Pheonix Engineering Road Runner

@pbnaudio

You may like DD turntables. Many people do, and they certainly have their conveniences. My own opinion is that for a DD turntable to provide the same quality sound as a good belt-drive TT it has to be very expensive. Like the forthcoming VPI DD which will be a relative bargain at $15,000. We have yet to see if it performs as well as its predecessor at $30,000 (?).

IMO the cheaper Japanese models like the Denons you write about have a distortion, hard to measure but easier to hear. It’s kind of a micro-flutter caused by the tiny, but constant, speed corrections. Michael Fremer described it as, "ultra-high-speed hunting and pecking as it over- and undercompensates in the attempt to produce a consistent speed can create a jitter effect in the mid-treble to which the human ear is particularly sensitive, adding a hard, brittle texture to music." I agree.

Beyond that I fail to understand why anyone with a DD turntable and its automatic speed control would want to have a Roadrunner type device. In effect the Roadrunner/Falcon functionality is already built in.

Melm,

The reason to put the Tachometers in the turntables to display their accuracy. If you got it flaunt it. :-)

I don't hear the "servo hunting" your describing rather I hear consistency in tempo, great pace and drive. I do add substantial weight to the platters of these tables by adding copper mats,  this of course increase inertia so if what your describing exist its effect is greatly diminished. 

I have built several plinths for the older style VPI DD table - even one for HW and it was a very nice machine.  I have the new one on order already from pictures I've seen its smaller than the old drive.

To get the same speed stability I have a hard time getting with any belt drive.  For an example I made several experiments with belt drive units one was adding more than one drive belt - 2 was better than one 3 was better than two and 4 was again better than 3 this must be because there is some microscopic belt slip.  Any one with a VPI Flywheel drive station should try more than one belt - you'd  be surprised by its effect.

https://pbnaudio.com/original-groovemaster/

Good Listening


Peter

@pbnaudio 

You wrote: "I don't hear the 'servo hunting' your describing rather I hear consistency in tempo, great pace and drive. I do add substantial weight to the platters of these tables by adding copper mats,  this of course increase inertia so if what your describing exist its effect is greatly diminished."

On the basis of what you say,, I believe that you DO hear the "servo hunting" described by Fremer.  You say you add "substantial weight" to the platters.  I presume you do that because the additional weight increases the SQ of the analog playback.  Increased platter weight almost always does.  The difference between what you heard with the light platters and the heavier platters is exactly what Fremer is writing about.  Heavy platters (and other flywheel devices) has always been the advantage of belt-drive TTs (with the exception of super-expensive DD TTs).  Also heavy platters are less likely to ring.

For the Japanese DD TTs you write about, though, the ability to add weight is severely limited by their comparatively weak motors.

Melm,

No actually not - any mat will change the sound of a turntable setup, and I prefer the sound a copper mat produce.  Im thinking about haven one made of Stainless Steel just to try that.

Now lets talk about motors on the DD tables I am talking about, I restore Denon DP3000/2000/6000/7000/80 and DN308.  The motors on these are substantially larger than any of the motors typically used on any belt drive http://www.hurst-motors.com/aabdirectdrive.html this link takes you to the first choice of belt drive manufactures.

The first 4 on my list use almost identical motors, the 80 is even larger, and the DN308 motor is the size of a gallon paint can.   https://pbnaudio.com/pbn-dp8/ - here you can see the motors on the first 4 and the DP80 which is 5.5" in diameter so you have come comparison.  https://pbnaudio.com/pbn-dn308/  This link shows you the motor on the DN 308 - the Bezel that holds the platter and motor is 15.375" just to give you some comparison.


Good Listening

Peter

pbnaudio

I don’t hear the "servo hunting" your describing rather I hear ...

The "servo hunting" common to many DD turntables isn’t detectable as speed variations, ime, but as a veil to the sound.

Before I went to belt drive, I had a Denon DP-6000 and then a DP-80. I can’t imagine ever returning to DD.