VPI Analog Drive System [ADS]

Precise platter speed in a high-end turntable was something that I always assumed was a given. After all, it seems a fundamental design goal. Yet, as I explored this subject further, I found it is not quite the simple matter to address as one might expect, particularly with the belt drive designs that many audiophiles favour.

This came to the fore recently when I accepted a deal I could not refuse: a no-cost trade-out of my 25-year-old Basis 1400 for a used VPI Scout with a Classic Platter upgrade.

It was during the replacement and installation of these two tables that I became aware of the fact that spot-on platter speed is more uncommon than not, even with these two well-designed belt drive turntables. The VPI was slightly off, and the Basis even more so. It wasn't just a matter of being slightly off speed. The fluctuations in the speed were what concerned me. Seeing this problem with stroboscopic discs and graphs was enough to trigger some anxiety!

My concerns were alleviated when my dealer, Oswaldo Martinez of Let There Be Sound, explained that in setting up hundreds of belt drive tables, virtually none were spot on and steady unless they employed a speed correction device. The reasons for this are complex, but one thing is certain: fluctuating line frequency from the electrical grid wreaks havoc on a motor’s ability to provide speed, accuracy and stability. As you might imagine, the electrical grid here in southern Florida is anything but stable. Voltage (and one would assume frequency) varies wildly throughout the day.

My first exposure to this type of device occurred during the setup of the VPI Scout. Oswaldo brought his VPI ADS to demonstrate how it worked. To see the ADS (USD 950) correct the speed and keep it locked in was striking. Though it was a brief demonstration in which it would be difficult to hear the benefit, if any, I knew it would at least provide a peace of mind that I found invaluable. I immediately ordered the Analog Drive System to complement my VPI Scout and listened to my “new” front end as I waited two weeks for the ADS to arrive.

From the website:

“The ADS design includes two pure analog frequency generators featuring low distortion and noise; a high current Class-A/B amplifier that is transformer-coupled to the turntable output; analog control logic for low noise operation; 33/45 RPM analog speed adjustment controls with center detent positions that are factory calibrated.”

The setup was relatively simple. The Analog Drive System was set up on a shelf below the Scout and plugged into a wall outlet. The power cord from the turntable’s motor is plugged into the back of the ADS. Setting the motor to “on” and leaving it in that position allows the user to control stopping and starting the platter from a push-button on the front panel of the ADS. There is a supplied stroboscopic disc with markings for 33 1/3 and 45. With the disc placed on the platter, the turntable is started. There are two knobs, one for 33 and another for 45, on the front panel. These are initially set to the factory-calibrated detent position while the disc is viewed with a 300hz strobe light. Fine-tuning, if necessary, is accomplished by a turn of the corresponding knob. When the strobe markings stand still, the speed is optimal. In my case, both speeds were spot on in the detent position. It's really that simple.

Peace of mind is one thing, but I wondered if I would be able to hear what kind of benefits the device could provide musically. Having lived with the Scout for two weeks without the ADS, I had some notion of where it might be of benefit. It was now time to make direct comparisons.

To do this, I first chose a record I thought might display an aspect that should be immediately noticeable: pitch instability on sustained piano notes. The Craft reissue of You Must Believe In Spring by Bill Evans seemed the perfect choice. It's also perfectly centred, which was important for this test.

Disconnecting the turntable from the ADS, I plugged it directly into the wall and listened carefully to Side One of the Craft edition of this album, which is cut at 45rpm. This was followed up with a listen to the same side with the ADS employed.

I first reviewed this record when I was using the Basis 1400. Hearing it today on what is a completely revamped system using the VPI Scout sans ADS was illuminating. The record was even better than I imagined, and the VPI / Hana ML brought it to life in a way that the Basis / Hana SL couldn't quite match. I wasn't surprised at all—virtually every record I’ve played since installing the VPI Scout has had better scale, dynamic nuance, extended bass, and more clearly defined spatial characteristics. I made certain to pay close attention to any pitch stability issues. There seemed to be something there, but I couldn't quite put my finger on it. I thought perhaps minor tape issues or the very slightest eccentricities of the pressing.

Reinstalling the Analog Drive System, I then repeated the side, not knowing what to expect. On “Minor Waltz,” there are several moments when a piano note is sustained and fades gently. I noticed a purity of tone and a continuousness in the way the note decayed that was not quite as evident before the switch. There was a solidity that gave the music freedom as if it had been unlocked from the confines of an LP. There was an uncanny sense of the intention of each note. Imaging was more defined and steady. I also noted the overall noise floor improved slightly. All of these improvements were subtle yet significant. The slight feeling of mechanical playback had been replaced by an exhilarating freedom of musical expression. I ended up playing the entire set and forgot about analytical listening and enjoyed the recording like never before.

Trusting my ears but wanting more validation over a longer period, I again removed the ADS, leaving it out for a few days. I listened to all types of music before returning the ADS to the system. There was no question that I preferred the ADS in the system.

Summary

As beautifully as the Scout performs on its own, I wouldn't care to be without the Analog Drive System (USD 950). It allows the turntable to exhibit its full potential, conveying every nuance of expression locked within each disc. It was much more than mere peace of mind or pitch stability. The subtle improvements across the board turned a great table into an extraordinary one. That it can be done for such a reasonable price, with the flexibility to work with almost all VPI turntables, means that this component will be an essential part of my system for years to come.

Reference System

-VPI Scout with Classic Platter Upgrade

-JMW Memorial Tonearm

-VPI Analog Drive System

-Hana ML MC Cartridge

-ModWright PH 9.0 Tube Phono Pre

-Cayin A-50T Integrated Tube Amplifier

-System Audio Pandion 30 Loudspeaker

-Tributaries Series 8 Interconnect

-Herron Audio Interconnect

-VPI 16.5 Vacuum Record Cleaner

-Sweetvinyl Sugarcube SC-1 Mini

-Studer Revox A77 Reel To Reel Tape Deck

Further information: VPI