Wow, I completely forgot about these, thanks everyone for sharing. There can be more than one way to tackle a problem. Usually I go for what I can do acoustically for some of the TT issues, but it is very interesting to see this. For me, some of the more major issues were solved by wall/shelf mounting, but what might this accomplish in addition?
A big one imho is a reduction (depending upon design of course) in intermodulation distortion, by reducing tonearm resonance. I think this was the primary source of the SQ improvement I discovered, when switching from the non-servo Denon to the servo Sony tt. I didn't do measurements but it seems likely 🙂
Lower wow/flutter is another - that one isn't as intuitive, but it is supposed to be measurable and significant.
Lower wow/flutter is another - that one isn't as intuitive, but it is supposed to be measurable and significant.
Pat Metheny Group - Travels 🙂
Like rockies914 says, less IM/sideband distortion is said to be an important improvement. I believe findings in the "Audible effects of mechanical resonances" by Ladegaard, 1977 was important for this development. http://www.cieri.net/Documenti/Misu...esonances in Turntables (AN17-233 - 1977).pdf
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I looked at the original graph. With the electronic servo switched in, the resonant peak due to cartridge compliance and effective mass is nicely damped. That's what the servo was meant to do. What you also see is an increase in amplitude of frequencies below resonance, and that's what you should expect from increasing damping in a high-pass filter. Remember that a magnetic cartridge is a velocity transducer, so increased amplitude at very low frequencies requires significant stylus excursion, using up its linear range of movement and increasing distortion for the audio we want. This is the key thing with damping the cartridge/arm's LF resonance, too much damping is worse, but some damping is needed. Electronic damping might seem over-complicated, but it's stable with temperature and doesn't involve messy silicone fluid. If anyone has any circuit diagrams, I'd be interested to see the detail of how they sensed the movement. I can't help feel that some sweeping assumptions had to be made and that it would be easy to over-damp.
I like the UFO look of the turntable but I suspect such a thing would meet considerable domestic opposition.
I like the UFO look of the turntable but I suspect such a thing would meet considerable domestic opposition.
The PS-X600 schematic can be found here (along with the other PS-X range, except for the X500):
https://www.audioservicemanuals.com/s/sony/sony-ps/sony-ps-x/
The service manual also has an exploded-view diagram. I'm (slowly) trying to figure that out too. So far, I haven't found discrete position sensors, and maybe they are sensing position through the servo actuation coils? That's a SWAG on my part though.
https://www.audioservicemanuals.com/s/sony/sony-ps/sony-ps-x/
The service manual also has an exploded-view diagram. I'm (slowly) trying to figure that out too. So far, I haven't found discrete position sensors, and maybe they are sensing position through the servo actuation coils? That's a SWAG on my part though.
Thanks for that. I will look through the PS-X600 manual. If you had coils facing a piece of steel, then DC through them would give you damping and you could look at the AC on them as a means of determining movement.
I've looked through the manual. I'm not convinced that arm had electromagnetic damping. The whole turntable appears to address the perceived problem of vinyl convenience. The arm has motors in both directions and is wildly complicated, but I don't see any of the features needed to provide damping. PS-X-75 claims it controls damping - I will have a look at that.
I've looked through the manual. I'm not convinced that arm had electromagnetic damping. The whole turntable appears to address the perceived problem of vinyl convenience. The arm has motors in both directions and is wildly complicated, but I don't see any of the features needed to provide damping. PS-X-75 claims it controls damping - I will have a look at that.
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As I suspected, there's no control of damping. In the PS-X-75, L502 detects movement, is amplified by the lower half of IC109 and is low-pass filtered at 34Hz by C151, R236. This signal then passes to the upper half of IC109 to drive the vertical motor L501, presumably in opposition. There ought to be a user-adjustable gain control between the two halves of IC109. Making R234 a rheostat would do it. Different cartridges need different damping. Looks like their main aim was user convenience, not optimum damping.
Always assuming that the arm and turntable were physically OK (undamaged bearings etc), it looks as though there is plenty of scope for DIY improvement by making that damping adjustable. At that point, it should be possible to produce graphs as were shown early in this thread, but without the degradation displayed below resonance.
Always assuming that the arm and turntable were physically OK (undamaged bearings etc), it looks as though there is plenty of scope for DIY improvement by making that damping adjustable. At that point, it should be possible to produce graphs as were shown early in this thread, but without the degradation displayed below resonance.
The schematic of the DP-67L shows both lateral and vertical, static and dynamic electronic control of the tonearm.
The steps to adjust vertical forces are as follows - first, with the table powered down, the cartridge mounted on the tonearm and the fine adjustment screw zeroed, adjust a substantial counterweight until the tonearm sits steady, balanced and horizontal. Then turn the power on, lower the stylus (on to a gauge, for instance) and adjust the fine adjustment screw (which positions a smaller counterweight internal to the tonearm assembly) to set the vertical tracking force to (say) 1.4g.
With the tracking force set, apply dynamic damping by setting the “Q-Damping” knob to read 1.4, the same as the vertical tracking force. Internally, “Q-Damping” adjusts one gang of a potentiometer to set the proportion of the voltage generated by the velocity of a vertical sensing coil that is fed back to the input of a small amplifier. That amplifier, in turn, drives a vertical moving coil motor to counter the velocity detected by the vertical sense coil.
The second gang of the “Q-Damping” potentiometer acts in a similar fashion to the first, acting instead on the output of a horizontal sensing coil, which drives a horizontal moving coil motor to counter the lateral velocity detected by the coil.
Another knob labled “Anti-skate” internally adjusts a separate potentiometer to drive the amplifier for the horizontal moving coil motor so that it delivers a static, lateral anti-skating force to the tonearm. As for the “Q-Damping” knob, Denon calibrated the recommended “Anti-skate” setting to read “1.4”, identical to the vertical tracking force of 1.4g.
Denon’s approach to the tonearm and other elements of the turntable are set out in the scan of the Denon turntable catalogue I received in 1986, attached to this post. The catalogue shows Denon’s range of direct drive turntables, along with their various features. It is a snapshot in time and by no means a comprehensive listing of Denon’s many direct drive turntables.
The steps to adjust vertical forces are as follows - first, with the table powered down, the cartridge mounted on the tonearm and the fine adjustment screw zeroed, adjust a substantial counterweight until the tonearm sits steady, balanced and horizontal. Then turn the power on, lower the stylus (on to a gauge, for instance) and adjust the fine adjustment screw (which positions a smaller counterweight internal to the tonearm assembly) to set the vertical tracking force to (say) 1.4g.
With the tracking force set, apply dynamic damping by setting the “Q-Damping” knob to read 1.4, the same as the vertical tracking force. Internally, “Q-Damping” adjusts one gang of a potentiometer to set the proportion of the voltage generated by the velocity of a vertical sensing coil that is fed back to the input of a small amplifier. That amplifier, in turn, drives a vertical moving coil motor to counter the velocity detected by the vertical sense coil.
The second gang of the “Q-Damping” potentiometer acts in a similar fashion to the first, acting instead on the output of a horizontal sensing coil, which drives a horizontal moving coil motor to counter the lateral velocity detected by the coil.
Another knob labled “Anti-skate” internally adjusts a separate potentiometer to drive the amplifier for the horizontal moving coil motor so that it delivers a static, lateral anti-skating force to the tonearm. As for the “Q-Damping” knob, Denon calibrated the recommended “Anti-skate” setting to read “1.4”, identical to the vertical tracking force of 1.4g.
Denon’s approach to the tonearm and other elements of the turntable are set out in the scan of the Denon turntable catalogue I received in 1986, attached to this post. The catalogue shows Denon’s range of direct drive turntables, along with their various features. It is a snapshot in time and by no means a comprehensive listing of Denon’s many direct drive turntables.
Thanks, bondini 🙂. For the record, I think the original publication date of this document was between June and October 1983. It includes DL-103M, released June 1983, but not DL-110 which was released October 1983.
See https://www-denon-jp.translate.goog...uto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp
See https://www-denon-jp.translate.goog...uto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp