be heard, but they can easily be measured. I plan to come up with some figures that will prove these effects (if you believe my measurements, of course). I have created a PC interface that allows for logging these speed drifts.
I have yet to experience measurable speed changes due to the groove modulations. I also did some experiments with a 100% DIY turntable made with a 3D printer (see my homepage) that uses a stepper motor (
) WITHOUT a platter to turn the record. There, you want to keep the torque as low as possible in order to allow for a low-noise drive. (This works quite well, but admittedly, its performance is very poor when compared to a "real" turntable.) But with this configuration, you can indeed hear the speed decreasing at the beginning of high signal bursts. Quite funny.
So I believe that the heavy platters of our Lencos and Duals well compensate speed variations that might be caused by groove modulations.
I believe it is possible to create a strobe disk that is slightly larger in diameter than a record. If placed under the record, it could be used to create a high-resolution timing signal. So, in theory, it would be possible to do that. And regarding the software, it would be just a matter to make the signals per rotation configurable. The software should be fast enough to do the measurements. Maybe I will experiment with this in the future. But honestly, I do not expect a real benefit from it.
Regarding noise shaping: I did some experiments with this as well, but it's very difficult to be implemented (especially the timing in the firmware). And you would need some circuity on the high-voltage side, which makes the whole construction much more complicated (and dangerous for DIYers).
From my experiences this is not necessary. The amplifier is capable of delivering enough current so that the quality of the sine does not decrease under load. Yes, there is a decrease of the generated voltage under load, but MagicQuartz is capable of compensating this. You have to manually configure the voltages for the motor being turned off and on, and motor calibration wizard in MagicQuartz helps you to do that. However, a future upgrade might do this 100% automatically (with a small PCB that measures the voltage on the high side and communicates the values to the main "low voltage" PCB). The initial version will also have some additional ports for future hardware upgrades, but I can not promise anything at this point of time.
Regarding the "recording idea": Yes, the firmware could "record" statistics about the overall speed changes and reuse them. For example, it could assume that the turntable is "cold" after MagicQuartz has been switched on, and assume that the needle has been moved to the beginning of the record after the motor has been switched off and on again. When using more powerful hardware, MagicQuartz could even detect which record is played back (by also recording the audio signal) and use this information. This would, however be a very advanced thing and the overall performance gain would be minimal. However, MagicQuartz is clever enough to remember the last calibration value. It resumes to this when it is started again (and yes, it can be "removed" manually if you want the true 50 or 60 Hz back).
Furthermore, MagicQuartz will automatically resume into the last mode of operation after being turned on (e.g. live quartz mode). This means that you do not have to spend additional time with MagicQuartz just to get your records playing correctly. Many aspects had been considered to make MagicQuartz as unintrusive as possible.
Cheers, Sebastian
