With the release of our Spring, 2019 drive system update, it seemed like a good time to trace the evolution of our motor drives.
We’ve included some details for the technically inclined, and we’ve tried to give you some insight into both our developent process and what we were trying to acccomplish.
The sonic attributes we report below echo the comments of our customers, although in many cases they describe them differently than we do.
We express our observations in terms of musical performance values where possible, and you’ll find minimal use of audiophile jargon unless there’s no other way to describe it.
2001-2013: The Legacy Drive
This is the drive system I developed during my involvement with Redpoint. We ran this drive system at Galibier up until early 2014. We loved its simplicity.
The drive had a low noise floor, in part because of the motor’s low torque which was dominated by the mass of the platter.
It’s charm was also its weakness, and over time, we realized that for all of its virtues, there was more speed stability to be had. We began looking at a redesign in early 2011.
It wasn’t until mid-2013 that we arrived at a replacement we felt addressed the legacy drive’s weaknesses, without compromising its virtues.
The legacy drive was quite simple – a 4 watt DC motor with a controller based on a 3-pin regulator circuit that we later learned was similar to the approach Verdier took. The Verdier differed primarily in motor selection, the obvious ergonomic layout differences and of course, the rectified AC power.
2014 – The Big Kahuna
The key improvement (and hence, the “Big Kahuna” moniker) this drive system delivered was speed stability and rhythmic pacing. It displays the legacy drive’s weakness in bold relief.
The drive was beginning to take on a rim-drive like characteristic of immediacy and pacing. One customer described the music as taking on a sense of inevitability.
Operation was simpler, and speed stability was “locked in”. No longer did the user have to get his strobe disk out on a regular basis to adjust speed. The move to dual push switches (from a single, dual-function toggle) met with general approval as well.
Shortly after release of the drive, we sourced a fabricator of Kapton belts. DIY belt splicing became a thing of the past.
The design centered around a 30 watt, electronically commutated DC motor with Hall (positioning) sensors. The onboard logic circuit monitors motor speed every 1/3 revolution to produce a solid speed lock. We abandoned the battery supply in favor of a linear supply.
2018 – a Refinement
This was a two-part change that brought more insight and “ease” to the performance, without sacrificing pacing and immediacy (which if anything, was also improved).
It included a minor circuit revision, combined with specification of a better power supply – the Teddy Pardo.
Both changes brought on similar improvements, but the combination multiplied their individual virtues.
Design-wise, we revisited our assumptions from 2014, and we began experimenting with elimination of the onboard regulation from the circuit. This circuit segment was a holdover from the legacy drive with its battery supply – a bit of a “belts and braces” approach, given that we had moved to a linear supply.
In short, we found that with the sophistication of the new power supply, our onboard regulation became a more of a drawback than a virtue and we eliminated it.
2019 – Lessons from the Eiger
We blogged about prototyping this change here.
One notable improvement of this release is improved intelligibility of complex musical lines. Performance nuances are more obvious, the noise floor is lower and there’s even more sense of “drive” and pacing. In short, it’s mo’ better.
The Eiger’s lessons came from the challenges of mounting a drive system directly to the chassis, combined with the potential for motor noise transmission directly through the idler (rim) to the platter.
We learned that by spinning the motor faster, the lessened load on the motor produces less vibration.
In the above referenced blog post, we wrote the following about the lessons the Eiger taught us – lessons that directly transferred to the Gavia/Stelvio belt drive and this new release:
While prototyping the Eiger, we learned that the higher the torque demand on the motor, the more noise and vibration it made.
Gearing down with a narrower diameter idler lessened the demands on the motor. It had to deliver less torque to perform the task of controlling the platter.
Having more “drive” in reserve results in cleaner note attack and decay along with a more nuanced presentation.
Overtones are beautifully fleshed out . Woodwinds sound more woody and horns are more like themselves – golden with just the right amount of “splat”. Rhythmic nuances and complex musical lines are all the more intelligible. All of the usual audiophile accolades apply.
As powerful as the motor is, it still benefits from gearing that makes its job easier.
The redesign (while simple in principle) required a circuit board redesign to set the motor’s speed range high enough to run the narrower pulley, and of course a new pulley was specified.