My AGD Audion monoblock amplifiers just received an upgrade to the GaNTube88KT MkIII. Let's see what differences it brings to the table and whether it is a worthwhile upgrade for existing owners.
Description
AGD builds their amplification stage into a glass envelope. While visually looking like a vacuum tube, they are solid-state devices. Some people have criticised AGD for this move. I found it visually appealing and an interesting talking point. With the introduction of new "tube" variants, AGD users are now able to upgrade their amplifiers without too much hassle. You could swap the "tube" in under 5 minutes per side, with most of the time spent undoing the hex screws to remove the protective cage for my Audion. This is not necessary, but gives my large fingers more room to work.
The MkIII has been two years in the making, and AGD claims that the PWM stage and output filter have been redesigned with more advanced materials to deliver reduced distortion, lowered noise, higher bandwidth and faster response times.
Class-D amplifiers require a low-pass filter to remove high-frequency circuit noise. Poor filtering designs result in a loss of high-frequency detail and air. According to AGD, the new filter results in flat response up to 60KHz.
Output power has been increased to 250W at 4 ohms, and with the Audion, 200W at 4 ohms, due to limitation of the power supply of the Audion. In comparison, the original "tube" delivered 170W at 4 ohms.
Sound Quality
Despite the increase in power rating, there is no noticeable increase in gain moving to the MkIII. The tonal balance remains close to the original, although there is a noticeable improvement in speed and neutrality. Bass quality immediately hits you with more power and articulation. Low frequency notes simply go deeper and with more detail.
On the midrange and high-frequencies, there is better vocal refinement, with an improved sense of air. Placement of voices and instruments are also improved, with better separation and dimensionality.
In tube terms, the improvements are similar to a change from KT88 to KT120 tubes. It's possible that some listeners may prefer the softer presentation of the original tube, but most would prefer the MkIII.
Conclusion
The improvements are not on a subtle level and are on par with the sonic gains associated with moving one model up the product line. This makes the MkIII an easy recommendation for AGD customers. My only criticism is that AGD should make available a trade-in program for customers to help defray the cost of the upgrade.
Hifistay is a Korean company that takes a novel approach to audio equipment support. The spike shoes on review here are part of the company's flagship "triple swing" line. The "triple swing" description refers to the three levels of ceramic ball bearings used within. No prizes for guessing how the "single swing" and "double swing" products compare.
Conditioned by years of audiophile training to suppress unnecessary motion in speakers, the Hifistay will challenge your beliefs. A gentle push on your speaker will result in free motion as the cabinets move back and forth. The Stella 80 is highly efficient in converting vibrations to horizontal movement. As the product stood on my study desk, I saw the top spike-cup gently move. I realised that the barely felt vibration was coming from construction work about 50 meters down the road!
Description
The "Swing" line-up consists of various products ranging from 60 mm to 100 mm diameter spike shoes. The 60mm model is only available as a "double swing", while the 80 mm model is available in both "double swing" and "triple swing". The 100mm model is only available as a "triple swing" model. The choice of shoe would depend on the component, and weight supported. In the case of the 80 Triple Swing, it is described as being suitable for speakers, heavy amplifiers and your equipment rack. Rated load is a maximum of 120 kg/shoe, with a recommended load of 10-60 kg per shoe. The main body of the shoe unscrews from the base to provide height adjustment, which allows precise levelling.
Sound Quality
I tried the 80 Triple Swing with a Partington Super Dreadnought speaker stand (replacing Isoacoustics Gaia footers), and my Tannoy Kensington GR speakers (replacing the stocks spikes). In both cases, they rested on hardwood parquet flooring. Once installed, the speakers rock gently as they are pushed. Audiophiles being fixated with non-movement will find this disconcerting initially.
In the case of the Partington Super Dreadnought speakers stands (with Elac Uni-Fi Reference UBR62 speakers perched on top), there is a useful cleaning-up, and tightening of the music across the frequency range.
Moving on to the Tannoys is when things really got interesting. The Tannoys have always sounded dynamic and fast in my setup, albeit with a tendency to sound a bit bright and bass light. I attributed this to a lack of power, although the Tannoys are easy to drive on paper at 93db sensitivity / 8 ohms. Nevertheless, I got the best bass using powerful amplifiers like the Apollon 1ET400A (227W) instead of low-powered tube amps.
With the Triple Swing installed, the increase in tight and deep bass was remarkable, almost as if I had upgraded my speakers. A dramatic improvement across the rest of the frequency range resulted in improved detail retrieval and focus. As a result, the soundstaging become pinpoint with very deep and distinct layering. High-frequencies were also improved, with a more defined leading edge and decay.
Unlike some other ball-bearing products that I have tried, the Triple Swing does not impact musicality nor coherency. It is far from sounding bright, and instead imparts a fluidity to music that is pleasing. There is no spotlighting of specific frequencies, nor aberrations in the tempo of music. Somehow, this product really manages to deliver the best of both worlds - reproducing plenty of details and improving speed, while retaining naturalness and musicality.
As a forewarning, I anticipate that this product will shift the tonal balance of your system. In particular, the increase in bass power will be a boon to some, and a bane to others. Judicious tweaking and adjustments post-installation will be required to maximise performance.
Conclusion
This product is expensive, and makes sense only in high-end setups. Nevertheless, the improvements made are worthwhile in my personal opinion. Considering that audiophiles typically spend significant amounts for that last degree of improvement, this is a well-justified investment given the magnitude of improvement - Highly Recommended.
I would like to thank KC from XPS Acoustic for arranging this review.
