DirectDrive - The Hows And Whys



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What's up with that Direct-Drives?

If you believe most audiophiles or your local Linn-dealer these are products for clubs or radiostations which don't belong into the home of a true audiophile because they "do not sound". Quite the point a good Direct-Driven Turntable has not that much sound of his own usually less than most (not all) belt-driven suspended or high-mass turntables - not necessarily a bad thing in my opinion considering what HiFi ought to be about...
How does it work?
What are the advantages?
How does it sound?
What does it cost?
How does it look?
Some words about plinths
Caveats and Drawbacks

How does it work?

In the end of the 60's engineers at National/Technics found that to better the reproduction of analog records you have to minimize the number of moving parts especially the number of bearings in a player-system. The first patent of a direct-drive for record-players goes back to 1929, it belonged to the suisse company Thorens - which is known among audiophiled mostly for its belt-driven players. So almost 40 years had to pass until - with the inventions of modern discrete regulation-circuits - it was finally possible to produce a direct-driven record-player of high quality.
With the first models the speed was regulated by reading the minute fluctuations of the platter with a tachometer and correcting the turning of the motor by comparing this signal with an electronic reference-signal. The drawback of this principle was that before correcting something a fluctuation already has to occur. These effects may be more or less audible depending on the quality of the deck.
Soon after that Denon introduced a new method by reading a difference-signal from a magnetic-ring inside the platter and thus generating a correcting-signal for the motor before any significant fluctuations in speed had occured. Later japanese players included a phase-locked-loop (PLL) around the reference- and the differential- circuits. That way the speed is corrected when a slight difference in phase of the two signals is detected, with only a minute and constant phase-difference between reference- and tachometer-signal left. The tendency for "trembling" of the first generation direct-drive turntables was almost completely eliminated that way and speed-fluctuation depended almost entirely on a clean reference-signal and the quality of the motor-bearing-platter triumvirat itself. Instead of hall-genarators or sythesizer-circuits during the middle of the 70's quarz-crystal-oscillators were introduced, which managed to put out a "quarz-constant" reference-signal.

What are the advantages?

A huge advantage of a direct-drive record-player is the fact, that the whole mechanical system consists of just one moveable part (the combined motor-shaft/platter-bearing) which turns quite slow and has a big mass (the platter) attached to it - almost a mechanical ideal for quiet rotation. The resonance of the combined motor/bearing assembly lies in the range of 0,5 Hz due to its slow speed compared with the 50/60Hz resonance of the motor of a typical belt-driven turntable. All belt - or idler-driven record-players incorporate a lot of mechanical parts for adapting the fast speed of the motor to the comparably slow speed of the platter. Each of this parts implies an own sonic footprint by inducing resonances and suffering from bearing-tolerances in this more or less complex mechanical system. Another advantage of good direct-drive decks is speed-stability.
The german magazine "Audio" once measured the frequency of a 3kHz burst played through a belt-driven state of the art turntable system. There were 4Hz missing! To compensate for the effect of slowing the platter during heavy modulations you need a fast and precise regulation and rigid coupling between the motor and the platter. Compare this to your typical belt-drive deck... Some might argue that a very heavy platter won't slow down because of its sheer mass - this is not the case. Even worse - when the motor regulation tries to speed up this platter will react much slower than a light one. It's like driving a mountaineous way with a truck - I would prefer a Porsche. Coupling the motor to a heavy platter with a string is questionable, too. Whoever changed the tension of the string of a Platine Verdier (platter weight around 50pds.) knows what I mean. Some enthusiasts take even tape instead of a belt to improve coupling the motor to the platter. Now speed stability may improve but there is no filtering of motor resonances any more...
Negative effects of the needle slowing the platter during heavy modulations are best avoided by incorporating a fast and precise speed-regulation, a not too heavy platter rigidly coupled to a strong motor (best the platter is bolted to the motor like with the Technics SP-10Mk2). With such a deck speed-fluctuations during playing a Wagner opera will eventually become neglectable.

How does it sound

Good direct-drive turntables tend to sound very neutral - they deliver what is on the record not less and not more, no foot-whipping effects like some scottish belt-drive - just pure information. Musicality is produced of course, but only if it's on the record. As this is true for the "top-of-the-line"- models covered on this site forget about most cheaper direct-drives of the same era that flooded the mass-market during the 70s and 80s. In the DirectDrive-Museum you will find some recommendable models. A good direct-drive machine delivers rock-steady positions of instruments, precise timing, high dynamics and razor sharp transients. Classical music has as much authority and weight like with the best high-mass belt-driven turntables - but without their timing-problems in the lower registers. The music lover who is ahead of spectacular effects should give a Technics SP-10MkII, an EMT 948 or a Denon DP-6000 a listen - he might well be surprised...

What does it cost?

A good Direct-Drive machine is very expensive to build. A SP-10MkII used to cost around 1000,- Dollars in the 70's, today that might be ten times as much. The EMT 948 pictured above carried a price-tag of 6000,- Dollars in the end of the 70's... Those machines were introduced to the stunning public during the heyday of japanese audio. The yen was low, production-costs were no object and lots of well-eduacated engineers were just waiting to put their expertise and creativity into a new "analog statement-product". At the end of the 70's almost every japanese audio-company had one or two of those flagships in their program, mostly for prestige and image-reasons. Obviously these battleships were calculated in a manner that they were subzidized by the huge sales of their little mass-market brothers. Today those machines seem to be THE ticket for a glimpse of analog nirvana. More about today's prices for differnet models in the DirectDrive-Museum.

How does it look?

Looking at those machines you clearly see the approach of a company to create a real statement-model, one that you will always associate with that company. No player in that days looked like the other, the designers wanted theit babies look unique and prestigous. Rosewood and brushed aluminium were the ingredients and cost was obviously no object. Build-quality was also exceptional, and these days noone dared to present a record-player without a strobe.

Some word about plinths and tonearms

If you want these machines sound as they can you need a dense and heavy plinth and a good decoupled stand. Many of the turntables in that days were developed as a simple chassis which the user could place into a plinth of his taste. Plinths offered by the companies looked good - but in most cases they suffered from resonnances and spoiled the sound of the players. Apparently plinths offered by Denon, JVC and Sony suffered from this. On the other hand having the possibility to make an own plinth means that you can somewhat tune the sound of your turntable for your own system and taste. You can also get the looks you like. Building your own plinth is covered here.
The same applies for tonearms which were mounted that days. Most recommended models which are covered in depth here were delivered without an arm, so the customer could install his own. So putting a decent, modern arm on such a turntable isn't a big problem.

Caveats and drawbacks

Yes, quite a lot. Almost 90% of the direct-drive record-players of the 70s and 80s were cheap and nasty machines - this is the real reason for the bad image of the Direct-Drive principle among most audiophiles. These players were composed out of light plinths, lots of plastic and cheap materials for platter and main-bearing and flooded the mass-market mostly because they were cheap. You won't see those models on this site.
As for the others most of them had absolutely no suspension, so you need to have a special turntable-table or - even better - a wall-mounted-shelf to decouple the player from its sorroundings.
You won't get any spare-parts for this machines, as right now most of them are more than 20 years old. A burned motor of a Denon usually means the end for that player unless you're lucky and find a second one which you use for the job. Electronic parts like hall-generators, or some Op-Amps and trannies are getting more and more difficult to find these days. If you'll need these, prepare yourself for a long search. Some kind of service is still available for EMT - at not so nice prices... - and for the Technics SP-10.
BUT - most machines you will see here were built like a tank and if not seriously abused will play a whole lifetime.

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